Title of Invention	A METHOD OF PERFORMING POLLING PROCEDURE IN A WIRELESS COMMUNICATION SYSTEM
Abstract	A method of generating a data block for performing a polling procedure in a wireless communication system, a method of transmitting data and a method of performing a polling procedure are disclosed. A protocol layer performs the polling procedure for requesting a receiving side to transmit status report if there are no data to be transmitted to the receiving side in both a transmission buffer and a retransmission buffer. When determining whether there are no data to be transmitted to the receiving side in the retransmission buffer, it is preferable that a data block for which retransmission request information is not received from the receiving side is excluded.

Title of Invention

A METHOD OF PERFORMING POLLING PROCEDURE IN A WIRELESS COMMUNICATION SYSTEM

Abstract

A method of generating a data block for performing a polling procedure in a wireless communication system, a method of transmitting data and a method of performing a polling procedure are disclosed. A protocol layer performs the polling procedure for requesting a receiving side to transmit status report if there are no data to be transmitted to the receiving side in both a transmission buffer and a retransmission buffer. When determining whether there are no data to be transmitted to the receiving side in the retransmission buffer, it is preferable that a data block for which retransmission request information is not received from the receiving side is excluded.

Full Text	A METHOD OF PERFORMING POLLING PROCEDURE IN A WIRELESS COMMUNICATION SYSTEM [DESCRIPTION] TECHNICAL FIELD The present invention relates to a wireless communication system, and more particularly, to a method of generating a data block for performing a polling procedure in a wireless communication system, a method of transmitting data and a method of performing a polling procedure. BACKGROUND ART Various types of data retransmission methods can be used to ensure certainty of data transmission to a receiving side in a wireless communication system. Particularly, the need to use a retransmission method increases when the receiving side should necessarily receive non-real time packet data such as signaling data or TCP/IP data. An example of the data transmission method used in the wireless communication system will be described as follows. The receiving side transmits a status report to a transmitting side to report that at least one or more data blocks transmitted from the transmitting side have been successfully received. The transmitting side retransmits data blocks that the receiving side has failed to receive, to the receiving side using the status report. For application of the retransmission method, data which have been transmitted once should be stored in a buffer for a certain time period without discard. Accordingly, a transmission buffer and a retransmission buffer are required, wherein data which have never been transmitted to the receiving side are stored in the transmission buffer and data which have been transmitted to the receiving side but need to be on standby for retransmission are stored in the retransmission buffer. The transmitting side can request the receiving side to transmit the status report. This procedure is referred to as a polling procedure. If the status report transmitted from the receiving side is lost during transmission or the receiving side does not transmit the status report to the transmitting side timely, the transmitting side can perform the polling procedure. Alternatively, the transmitting side can perform the polling procedure periodically. DISCLOSURE OF THE INVENTION A transmitting side has to use additional radio resources to perform a polling procedure. Accordingly, for efficient use of radio resources, the polling procedure should be prevented from being used unnecessarily. To this end, reasonable standards as to when the transmitting side should perform the polling procedure are required. Accordingly, the present invention is directed to a method of generating a data block for performing a polling procedure in a wireless communication system, a method of transmitting data and a method of performing a polling procedure, which substantially obviate one or more problems due to limitations and disadvantages of the related art. An object of the present invention is to provide a method of generating a data block for performing a polling procedure in a wireless communication system, a method of transmitting data and a method of performing a polling procedure, in which the polling procedure is performed while radio resources are being used efficiently. Another object of the present invention is to provide a method of generating a data block for performing a polling procedure in a wireless communication system, a method of transmitting data and a method of performing a polling procedure, in which a transmitting side performs the polling procedure timely to prevent communication from being stopped unexpectedly. In a wireless communication system, a data retransmission function is performed by a specific protocol layer. To perform the data retransmission function, the protocol layer is equipped with a transmission buffer and a retransmission buffer. The protocol layer can determine whether to perform a polling procedure considering statuses of the transmission buffer and the retransmission buffer, i.e., the amount of data stored in the transmission buffer and the retransmission buffer. In one aspect of the present invention, the protocol layer performs the polling procedure for requesting a receiving side to transmit a status report if there are no data to be transmitted to the receiving side in both the transmission buffer and the retransmission buffer. When determining whether there are no data to be transmitted to the receiving side in the retransmission buffer, it is preferable that a data block for which retransmission request information is not received from the receiving side is excluded. In another aspect of the present invention, the protocol layer performs the polling procedure considering the amount of data transmitted to the receiving side. Namely, the protocol layer performs the polling procedure if the amount of data transmitted to the receiving side reaches a certain level or greater. This procedure can be performed repeatedly. According to the present invention, radio resources can efficiently be used during the polling procedure, and the transmitting side can perform the polling procedure timely, whereby communication can be prevented from being slopped unexpectedly. BRIEF DESCRIPTION OF THE 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 application, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. FIG 1 is a diagram illustrating a network structure of an E-UMTS (Evolved Universal Mobile Telecommunications System); FIG. 2 is a schematic view illustrating an E-UTRAN (Evolved Universal