Title of Invention	METHOD OF RETRANSMISSION TO REDUCE THE OVERHEAD
Abstract	A method of transmitting data in a wireless access system and a packet retransmitting method therein arc disclosed. The present invention includes receiving an initial control message including information required for a packet retransmission from a base station, transmitting the packet to be provided with a service from the base station, and if a NACK (non-acknowledgement) signal is received from the base station, retransmitting the packet corresponding to the NACK signal to the base station using the information required for the packet retransmission and included in the initial control message. Therefore, since a separate control message needs not to be transmitted in case of packet retransmission, it is able to save radio resources and reduce an overhead by retransmitting a packet via a previously allocated retransmission region without the separate control message.

Title of Invention

METHOD OF RETRANSMISSION TO REDUCE THE OVERHEAD

Abstract

A method of transmitting data in a wireless access system and a packet retransmitting method therein arc disclosed. The present invention includes receiving an initial control message including information required for a packet retransmission from a base station, transmitting the packet to be provided with a service from the base station, and if a NACK (non-acknowledgement) signal is received from the base station, retransmitting the packet corresponding to the NACK signal to the base station using the information required for the packet retransmission and included in the initial control message. Therefore, since a separate control message needs not to be transmitted in case of packet retransmission, it is able to save radio resources and reduce an overhead by retransmitting a packet via a previously allocated retransmission region without the separate control message.