Terrestrial Radio Access Network); FIG. 3A and FIG 3B are diagrams illustrating a structure of a radio interface protocol between a user equipment (UE) and E-UTRAN, in which FIG 3A is a schematic view of a control plane protocol and FIG. 3B is a schematic view of a user plane protocol; FIG 4 is a diagram illustrating an example of a functional block of RLC AM entity; FIG 5 is a diagram illustrating a basic structure of AMD PDU; FIG 6 is a flow chart illustrating a procedure according to one embodiment of the present invention; FIG 7 is a diagram illustrating the embodiment of FIG 6 in view of another aspect; and FIG 8 is a diagram illustrating another embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, structures, operations, and other features of the present invention will be understood readily by the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Embodiments described later are examples in which technical features of the present invention are applied to an E-UMTS (Evolved Universal Mobile Telecommunications System). However, it should be noted that an embodiment of the present invention can be applied to a wireless communication system other that the E-UMTS. FIG. 1 is a diagram illustrating a network structure of an E-UMTS. An E- UMTS is a system evolving from the conventional WCDMA UMTS and its basic standardization is currently handled by the 3GPP (3rd Generation Partnership Project). The E-UMTS can also be called an LTE (Long Term Evolution) system. Referring to FIG. 1, an E-UTRAN includes base stations (hereinafter, referred to as 'eNode B' or 'eNB'), wherein respective eNBs are connected with each other through X2 interface. Also, each of eNBs is connected with a user equipment (UE) through a radio interface and connected with EPC (Evolved Packet Core) through SI interface. The EPC includes a mobility management entity/system architecture evolution (MME/SAE) gateway. Layers of a radio interface protocol between a user equipment and a network can be classified into a first layer L1, a second layer L2 and a third layer L3 based on three lower layers of OSI (open system interconnection) standard model widely known in communication systems. A physical layer belonging to the first layer L1 provides an information transfer service using a physical channel. A radio resource control (hereinafter abbreviated as 'RRC') located at the third layer plays a role in controlling radio resources between the user equipment and the network. For this, the RRC layer enables RRC messages to be exchanged between the UE and the network. The RRC layer can be distributively located at network nodes including Node B, an AG and the like or can be independently located at either the Node B or the AG. FIG. 2 is a schematic view illustrating an E-UTRAN (Evolved Universal Terrestrial Radio Access Network). In FIG. 2, a hatching part represents functional entities of a user plane, and a non-hatching part represents functional entities of a control plane. FIG. 3A and FIG. 3B illustrate a structure of a radio interface protocol between the user equipment (UE) and the E-UTRAN, in which FIG. 3A is a schematic view of a control plane protocol and FIG. 3B is a schematic view of a user plane protocol. Referring to FIG. 3A and FIG 3B, a radio interface protocol horizontally includes a physical layer, a data link layer, and a network layer, and vertically includes a user plane for data information transfer and a control plane for signaling transfer. The protocol layers in FIG. 3A and FIG. 3B can be classified into LI (first iayer), L2 (second layer), and L3 (third layer) based on three lower layers of the open system interconnection (OSI) standard model widely known in the communications systems. The physical layer as the first layer provides an information transfer service to an upper layer using physical channels. The physical layer (PHY) is connected to a medium access control (hereinafter, abbreviated as 'MAC') layer above the physical layer via transport channels. Data are transferred between the medium access control layer and the physical layer via the transport channels. Moreover, data are transferred between different physical layers, and more particularly, between one physical layer of a transmitting side and the other physical layer of a receiving side via the physical channels. The physical channel of the E-UMTS is modulated in accordance with an orthogonal frequency division multiplexing (OFDM) scheme, and time and frequency are used as radio resources. The medium access control (hereinafter, abbreviated as ;MAC) layer of the second layer provides a service to a radio link control (hereinafter, abbreviated as 'RLC') layer above the MAC layer via logical channels. The RLC layer of the second layer supports reliable data transfer. In order to effectively transmit data using IP packets (e.g., IPv4 or IPv6) within a radio-communication period having a narrow bandwidth, a PDCP layer of the second layer (L2) performs header compression to reduce the size of unnecessary control information. A radio resource control (hereinafter, abbreviated as 'RRC) layer located on a lowest part of the third layer is defined in the control plane only and is associated with configuration, reconfiguration and release of radio bearers (hereinafter, abbreviated as 'RBs') to be in charge of controlling the logical, transport and physical channels. In this case, the RB means a service provided by the second layer for the data transfer between the user equipment and the UTRAN. Examples of downlink transport channels carrying data from the network to the user equipments include a broadcast channel (BCH) carrying system information, a paging channel (PCH) carrying paging message, and a downlink shared channel (SCH) carrying user traffic or control messages. The traffic or control messages of a downlink multicast or broadcast service can be transmitted via the downlink SCH or an additional downlink multicast channel (MCH). Meanwhile, examples of uplink transport channels carrying data from the user equipments to the network include a random access channel (RACH) carrying an initial control message and an uplink shared channel (UL-SCH) carrying user traffic or controi message. Examples of logical channels located above the transport channels and mapped with the transport channels include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic channel (MTCH). As described above, the RLC layer of the second layer supports reliable data transfer. Also, the RLC layer serves to perform segmentation and/or concatenation for data received from its upper layer to control a size of the data so that the lower layer can transmit the data to a radio interval. Also, in order to ensure various quality of services (QoS) required by each radio bearer, the RLC layer of the second layer provides three types of operation modes, transparent mode (TM), un-acknowledged mode (UM), and an acknowledged mode (AM). Particularly, the AM RLC layer performs a retransmission function through an automatic repeat and request (ARQ) function for reliable data transmission. Hereinafter, the UM mode and the AM mode of the RLC layer will be described in more detail. The UM RLC layer transmits PDUs by adding a PDU header to each PDU, so that the receiving side can identify what PDU has been lost during transmission, wherein the PDU header includes a sequence number (hereinafter, abbreviated as "SN"). In accordance with this function, the UM RLC layer mainly serves to transmit broadcast/multicast data or real-time data such as voice (for example, VoIP) or streaming of a packet service domain (hereinafter, abbreviated as "PS domain") in a user plane. Also, the UM RLC layer serves to transmit RRC message, which does not need acknowledgement, among RRC messages transmitted to a specific user equipment or a specific user equipment group within a cell, in a control plane. Like the UM RLC layer, the AM RLC layer constitutes RLC PDUs by adding a PDU header including SN thereto. However, the AM RLC layer is different from the UM RLC layer in that the receiving side performs acknowledgement in response to the PDUs transmitted from the transmitting side. The reason why the receiving side performs acknowledgement in the AM RLC layer is to request the transmitting side to re-transmit PDU which the receiving side has not received. This retransmission function is a main feature of the AM RLC layer. Accordingly, the AM RLC layer is to ensure error-free data transmission through re-transmission. For this reason, the AM RLC layer serves to transmit unreal time packet data such as TCP/IP of the PS domain in the user plane. Also, the AM RLC layer serves to transmit RRC message, which necessarily requires acknowledgement, among the RRC messages transmitted to a specific user equipment within a cell, in the control plane. In view of a directional aspect, the UM RLC layer is used for uni-directional communication whereas the AM RLC layer is used for bi-directional communication due to a feedback from the receiving side. The UM RLC layer is also different from the AM RLC layer in view of a structural aspect. Namely, although the UM RLC layer allows one RLC entity to perform a transmission function or a receiving function, the AM RLC layer allows both an entity performing a transmission function and an entity performing a receiving function to exist in one RLC entity. The reason why that the AM RLC layer is complicated is caused by a retransmission function. For retransmission management, the AM RLC entity includes a retransmission buffer in addition to a transmission buffer and uses a transmission and reception window for flow control. The AM RLC entity of the transmitting side performs a polling procedure to request a peer RLC entity of the receiving side to transmit a status report, and the receiving side transmits the status report to the transmitting side to report reception acknowledgement information. Also, the AM RLC entity performs a function constituting a status PDU to transfer the status report. The AM RLC entity supports the aforementioned functions using a plurality of protocol parameters, status parameters, timers, etc. In the AM RLC layer, PDUs used to control transmission of data such as status report or status PDU will be referred to as control PDUs, and PDUs used to transfer user data will be referred to as data PDUs. As described above, the AM RLC entity of the transmitting side includes two buffers, i.e., a transmission buffer and a retransmission buffer. Data which have not yet been included in RLC PDU, among data transferred from an upper entity, are stored in the transmission buffer. RLC PDU transferred to a lower entity is stored in the retransmission buffer until the receiving side acknowledges that the RLC PDU has been successfully received therein. FIG. 4 is a diagram illustrating an example of a functional block of the RLC AM entity. Referring to FIG 4, an RLC SDU (Service Data Unit) transferred from the upper layer (RRC layer or PDCP sub-layer) is stored in a transmission buffer 41. A segmentation/concatenation module 42 performs segmentation and/or concatenation for at least one RLC SDU transferred from the transmission buffer 41. Segmentation and/or concatenation is performed at a specific transmission opportunity in accordance with a transport block size reported from the lower layer. As a result, the RLC PDU generated by the RLC AM entity can have a size desired by the lower layer. An RLC header adding module 43 adds an RLC header to a data block transferred from the segmentation/concatenation module 42. An RLC AMD PDU is generated as the RLC PDU header is added to the data block. FIG. 5 is a diagram illustrating a basic structure of the AMD PDU. The AMD PDU includes a PDU header part and a data field part. The header can include a fixed part and an extended part, wherein the fixed part exists in every AMD PDU and the extended part is included in the AMD PDU only if necessary. The extended part is included in the AMD PDU if one or more data field elements exist in the AMD PDU. The fixed part includes a D/C field, a re-segmentation flag (RF) field, a polling (P) field, a framing info (Fl) field, an extension bit (E) field and a sequence number (SN) field. The D/C field includes information identifying whether a corresponding AMD PDU is a data PDU or a control PDU. The RF field includes information indicating whether a corresponding RLC PDU is a single perfect AMD PDU or a part of another AMD PDU. The polling field includes information indicating whether the AM RLC entity of the transmitting side will request the peer AM RLC entity of the receiving side to transmit status report. The Fl field includes information indicating that the RLC SDU included in the AMD PDU has been segmented from a start part and/or an end part of the data field. The E field includes information indicating whether the data field starts behind the fixed part or whether additional E field and LI field follow behind the fixed part. The SN field includes a sequence number of the AMD PDU. Referring to FIG. 4 again, the AMD PDU generated as the header is added by the RLC header adding module 43 is transferred to the lower layer, for example, a MAC layer. Before the AMD PDU is transferred to the lower layer, additional procedure such as ciphering can be performed for the AMD PDU if necessary. The AMD PDU transferred to the lower layer is stored in the retransmission buffer 44 to perform a retransmission function. If the RLC AM entity performs a receiving function, a routing module 46 performs routing for the received RLC PDU in accordance with a type of the RLC PDU, so as to transfer a control PDU to an RLC control module 45 and an AMD PDU to a receiving buffer/HARQ reordering module 47. The receiving buffer/HARQ reordering module 47 stores AMD PDUs transferred from the routing module 46, and aligns them in the order of SN if they are not received in the order of SN. An RLC