Full Text	METHOD OF RETRANSMISSION TO REDUCE THE OVERHEAD TECHNICAL FIELD The present invention relates to a method of transmitting data in a wireless access system, and more particularly, to various packet retransmission methods in the data transmitting method. BACKGROUND ART In the following description, explained is a method of transmitting packets in terminals that use IP based voice over internet protocol (hereinafter abbreviated 'VoIP') in a broadband wireless access system. For this, VoIP traffic is described as follows. Yet, a packet transmitting method according to the present invention needs not to be limited to the VoIP packet transmission described in the following. First of all, VoIP traffic is characterized in being generated in a fixed size with a fixed period in VoIP codec. And, VoIP communication can be divided into a talk period (talk-spurt), for which inter-user call is in progress, and a silence period for which a user is not talking but listening. In general, the silence period occupies over 50% in a whole call session. In order to allocate bandwidths differing in size to the talk-spurt and the silence period, various kinds of audio codecs are used. A representative one of the various kinds of audio codecs is AMR (adaptive multi-rate) scheme used by GSM (global system for mobile communication) or UMTS (universal mobile telecommunication system). Since voice data is not generated for the silence period, if a bandwidth is allocated to the silence period, it may bring about a resource waste. To prevent the resource waste, VoIP supports a silence suppression scheme. According to the silence suppression scheme, a vocoder for generating VoIP traffic does not generate traffic for the silence period and periodically generates a comfort noise to inform a correspondent user that a call keeps being maintained. For instance, a vocoder, which uses the. AMR codec, generates a packet in a fixed size once per 20ms for a talk-spurt or generates a comfort noise per 160ms. Meanwhile, for resource allocation to the traffic having a predetermined period in a fixed size like VoIP in general, a base station is able to use a method of allocating a designated region to a specific terminal fixedly. Namely, a region having an initially determined size is allocated to a terminal supporting the VoIP service. And, it is able to inform the terminal of the allocated region information via an initially transmitted control channel or message (e.g., UL-MAP or DL-MAP). Thus, the initially transmitted control channel or message can contain period information of a region that will be allocated in the future as well. Subsequently, for a next period, the base station is able to keep allocating the corresponding region having been notified to the terminal via the initially transmitted control channel or message without a special notice. Therefore, the terminal transmits VoIP packets via the allocated region using the region information allocated by a MAP in the early stage and then transmits VoIP packets via the same region from a next period using period information. Assume that a length of a frame is set to 5ms to consider a VoIP service. And, assume that a frame period allocated to a terminal for VoIP packet transmission is set to 4 frames. In this case, a frame period allocated to a terminal for VoIP packet transmission may vary according to characteristics of a service. In particular, in case of a same VoIP service, the frame period allocated for the VoIP packet transmission may be used by being defined different according to the respective consideration factors such as system characteristics (e.g., a system characteristic according to a frame length), a VoIP service status (e.g., a talk-spurt, a silence period) and the like. In an initial frame, a base station notifies a terminal of allocated region information for VoIP packet transmission via UL-MAP. Thereafter, in a fourth frame or an eighth frame corresponding to each period, the base station does not announce region information via the UP-MAP but allocates a region for the VoIP packet transmission only. In this case, a period allocated for the VoIP packet transmission corresponds to four frames (i.e., 20ms). In particular, the terminal keeps storing the region allocation information contained in the UL-MAP received in the initial frame and is then able to transmit a VoIP packet via a corresponding region if there is not reception of UL-MAP in the fourth or eighth frame. Thus, the base station is able to allocate the resource for a single VoIP connection fixedly and constantly due to the VoIP traffic characteristics. In the following description, briefly described is a method of transmitting data between a transmitting side and a receiving side. In a data transmitting method, if a transmission failure occurs, a receiving side makes a retransmission request for corresponding data. In this case, ARQ (automatic repeat request) scheme is generally used as a data retransmission scheme. In the ARQ scheme, an acknowledgement/non- acknowledgement (hereinafter abbreviated ACK/NACK) signal indicating whether a receiving side correctly receives data is notified to a transmitting side. The receiving side then retransmits the data for the corresponding signal in case of receiving the NACK signal. The ARQ scheme can be categorized into SAW (stop-and-wait) ARQ, GBN (go-back-N) ARQ and SR (selective-repeat) ARQ. In the SAQ ARQ scheme, a transmitting side waits after data transmission until receiving ACK or NACK signal. If the ACK signal is received, the transmitting side newly transmits next data. If the NACK signal is received, the transmitting side retransmits the previous data. Namely, the SAW ARQ scheme is a scheme for transmitting a single frame at a time only. If it is confirmed that a corresponding frame is successfully delivered, a next frame is transmitted. The GBN ARQ scheme is a scheme for continuously transmitting data regardless of a response message. In case that a receiving side fails to receive data of a specific frame in the course of receiving data, the receiving side is unable to transmit an ACK signal for the specific frame to a transmitting side. Since the transmitting side is unable to receive the ACK signal for the specific frame, the transmitting side retransmits data from the data of the specific frame. In the SR ARQ scheme, while data keeps being transmitted, data corresponding to a received NACK signal is retransmitted only. If a receiving side fails to receive data of a specific frame, the receiving side transmits a NACK signal to a transmitting side. The transmitting side having received the NACK signal then retransmits the data of the frame indicated by the NACK signal to the receiving side to transmit the whole data. Since the SR ARQ scheme gives a sequence to each frame and manages it, the implementation of the SR ARQ scheme may becomes complicated relatively. In the scheme for transmitting data in packet format, as a higher data rate becomes necessary, a coding rate or a modulation scheme, which has a suitable level to prevent error generated in high-speed transmission environment, is applied to a communication system. And, ARQ scheme suitable for the high-speed transmission environment, i.e., Hybrid ARQ (hereinafter abbreviated HARQ) has been proposed. In the ARQ scheme, if error is generated, the corresponding information is discarded. Yet, in the HARQ scheme, a receiving side stores erroneous information in s buffer. The receiving side combines the stored information with retransmitted information and then applies FEC (forward error correction) thereto. Namely, the HARQ scheme may be regarded as the scheme generated from combining the ARQ scheme with the FEC. The HARQ can be mainly categorized into the following four types. In a first type HARQ scheme, a receiving side always checks an error detection code in data and then primarily applies FEC thereto. If error still remains in a packet, the receiving side makes a request for a retransmission to a transmitting side. The receiving side discards an erroneous packet. The transmitting side then retransmits a packet by applying the same FEC code of the discarded packet to the retransmitted packet. Second type HARQ scheme is called IR (incremental redundancy) ARQ scheme. In the second type HARQ scheme, a receiving side stores a first transmitted packet in a buffer instead of discarding it and then combines it with retransmitted redundancy bits. In case of retransmission, a transmitting side retransmits parity bits only except data bits. Each time the parity bits are retransmitted by the transmitting side, different ones are used. A third type HARQ scheme corresponds to a special case of the second type HARQ scheme. Each packet is self- decodable. In case that a transmitting side performs retransmission, the transmitting side configures a packet containing an erroneous part and data together and then retransmits the corresponding packet. Although this scheme enables decoding more accurate than the second type HARQ scheme, it has efficiency poorer than that of the second type HARQ scheme in aspect of coding gain. In a fourth type HARQ scheme, a function of combining the data initially received and stored by a receiving side with retransmitted data is added to a function of the first type HARQ scheme. And, the fourth type HARQ scheme may be called a matrix combining scheme or a chase combining scheme. .Moreover, the fourth type HARQ scheme has a gain in aspect of SINR (signal to interference noise ratio) and always uses the same parity bits of the retransmitted data. In case that error is generated in data transmission or data is lost in the data transmission, the above- described data transmitting methods enable reconstruction of original data. DISCLOSURE OF THE INVENTION TECHNICAL PROBLEM However, in case that transmission/reception of packets is frequently required like VoIP, it becomes highly- probable that error is generated from the transmitted/received packets. Since the number of transmissions for control messages to allocate new resource regions and the like is incremented, an overhead is increased in a MAC layer. TECHNICAL SOLUTION Accordingly, the present invention is directed to a method of transmitting data in a wireless access system that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. An object of the present invention is to provide a method of transmitting data, by which data can be efficiently transmitted. Another object of the present invention is to provide a method of reducing a message overhead in case that packet retransmissions are frequently necessary. Another object of the present invention is to provide a method of reducing an overhead generated from retransmitting an erroneous packet for continuously transmitted VoIP packets and the like. Another object of the present invention is to provide a method of allocating a retransmission region to an least one mobile station, by which data processing efficiency can be raised despite that VoIP packet is transmitted to a plurality of mobile stations. A further object of the present invention is to provide a method of allocating a new retransmission region instead of a previously allocated retransmission region if error keeps being generated despite that a retransmission packet is transmitted by allocating a fixed transmission region, by which efficiency in processing data can be raised. Therefore, the present invention relates to a data transmitting method in a wireless access system and a packet retransmission method in a wireless access system. And, in case that frequent packet transmissions/receptions are necessary, methods for efficiently using resources by reducing a control overhead are disclosed. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings. To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a method of retransmitting a packet in a wireless access system according to the present invention includes receiving an initial control message including information required for a packet retransmission from a base station, transmitting the packet to be provided with a service from the base station, and if a NACK (non-acknowledgement) signal is received from the base station, retransmitting the packet corresponding to the NACK signal to the base station using the information required for the packet retransmission and included in the initial control message. Preferably, the information required for the packet retransmission includes information for allocating different resource allocation regions required for the packet transmission to at least one or more terminals, respectively. Preferably, the information required for the packet retransmission includes information for configuring at least one group including terminals having resource allocation regions equal to each other in size among at least one or more terminals and for allocating a resource allocation region required for the packet retransmission to the at least one group. Preferably, the information required for the packet retransmission includes information for setting a retransmission dedicated channel for the packet retransmission of at least one terminal and on a specific region required for the packet retransmission in the retransmission dedicated channel. To further achieve these and other advantages and in accordance with the purpose of the present invention, a method of retransmitting a packet in a wireless access system includes the steps of transmitting an initial control message including information required for a packet retransmission to at least one terminal, providing a service to the at least one terminal, and if a NACK (non- acknowledgement) signal is received from the at least one terminal, retransmitting the packet corresponding to the NACK signal to the at least one terminal using the information required for the packet retransmission and included in the initial control message. Preferably, the method further includes the step of if the base station receives the NACK signal repeatedly over a prescribed count, transmitting a control signal to the at least one terminal by updating the information required for the packet retransmission and then including the updated information in the control message for the packet retransmission. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. ADVANTAGEOUS EFFECTS Accordingly, the present invention provides the following effects or advantages. First of all, data communication can be efficiently performed using the embodiments of the present invention. Secondly, in case that frequent packet retransmissions are necessary, a fixed retransmission region can be allocated to a mobile station via an initial control message instead of allocating a retransmission region each time. In particular, if it becomes necessary to perform a retransmission, it is able to retransmit a packet via a previously allocated retransmission region without a separate control message. Therefore, since an additional and separated control message needs not to be transmitted in case of packet retransmission, it is able to save radio resources and reduce an overhead. Thirdly, in case that frequent packet transmissions/receptions are necessary like VoIP service, the present invention is able to reduce an overhead generated from retransmitting an erroneous packet. Fourthly, by allocating a retransmission region to each of at least one or more mobile stations, packets can be quickly retransmitted via the allocated resource region in case that the mobile stations perform retransmissions. Therefore, efficient data processing is enabled. And, at least one or more mobile stations having the same attributes are grouped together and a retransmission region is then allocated per group. Therefore, it is able to save radio resources. Moreover, by allocating a dedicated retransmission channel for a plurality of mobile stations, it is able to perform more efficient retransmission. Fifthly, despite that packets are transmitted by allocating a fixed retransmission region, if errors keep being generated from the packets, a new retransmission region is allocated instead of a previously allocated retransmission region. Therefore, it is able to effectively cope with the repeatedly generated errors. DESCRIPTION OF DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: FIG. 1 a flowchart for an embodiment of using HARQ in transmitting VoIP packets in downlink; FIG. 2 a flowchart for an embodiment of using HARQ in transmitting VoIP packets in uplink; FIG. 3 is a diagram for a method of allocating a fixed radio resource region for retransmission from a base station to a mobile station according to one embodiment of the present invention; FIG. 4 is a diagram for a method of allocating a radio resource region for retransmission from a base station to a mobile station according to another embodiment of the present invention; FIG. 5 is a diagram for a method of allocating a radio resource region for retransmission from a base station to a mobile station according to a further embodiment of the present invention; FIG. 6 is a flowchart for performing a retransmission using a continuous HARQ setting method in downlink according to one embodiment of the present invention; FIG. 7 is a flowchart for performing a retransmission using a continuous HARQ setting method in uplink according to another embodiment of the present invention; FIG. 8 is a flowchart of a packet error processing method in performing retransmission using a continuous HARQ setting method in downlink/uplink according to a further embodiment of the present invention; FIG. 9 is a flowchart of a packet error processing method in case of detecting error repeatedly in performing retransmission using a continuous HARQ setting method in downlink/uplink according to a further embodiment of the present invention; and FIG. 10 is a flowchart for a method of performing retransmission in the course of transceiving VoIP service between a base station and at least one mobile station in uplink according to a further embodiment of the present invention. BEST MODE MODE FOR INVENTION Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. To solve the above-mentioned technical problem, the present invention provides an efficient data transmitting method in a wireless access system and an efficient packet retransmitting method therein. Moreover, the present invention provides a packet transmitting method to use resources efficiently by reducing a control overhead of a MAC layer in case that frequent packet transmission/receptions are necessary. The following embodiments are implemented by combining the elements and features of the present invention in specific forms, respectively. Each of the elements or features can be considered selective if there is no separate explicit description. Each of the elements or features can be implemented without being combined with another one. And, an embodiment of the present invention can be configured by combining the elements and/or features in part. The order or sequence of the operations mentioned in the descriptions of the embodiments of the present invention may be changed. Configurations or features of one of the embodiments can be partially included in another or can be replaced by corresponding configurations or features of another embodiment. In the description of the drawings, procedures or steps, which may dilute the gist or substance of the present invention, are not described. And, procedures or steps understandable on a level for those skilled in the art are not described as well. In this disclosure, embodiments of the present invention are described centering on data transceiving relation between a base station and a terminal. In this case, the base station has the meaning as a terminal node of a network for performing communication directly with the terminal. In this disclosure, a specific operation or action described as performed by a base station can be performed by an upper node of the base station. Namely, various operations performed for communication with a terminal in a network constructed with a plurality of network nodes and a base station can be performed by the base station or the network nodes except the base station. In this case, the 'base station' can be replaced by such a terminology as a fixed station, a Node B, an eNode B (eNB), an access point and the like. And, 'mobile station' can be replaced by such a terminology as a user equipment (DE), a subscriber station (SS), a mobile subscriber station (MSS), a mobile terminal and the like. A transmitting end means a node for transmitting data or a voice service and a receiving end means a node for receiving data or a voice service. Hence, a terminal and a base station can become a transmitting end and a receiving end in uplink, respectively. Likewise, a terminal and a base station can become a receiving end and a transmitting end in downlink, respectively. Meanwhile, a mobile station of the present invention can include one of a personal digital assistant (PDA), a cellular phone, a personal communication service (PCS) phone, a GSM (global system for mobile) phone, a wideband CDMA (WCDMA) phone, a mobile broadband system (MBS) phone and the like. Embodiments of the present invention can be implemented through diverse means. For instance, embodiments of the present invention can be implemented through hardware, firmware, software or any combination thereof. In case of the implementation by hardware, methods according to the present invention can be implemented at least one selected from the group consisting of ASICs (application specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), a processor, a controller, a microcontroller, a microprocessor and the like. In case of the implementation by firmware or software, methods according to embodiments of the present invention can be implemented by a module, procedure or function for performing the above-mentioned functions or operations. Software code is stored in a memory unit and can be driven by a processor. In this case, the memory unit is placed within or outside the processor and is able to transceive data with the processor by various means which are already known in public. Embodiments according to the present invention can be supported by at least one documents disclosed for at least one of wireless access systems (e.g., IEEE 802 system, 3GPP system, 3GPP LTE system, 3GPP2 system) . In particular, the document of IEEE 802.16e Rev2_D4 (April 2008) is able to sufficiently support the embodiments according to the present invention. Specific terminologies used in the following description are provided to help the understanding of the present invention. And, the usages of the specific terminologies can be modified into other forms within the scope not departing from the technical idea of the present invention. In the following description, VoIP packet transmission among services, for which frequent packet retransmissions are required, is taken as an example for one preferred embodiment of the present invention. According to one preferred embodiment of the present invention, in case of setting a continuous resource allocating method for VoIP packet transmission, a base station enables continuous resource allocation information for retransmission to be included in an initial control message and then provides the information to a mobile station in advance. In uplink, the mobile station is able to transmit a packet and the like to the base station via the retransmission region in case that a retransmission occurs in the base station. In downlink, the base station is able to transmit a retransmission packet to the mobile station based on information for retransmission included in the initial control message provided to the mobile station. The initial control message may be usable for various kinds of systems. In particular, the IEEE 802.16 system is able to use MAP IE (MAP information element) contained