header removing module 48 removes the RLC header from the AMD PDU and transfers the resultant data to an SDU reassembly module 49. The SDU reassembly module 49 reassembles at least one or more RLC SDUs using the data transferred from the RLC header removing module and then transfers the resultant data to the upper layer. The RLC AM entity of the receiving side transfers the status report lo the transmitting side through the status PDU to report whether the at least one or more RLC PDUs transmitted from the transmitting side have been successfully received. FIG. 6 is a flow chart illustrating a procedure according to one embodiment of the present invention. The embodiment of FIG. 6 relates to an example of determining whether the RLC AM entity performs a polling procedure in accordance with the statuses of the transmission buffer and the retransmission buffer. Namely, if there are no data to be transmitted to the receiving side in both the transmission buffer and the retransmission buffer, the RLC AM entity performs the polling procedure to request the receiving side to transmit the status report. When determining whether there are data to be transmitted to the receiving side in the retransmission buffer, a data block for which etransmission request information is not received from the receiving side is excluded. Referring to FIG. 4 and FIG. 6, the AM RLC entity checks the status of the ransmission buffer 41 [S61] and identifies whether data to be transmitted to the receiving side are stored in the transmission buffer 4] [S62]. If the data to be transmitted to the receiving side are stored in the transmission buffer 41, the AM RLC entity does not perform the polling procedure. Namely, the AM RLC entity sets the P field to "0," wherein the P field exists in a header of the AMD PDU to be transmitted to the receiving side [S66]. If the P field receives the AMD PDU set to "0," the receiving side regards that the transmitting side does not request transmission of the status report. If the data to be transmitted to the receiving side are not stored in the transmission buffer 41, i.e., if the transmission buffer 41 is empty, the AM RLC entity checks the status of the retransmission buffer 44 [S63] to identify whether data to be transmitted to the receiving side are stored in the retransmission buffer [S64]. When determining whether the data to be transmitted to the receiving side are stored in the retransmission buffer 44, a data block for which retransmission request information is not received from the receiving side is excluded. In other words, even though at least one RLC PDU is stored in the retransmission buffer 44, if the status report or acknowledgement for the at least one RLC PDU is not received from the receiving side, it is regarded that the retransmission buffer 44 is empty. In step S64, if the data to be transmitted to the receiving side are stored in the retransmission buffer 44, the AM RLC entity does not perform the polling procedure. Namely, the AM RLC entity sets the P field to "0," wherein the P field exists in the header of the AMD PDU to be transmitted to the receiving side [S66]. If the data to be transmitted to the receiving side are not stored in the retransmission buffer 44, the AM RLC entity performs the polling procedure. Namely, the AM RLC entity sets the P field to "1," wherein the P field exists in the header of the AMD PDU to be transmitted to the receiving side [S65]. If the P field receives the AMD PDU set to "1", the receiving side regards that the transmitting side requests transmission of the status report, and transmits to the transmitting side the status report for at least one RLC PDU received from the transmitting side. In the embodiment of FIG. 6, although the status of the retransmission buffer has been checked after the status of the transmission buffer is checked, this checking order may be changed. Namely, the status of the transmission buffer may be checked after the status of the retransmission buffer is checked. Also, the status of the transmission buffer and the status of the retransmission buffer may simultaneously be checked. FIG. 7 is a diagram illustrating the embodiment of FIG. 6 in view of another aspect. In FIG. 7, a horizontal axis is a lime axis, and a vertical axis represents the amount of data stored in the transmission buffer and the retransmission buffer. Although the transmission buffer is empty at a timing point "A," since data to be transmitted to the receiving side are stored in the retransmission buffer, the polling procedure is not triggered. The data to be transmitted to the receiving side will not remain in the transmission buffer and the retransmission buffer at a timing point "B" At this time, the AM RLC layer performs the polling procedure. There are no data to be transmitted to the receiving side in the transmission buffer at a timing point "C" but at least one RLC PDU is stored in the retransmission buffer. However, if acknowledgements for the at least one RLC PDU stored in the retransmission buffer is not received from the receiving side, it is regarded that there are no data to be transmitted to the receiving side in the retransmission buffer. Accordingly, the RLC AM entity performs the polling procedure even at the timing point "C." Although the retransmission buffer is empty at a timing point "D," since data to be transmitted to the receiving side are stored in the transmission buffer, the RLC AM entity does not perform the polling procedure. According to other embodiments of the present invention, it is considered that the RLC AM entity performs the polling procedure considering the sequence number of the RLC PDU in addition to the status of the transmission buffer and the status of the retransmission buffer. Namely, in a state that data to be transmitted to the receiving side do not remain in the transmission buffer and the retransmission buffer, the polling procedure can be performed for each of the following cases: 1. When an AMD PDU stored in the retransmission buffer is transmitted, in case where the AMD PDU has the highest sequence number among AMD PDUs to be retransmitted; 2. When an AMD PDU stored in the retransmission buffer is transmitted, in case where the AMD PDU has the highest sequence number among AMD PDUs for which status report indicating that the receiving side has not received successfully the AMD PDUs is received; 3. When an AMD PDU stored in the retransmission buffer is transmitted, in case where the AMD PDU is generated most recently among AMD PDUs to be retransmitted; 4. When an AMD PDU stored in the retransmission buffer is transmitted, in case where the AMD PDU is generated most recently among AMD PDUs for which NACKs have been received from the receiving side; 5. When an AMD PDU is transmitted from the transmission buffer, in case where the AMD PDU is generated most recently; 6. When an AMD PDU is transmitted from the transmission buffer, in case where data to be trancemitted to the receiving side do not remain in the transmission buffer and the retransmission buffer any more; 7. When an AMD PDU is transmitted from the transmission buffer, in case where neither data to be transmitted to the receiving side nor AMD PDU to be retransmitted remain in the transmission buffer; 8. When an AMD PDU is transmitted from the transmission buffer, in case where neither data to be transmitted to the receiving side nor AMD PDU waiting for retransmission remain in the transmission buffer; 9. When an AMD PDU is transmitted from the transmission buffer, in case where data to be transmitted to the receiving side do not remain in the transmission buffer any more and at the same time an AMD PDU for which NACK has been received from the receiving side does not remain in the retransmission buffer; 10. When an AMD PDU is transmitted from the retransmission buffer, in case where the AMD PDU has the highest sequence number among the AMD PDUs to be retransmitted, and data to be transmitted to the receiving side do not remain in the transmission buffer; 11. When an AMD PDU is transmitted from the retransmission buffer, in case where the AMD PDU has the highest sequence number among the AMD PDUs for which NACKs have been received from the receiving side, and data to be transmitted to the receiving side do not remain in the transmission buffer; and 12. When an AMD PDU is transmitted from the retransmission buffer, in case where the AMD PDU is generated most recently among the AMD PDUs to be retransmitted, and data to be transmitted to the receiving side do not remain in the transmission buffer. FIG 8 is a diagram illustrating another embodiment of the present invention. In the embodiment of FIG. 8, an AM RLC entity performs a polling procedure at the time when sum of data included in AMD PDUs transmitted to the receiving side reaches a threshold value, which is previously set. Referring to FIG 8, supposing that PDU 1 to PDU 5 are transmitted to the receiving side in due order, sum of the data transmitted to the receiving side reaches a threshold value or greater at the time when PDU 5 is transmitted. At this time, the AM RLC entity performs the polling procedure. Namely, the AM RLC entity requests the receiving side to transmit the status report by setting a P field included in a header of PDU 5 to "1". If the polling procedure is performed once, sum of data calculated to trigger the polling procedure is calculated again from the beginning. Namely, in FIG 8, since sum of data exceeds the threshold value at the time when PDU 6 to PDU 13 are transmitted after the polling procedure is performed through PDU 5, the P field included in a header of PDU 13 is set to "I" again. The embodiment of FIG 8 can be achieved using a parameter named BYTE_SENT. Namely, BYTE_SENT is initiated to 0, and the RLC AM entity adds a size value of data included in an AMD PDU to BYTE_SENT whenever the AMD PDU is transmitted. The RLC AM entity performs the polling procedure by selling the P field included in the header of the AMD PDU transmitted at the time when BYTE_SENT exceeds the threshold value to "1". If the polling procedure is performed, the RLC AM entity resets BYTE_SENT to "0" and repeats the same procedure. If the size of the data included in the AMD PDU transmitted to the receiving . side is added to BYTE_SENT, various methods can be considered with respect to what value is taken as the size of the data. As described above, an AMD PDU includes a header part and a data field part, wherein the header part includes a fixed part and an extended part. Accordingly, a total size of the AMD PDU, a size of the data field part, or the size of the other part excluding the fixed part in the header could be the part added to the value BYTE_SENT. For example, if the size of the data included in the data field part of the AMD PDU is only considered when sum of the size of the data is calculated, the data field is aligned per 1 byte. Accordingly, a counter can be increased per 1 byte of the data field included in each AMD PDU, and the polling procedure can be performed at the time when the counter value calculated for the AMD PDUs transmitted to the receiving side exceeds a predetermined threshold. The aforementioned embodiments are achieved by combination of structural elements and features of the present invention in a predetermined type. Each of the structural elements or features should be considered selectively unless specified separately. Each of the structural elements or features may be carried out without being combined with other structural elements or features. Also, some structural elements and/or features may be combined with one another to constitute the embodiments of the present invention. The order of operations described in the embodiments of the present invention may be changed. Some structural elements or features of one embodiment may be included in another embodiment, or may be replaced with corresponding structural elements or features of another embodiment. Moreover, it will be apparent that some claims referring to specific claims may be combined with another claims referring to the other claims other than the specific claims to constitute the embodiment or add new claims by means of amendment after the application is filed. The embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or their combination. If the embodiment according to the present invention is implemented by hardware, the embodiment of the present invention may be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc. If the embodiment according to the present invention is implemented by firmware or software, the method of transmitting and receiving data in the wireless communication system according to the embodiment of the present invention may be implemented by a type of a module, a procedure, or a function, which performs functions or operations described as above. A software code may be stored in a memory unit and then may be driven by a processor. The memory unit may be located inside or outside the processor to transmit and receive data to and from the processor through various means which are well known. It will be apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit and essential characteristics of the invention. Thus, the above embodiments are to be considered in ail respects as illustrative and not restrictive. The scope of the invention should be determined by reasonable interpretation of the appended claims and all change which comes within the equivalent scope of the invention are included in the scope of the invention. INDUSTRIAL APPLICABILITY The present invention can be used in a wireless communication system such as a mobile communication system or a wireless Internet system. [CLAIMS] 1. A method of generating data blocks in a protocol layer performing a data retransmission function in a wireless communication system, the method comprising: receiving a first data block from an upper layer; and generating a second data block which includes a polling field set in accordance with statuses of a transmission buffer and a retransmission buffer and at least part of the first data block, wherein, in case that there are no data to be transmitted to a receiving side in the transmission buffer and the retransmission buffer, the polling field includes a value instructing the receiving side to transmit status report. 