in a MAP message, a MAC management message or the like as the initial control message. When a mobile station performs handover in entering a network of a base station, an initial control message is usable in the course of setting an interconnection. An initial control message may be a control message initially provided when a base station and a mobile station generate a new service. Namely, an initial control message may be a control message for allocation to transmit a first VoIP packet. Moreover, when a service is provided for a talk- spurt after a silence period, an initial control message is usable as well. And, it is understood that other control messages is usable as an initial control message as well as the above-described message. As an example for one of various MAC management messages, there are dynamic service addition messages (e.g. DSA-REQ or DSA-RSP), channel descriptor messages (e.g. UCD or DCD), Subscriber Station basic capability messages (e.g. SBC-REQ or SBC-RSP) or the like. Besides, by non-limiting various examples for the above-described messages, various MAC management messages are available according to system requirements. In particular, in case of providing a VoIP service to a mobile station initially, a base station is able to transmit informations required for retransmission to the mobile station using such a downlink control message as DL- MAP IE, UL-MAP IE or the like. When a base station initially provides a VoIP service to a mobile station, the base station and the mobile station can negotiate informations relevant to retransmission. The information required for retransmission can contain fixed resource allocation information for retransmission, MCS (modulation and coding scheme level) information, a retransmission timing point (e.g., information for determining that a retransmission will be performed in a prescribed frame after receiving a NACK signal) or the like. For the information required for retransmission, even if a mobile station and a base station transceiver packets via a pre-designated resource allocation region, if a NACK signal keeps being generated, the base station is able to allocate a radio resource region for a new retransmission by transmitting a control message for the new retransmission to the mobile station after having received a prescribed number of NACK signals. In this case, the prescribed number of NACK signals may vary according to a requirement of a system. In preferred embodiments of the present invention, a case of consecutively receiving NACK signals twice is taken as an example to be described in the following description. In the following preferred embodiments of the present invention, a region previously allocated for retransmission is used only if the retransmission is generated only. If the retransmission is unnecessary, the previously allocated region is usable to transmit other general messages. This is to reduce waste of radio resources that may be generated when a specific region is unnecessarily secured unnecessarily. In the process for transceiving VoIP packets between a base station and a mobile station, if a retransmission is generated in downlink, the base station transmits a retransmission packet via a pre-designated resource region. The mobile station is then able to receive the packet based on information about a pre-designated region for the retransmission. If a retransmission is generated in uplink, the mobile station transmits a retransmission packet via a fixed resource region pre-allocated by the base station. The base station is then able to receive the packet via a pre-designated region. In particular, if error is generated from a packet having been retransmitted, a retransmission is performed using the same method (using a region allocated in the early time of a specific frame after completion of receiving NACK) of the initial retransmission. Alternatively, when the base station performs a retransmission using region information for the retransmission, the base station is able to inform the mobile station of the error generation using a control message. In the preferred embodiments of the present invention, 'the error generation from a packet' includes a case that a mobile station or a base station is unable to receive a packet lost on a wireless/wire line as well as a case that error is generated from a transmitted or received packet itself. And, 'the error generation from a packet' also includes a case that a mobile station or a base station is unable to reconstruct an erroneous packet into an original packet. In the following description, explained is a retransmission method used in a MAC layer. FIG. 1 a flowchart for an embodiment of using HARQ in transmitting VoIP packets in downlink. Referring to FIG. 1, a method of transmitting VoIP packets to provide a VoIP service from a base station (BS) to a mobile station (MS) can be observed. When the base station BS transmits a DL VoIP packet #1 in downlink, as error is generated or the DL VoIP packet #1 is lost on wireless/wire line, if the mobile station is unable to receive the DL VoIP packet #1 [S101], the mobile station transmits a NACK signal to the base station [S102]. In this case, in order to retransmit the DL VoIP packet #1 having been transmitted to the mobile station in the step S101, the base station transmits a control message for retransmission by enabling new MCS (modulation and coding scheme) level information and new resource allocation region information to be included in the control message [S103]. The base station, which allocates a new resource region by transmitting the control message to the mobile station, retransmits the DL VoIP packet #1 to the mobile station via the newly allocated resource region [S104]. If the mobile station normally receives the packet in the step S104, the mobile station transmits an ACK signal to the base station [S105]. In order to provide the VoIP service continuously, the base station transmits a next VoIP packet, i.e., a DL VoIP packet #2 to the mobile station. Yet, if the DL VoIP packet #2 is erroneous or lost on wire/wireless line in the course of reception, the mobile station is unable to receive the packet normally [S106]. The mobile station failing to receive the VoIP packet normally transmits a NACK signal to the base station [S107]. Having received the NACK signal from the mobile station in the step S107, the base station transmits a control message for retransmission to the mobile station by enabling MCS level and resource allocation region information to be included in the control message [S108]. In the step S108, the mobile station is able to receive data via a new resource region allocated using the informations included in the control message for the retransmission. The base station then retransmits the DL VoIP packet #2 corresponding to the NACK signal received in the step S107 to the mobile station [S109]. PIG. 2 a flowchart for an embodiment of using HARQ in transmitting VoIP packets in uplink. Referring to FIG. 2, a method of transmitting VoIP packets to provide a VoIP service to a base station (BS) from a mobile station (MS) can be observed. When the mobile station MS transmits a UL VoIP packet #1 in uplink, as error is generated or the DL VoIP packet #1 is lost on wireless/wire line, if the base station is unable to receive the DL VoIP packet #1 [S201] , the base station transmits a NACK signal to the mobile station [S202]. In this case, in order to receive the erroneous UL VoIP packet #1 in the step 2101, the base station transmits a control message for retransmission to the mobile by enabling a new MCS (modulation and coding scheme) level and new resource allocation region information to be included in the control message [S203]. The mobile station has a new resource region allocated thereto by receiving the control message for the retransmission and then retransmits the DL VoIP packet #1 to the base station via the newly allocated resource region [S204] . If the base station normally receives the packet in the step S204, the base station transmits an ACK signal to the mobile station [S205]. In order to receive the VoIP service continuously, the mobile station transmits a next VoIP packet, i.e., a DL VoIP packet #2 to the base station. Yet, if the DL VoIP packet #2 is erroneous or lost on wire/wireless line in the course of reception, the base station may be unable to receive the packet normally [S206]. The base station failing to receive the VoIP packet normally transmits a NACK signal to the mobile station [S207]. Having transmitted the NACK signal to the mobile station in the step S207, the base station transmits a control message for retransmission to the mobile station by enabling MCS level and resource allocation region information different from the former information provided in the step S203 to be included in the control message [S208]. In the step S208, the mobile station is able to transmit data via a new resource region allocated using the informations included in the control message for the retransmission. The mobile station then retransmits the UL VoIP packet #2 corresponding to the NACK signal received in the step S207 to the base station [S209]. As mentioned in the foregoing description of FIG. 1 and FIG. 2, in order for the base or mobile station to perform the retransmission of the erroneous packet, the base station repeatedly transmits the control message (e.g., MAP IE) including the new resource allocation region information (or MCS level information) for the retransmission to the mobile station each time the error is generated. FIG. 3 is a diagram for a method of allocating a fixed radio resource region for retransmission from a base station to a mobile station according to one embodiment of the present invention. In FIG. 3, a horizontal axis indicates a time unit as a frame unit and a vertical axis indicates a frequency unit. 'P1' in Frame 1 or Frame 5 indicates a region allocated to a first mobile station by a base station for a continuous VoIP packet transmission/reception to/from the first mobile station in downlink/uplink. 'P2' indicates a radio resource region allocated to a second mobile station, 'P3' indicates a radio resource region allocated to a third mobile station, and 'P4' indicates a radio resource region allocated to a fourth mobile station. Referring to FIG. 3, the base station allocates a region for retransmission to each mobile station having a VoIP connection by identifying the corresponding mobile station one by one. In downlink, the base station transmits a VoIP packet to the mobile station via the allocated region. In uplink, the mobile station transmits a VoIP packet to the base station via the allocated region. In particular, the first mobile station transmits VoIP packets with the base station via P1. And, the rest of the mobile stations transmit/receive VoIP packets to/from the base station via the allocated regions, respectively. In Frame 3 or Frame 7, 'R1' indicates a region allocated for retransmission to correspond to P1, 'R2' indicates a region allocated for retransmission to correspond to P2, 'R3' indicates a region allocated for retransmission to correspond to P3, and 'R4' indicates a region allocated for retransmission to correspond to P4. The base station enables informations for retransmission to be included in an initial control message and is then able to transmit the control message to each of the mobile stations. Hence, if a retransmission takes place, the base station and the mobile stations can transmit the retransmitted packets with each other via the preset retransmission regions. In particular, in case that error is generated from the VoIP packet transmitted between the base station and each of the mobile stations via P1/P2/P3/P4, the base station and each of the mobile stations can transmit the retransmitted packet via the pre- allocated radio resource region R1/R2/R3/R4. Even if error is not generated in the course of transmitting packets between one of the first to fourth mobile stations and the base station, keeping the pre- allocated region for retransmission will be a waste of radio resources. Hence, if the retransmission is unnecessary, the pre-allocated region for the retransmission can be used to transmit a different packet of each of the mobile stations or packet of the base station. This agreement can be established through mutual negotiation in case that the base station and the mobile station are interconnected to each other or an initial service is provided. FIG. 4 is a diagram for a method of allocating a radio resource region for retransmission from a base station to a mobile station according to another embodiment of the present invention. In FIG. 4, a horizontal axis indicates a time unit as a frame unit and a vertical axis indicates a frequency unit. 'P1' in Frame 1 or Frame 5 indicates a region allocated to a first mobile station by a base station for a continuous VoIP packet transmission/reception to/from the first mobile station in downlink/up link. 'P2' indicates a radio resource region allocated to a second mobile station by the base station, 'P3' indicates a radio resource region allocated to a third mobile station by the base station, and 'P4' indicates a radio resource region allocated to a fourth mobile station by the base station. Referring to FIG. 4, in downlink, the base station transmits a VoIP packet to the mobile station via the allocated region. In uplink, the mobile station transmits a VoIP packet to the base station via the allocated region. In particular, the first mobile station transmits VoIP packets with the base station via P1. And, the rest of the mobile stations transmit/receive VoIP packets to/from the base station via the allocated regions, respectively. In FIG. 4, assume that a region allocated to a mobile station to transmit VoIP packets is equal to the region shown in FIG. 3. Yet, FIG. 4 differs from FIG. 3 in allocating a retransmission region. The base station puts mobile stations having the same attribute (e.g., the same size of the resource region allocated for packet transmission) into one group and is then able to allocate a radio resource for retransmission. In particular, in case that the base station configures a retransmission region, mobile stations having the same resource allocation region size in the same frame into at least one or more groups and is then able to allocate a resource allocation region for retransmission to each of the groups. Referring to FIG. 4, since a size of a radio resource region allocated to the first mobile station is equal to a size of a radio resource region allocated to the second mobile station, the first and second mobile stations can be put into one group. Since a size of a radio resource region allocated to the third mobile station is equal to a size of a radio resource region allocated to the fourth mobile station, the third and fourth mobile stations can be put into another group. Hence, in Frame 3 or Frame 7, 'R1 (retransmission region allocated for retransmissions of regions P1 and P2)' is allocated as a retransmission region of the first and second mobile stations. And, 'R2 (retransmission region allocated for retransmissions of regions P3 and P4)' is allocated as a retransmission region of the third and fourth mobile stations. In another embodiment of the present invention, when retransmission take place in all of the mobile stations having the same retransmission region allocated thereto, if VoIP packets are transmitted using the same retransmission regions, collisions may cause a problem that retransmission packets are unable to be normally retransmitted. To solve this problem, one mobile station keeps using a previously allocated retransmission. Yet, it is necessary to allocate a region different from the previously allocated region to the other mobile station for retransmission. For instance, assume that the first and second mobile stations transmit VoIP packets to the base station in uplink through P1 and P2, respectively. In this case, if both of the VoIP packets received by the base station through P1 and P2 are erroneous, the base station transmits NACK signals to the mobile stations to make requests for retransmissions of the corresponding packets, respectively. After the mobile stations have received the NACK signals, if the mobile stations simultaneously transmit retransmission packets via a fixed retransmission region R1, which was previously allocated by the base station through an initial control message, the retransmission packets may collide with one another. Therefore, after a retransmission region is allocated per group, if errors simultaneously generated from mobile stations belonging to the same group, the base station needs to allocate a new retransmission region. In particular, the first mobile station is made to retransmit a packet via R1 which is a retransmission region allocated via an initial control message and the second mobile station additionally transmits a control message for retransmission to allocate another resource region, which is not Rl, for retransmission. Hence, it is ale to control mutual collision to be avoided. PIG. 5 is a diagram for a method of allocating a radio resource region for retransmission from a base station to a mobile station according to a further embodiment of the present invention. In FIG. 5, a horizontal axis indicates a time unit as a frame unit and a vertical axis indicates a frequency unit. 'P1' in Frame 1 or Frame 5 indicates a region allocated to a first mobile station by a base station for a continuous VoIP packet transmission to the mobile station in downlink or 'P1' in Frame 1 or Frame 5 indicates a region allocated to a first mobile station by a base station for a VoIP packet reception from the first mobile station in uplink. 'P2' indicates a radio resource region allocated to a second mobile station by the base station, 'P3' indicates a radio resource region allocated to a third mobile station by the base station, and 'P4' indicates a radio resource region allocated to a fourth mobile station by the base station. Referring to FIG. 5, in downlink, the base station transmits a VoIP packet to the mobile station via the allocated region. In uplink, the mobile station transmits a VoIP packet to the base station via the allocated region. In particular, the first mobile station transmits VoIP packets with the base station via P1. And, the rest of the mobile stations transmit/receive VoIP packets to/from the base station via the allocated regions, respectively. FIG. 5 shows that the base station transmits VoIP packets with each of the mobile stations by allocating radio resources to the respective mobile stations, which is as good as FIG. 3 or FIG. 4. Yet, FIG. 5 differs from FIG. 3 or FIG. 4 in that mobile stations perform retransmission using a common retransmission channel (common ReTx channel) set for the retransmission instead of allocating retransmission regions to the mobile stations, respectively. In particular, after a common retransmission channel has been set as a resource region available for VoIP packet retransmission, it can be used in case of retransmission occurrence. For instance, in case that retransmissions take place for at least two mobile stations in VoIP downlink, a base station selects one of the at least two mobile stations and then enables a packet to be retransmitted to the selected mobile station using a common retransmission channel. The base station enables a retransmission process to be performed by allocating a resource region designated in the same frame to the unselected mobile stations. In case that retransmissions take place for at least two mobile stations in uplink, a base station designates a single mobile terminal to transmit a retransmission packet via a common retransmission channel in the same frame only and then notifies it to the mobile stations. To enable the unselected mobile stations to perform retransmissions, the base station can allocate a different region for retransmission in the same frame. Referring to PIG. 5, mobile stations transmitting VoIP packets in the same frame use a common retransmission channel for retransmission. 'R1' indicates a resource region for allocating a portion of a common retransmission channel for retransmissions of P1 and P2. And, 'R2' indicates a resource region for allocating a portion of a common retransmission channel for retransmissions of P3 and P4. Moreover, a region of R2 can include a region of R1. When retransmissions are generated from at least one or more mobile stations in uplink, if the at least one or more mobile stations perform retransmissions via the same retransmission region, collisions may occur. Hence, if retransmissions are generated from a plurality of mobile stations in case of using the same retransmission channel, a single mobile station performs a retransmission process (base station to mobile station in case of downlink, mobile station to base station in case of uplink) using the common retransmission channel only while the rest of the mobile stations are made to perform a retransmission process in a manner of allocating resource regions to the rest of the mobile stations, respectively. In case that a retransmission is performed using a common retransmission channel, an unused region of the common retransmission channel is available for a transmission of other packets. For instance, in case that a retransmission is performed using a region R1, a base station is able to transmit VoIP packets using a different region not including a region R1 in a region R2. The resource allocation for retransmission in FIGs. 3 to 5 can use the same region for initial transmission or a different region. If the same region for the initial transmission is used, packets can be just transmitted via a resource area equal to a previously allocated region without announcing resource allocation region information separately. FIG. 6 is a flowchart for performing a retransmission using a continuous HARQ setting method in downlink according to one embodiment of the present invention. Referring to FIG. 6, a base station delivers information for retransmission to a mobile station using a initial control message [S601]. In the step S601, the initial control message for retransmission can include a specific DL/DL-MAP IE message, a DSA-REQ/RSP message, or another MAC management message according to system requirements. And, the information for the retransmission can include information on a fixed resource allocation region and MAC level information or a transmission timing point (e.g., information indicating that a retransmission will be performed after duration of prescribed frames from a timing point of NACK reception). Preferably, the methods described with reference to FIGs. 3 to 5 are usable as a method of allocating a fixed radio resource region for retransmission. According to one embodiment of the present invention, a case of performing communication between a single mobile station and a base station is assumed. In case that communications are performed between at least one or more mobile stations and a base station, it is able to allocate a radio resource region for retransmission using one of the methods described with reference to FIGs. 3 to 5. Referring to FIG. 6, the base station transmits DL VoIP packet #1 to the mobile station to provide a VoIP service thereto. Yet, if error is generated from the DL VoIP packet #1, the mobile station may not decode the corresponding packet [S602]. In this case, the mobile station is able to transmit a NACK signal to the base station to announce that error has been generated [S603]. Having received the NACK signal, the base station retransmits the DL VoIP packet #1 to the mobile station via a region allocated for retransmission without side information using the information on the resource allocation region previously negotiated with the mobile station in the step S601 [S604] . In this case, the mobile station is able to receive VoIP packet from the base station via a region allocated for a pre-designated retransmission. Having received the VoIP packet normally, the mobile station transmits an acknowledgement (ACK) signal to the base station [S605]. To provide the VoIP service continuously, the base station transmits DL VoIP packet #2 to the mobile station [S606] . Yet, in case that the DL VoIP packet #2 transmitted in the step S606 is erroneous or lost on wire/wireless line, the mobile station is unable to receive the packet normally. Therefore, the mobile station transmits a NACK signal to the base station [S607]. Having received the NACK signal, the base station retransmits the DL VoIP packet #2 based on information on fixed resource allocation region, information on MCS level or retransmission timing point contained in the control message for the retransmission and the like [S608]. FIG. 7 is a flowchart for performing a retransmission using a continuous HARQ setting method in uplink according to another embodiment of the present invention. Referring to PIG. 7, a base station is able to deliver information on a resource allocation region for retransmission and the like using an initial control message for retransmission [S701] . In the step S701, the control message for retransmission can include a specific DL/DL-MAP IE message, a DSA-REQ/RSP message, or another MAC management message according to system requirements. And, the information for the retransmission can include information on a fixed resource allocation region and MAC level information or a transmission timing point (e.g., information indicating that a retransmission will be performed after duration of prescribed frames from a timing point of NACK reception). Preferably, the methods described with reference to FIGs. 3 to 5 are usable as a method of allocating a fixed radio resource region for retransmission. According to another embodiment of the present invention, a case of performing communication between a single mobile station and a base station is assumed. In case that communications are performed between at least one or more mobile stations and a base station, it is able to allocate a radio resource region for retransmission using one of the methods described with reference to FIGs. 3 to 5. Referring to FIG. 7, the mobile station transmits UL VoIP packet #1 to the base station to provide a VoIP service thereto. Yet, if error is generated from the UL VoIP packet #1, the base station may not decode the corresponding packet [S702]. In this case, the base station is able to transmit a NACK signal to the mobile station to announce that error has been generated [S703]. Having received the NACK signal, the mobile station retransmits the UL VoIP packet #1 to the base station via a region allocated for retransmission without side information using the information on the resource allocation region previously negotiated with the base station in the step S701 [S704] . In this case, the base station is able to receive VoIP packet from the mobile station via a region allocated for a pre-designated retransmission. Having received the VoIP packet normally, the base station transmits an acknowledgement (ACK) signal to the mobile station [S705]. For the continuous VoIP service, the mobile station transmits UL VoIP packet #2 to the base station [S706]. Yet, in case that the UL VoIP packet #2 transmitted in the step S706 is erroneous or lost on wire/wireless line, the base station is unable to receive the packet normally. Therefore, the base station transmits a NACK signal to the mobile station [S707]. Having received the NACK signal, the mobile station retransmits the DL VoIP packet #2 based on information on fixed resource allocation region, information on MCS level or retransmission timing point contained in the control message for the retransmission and the like [S708]. In FIG. 6 and FIG. 7, in case that the mobile station and the base station need frequent transmissions and receptions of packets like the VoIP service, the base station sets a fixed resource allocation region for retransmission in advance and is then able to transmit it to the mobile station via the initial control message. Therefore, each time a retransmission is necessary, data packets can be efficiently transmitted by directly retransmitting the data packet via the pre-designated region without transmitting the control message for the retransmission. Since the base station needs not to transmit the control message to the mobile station in case of necessity of retransmission, it is able to reduce overhead of a MAC layer. FIG. 8 is a flowchart of a packet error processing method in performing retransmission using a continuous HARQ setting method in downlink/uplink according to a further embodiment of the present invention. Referring to FIG. 8, a base station is able to deliver information on a resource allocation region for retransmission and the like using an initial control message for retransmission [S801]. In the step S801, the initial control message for retransmission can include a specific UL/DL-MAP IE message, a DSA-REQ/RSP message, or another MAC management message according to system requirements. And, the information for the retransmission can include information on a fixed resource allocation region and MAC level information or a transmission timing point (e.g., information indicating that a retransmission will be performed after duration of prescribed frames from a timing point of NACK reception). Preferably, the methods described with reference to FIGs. 3 to 5 are usable as a method of allocating a fixed radio resource region for retransmission. According to a further embodiment of the present invention, a case of performing communication between a single mobile station and a base station is assumed. In case that communications are performed between at least one or more mobile stations and a base station, it is able to allocate a radio resource region for retransmission using one of the methods described with reference to FIGs. 3 to 5. Referring to FIG. 8, in case that VoIP service is transmitted between the base station and the mobile station, it may frequently happen that VoIP packet is retransmitted. In FIG. 8, although the base station transmits a downlink packet DL VoIP packet #1, error is generated. Therefore, the base station retransmits the DL VoIP packet #1 to the mobile station via a pre-designated resource region using resource allocation region information contained in an initial control message. Yet, since the retransmitted DL VoIP packet #1 is erroneous or lost on wire/wireless line, it may happen that the mobile station is unable to receive the corresponding packet normally [S802]. If the case of the step S802 takes place, the mobile terminal transmits a NACK signal to the base station to announce that the packet was not normally received [S803]. Having received the NACK signal, the base station is able to retransmit the DL VoIP packet #1 to the mobile station using the information set for the retransmission in the initial control message [S804]. While the mobile station and the base station keep performing the VoIP service, an uplink communication for transmitting VoIP packet to the base station from the mobile station can be performed. In the course of transmitting UL VoIP packet #1 to the base station from the mobile station, it may happen that the UL VoIP packet #1 is retransmitted. In this case, even if the UL VoIP packet #1 is retransmitted, error can be generated from the retransmitted packet again [S805]. If so, the base station retransmits the NACK signal to the mobile station to announce that the uplink packet having been transmitted by the mobile station is erroneous [S806]. Having received the NACK signal, the mobile station is able to retransmit the UL VoIP packet #1 to the base station using the resource allocation region information for the retransmission included in the initial control message and the like. In FIG. 8, shown is the case that error is generated from VoIP packet retransmitted in uplink or downlink in the course of providing VoIP service to the mobile station from the base station. And, FIG. 8 depicts the case that the retransmission region allocated via the initial control message keeps being used despite that error keeps being generated from the retransmitted VoIP packet. Yet, it may happen that the initially set retransmission region is not suitable for communication environment. In this case, by allocating a new retransmission region instead of a channel having error kept being generated therefrom, packets are transmitted via the new retransmission region to achieve a better gain in aspect of data processing efficiency. FIG. 9 is a flowchart of a packet error processing method in case of detecting error repeatedly in performing retransmission using a continuous HARQ setting method in downlink/uplink according to a further embodiment of the present invention. Referring to FIG. 9, a base station is able to inform a mobile station of retransmission region information in advance in a manner of continuous resource allocation information for retransmission is made to be included in an initial control message [S901]. In the step S901, the information required for the retransmission may include information on a fixed resource allocation region and MAC level information or a transmission timing point (e.g., information indicating that a retransmission will be performed after duration of prescribed frames from a timing point of NACK signal reception). To prepare for a case that error keeps being generated despite performing a retransmission via a new transmission region, the base station is able to negotiate a prescribed count for receiving a NACK signal repeatedly with the mobile station. If the base or mobile station receives the NACK signal over the prescribed count, the base station is able to transmit a control message for allocating a new retransmission region again. According to a further embodiment of the present invention, assume that the prescribed count for receiving the NACK signal is set to 2. Of course, the prescribed count for receiving the NACK signal may vary according to system requirements or communication environment. Preferably, the methods described with reference to FIGs. 3 to 5 are usable as a method of allocating a fixed radio resource region for retransmission. According to a further embodiment of the present invention, a case of performing communication between a single mobile station and a base station is assumed. In case that communications are performed between at least one or more mobile stations and a base station, it is able to allocate a radio resource region for retransmission using one of the methods described with reference to FIGs. 3 to 5. Referring to FIG. 9, in downlink transmission, the base station transmits DL VoIP packet #1 to the mobile station. Yet, it may happen that the DL VoIP packet #1 is erroneous or lost on wire/wireless line [S902]. If the mobile station is unable to normally know the information included in the packet as the received packet is erroneous or if the mobile station is unable to receive the packet that is lost, the mobile station transmits a NACK signal to the base station to announce the reception failure [S903]. Having received the NACK signal, the base station is able to retransmit the DL VoIP packet #1 via a preset retransmission region using the resource allocation region information included in the initial control message [S904]. Yet, if the retransmitted VoIP packet is erroneous as well, the mobile station transmits a NACK signal to the base station again [S905]. As the count of the NACK signal received by the base station from the mobile station becomes 2, the count negotiated with the mobile station in the initial service setting is met. Therefore, the base station transmits a control message for retransmission to the mobile station to allocate a new retransmission region again [S906]. In the control message to allocate the retransmission region in the step S906, information on a new retransmission region, MCS level information or information or a transmission timing point can be included. The base station allocates a new retransmission region to the mobile station via the control message in the step S906 and is then able to retransmit the DL VoIP packet #1 again [S907]. In case of receiving the DL VoIP packet #1 normally, the mobile station transmits an ACK signal to the base station to announce the transmission success. In the course of transmitting or receiving the VoIP service, it may happen that a data packet is transmitted in uplink. In particular, while the mobile station transmits VoIP packet to the base station, it may happen that UP VoIP packet #1 is retransmitted to the base station [S908]. Yet, if the VoIP packet retransmitted in the step S908 becomes erroneous, the base station transmits NACK signal to the mobile station to announce that the corresponding packet is erroneous [S909]. Having received the NACK signal in the step S909, the mobile station receives the NACK signal consecutively twice. Hence, the NACK signal reception count negotiated with the base station in the initial service configuration is met. In this case, since the base station already knows the fact that errors are at least twice generated from the received VoIP packet received from the mobile terminal, the mobile station is able to transmit a control message to allocate a new retransmission region to the mobile station despite an absence of a request made by the mobile station [S910]. Having allocated the new retransmission region thereto in the step S190, the mobile station is able to retransmit UL VoIP packet #1 to the base station [S911]. According to a further embodiment of the present invention, error occurs repeatedly even if the retransmission is performed by allocating the retransmission region in uplink or downlink. In this case, it is able to raise data processing efficiency in a manner of allocating a new retransmission region again and then transmitting VoIP packet via another channel instead of the channel on which the error keeps being generated. FIG. 10 is a flowchart for a method of performing retransmission in the course of transceiving VoIP service between a base station and at least one mobile station in uplink according to a further embodiment of the present invention. Referring to FIG. 10, a base station is able to provide VoIP service to at least one or more mobile stations existing within its service area. In this case, the base station is able to deliver information on resource allocation region for packet retransmission and the like to a first mobile station MSI and a second mobile station MS2 among a plurality of the mobile stations using an initial control message for retransmission [S1001, S1002]. In the step S1001 or S1002, the initial control message for retransmission can include a specific UL/DL-MAP IE message, a DSA-REQ/RSP message, or another MAC management message according to system requirements. And, the information for the retransmission can include information on a fixed resource allocation region and MAC level information or a transmission timing point (e.g., information indicating that a retransmission will be performed after duration of prescribed frames from a timing point of NACK reception). Preferably, the methods described with reference to FIG. 4 and FIG. 5 are usable as a method of allocating a fixed radio resource region for retransmission. According to a further embodiment of the present invention, the base station puts the first mobile station MS1 and the second mobile station MS2, which have the same attribute (e.g., equal size in an allocated resource region), into a group. The base station then allocates a same retransmission region to both of the first mobile station MS1 and the second mobile station MS2 or designates a common retransmission channel for VoIP packet retransmission. The first mobile station MS1 transmits UL VoIP packet #1 to the base station for the VoIP packet transmission [S1003]. And, the second mobile station MS2 transmits UL VoIP packet #2 to the base station for the VoIP packet transmission [S1004] . Yet, if the UL VoIP packet #1 or the DL VoIP packet #2 is erroneous, it may happen that the base station is unable to reconstruct the corresponding packet. The base station informs the first mobile station MS1 or the second mobile station MS2 that the corresponding uplink packet is erroneous [S1005, S1006]. In case that both of the first mobile station MS1 or the second mobile station MS2 perform retransmissions, as the same retransmission region is allocated to both of the first mobile station MS1 or the second mobile station MS2, it is unable to simultaneously transmit packets via the same region. In this case, the base station enables the first mobile station MS1 to retransmit the corresponding packet via the previously allocated retransmission region and should control the second mobile station MS2 to retransmit the corresponding packet via another retransmission region. Therefore, the base station is able to allocate a new retransmission region to the second mobile station MS2 via a control message for retransmission [S1007]. The first mobile station MS1 retransmits the UL VoIP packet #1 via the retransmission region previously allocated in the step S1001 [S1008]. And, the second mobile station MS2 retransmits the DL VoIP packet #2 via the retransmission region re-allocated in the step S1007 [S1009] . Thus, it is able to prevent the retransmitted packets from colliding with each other. Therefore, packet retransmissions can be more efficiently performed by avoiding collisions between the retransmitted packets. INDUSTRIAL APPLICABILITY Accordingly, the embodiments of the present invention are applicable to various wireless access systems. Moreover, the embodiments of the present invention are applicable to every industrial field having the same or similar technical idea of the present invention or using the same. While the present invention has been described and illustrated herein with reference to the preferred embodiments thereof, it will be apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of the appended claims and their equivalents. WHAT IS CLAIMED IS: 1. A method of retransmitting a packet in a wireless access system, comprising the steps of: receiving an control message including information required for a packet retransmission from a base station; transmitting the packet to be provided with a service from the base station; and if a NACK (non-acknowledgement) signal is received from the base station, retransmitting the packet corresponding to the NACK signal to the base station using the information required for the packet retransmission and included in the initial control message. 2. The method of claim 1, wherein the information required for the packet retransmission includes at least one of resource allocation region information for the packet retransmission, modulation and coding scheme (MCS) level information and a transmission timing point. 3. The method of claim 1, wherein the information required for the packet retransmission includes information for allocating different resource allocation regions required for the packet transmission to at least one or more terminals, respectively. 4. The method of claim 1, wherein the information required for the packet retransmission includes information for configuring at least one group including terminals having resource allocation regions equal to each other in size among at least one or more terminals and for allocating a resource allocation region required for the packet retransmission to the at least one group. 5. The method of claim 1, wherein the information required for the packet retransmission includes information for setting a retransmission dedicated channel for the packet retransmission of at least one terminal and information of a specific region required for the packet retransmission in the retransmission dedicated channel. 6. The method of claim 5, wherein the specific region required for the packet retransmission is partial region of the retransmission dedicated channel. 7. The method of claim 1, wherein the control message is a UL MAP (uplink MAP) message or a MAC (media access control) management message, and wherein the MAC management message is one of a dynamic service addition message, a channel descriptor message, and a subscribe station basic capability message. 8. A method of retransmitting a packet in a wireless access system, comprising the steps of: transmitting an control message including information required for a packet retransmission to at least one terminal; providing a service to the at least one terminal; and if a NACK (non-acknowledgement) signal is received from the at least one terminal, retransmitting the packet corresponding to the NACK signal to the at least one terminal using the information required for the packet retransmission and included in the initial control message. 9. The method of claim 8, wherein the information required for the packet retransmission includes at least one of resource region allocation information for the packet retransmission, modulation and coding scheme (MCS) level information and a transmission timing point. 10. The method of claim 8, further comprising: if the base station receives the NACK signal repeatedly over a prescribed count, transmitting a control signal to the at least one terminal by updating the information required for the packet retransmission and then including the updated information in the control message for the packet retransmission. 11. The method of claim 8, wherein the information required for the packet retransmission includes information for allocating different resource allocation regions required for the packet transmission to the at least one or more terminals, respectively. 12. The method of claim 8, wherein the information required for the packet retransmission includes information for configuring at least one group including terminals having resource allocation regions equal to each other in size among at least one or more terminals and for allocating a resource allocation region required for the packet retransmission to the at least one group. 13. The method of claim 8, wherein the information required for the packet retransmission includes information for setting a retransmission dedicated channel for the packet retransmission of at least one terminal and information of a specific region required for the packet retransmission in the retransmission dedicated channel. 14. The method of claim 13, wherein the specific region required for the packet retransmission is partial region of the retransmission dedicated channel. 15. The method of claim 8, wherein the control message is one of a DL MAP (downlink MAP) message or a MAC management message, and wherein the MAC management message is one of a dynamic service addition message, a channel descriptor message, and a subscribe station basic A method of transmitting data in a wireless access system and a packet retransmitting method therein arc disclosed. The present invention includes receiving an initial control message including information required for a packet retransmission from a base station, transmitting the packet to be provided with a service from the base station, and if a NACK (non-acknowledgement) signal is received from the base station, retransmitting the packet corresponding to the NACK signal to the base station using the information required for the packet retransmission and included in the initial control message. Therefore, since a separate control message needs not to be transmitted in case of packet retransmission, it is able to save radio resources and reduce an overhead by retransmitting a packet via a previously allocated retransmission region without the separate control message.