2. The method of claim 1, wherein a data block waiting for an acknowledgement from the receiving side is excluded when determining whether there are data to be transmitted to the receiving side in the retransmission buffer. 3. The method of claim 1, wherein the case where there are no data to be transmitted to the receiving side in the retransmission buffer includes a case where all data blocks for which retransmission request information has been received from the receiving side are retransmitted. 4. The method of claim 1, wherein the protocol layer is a radio link control (RLC) layer. 5. A method of transmitting data in a protocol layer performing a data retransmission function in a wireless communication system, the method comprising: receiving status report from a receiving side, the status report requesting retransmission with respect to a data block stored in a retransmission buffer; setting a polling field included in the data block in accordance with statuses of a transmission buffer and a retransmission buffer of the protocol layer; and transmitting the data block to the receiving side, wherein, in case that there are no data to be transmitted to a receiving side in the transmission buffer and the retransmission buffer after transmission of the data block, the polling field includes a value instructing the receiving side to transmit status report. 6. The method of claim 5, wherein a data block waiting for an acknowledgement from the receiving side is excluded when determining whether there are data to be transmitted to the receiving side in the retransmission buffer. 7. A method of performing a polling procedure in a protocol layer performing a data retransmission function in a wireless communication system, the method comprising: checking statuses of a transmission buffer and a retransmission buffer of the protocol layer; and performing a polling procedure for requesting a receiving side to transmit status report if there are no data to be transmitted to the receiving side in both the transmission buffer and the retransmission buffer. 8. The method of claim 7, wherein performing the polling procedure comprises: setting a polling field of a data block to be transmitted to the receiving field to a specific value; and transmitting the data block to the receiving side. 9. The method of claim 8, wherein a data block waiting for an acknowledgement from the receiving side is excluded when determining whether there are data to be transmitted to the receiving side in the retransmission buffer. 10. A method of performing a polling procedure in a protocol layer performing a data retransmission function in a wireless communication system, the method comprising: generating a data block including a header part and a data field part; checking whether sum of a size of data included in at least one data block transmitted to a receiving side and a size of data included in the generated data block exceeds a predetermined threshold; and performing a polling procedure if the sum of the sizes of the data exceeds the threshold value. 11. The method of claim 10, wherein the size of data included in data field parts of the at least one data block and the generated data block is only considered when the sum of the sizes of the data is calculated. 12. The method of claim 10, wherein the polling procedure is performed by setting a polling field included in a header of the generated data block to a specific value. A method of generating a data block for performing a polling procedure in a wireless communication system, a method of transmitting data and a method of performing a polling procedure are disclosed. A protocol layer performs the polling procedure for requesting a receiving side to transmit status report if there are no data to be transmitted to the receiving side in both a transmission buffer and a retransmission buffer. When determining whether there are no data to be transmitted to the receiving side in the retransmission buffer, it is preferable that a data block for which retransmission request information is not received from the receiving side is excluded.

Full Text

A METHOD OF PERFORMING POLLING PROCEDURE
IN A WIRELESS COMMUNICATION SYSTEM
[DESCRIPTION]
TECHNICAL FIELD
The present invention relates to a wireless communication system, and more
particularly, to a method of generating a data block for performing a polling procedure
in a wireless communication system, a method of transmitting data and a method of
performing a polling procedure.
BACKGROUND ART
Various types of data retransmission methods can be used to ensure certainty of
data transmission to a receiving side in a wireless communication system. Particularly,
the need to use a retransmission method increases when the receiving side should
necessarily receive non-real time packet data such as signaling data or TCP/IP data.
An example of the data transmission method used in the wireless
communication system will be described as follows. The receiving side transmits a
status report to a transmitting side to report that at least one or more data blocks
transmitted from the transmitting side have been successfully received. The transmitting
side retransmits data blocks that the receiving side has failed to receive, to the receiving
side using the status report. For application of the retransmission method, data which
have been transmitted once should be stored in a buffer for a certain time period without
discard. Accordingly, a transmission buffer and a retransmission buffer are required,
wherein data which have never been transmitted to the receiving side are stored in the
transmission buffer and data which have been transmitted to the receiving side but need
to be on standby for retransmission are stored in the retransmission buffer.
The transmitting side can request the receiving side to transmit the status report.
This procedure is referred to as a polling procedure. If the status report transmitted from
the receiving side is lost during transmission or the receiving side does not transmit the
status report to the transmitting side timely, the transmitting side can perform the
polling procedure. Alternatively, the transmitting side can perform the polling procedure
periodically.
DISCLOSURE OF THE INVENTION
A transmitting side has to use additional radio resources to perform a polling
procedure. Accordingly, for efficient use of radio resources, the polling procedure
should be prevented from being used unnecessarily. To this end, reasonable standards as
to when the transmitting side should perform the polling procedure are required.