Full Text

METHOD OF RETRANSMISSION TO REDUCE THE OVERHEAD
TECHNICAL FIELD
The present invention relates to a method of
transmitting data in a wireless access system, and more
particularly, to various packet retransmission methods in
the data transmitting method.
BACKGROUND ART
In the following description, explained is a method
of transmitting packets in terminals that use IP based
voice over internet protocol (hereinafter abbreviated
'VoIP') in a broadband wireless access system. For this,
VoIP traffic is described as follows. Yet, a packet
transmitting method according to the present invention
needs not to be limited to the VoIP packet transmission
described in the following.
First of all, VoIP traffic is characterized in being
generated in a fixed size with a fixed period in VoIP codec.
And, VoIP communication can be divided into a talk period
(talk-spurt), for which inter-user call is in progress, and
a silence period for which a user is not talking but
listening. In general, the silence period occupies over 50%
in a whole call session.
In order to allocate bandwidths differing in size to
the talk-spurt and the silence period, various kinds of
audio codecs are used. A representative one of the various
kinds of audio codecs is AMR (adaptive multi-rate) scheme
used by GSM (global system for mobile communication) or
UMTS (universal mobile telecommunication system).
Since voice data is not generated for the silence
period, if a bandwidth is allocated to the silence period,
it may bring about a resource waste. To prevent the
resource waste, VoIP supports a silence suppression scheme.
According to the silence suppression scheme, a vocoder for
generating VoIP traffic does not generate traffic for the
silence period and periodically generates a comfort noise
to inform a correspondent user that a call keeps being
maintained. For instance, a vocoder, which uses the. AMR
codec, generates a packet in a fixed size once per 20ms for
a talk-spurt or generates a comfort noise per 160ms.
Meanwhile, for resource allocation to the traffic
having a predetermined period in a fixed size like VoIP in
general, a base station is able to use a method of
allocating a designated region to a specific terminal
fixedly. Namely, a region having an initially determined
size is allocated to a terminal supporting the VoIP service.
And, it is able to inform the terminal of the allocated
region information via an initially transmitted control
channel or message (e.g., UL-MAP or DL-MAP). Thus, the
initially transmitted control channel or message can
contain period information of a region that will be
allocated in the future as well.
Subsequently, for a next period, the base station is
able to keep allocating the corresponding region having
been notified to the terminal via the initially transmitted
control channel or message without a special notice.
Therefore, the terminal transmits VoIP packets via the
allocated region using the region information allocated by
a MAP in the early stage and then transmits VoIP packets
via the same region from a next period using period
information.
Assume that a length of a frame is set to 5ms to
consider a VoIP service. And, assume that a frame period
allocated to a terminal for VoIP packet transmission is set
to 4 frames. In this case, a frame period allocated to a
terminal for VoIP packet transmission may vary according to
characteristics of a service. In particular, in case of a
same VoIP service, the frame period allocated for the VoIP
packet transmission may be used by being defined different
according to the respective consideration factors such as
system characteristics (e.g., a system characteristic
according to a frame length), a VoIP service status (e.g.,
a talk-spurt, a silence period) and the like.
In an initial frame, a base station notifies a
terminal of allocated region information for VoIP packet
transmission via UL-MAP. Thereafter, in a fourth frame or
an eighth frame corresponding to each period, the base
station does not announce region information via the UP-MAP
but allocates a region for the VoIP packet transmission
only.
In this case, a period allocated for the VoIP packet
transmission corresponds to four frames (i.e., 20ms). In
particular, the terminal keeps storing the region
allocation information contained in the UL-MAP received in
the initial frame and is then able to transmit a VoIP
packet via a corresponding region if there is not reception
of UL-MAP in the fourth or eighth frame. Thus, the base
station is able to allocate the resource for a single VoIP
connection fixedly and constantly due to the VoIP traffic
characteristics.
In the following description, briefly described is a
method of transmitting data between a transmitting side and
a receiving side. In a data transmitting method, if a
transmission failure occurs, a receiving side makes a
retransmission request for corresponding data. In this case,
ARQ (automatic repeat request) scheme is generally used as
a data retransmission scheme.
In the ARQ scheme, an acknowledgement/non-
acknowledgement (hereinafter abbreviated ACK/NACK) signal
indicating whether a receiving side correctly receives data
is notified to a transmitting side. The receiving side then
retransmits the data for the corresponding signal in case
of receiving the NACK signal. The ARQ scheme can be
categorized into SAW (stop-and-wait) ARQ, GBN (go-back-N)
ARQ and SR (selective-repeat) ARQ.
In the SAQ ARQ scheme, a transmitting side waits
after data transmission until receiving ACK or NACK signal.
If the ACK signal is received, the transmitting side newly
transmits next data. If the NACK signal is received, the
transmitting side retransmits the previous data. Namely,
the SAW ARQ scheme is a scheme for transmitting a single
frame at a time only. If it is confirmed that a
corresponding frame is successfully delivered, a next frame
is transmitted.
The GBN ARQ scheme is a scheme for continuously
transmitting data regardless of a response message. In case
that a receiving side fails to receive data of a specific
frame in the course of receiving data, the receiving side
is unable to transmit an ACK signal for the specific frame
to a transmitting side. Since the transmitting side is
unable to receive the ACK signal for the specific frame,
the transmitting side retransmits data from the data of the
specific frame.
In the SR ARQ scheme, while data keeps being
transmitted, data corresponding to a received NACK signal
is retransmitted only. If a receiving side fails to receive
data of a specific frame, the receiving side transmits a
NACK signal to a transmitting side. The transmitting side
having received the NACK signal then retransmits the data
of the frame indicated by the NACK signal to the receiving
side to transmit the whole data. Since the SR ARQ scheme
gives a sequence to each frame and manages it, the
implementation of the SR ARQ scheme may becomes complicated
relatively.
In the scheme for transmitting data in packet format,
as a higher data rate becomes necessary, a coding rate or a
modulation scheme, which has a suitable level to prevent
error generated in high-speed transmission environment, is
applied to a communication system. And, ARQ scheme suitable
for the high-speed transmission environment, i.e., Hybrid
ARQ (hereinafter abbreviated HARQ) has been proposed.
In the ARQ scheme, if error is generated, the
corresponding information is discarded. Yet, in the HARQ
scheme, a receiving side stores erroneous information in s
buffer. The receiving side combines the stored information
with retransmitted information and then applies FEC
(forward error correction) thereto. Namely, the HARQ scheme
may be regarded as the scheme generated from combining the
ARQ scheme with the FEC. The HARQ can be mainly categorized
into the following four types.
In a first type HARQ scheme, a receiving side always
checks an error detection code in data and then primarily
applies FEC thereto. If error still remains in a packet,
the receiving side makes a request for a retransmission to
a transmitting side. The receiving side discards an
erroneous packet. The transmitting side then retransmits a
packet by applying the same FEC code of the discarded
packet to the retransmitted packet.
Second type HARQ scheme is called IR (incremental
redundancy) ARQ scheme. In the second type HARQ scheme, a
receiving side stores a first transmitted packet in a
buffer instead of discarding it and then combines it with
retransmitted redundancy bits. In case of retransmission, a
transmitting side retransmits parity bits only except data
bits. Each time the parity bits are retransmitted by the
transmitting side, different ones are used.
A third type HARQ scheme corresponds to a special
case of the second type HARQ scheme. Each packet is self-
decodable. In case that a transmitting side performs
retransmission, the transmitting side configures a packet
containing an erroneous part and data together and then
retransmits the corresponding packet. Although this scheme
enables decoding more accurate than the second type HARQ
scheme, it has efficiency poorer than that of the second
type HARQ scheme in aspect of coding gain.
In a fourth type HARQ scheme, a function of combining
the data initially received and stored by a receiving side
with retransmitted data is added to a function of the first
type HARQ scheme. And, the fourth type HARQ scheme may be
called a matrix combining scheme or a chase combining
scheme. .Moreover, the fourth type HARQ scheme has a gain in
aspect of SINR (signal to interference noise ratio) and
always uses the same parity bits of the retransmitted data.
In case that error is generated in data transmission
or data is lost in the data transmission, the above-
described data transmitting methods enable reconstruction
of original data.
DISCLOSURE OF THE INVENTION
TECHNICAL PROBLEM
However, in case that transmission/reception of
packets is frequently required like VoIP, it becomes highly-
probable that error is generated from the
transmitted/received packets. Since the number of
transmissions for control messages to allocate new resource
regions and the like is incremented, an overhead is
increased in a MAC layer.
TECHNICAL SOLUTION
Accordingly, the present invention is directed to a
method of transmitting data in a wireless access system
that substantially obviates one or more of the problems due
to limitations and disadvantages of the related art.
An object of the present invention is to provide a
method of transmitting data, by which data can be
efficiently transmitted.
Another object of the present invention is to provide
a method of reducing a message overhead in case that packet
retransmissions are frequently necessary.
Another object of the present invention is to provide
a method of reducing an overhead generated from
retransmitting an erroneous packet for continuously
transmitted VoIP packets and the like.
Another object of the present invention is to provide
a method of allocating a retransmission region to an least
one mobile station, by which data processing efficiency can
be raised despite that VoIP packet is transmitted to a
plurality of mobile stations.
A further object of the present invention is to
provide a method of allocating a new retransmission region
instead of a previously allocated retransmission region if
error keeps being generated despite that a retransmission
packet is transmitted by allocating a fixed transmission
region, by which efficiency in processing data can be
raised.
Therefore, the present invention relates to a data
transmitting method in a wireless access system and a
packet retransmission method in a wireless access system.
And, in case that frequent packet transmissions/receptions
are necessary, methods for efficiently using resources by
reducing a control overhead are disclosed.
Additional features and advantages of the invention
will be set forth in the description which follows, and in
part will be apparent from the description, or may be
learned by practice of the invention. The objectives and
other advantages of the invention will be realized and
attained by the structure particularly pointed out in the
written description and claims thereof as well as the
appended drawings.
To achieve these and other advantages and in
accordance with the purpose of the present invention, as
embodied and broadly described, a method of retransmitting
a packet in a wireless access system according to the
present invention includes receiving an initial control
message including information required for a packet
retransmission from a base station, transmitting the packet
to be provided with a service from the base station, and if
a NACK (non-acknowledgement) signal is received from the
base station, retransmitting the packet corresponding to
the NACK signal to the base station using the information
required for the packet retransmission and included in the
initial control message.
Preferably, the information required for the packet
retransmission includes information for allocating
different resource allocation regions required for the
packet transmission to at least one or more terminals,
respectively.
Preferably, the information required for the packet
retransmission includes information for configuring at
least one group including terminals having resource
allocation regions equal to each other in size among at
least one or more terminals and for allocating a resource
allocation region required for the packet retransmission to
the at least one group.
Preferably, the information required for the packet
retransmission includes information for setting a
retransmission dedicated channel for the packet
retransmission of at least one terminal and on a specific
region required for the packet retransmission in the
retransmission dedicated channel.
To further achieve these and other advantages and in
accordance with the purpose of the present invention, a
method of retransmitting a packet in a wireless access
system includes the steps of transmitting an initial
control message including information required for a packet
retransmission to at least one terminal, providing a
service to the at least one terminal, and if a NACK (non-
acknowledgement) signal is received from the at least one
terminal, retransmitting the packet corresponding to the
NACK signal to the at least one terminal using the
information required for the packet retransmission and
included in the initial control message.
Preferably, the method further includes the step of
if the base station receives the NACK signal repeatedly
over a prescribed count, transmitting a control signal to
the at least one terminal by updating the information
required for the packet retransmission and then including
the updated information in the control message for the
packet retransmission.
It is to be understood that both the foregoing
general description and the following detailed description
are exemplary and explanatory and are intended to provide
further explanation of the invention as claimed.
ADVANTAGEOUS EFFECTS
Accordingly, the present invention provides the
following effects or advantages.
First of all, data communication can be efficiently
performed using the embodiments of the present invention.
Secondly, in case that frequent packet
retransmissions are necessary, a fixed retransmission
region can be allocated to a mobile station via an initial
control message instead of allocating a retransmission
region each time. In particular, if it becomes necessary to
perform a retransmission, it is able to retransmit a packet
via a previously allocated retransmission region without a
separate control message. Therefore, since an additional
and separated control message needs not to be transmitted
in case of packet retransmission, it is able to save radio
resources and reduce an overhead.
Thirdly, in case that frequent packet
transmissions/receptions are necessary like VoIP service,
the present invention is able to reduce an overhead
generated from retransmitting an erroneous packet.
Fourthly, by allocating a retransmission region to
each of at least one or more mobile stations, packets can
be quickly retransmitted via the allocated resource region
in case that the mobile stations perform retransmissions.
Therefore, efficient data processing is enabled.
And, at least one or more mobile stations having the
same attributes are grouped together and a retransmission
region is then allocated per group. Therefore, it is able
to save radio resources.
Moreover, by allocating a dedicated retransmission
channel for a plurality of mobile stations, it is able to
perform more efficient retransmission.
Fifthly, despite that packets are transmitted by
allocating a fixed retransmission region, if errors keep
being generated from the packets, a new retransmission
region is allocated instead of a previously allocated
retransmission region. Therefore, it is able to effectively
cope with the repeatedly generated errors.
DESCRIPTION OF DRAWINGS
The accompanying drawings, which are included to
provide a further understanding of the invention and are
incorporated in and constitute a part of this specification,
illustrate embodiments of the invention and together with
the description serve to explain the principles of the
invention.
In the drawings:
FIG. 1 a flowchart for an embodiment of using HARQ in
transmitting VoIP packets in downlink;
FIG. 2 a flowchart for an embodiment of using HARQ in
transmitting VoIP packets in uplink;
FIG. 3 is a diagram for a method of allocating a
fixed radio resource region for retransmission from a base
station to a mobile station according to one embodiment of
the present invention;
FIG. 4 is a diagram for a method of allocating a
radio resource region for retransmission from a base
station to a mobile station according to another embodiment
of the present invention;
FIG. 5 is a diagram for a method of allocating a
radio resource region for retransmission from a base
station to a mobile station according to a further
embodiment of the present invention;
FIG. 6 is a flowchart for performing a retransmission
using a continuous HARQ setting method in downlink
according to one embodiment of the present invention;
FIG. 7 is a flowchart for performing a retransmission
using a continuous HARQ setting method in uplink according
to another embodiment of the present invention;
FIG. 8 is a flowchart of a packet error processing
method in performing retransmission using a continuous HARQ
setting method in downlink/uplink according to a further
embodiment of the present invention;
FIG. 9 is a flowchart of a packet error processing
method in case of detecting error repeatedly in performing
retransmission using a continuous HARQ setting method in
downlink/uplink according to a further embodiment of the
present invention; and
FIG. 10 is a flowchart for a method of performing
retransmission in the course of transceiving VoIP service
between a base station and at least one mobile station in
uplink according to a further embodiment of the present
invention.
BEST MODE
MODE FOR INVENTION
Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings.
To solve the above-mentioned technical problem, the
present invention provides an efficient data transmitting
method in a wireless access system and an efficient packet
retransmitting method therein. Moreover, the present
invention provides a packet transmitting method to use
resources efficiently by reducing a control overhead of a
MAC layer in case that frequent packet
transmission/receptions are necessary.
The following embodiments are implemented by
combining the elements and features of the present
invention in specific forms, respectively. Each of the
elements or features can be considered selective if there
is no separate explicit description. Each of the elements
or features can be implemented without being combined with
another one. And, an embodiment of the present invention
can be configured by combining the elements and/or features
in part. The order or sequence of the operations mentioned
in the descriptions of the embodiments of the present
invention may be changed. Configurations or features of one
of the embodiments can be partially included in another or
can be replaced by corresponding configurations or features
of another embodiment.
In the description of the drawings, procedures or
steps, which may dilute the gist or substance of the
present invention, are not described. And, procedures or
steps understandable on a level for those skilled in the
art are not described as well.
In this disclosure, embodiments of the present
invention are described centering on data transceiving
relation between a base station and a terminal. In this
case, the base station has the meaning as a terminal node
of a network for performing communication directly with the
terminal. In this disclosure, a specific operation or
action described as performed by a base station can be
performed by an upper node of the base station.
Namely, various operations performed for
communication with a terminal in a network constructed with
a plurality of network nodes and a base station can be
performed by the base station or the network nodes except
the base station. In this case, the 'base station' can be
replaced by such a terminology as a fixed station, a Node B,
an eNode B (eNB), an access point and the like. And,
'mobile station' can be replaced by such a terminology as a
user equipment (DE), a subscriber station (SS), a mobile
subscriber station (MSS), a mobile terminal and the like.
A transmitting end means a node for transmitting data
or a voice service and a receiving end means a node for
receiving data or a voice service. Hence, a terminal and a
base station can become a transmitting end and a receiving
end in uplink, respectively. Likewise, a terminal and a
base station can become a receiving end and a transmitting
end in downlink, respectively.
Meanwhile, a mobile station of the present invention
can include one of a personal digital assistant (PDA), a
cellular phone, a personal communication service (PCS)
phone, a GSM (global system for mobile) phone, a wideband
CDMA (WCDMA) phone, a mobile broadband system (MBS) phone
and the like.
Embodiments of the present invention can be
implemented through diverse means. For instance,
embodiments of the present invention can be implemented
through hardware, firmware, software or any combination
thereof.
In case of the implementation by hardware, methods
according to the present invention can be implemented at
least one selected from the group consisting of ASICs
(application specific integrated circuits), DSPs (digital
signal processors), DSPDs (digital signal processing
devices), PLDs (programmable logic devices), FPGAs (field
programmable gate arrays), a processor, a controller, a
microcontroller, a microprocessor and the like.
In case of the implementation by firmware or software,
methods according to embodiments of the present invention
can be implemented by a module, procedure or function for
performing the above-mentioned functions or operations.
Software code is stored in a memory unit and can be driven
by a processor. In this case, the memory unit is placed
within or outside the processor and is able to transceive
data with the processor by various means which are already
known in public.
Embodiments according to the present invention can be
supported by at least one documents disclosed for at least
one of wireless access systems (e.g., IEEE 802 system, 3GPP
system, 3GPP LTE system, 3GPP2 system) . In particular, the
document of IEEE 802.16e Rev2_D4 (April 2008) is able to
sufficiently support the embodiments according to the
present invention.
Specific terminologies used in the following
description are provided to help the understanding of the
present invention. And, the usages of the specific
terminologies can be modified into other forms within the
scope not departing from the technical idea of the present
invention.
In the following description, VoIP packet
transmission among services, for which frequent packet
retransmissions are required, is taken as an example for
one preferred embodiment of the present invention.
According to one preferred embodiment of the present
invention, in case of setting a continuous resource
allocating method for VoIP packet transmission, a base
station enables continuous resource allocation information
for retransmission to be included in an initial control
message and then provides the information to a mobile
station in advance. In uplink, the mobile station is able
to transmit a packet and the like to the base station via
the retransmission region in case that a retransmission
occurs in the base station. In downlink, the base station
is able to transmit a retransmission packet to the mobile
station based on information for retransmission included in
the initial control message provided to the mobile station.
The initial control message may be usable for various
kinds of systems. In particular, the IEEE 802.16 system is
able to use MAP IE (MAP information element) contained in a
MAP message, a MAC management message or the like as the
initial control message.
When a mobile station performs handover in entering a
network of a base station, an initial control message is
usable in the course of setting an interconnection. An
initial control message may be a control message initially
provided when a base station and a mobile station generate
a new service. Namely, an initial control message may be a
control message for allocation to transmit a first VoIP
packet. Moreover, when a service is provided for a talk-
spurt after a silence period, an initial control message is
usable as well. And, it is understood that other control
messages is usable as an initial control message as well as
the above-described message.
As an example for one of various MAC management
messages, there are dynamic service addition messages (e.g.
DSA-REQ or DSA-RSP), channel descriptor messages (e.g. UCD
or DCD), Subscriber Station basic capability messages (e.g.
SBC-REQ or SBC-RSP) or the like. Besides, by non-limiting
various examples for the above-described messages, various
MAC management messages are available according to system
requirements.
In particular, in case of providing a VoIP service to
a mobile station initially, a base station is able to
transmit informations required for retransmission to the
mobile station using such a downlink control message as DL-
MAP IE, UL-MAP IE or the like. When a base station
initially provides a VoIP service to a mobile station, the
base station and the mobile station can negotiate
informations relevant to retransmission.
The information required for retransmission can
contain fixed resource allocation information for
retransmission, MCS (modulation and coding scheme level)
information, a retransmission timing point (e.g.,
information for determining that a retransmission will be
performed in a prescribed frame after receiving a NACK
signal) or the like.
For the information required for retransmission, even
if a mobile station and a base station transceiver packets
via a pre-designated resource allocation region, if a NACK
signal keeps being generated, the base station is able to
allocate a radio resource region for a new retransmission
by transmitting a control message for the new
retransmission to the mobile station after having received
a prescribed number of NACK signals. In this case, the
prescribed number of NACK signals may vary according to a
requirement of a system. In preferred embodiments of the
present invention, a case of consecutively receiving NACK
signals twice is taken as an example to be described in the
following description.
In the following preferred embodiments of the present
invention, a region previously allocated for retransmission
is used only if the retransmission is generated only. If
the retransmission is unnecessary, the previously allocated
region is usable to transmit other general messages. This
is to reduce waste of radio resources that may be generated
when a specific region is unnecessarily secured
unnecessarily.
In the process for transceiving VoIP packets between
a base station and a mobile station, if a retransmission is
generated in downlink, the base station transmits a
retransmission packet via a pre-designated resource region.
The mobile station is then able to receive the packet based
on information about a pre-designated region for the
retransmission.
If a retransmission is generated in uplink, the
mobile station transmits a retransmission packet via a
fixed resource region pre-allocated by the base station.
The base station is then able to receive the packet via a
pre-designated region. In particular, if error is generated
from a packet having been retransmitted, a retransmission
is performed using the same method (using a region
allocated in the early time of a specific frame after
completion of receiving NACK) of the initial retransmission.
Alternatively, when the base station performs a
retransmission using region information for the
retransmission, the base station is able to inform the
mobile station of the error generation using a control
message.
In the preferred embodiments of the present invention,
'the error generation from a packet' includes a case that a
mobile station or a base station is unable to receive a
packet lost on a wireless/wire line as well as a case that
error is generated from a transmitted or received packet
itself. And, 'the error generation from a packet' also
includes a case that a mobile station or a base station is
unable to reconstruct an erroneous packet into an original
packet.
In the following description, explained is a
retransmission method used in a MAC layer.
FIG. 1 a flowchart for an embodiment of using HARQ in
transmitting VoIP packets in downlink.
Referring to FIG. 1, a method of transmitting VoIP
packets to provide a VoIP service from a base station (BS)
to a mobile station (MS) can be observed. When the base
station BS transmits a DL VoIP packet #1 in downlink, as
error is generated or the DL VoIP packet #1 is lost on
wireless/wire line, if the mobile station is unable to
receive the DL VoIP packet #1 [S101], the mobile station
transmits a NACK signal to the base station [S102].
In this case, in order to retransmit the DL VoIP
packet #1 having been transmitted to the mobile station in
the step S101, the base station transmits a control message
for retransmission by enabling new MCS (modulation and
coding scheme) level information and new resource
allocation region information to be included in the control
message [S103].
The base station, which allocates a new resource
region by transmitting the control message to the mobile
station, retransmits the DL VoIP packet #1 to the mobile
station via the newly allocated resource region [S104]. If
the mobile station normally receives the packet in the step
S104, the mobile station transmits an ACK signal to the
base station [S105].
In order to provide the VoIP service continuously,
the base station transmits a next VoIP packet, i.e., a DL
VoIP packet #2 to the mobile station. Yet, if the DL VoIP
packet #2 is erroneous or lost on wire/wireless line in the
course of reception, the mobile station is unable to
receive the packet normally [S106]. The mobile station
failing to receive the VoIP packet normally transmits a
NACK signal to the base station [S107].
Having received the NACK signal from the mobile
station in the step S107, the base station transmits a
control message for retransmission to the mobile station by
enabling MCS level and resource allocation region
information to be included in the control message [S108].
In the step S108, the mobile station is able to receive
data via a new resource region allocated using the
informations included in the control message for the
retransmission.
The base station then retransmits the DL VoIP packet
#2 corresponding to the NACK signal received in the step
S107 to the mobile station [S109].
PIG. 2 a flowchart for an embodiment of using HARQ in
transmitting VoIP packets in uplink.
Referring to FIG. 2, a method of transmitting VoIP
packets to provide a VoIP service to a base station (BS)
from a mobile station (MS) can be observed. When the mobile
station MS transmits a UL VoIP packet #1 in uplink, as
error is generated or the DL VoIP packet #1 is lost on
wireless/wire line, if the base station is unable to
receive the DL VoIP packet #1 [S201] , the base station
transmits a NACK signal to the mobile station [S202].
In this case, in order to receive the erroneous UL
VoIP packet #1 in the step 2101, the base station transmits
a control message for retransmission to the mobile by
enabling a new MCS (modulation and coding scheme) level and
new resource allocation region information to be included
in the control message [S203].
The mobile station has a new resource region
allocated thereto by receiving the control message for the
retransmission and then retransmits the DL VoIP packet #1
to the base station via the newly allocated resource region
[S204] . If the base station normally receives the packet in
the step S204, the base station transmits an ACK signal to
the mobile station [S205].
In order to receive the VoIP service continuously,
the mobile station transmits a next VoIP packet, i.e., a DL
VoIP packet #2 to the base station. Yet, if the DL VoIP
packet #2 is erroneous or lost on wire/wireless line in the
course of reception, the base station may be unable to
receive the packet normally [S206]. The base station
failing to receive the VoIP packet normally transmits a
NACK signal to the mobile station [S207].
Having transmitted the NACK signal to the mobile
station in the step S207, the base station transmits a
control message for retransmission to the mobile station by
enabling MCS level and resource allocation region
information different from the former information provided
in the step S203 to be included in the control message
[S208]. In the step S208, the mobile station is able to
transmit data via a new resource region allocated using the
informations included in the control message for the
retransmission.
The mobile station then retransmits the UL VoIP
packet #2 corresponding to the NACK signal received in the
step S207 to the base station [S209].
As mentioned in the foregoing description of FIG. 1
and FIG. 2, in order for the base or mobile station to
perform the retransmission of the erroneous packet, the
base station repeatedly transmits the control message (e.g.,
MAP IE) including the new resource allocation region
information (or MCS level information) for the
retransmission to the mobile station each time the error is
generated.
FIG. 3 is a diagram for a method of allocating a
fixed radio resource region for retransmission from a base
station to a mobile station according to one embodiment of
the present invention.
In FIG. 3, a horizontal axis indicates a time unit as
a frame unit and a vertical axis indicates a frequency unit.
'P1' in Frame 1 or Frame 5 indicates a region allocated to
a first mobile station by a base station for a continuous
VoIP packet transmission/reception to/from the first mobile
station in downlink/uplink. 'P2' indicates a radio resource
region allocated to a second mobile station, 'P3' indicates
a radio resource region allocated to a third mobile station,
and 'P4' indicates a radio resource region allocated to a
fourth mobile station.
Referring to FIG. 3, the base station allocates a
region for retransmission to each mobile station having a
VoIP connection by identifying the corresponding mobile
station one by one. In downlink, the base station transmits
a VoIP packet to the mobile station via the allocated
region. In uplink, the mobile station transmits a VoIP
packet to the base station via the allocated region. In
particular, the first mobile station transmits VoIP packets
with the base station via P1. And, the rest of the mobile
stations transmit/receive VoIP packets to/from the base
station via the allocated regions, respectively.
In Frame 3 or Frame 7, 'R1' indicates a region
allocated for retransmission to correspond to P1, 'R2'
indicates a region allocated for retransmission to
correspond to P2, 'R3' indicates a region allocated for
retransmission to correspond to P3, and 'R4' indicates a
region allocated for retransmission to correspond to P4.
The base station enables informations for retransmission to
be included in an initial control message and is then able
to transmit the control message to each of the mobile
stations. Hence, if a retransmission takes place, the base
station and the mobile stations can transmit the
retransmitted packets with each other via the preset
retransmission regions. In particular, in case that error
is generated from the VoIP packet transmitted between the
base station and each of the mobile stations via
P1/P2/P3/P4, the base station and each of the mobile
stations can transmit the retransmitted packet via the pre-
allocated radio resource region R1/R2/R3/R4.
Even if error is not generated in the course of
transmitting packets between one of the first to fourth
mobile stations and the base station, keeping the pre-
allocated region for retransmission will be a waste of
radio resources. Hence, if the retransmission is
unnecessary, the pre-allocated region for the
retransmission can be used to transmit a different packet
of each of the mobile stations or packet of the base
station. This agreement can be established through mutual
negotiation in case that the base station and the mobile
station are interconnected to each other or an initial
service is provided.
FIG. 4 is a diagram for a method of allocating a
radio resource region for retransmission from a base
station to a mobile station according to another embodiment
of the present invention.
In FIG. 4, a horizontal axis indicates a time unit as
a frame unit and a vertical axis indicates a frequency unit.
'P1' in Frame 1 or Frame 5 indicates a region allocated to
a first mobile station by a base station for a continuous
VoIP packet transmission/reception to/from the first mobile
station in downlink/up link. 'P2' indicates a radio
resource region allocated to a second mobile station by the
base station, 'P3' indicates a radio resource region
allocated to a third mobile station by the base station,
and 'P4' indicates a radio resource region allocated to a
fourth mobile station by the base station.
Referring to FIG. 4, in downlink, the base station
transmits a VoIP packet to the mobile station via the
allocated region. In uplink, the mobile station transmits a
VoIP packet to the base station via the allocated region.
In particular, the first mobile station transmits VoIP
packets with the base station via P1. And, the rest of the
mobile stations transmit/receive VoIP packets to/from the
base station via the allocated regions, respectively.
In FIG. 4, assume that a region allocated to a mobile
station to transmit VoIP packets is equal to the region
shown in FIG. 3. Yet, FIG. 4 differs from FIG. 3 in
allocating a retransmission region. The base station puts
mobile stations having the same attribute (e.g., the same
size of the resource region allocated for packet
transmission) into one group and is then able to allocate a
radio resource for retransmission. In particular, in case
that the base station configures a retransmission region,
mobile stations having the same resource allocation region
size in the same frame into at least one or more groups and
is then able to allocate a resource allocation region for
retransmission to each of the groups.
Referring to FIG. 4, since a size of a radio resource
region allocated to the first mobile station is equal to a
size of a radio resource region allocated to the second
mobile station, the first and second mobile stations can be
put into one group. Since a size of a radio resource region
allocated to the third mobile station is equal to a size of
a radio resource region allocated to the fourth mobile
station, the third and fourth mobile stations can be put
into another group.
Hence, in Frame 3 or Frame 7, 'R1 (retransmission
region allocated for retransmissions of regions P1 and P2)'
is allocated as a retransmission region of the first and
second mobile stations. And, 'R2 (retransmission region
allocated for retransmissions of regions P3 and P4)' is
allocated as a retransmission region of the third and
fourth mobile stations.
In another embodiment of the present invention, when
retransmission take place in all of the mobile stations
having the same retransmission region allocated thereto, if
VoIP packets are transmitted using the same retransmission
regions, collisions may cause a problem that retransmission
packets are unable to be normally retransmitted.
To solve this problem, one mobile station keeps using
a previously allocated retransmission. Yet, it is necessary
to allocate a region different from the previously
allocated region to the other mobile station for
retransmission.
For instance, assume that the first and second mobile
stations transmit VoIP packets to the base station in
uplink through P1 and P2, respectively. In this case, if
both of the VoIP packets received by the base station
through P1 and P2 are erroneous, the base station transmits
NACK signals to the mobile stations to make requests for
retransmissions of the corresponding packets, respectively.
After the mobile stations have received the NACK signals,
if the mobile stations simultaneously transmit
retransmission packets via a fixed retransmission region R1,
which was previously allocated by the base station through
an initial control message, the retransmission packets may
collide with one another.
Therefore, after a retransmission region is allocated
per group, if errors simultaneously generated from mobile
stations belonging to the same group, the base station
needs to allocate a new retransmission region.
In particular, the first mobile station is made to
retransmit a packet via R1 which is a retransmission region
allocated via an initial control message and the second
mobile station additionally transmits a control message for
retransmission to allocate another resource region, which
is not Rl, for retransmission. Hence, it is ale to control
mutual collision to be avoided.
PIG. 5 is a diagram for a method of allocating a
radio resource region for retransmission from a base
station to a mobile station according to a further
embodiment of the present invention.
In FIG. 5, a horizontal axis indicates a time unit as
a frame unit and a vertical axis indicates a frequency unit.
'P1' in Frame 1 or Frame 5 indicates a region allocated to
a first mobile station by a base station for a continuous
VoIP packet transmission to the mobile station in downlink
or 'P1' in Frame 1 or Frame 5 indicates a region allocated
to a first mobile station by a base station for a VoIP
packet reception from the first mobile station in uplink.
'P2' indicates a radio resource region allocated to a
second mobile station by the base station, 'P3' indicates a
radio resource region allocated to a third mobile station
by the base station, and 'P4' indicates a radio resource
region allocated to a fourth mobile station by the base
station.
Referring to FIG. 5, in downlink, the base station
transmits a VoIP packet to the mobile station via the
allocated region. In uplink, the mobile station transmits a
VoIP packet to the base station via the allocated region.
In particular, the first mobile station transmits VoIP
packets with the base station via P1. And, the rest of the
mobile stations transmit/receive VoIP packets to/from the
base station via the allocated regions, respectively.
FIG. 5 shows that the base station transmits VoIP
packets with each of the mobile stations by allocating
radio resources to the respective mobile stations, which is
as good as FIG. 3 or FIG. 4.
Yet, FIG. 5 differs from FIG. 3 or FIG. 4 in that
mobile stations perform retransmission using a common
retransmission channel (common ReTx channel) set for the
retransmission instead of allocating retransmission regions
to the mobile stations, respectively. In particular, after
a common retransmission channel has been set as a resource
region available for VoIP packet retransmission, it can be
used in case of retransmission occurrence.
For instance, in case that retransmissions take place
for at least two mobile stations in VoIP downlink, a base
station selects one of the at least two mobile stations and
then enables a packet to be retransmitted to the selected
mobile station using a common retransmission channel. The
base station enables a retransmission process to be
performed by allocating a resource region designated in the
same frame to the unselected mobile stations.
In case that retransmissions take place for at least
two mobile stations in uplink, a base station designates a
single mobile terminal to transmit a retransmission packet
via a common retransmission channel in the same frame only
and then notifies it to the mobile stations. To enable the
unselected mobile stations to perform retransmissions, the
base station can allocate a different region for
retransmission in the same frame.
Referring to PIG. 5, mobile stations transmitting
VoIP packets in the same frame use a common retransmission
channel for retransmission. 'R1' indicates a resource
region for allocating a portion of a common retransmission
channel for retransmissions of P1 and P2. And, 'R2'
indicates a resource region for allocating a portion of a
common retransmission channel for retransmissions of P3 and
P4. Moreover, a region of R2 can include a region of R1.
When retransmissions are generated from at least one
or more mobile stations in uplink, if the at least one or
more mobile stations perform retransmissions via the same
retransmission region, collisions may occur. Hence, if
retransmissions are generated from a plurality of mobile
stations in case of using the same retransmission channel,
a single mobile station performs a retransmission process
(base station to mobile station in case of downlink, mobile
station to base station in case of uplink) using the common
retransmission channel only while the rest of the mobile
stations are made to perform a retransmission process in a
manner of allocating resource regions to the rest of the
mobile stations, respectively.
In case that a retransmission is performed using a
common retransmission channel, an unused region of the
common retransmission channel is available for a
transmission of other packets. For instance, in case that a
retransmission is performed using a region R1, a base
station is able to transmit VoIP packets using a different
region not including a region R1 in a region R2.
The resource allocation for retransmission in FIGs. 3
to 5 can use the same region for initial transmission or a
different region. If the same region for the initial
transmission is used, packets can be just transmitted via a
resource area equal to a previously allocated region
without announcing resource allocation region information
separately.
FIG. 6 is a flowchart for performing a retransmission
using a continuous HARQ setting method in downlink
according to one embodiment of the present invention.
Referring to FIG. 6, a base station delivers
information for retransmission to a mobile station using a
initial control message [S601].
In the step S601, the initial control message for
retransmission can include a specific DL/DL-MAP IE message,
a DSA-REQ/RSP message, or another MAC management message
according to system requirements. And, the information for
the retransmission can include information on a fixed
resource allocation region and MAC level information or a
transmission timing point (e.g., information indicating
that a retransmission will be performed after duration of
prescribed frames from a timing point of NACK reception).
Preferably, the methods described with reference to
FIGs. 3 to 5 are usable as a method of allocating a fixed
radio resource region for retransmission. According to one
embodiment of the present invention, a case of performing
communication between a single mobile station and a base
station is assumed. In case that communications are
performed between at least one or more mobile stations and
a base station, it is able to allocate a radio resource