Accordingly, the present invention is directed to a method of generating a data
block for performing a polling procedure in a wireless communication system, a method
of transmitting data and a method of performing a polling procedure, which
substantially obviate one or more problems due to limitations and disadvantages of the
related art.
An object of the present invention is to provide a method of generating a data
block for performing a polling procedure in a wireless communication system, a method
of transmitting data and a method of performing a polling procedure, in which the
polling procedure is performed while radio resources are being used efficiently.
Another object of the present invention is to provide a method of generating a
data block for performing a polling procedure in a wireless communication system, a
method of transmitting data and a method of performing a polling procedure, in which a
transmitting side performs the polling procedure timely to prevent communication from
being stopped unexpectedly.
In a wireless communication system, a data retransmission function is
performed by a specific protocol layer. To perform the data retransmission function, the
protocol layer is equipped with a transmission buffer and a retransmission buffer. The
protocol layer can determine whether to perform a polling procedure considering
statuses of the transmission buffer and the retransmission buffer, i.e., the amount of data
stored in the transmission buffer and the retransmission buffer.
In one aspect of the present invention, the protocol layer performs the polling
procedure for requesting a receiving side to transmit a status report if there are no data
to be transmitted to the receiving side in both the transmission buffer and the
retransmission buffer. When determining whether there are no data to be transmitted to
the receiving side in the retransmission buffer, it is preferable that a data block for
which retransmission request information is not received from the receiving side is
excluded.
In another aspect of the present invention, the protocol layer performs the
polling procedure considering the amount of data transmitted to the receiving side.
Namely, the protocol layer performs the polling procedure if the amount of data
transmitted to the receiving side reaches a certain level or greater. This procedure can be
performed repeatedly.
According to the present invention, radio resources can efficiently be used
during the polling procedure, and the transmitting side can perform the polling
procedure timely, whereby communication can be prevented from being slopped
unexpectedly.
BRIEF DESCRIPTION OF THE 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
application, illustrate embodiments of the invention and together with the description
serve to explain the principles of the invention.
FIG 1 is a diagram illustrating a network structure of an E-UMTS (Evolved
Universal Mobile Telecommunications System);
FIG. 2 is a schematic view illustrating an E-UTRAN (Evolved Universal
Terrestrial Radio Access Network);
FIG. 3A and FIG 3B are diagrams illustrating a structure of a radio interface
protocol between a user equipment (UE) and E-UTRAN, in which FIG 3A is a
schematic view of a control plane protocol and FIG. 3B is a schematic view of a user
plane protocol;
FIG 4 is a diagram illustrating an example of a functional block of RLC AM
entity;
FIG 5 is a diagram illustrating a basic structure of AMD PDU;
FIG 6 is a flow chart illustrating a procedure according to one embodiment of
the present invention;
FIG 7 is a diagram illustrating the embodiment of FIG 6 in view of another
aspect; and
FIG 8 is a diagram illustrating another embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, structures, operations, and other features of the present invention
will be understood readily by the preferred embodiments of the present invention,
examples of which are illustrated in the accompanying drawings. Embodiments
described later are examples in which technical features of the present invention are
applied to an E-UMTS (Evolved Universal Mobile Telecommunications System).
However, it should be noted that an embodiment of the present invention can be applied
to a wireless communication system other that the E-UMTS.
FIG. 1 is a diagram illustrating a network structure of an E-UMTS. An E-
UMTS is a system evolving from the conventional WCDMA UMTS and its basic
standardization is currently handled by the 3GPP (3rd Generation Partnership Project).
The E-UMTS can also be called an LTE (Long Term Evolution) system.
Referring to FIG. 1, an E-UTRAN includes base stations (hereinafter, referred
to as 'eNode B' or 'eNB'), wherein respective eNBs are connected with each other
through X2 interface. Also, each of eNBs is connected with a user equipment (UE)
through a radio interface and connected with EPC (Evolved Packet Core) through SI
interface. The EPC includes a mobility management entity/system architecture
evolution (MME/SAE) gateway.
Layers of a radio interface protocol between a user equipment and a network
can be classified into a first layer L1, a second layer L2 and a third layer L3 based on
three lower layers of OSI (open system interconnection) standard model widely known
in communication systems. A physical layer belonging to the first layer L1 provides
an information transfer service using a physical channel. A radio resource control
(hereinafter abbreviated as 'RRC') located at the third layer plays a role in controlling
radio resources between the user equipment and the network. For this, the RRC layer
enables RRC messages to be exchanged between the UE and the network. The RRC
layer can be distributively located at network nodes including Node B, an AG and the
like or can be independently located at either the Node B or the AG.
FIG. 2 is a schematic view illustrating an E-UTRAN (Evolved Universal
Terrestrial Radio Access Network). In FIG. 2, a hatching part represents functional
entities of a user plane, and a non-hatching part represents functional entities of a
control plane.
FIG. 3A and FIG. 3B illustrate a structure of a radio interface protocol between
the user equipment (UE) and the E-UTRAN, in which FIG. 3A is a schematic view of a
control plane protocol and FIG. 3B is a schematic view of a user plane protocol.
Referring to FIG. 3A and FIG 3B, a radio interface protocol horizontally includes a
physical layer, a data link layer, and a network layer, and vertically includes a user plane
for data information transfer and a control plane for signaling transfer. The protocol
layers in FIG. 3A and FIG. 3B can be classified into LI (first iayer), L2 (second layer),
and L3 (third layer) based on three lower layers of the open system interconnection
(OSI) standard model widely known in the communications systems.