region for retransmission using one of the methods
described with reference to FIGs. 3 to 5.
Referring to FIG. 6, the base station transmits DL
VoIP packet #1 to the mobile station to provide a VoIP
service thereto. Yet, if error is generated from the DL
VoIP packet #1, the mobile station may not decode the
corresponding packet [S602].
In this case, the mobile station is able to transmit
a NACK signal to the base station to announce that error
has been generated [S603].
Having received the NACK signal, the base station
retransmits the DL VoIP packet #1 to the mobile station via
a region allocated for retransmission without side
information using the information on the resource
allocation region previously negotiated with the mobile
station in the step S601 [S604] . In this case, the mobile
station is able to receive VoIP packet from the base
station via a region allocated for a pre-designated
retransmission.
Having received the VoIP packet normally, the mobile
station transmits an acknowledgement (ACK) signal to the
base station [S605].
To provide the VoIP service continuously, the base
station transmits DL VoIP packet #2 to the mobile station
[S606] .
Yet, in case that the DL VoIP packet #2 transmitted
in the step S606 is erroneous or lost on wire/wireless line,
the mobile station is unable to receive the packet normally.
Therefore, the mobile station transmits a NACK signal to
the base station [S607].
Having received the NACK signal, the base station
retransmits the DL VoIP packet #2 based on information on
fixed resource allocation region, information on MCS level
or retransmission timing point contained in the control
message for the retransmission and the like [S608].
FIG. 7 is a flowchart for performing a retransmission
using a continuous HARQ setting method in uplink according
to another embodiment of the present invention.
Referring to PIG. 7, a base station is able to
deliver information on a resource allocation region for
retransmission and the like using an initial control
message for retransmission [S701] .
In the step S701, the control message for
retransmission can include a specific DL/DL-MAP IE message,
a DSA-REQ/RSP message, or another MAC management message
according to system requirements. And, the information for
the retransmission can include information on a fixed
resource allocation region and MAC level information or a
transmission timing point (e.g., information indicating
that a retransmission will be performed after duration of
prescribed frames from a timing point of NACK reception).
Preferably, the methods described with reference to
FIGs. 3 to 5 are usable as a method of allocating a fixed
radio resource region for retransmission. According to
another embodiment of the present invention, a case of
performing communication between a single mobile station
and a base station is assumed. In case that communications
are performed between at least one or more mobile stations
and a base station, it is able to allocate a radio resource
region for retransmission using one of the methods
described with reference to FIGs. 3 to 5.
Referring to FIG. 7, the mobile station transmits UL
VoIP packet #1 to the base station to provide a VoIP
service thereto. Yet, if error is generated from the UL
VoIP packet #1, the base station may not decode the
corresponding packet [S702].
In this case, the base station is able to transmit a
NACK signal to the mobile station to announce that error
has been generated [S703].
Having received the NACK signal, the mobile station
retransmits the UL VoIP packet #1 to the base station via a
region allocated for retransmission without side
information using the information on the resource
allocation region previously negotiated with the base
station in the step S701 [S704] . In this case, the base
station is able to receive VoIP packet from the mobile
station via a region allocated for a pre-designated
retransmission.
Having received the VoIP packet normally, the base
station transmits an acknowledgement (ACK) signal to the
mobile station [S705].
For the continuous VoIP service, the mobile station
transmits UL VoIP packet #2 to the base station [S706].
Yet, in case that the UL VoIP packet #2 transmitted
in the step S706 is erroneous or lost on wire/wireless line,
the base station is unable to receive the packet normally.
Therefore, the base station transmits a NACK signal to the
mobile station [S707].
Having received the NACK signal, the mobile station
retransmits the DL VoIP packet #2 based on information on
fixed resource allocation region, information on MCS level
or retransmission timing point contained in the control
message for the retransmission and the like [S708].
In FIG. 6 and FIG. 7, in case that the mobile station
and the base station need frequent transmissions and
receptions of packets like the VoIP service, the base
station sets a fixed resource allocation region for
retransmission in advance and is then able to transmit it
to the mobile station via the initial control message.
Therefore, each time a retransmission is necessary, data
packets can be efficiently transmitted by directly
retransmitting the data packet via the pre-designated
region without transmitting the control message for the
retransmission. Since the base station needs not to
transmit the control message to the mobile station in case
of necessity of retransmission, it is able to reduce
overhead of a MAC layer.
FIG. 8 is a flowchart of a packet error processing
method in performing retransmission using a continuous HARQ
setting method in downlink/uplink according to a further
embodiment of the present invention.
Referring to FIG. 8, a base station is able to
deliver information on a resource allocation region for
retransmission and the like using an initial control
message for retransmission [S801].
In the step S801, the initial control message for
retransmission can include a specific UL/DL-MAP IE message,
a DSA-REQ/RSP message, or another MAC management message
according to system requirements. And, the information for
the retransmission can include information on a fixed
resource allocation region and MAC level information or a
transmission timing point (e.g., information indicating
that a retransmission will be performed after duration of
prescribed frames from a timing point of NACK reception).
Preferably, the methods described with reference to
FIGs. 3 to 5 are usable as a method of allocating a fixed
radio resource region for retransmission. According to a
further embodiment of the present invention, a case of
performing communication between a single mobile station
and a base station is assumed. In case that communications
are performed between at least one or more mobile stations
and a base station, it is able to allocate a radio resource
region for retransmission using one of the methods
described with reference to FIGs. 3 to 5.
Referring to FIG. 8, in case that VoIP service is
transmitted between the base station and the mobile station,
it may frequently happen that VoIP packet is retransmitted.
In FIG. 8, although the base station transmits a downlink
packet DL VoIP packet #1, error is generated. Therefore,
the base station retransmits the DL VoIP packet #1 to the
mobile station via a pre-designated resource region using
resource allocation region information contained in an
initial control message. Yet, since the retransmitted DL
VoIP packet #1 is erroneous or lost on wire/wireless line,
it may happen that the mobile station is unable to receive
the corresponding packet normally [S802].
If the case of the step S802 takes place, the mobile
terminal transmits a NACK signal to the base station to
announce that the packet was not normally received [S803].
Having received the NACK signal, the base station is
able to retransmit the DL VoIP packet #1 to the mobile
station using the information set for the retransmission in
the initial control message [S804].
While the mobile station and the base station keep
performing the VoIP service, an uplink communication for
transmitting VoIP packet to the base station from the
mobile station can be performed.
In the course of transmitting UL VoIP packet #1 to
the base station from the mobile station, it may happen
that the UL VoIP packet #1 is retransmitted. In this case,
even if the UL VoIP packet #1 is retransmitted, error can
be generated from the retransmitted packet again [S805].
If so, the base station retransmits the NACK signal
to the mobile station to announce that the uplink packet
having been transmitted by the mobile station is erroneous
[S806].
Having received the NACK signal, the mobile station
is able to retransmit the UL VoIP packet #1 to the base
station using the resource allocation region information
for the retransmission included in the initial control
message and the like.
In FIG. 8, shown is the case that error is generated
from VoIP packet retransmitted in uplink or downlink in the
course of providing VoIP service to the mobile station from
the base station. And, FIG. 8 depicts the case that the
retransmission region allocated via the initial control
message keeps being used despite that error keeps being
generated from the retransmitted VoIP packet.
Yet, it may happen that the initially set
retransmission region is not suitable for communication
environment. In this case, by allocating a new
retransmission region instead of a channel having error
kept being generated therefrom, packets are transmitted via
the new retransmission region to achieve a better gain in
aspect of data processing efficiency.
FIG. 9 is a flowchart of a packet error processing
method in case of detecting error repeatedly in performing
retransmission using a continuous HARQ setting method in
downlink/uplink according to a further embodiment of the
present invention.
Referring to FIG. 9, a base station is able to inform
a mobile station of retransmission region information in
advance in a manner of continuous resource allocation
information for retransmission is made to be included in an
initial control message [S901].
In the step S901, the information required for the
retransmission may include information on a fixed resource
allocation region and MAC level information or a
transmission timing point (e.g., information indicating
that a retransmission will be performed after duration of
prescribed frames from a timing point of NACK signal
reception).
To prepare for a case that error keeps being
generated despite performing a retransmission via a new
transmission region, the base station is able to negotiate
a prescribed count for receiving a NACK signal repeatedly
with the mobile station. If the base or mobile station
receives the NACK signal over the prescribed count, the
base station is able to transmit a control message for
allocating a new retransmission region again.
According to a further embodiment of the present
invention, assume that the prescribed count for receiving
the NACK signal is set to 2. Of course, the prescribed
count for receiving the NACK signal may vary according to
system requirements or communication environment.
Preferably, the methods described with reference to
FIGs. 3 to 5 are usable as a method of allocating a fixed
radio resource region for retransmission. According to a
further embodiment of the present invention, a case of
performing communication between a single mobile station
and a base station is assumed. In case that communications
are performed between at least one or more mobile stations
and a base station, it is able to allocate a radio resource
region for retransmission using one of the methods
described with reference to FIGs. 3 to 5.
Referring to FIG. 9, in downlink transmission, the
base station transmits DL VoIP packet #1 to the mobile
station. Yet, it may happen that the DL VoIP packet #1 is
erroneous or lost on wire/wireless line [S902].
If the mobile station is unable to normally know the
information included in the packet as the received packet
is erroneous or if the mobile station is unable to receive
the packet that is lost, the mobile station transmits a
NACK signal to the base station to announce the reception
failure [S903].
Having received the NACK signal, the base station is
able to retransmit the DL VoIP packet #1 via a preset
retransmission region using the resource allocation region
information included in the initial control message [S904].
Yet, if the retransmitted VoIP packet is erroneous as well,
the mobile station transmits a NACK signal to the base
station again [S905].
As the count of the NACK signal received by the base
station from the mobile station becomes 2, the count
negotiated with the mobile station in the initial service
setting is met. Therefore, the base station transmits a
control message for retransmission to the mobile station to
allocate a new retransmission region again [S906]. In the
control message to allocate the retransmission region in
the step S906, information on a new retransmission region,
MCS level information or information or a transmission
timing point can be included.
The base station allocates a new retransmission
region to the mobile station via the control message in the
step S906 and is then able to retransmit the DL VoIP packet
#1 again [S907]. In case of receiving the DL VoIP packet #1
normally, the mobile station transmits an ACK signal to the
base station to announce the transmission success.
In the course of transmitting or receiving the VoIP
service, it may happen that a data packet is transmitted in
uplink. In particular, while the mobile station transmits
VoIP packet to the base station, it may happen that UP VoIP
packet #1 is retransmitted to the base station [S908].
Yet, if the VoIP packet retransmitted in the step
S908 becomes erroneous, the base station transmits NACK
signal to the mobile station to announce that the
corresponding packet is erroneous [S909].
Having received the NACK signal in the step S909, the
mobile station receives the NACK signal consecutively twice.
Hence, the NACK signal reception count negotiated with the
base station in the initial service configuration is met.
In this case, since the base station already knows the fact
that errors are at least twice generated from the received
VoIP packet received from the mobile terminal, the mobile
station is able to transmit a control message to allocate a
new retransmission region to the mobile station despite an
absence of a request made by the mobile station [S910].
Having allocated the new retransmission region
thereto in the step S190, the mobile station is able to
retransmit UL VoIP packet #1 to the base station [S911].
According to a further embodiment of the present
invention, error occurs repeatedly even if the
retransmission is performed by allocating the
retransmission region in uplink or downlink. In this case,
it is able to raise data processing efficiency in a manner
of allocating a new retransmission region again and then
transmitting VoIP packet via another channel instead of the
channel on which the error keeps being generated.
FIG. 10 is a flowchart for a method of performing
retransmission in the course of transceiving VoIP service
between a base station and at least one mobile station in
uplink according to a further embodiment of the present
invention.
Referring to FIG. 10, a base station is able to
provide VoIP service to at least one or more mobile
stations existing within its service area. In this case,
the base station is able to deliver information on resource
allocation region for packet retransmission and the like to
a first mobile station MSI and a second mobile station MS2
among a plurality of the mobile stations using an initial
control message for retransmission [S1001, S1002].
In the step S1001 or S1002, the initial control
message for retransmission can include a specific UL/DL-MAP
IE message, a DSA-REQ/RSP message, or another MAC
management message according to system requirements. And,
the information for the retransmission can include
information on a fixed resource allocation region and MAC
level information or a transmission timing point (e.g.,
information indicating that a retransmission will be
performed after duration of prescribed frames from a timing
point of NACK reception). Preferably, the methods described
with reference to FIG. 4 and FIG. 5 are usable as a method
of allocating a fixed radio resource region for
retransmission.
According to a further embodiment of the present
invention, the base station puts the first mobile station
MS1 and the second mobile station MS2, which have the same
attribute (e.g., equal size in an allocated resource
region), into a group. The base station then allocates a
same retransmission region to both of the first mobile
station MS1 and the second mobile station MS2 or designates
a common retransmission channel for VoIP packet
retransmission.
The first mobile station MS1 transmits UL VoIP packet
#1 to the base station for the VoIP packet transmission
[S1003]. And, the second mobile station MS2 transmits UL
VoIP packet #2 to the base station for the VoIP packet
transmission [S1004] . Yet, if the UL VoIP packet #1 or the
DL VoIP packet #2 is erroneous, it may happen that the base
station is unable to reconstruct the corresponding packet.
The base station informs the first mobile station MS1
or the second mobile station MS2 that the corresponding
uplink packet is erroneous [S1005, S1006].
In case that both of the first mobile station MS1 or
the second mobile station MS2 perform retransmissions, as
the same retransmission region is allocated to both of the
first mobile station MS1 or the second mobile station MS2,
it is unable to simultaneously transmit packets via the
same region. In this case, the base station enables the
first mobile station MS1 to retransmit the corresponding
packet via the previously allocated retransmission region
and should control the second mobile station MS2 to
retransmit the corresponding packet via another
retransmission region. Therefore, the base station is able
to allocate a new retransmission region to the second
mobile station MS2 via a control message for retransmission
[S1007].
The first mobile station MS1 retransmits the UL VoIP
packet #1 via the retransmission region previously
allocated in the step S1001 [S1008]. And, the second mobile
station MS2 retransmits the DL VoIP packet #2 via the
retransmission region re-allocated in the step S1007
[S1009] . Thus, it is able to prevent the retransmitted
packets from colliding with each other. Therefore, packet
retransmissions can be more efficiently performed by
avoiding collisions between the retransmitted packets.
INDUSTRIAL APPLICABILITY
Accordingly, the embodiments of the present invention
are applicable to various wireless access systems. Moreover,
the embodiments of the present invention are applicable to
every industrial field having the same or similar technical
idea of the present invention or using the same.
While the present invention has been described and
illustrated herein with reference to the preferred
embodiments thereof, it will be apparent to those skilled
in the art that various modifications and variations can be
made therein without departing from the spirit and scope of
the invention. Thus, it is intended that the present
invention covers the modifications and variations of this
invention that come within the scope of the appended claims
and their equivalents.
WHAT IS CLAIMED IS:
1. A method of retransmitting a packet in a
wireless access system, comprising the steps of:
receiving an control message including information
required for a packet retransmission from a base station;
transmitting the packet to be provided with a service
from the base station; and
if a NACK (non-acknowledgement) signal is received
from the base station, retransmitting the packet
corresponding to the NACK signal to the base station using
the information required for the packet retransmission and
included in the initial control message.
2. The method of claim 1,
wherein the information required for the packet
retransmission includes at least one of resource allocation
region information for the packet retransmission,
modulation and coding scheme (MCS) level information and a
transmission timing point.
3. The method of claim 1,
wherein the information required for the packet
retransmission includes information for allocating
different resource allocation regions required for the
packet transmission to at least one or more terminals,
respectively.
4. The method of claim 1,
wherein the information required for the packet
retransmission includes information for configuring at
least one group including terminals having resource
allocation regions equal to each other in size among at
least one or more terminals and for allocating a resource
allocation region required for the packet retransmission to
the at least one group.
5. The method of claim 1,
wherein the information required for the packet
retransmission includes information for setting a
retransmission dedicated channel for the packet
retransmission of at least one terminal and information of
a specific region required for the packet retransmission in
the retransmission dedicated channel.
6. The method of claim 5,
wherein the specific region required for the packet
retransmission is partial region of the retransmission
dedicated channel.
7. The method of claim 1,
wherein the control message is a UL MAP (uplink MAP)
message or a MAC (media access control) management message,
and wherein the MAC management message is one of a dynamic
service addition message, a channel descriptor message, and
a subscribe station basic capability message.
8. A method of retransmitting a packet in a
wireless access system, comprising the steps of:
transmitting an control message including information
required for a packet retransmission to at least one
terminal;
providing a service to the at least one terminal; and
if a NACK (non-acknowledgement) signal is received
from the at least one terminal, retransmitting the packet
corresponding to the NACK signal to the at least one
terminal using the information required for the packet
retransmission and included in the initial control message.
9. The method of claim 8,
wherein the information required for the packet
retransmission includes at least one of resource region
allocation information for the packet retransmission,
modulation and coding scheme (MCS) level information and a
transmission timing point.
10. The method of claim 8, further comprising:
if the base station receives the NACK signal
repeatedly over a prescribed count,
transmitting a control signal to the at least one
terminal by updating the information required for the
packet retransmission and then including the updated
information in the control message for the packet
retransmission.
11. The method of claim 8,
wherein the information required for the packet
retransmission includes information for allocating
different resource allocation regions required for the
packet transmission to the at least one or more terminals,
respectively.
12. The method of claim 8,
wherein the information required for the packet
retransmission includes information for configuring at
least one group including terminals having resource
allocation regions equal to each other in size among at
least one or more terminals and for allocating a resource
allocation region required for the packet retransmission to
the at least one group.
13. The method of claim 8,
wherein the information required for the packet
retransmission includes information for setting a
retransmission dedicated channel for the packet
retransmission of at least one terminal and information of
a specific region required for the packet retransmission in
the retransmission dedicated channel.
14. The method of claim 13,
wherein the specific region required for the packet
retransmission is partial region of the retransmission
dedicated channel.
15. The method of claim 8, wherein the control
message is one of a DL MAP (downlink MAP) message or a MAC
management message, and wherein the MAC management message
is one of a dynamic service addition message, a channel
descriptor message, and a subscribe station basic

A method of transmitting data in a wireless access system and a packet retransmitting method therein arc disclosed.
The present invention includes receiving an initial control message including information required for a packet retransmission from
a base station, transmitting the packet to be provided with a service from the base station, and if a NACK (non-acknowledgement)
signal is received from the base station, retransmitting the packet corresponding to the NACK signal to the base station using the
information required for the packet retransmission and included in the initial control message. Therefore, since a separate control
message needs not to be transmitted in case of packet retransmission, it is able to save radio resources and reduce an overhead by
retransmitting a packet via a previously allocated retransmission region without the separate control message.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=qUSWfAgXjwJKleFz3AfM3w==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

270524

Indian Patent Application Number

693/KOLNP/2010

PG Journal Number

01/2016

Publication Date

01-Jan-2016

Grant Date

29-Dec-2015

Date of Filing

23-Feb-2010

Name of Patentee

LG ELECTRONICS INC.

Applicant Address

20, YEOUIDO-DONG, YEONGDEUNGPO-GU, SEOUL 150-721 REPUBLIC OF KOREA

Inventors:

#	Inventor's Name	Inventor's Address
1	RYU, KI SEON	LG INSTITUTE, HOGYE 1(IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO 431-080 REPUBLIC OF KOREA
2	SUNG, DOO HYUN	LG INSTITUTE, HOGYE 1(IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO 431-080 REPUBLIC OF KOREA
3	LEE, WOOK BONG	LG INSTITUTE, HOGYE 1(IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO 431-080 REPUBLIC OF KOREA
4	KIM, JEONG KI	LG INSTITUTE, HOGYE 1(IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO 431-080 REPUBLIC OF KOREA

PCT International Classification Number

H04L 1/18

PCT International Application Number

PCT/KR2008/004703

PCT International Filing date

2008-08-13

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10-2007-0084615	2007-08-22	Republic of Korea