The physical layer as the first layer provides an information transfer service to
an upper layer using physical channels. The physical layer (PHY) is connected to a
medium access control (hereinafter, abbreviated as 'MAC') layer above the physical
layer via transport channels. Data are transferred between the medium access control
layer and the physical layer via the transport channels. Moreover, data are transferred
between different physical layers, and more particularly, between one physical layer of a
transmitting side and the other physical layer of a receiving side via the physical
channels. The physical channel of the E-UMTS is modulated in accordance with an
orthogonal frequency division multiplexing (OFDM) scheme, and time and frequency
are used as radio resources.
The medium access control (hereinafter, abbreviated as ;MAC) layer of the
second layer provides a service to a radio link control (hereinafter, abbreviated as
'RLC') layer above the MAC layer via logical channels. The RLC layer of the second
layer supports reliable data transfer. In order to effectively transmit data using IP
packets (e.g., IPv4 or IPv6) within a radio-communication period having a narrow
bandwidth, a PDCP layer of the second layer (L2) performs header compression to
reduce the size of unnecessary control information.
A radio resource control (hereinafter, abbreviated as 'RRC) layer located on a
lowest part of the third layer is defined in the control plane only and is associated with
configuration, reconfiguration and release of radio bearers (hereinafter, abbreviated as
'RBs') to be in charge of controlling the logical, transport and physical channels. In
this case, the RB means a service provided by the second layer for the data transfer
between the user equipment and the UTRAN.
Examples of downlink transport channels carrying data from the network to the
user equipments include a broadcast channel (BCH) carrying system information, a
paging channel (PCH) carrying paging message, and a downlink shared channel (SCH)
carrying user traffic or control messages. The traffic or control messages of a
downlink multicast or broadcast service can be transmitted via the downlink SCH or an
additional downlink multicast channel (MCH). Meanwhile, examples of uplink
transport channels carrying data from the user equipments to the network include a
random access channel (RACH) carrying an initial control message and an uplink
shared channel (UL-SCH) carrying user traffic or controi message.
Examples of logical channels located above the transport channels and mapped
with the transport channels include a broadcast control channel (BCCH), a paging
control channel (PCCH), a common control channel (CCCH), a multicast control
channel (MCCH), and a multicast traffic channel (MTCH).
As described above, the RLC layer of the second layer supports reliable data
transfer. Also, the RLC layer serves to perform segmentation and/or concatenation for
data received from its upper layer to control a size of the data so that the lower layer can
transmit the data to a radio interval. Also, in order to ensure various quality of services
(QoS) required by each radio bearer, the RLC layer of the second layer provides three
types of operation modes, transparent mode (TM), un-acknowledged mode (UM), and
an acknowledged mode (AM). Particularly, the AM RLC layer performs a
retransmission function through an automatic repeat and request (ARQ) function for
reliable data transmission. Hereinafter, the UM mode and the AM mode of the RLC
layer will be described in more detail.
The UM RLC layer transmits PDUs by adding a PDU header to each PDU, so
that the receiving side can identify what PDU has been lost during transmission,
wherein the PDU header includes a sequence number (hereinafter, abbreviated as "SN").
In accordance with this function, the UM RLC layer mainly serves to transmit
broadcast/multicast data or real-time data such as voice (for example, VoIP) or
streaming of a packet service domain (hereinafter, abbreviated as "PS domain") in a
user plane. Also, the UM RLC layer serves to transmit RRC message, which does not
need acknowledgement, among RRC messages transmitted to a specific user equipment
or a specific user equipment group within a cell, in a control plane.
Like the UM RLC layer, the AM RLC layer constitutes RLC PDUs by adding a
PDU header including SN thereto. However, the AM RLC layer is different from the
UM RLC layer in that the receiving side performs acknowledgement in response to the
PDUs transmitted from the transmitting side. The reason why the receiving side
performs acknowledgement in the AM RLC layer is to request the transmitting side to
re-transmit PDU which the receiving side has not received. This retransmission function
is a main feature of the AM RLC layer. Accordingly, the AM RLC layer is to ensure
error-free data transmission through re-transmission. For this reason, the AM RLC layer
serves to transmit unreal time packet data such as TCP/IP of the PS domain in the user
plane. Also, the AM RLC layer serves to transmit RRC message, which necessarily
requires acknowledgement, among the RRC messages transmitted to a specific user
equipment within a cell, in the control plane.
In view of a directional aspect, the UM RLC layer is used for uni-directional
communication whereas the AM RLC layer is used for bi-directional communication
due to a feedback from the receiving side. The UM RLC layer is also different from the
AM RLC layer in view of a structural aspect. Namely, although the UM RLC layer
allows one RLC entity to perform a transmission function or a receiving function, the
AM RLC layer allows both an entity performing a transmission function and an entity
performing a receiving function to exist in one RLC entity.
The reason why that the AM RLC layer is complicated is caused by a
retransmission function. For retransmission management, the AM RLC entity includes a
retransmission buffer in addition to a transmission buffer and uses a transmission and
reception window for flow control. The AM RLC entity of the transmitting side
performs a polling procedure to request a peer RLC entity of the receiving side to
transmit a status report, and the receiving side transmits the status report to the
transmitting side to report reception acknowledgement information. Also, the AM RLC
entity performs a function constituting a status PDU to transfer the status report.
The AM RLC entity supports the aforementioned functions using a plurality of
protocol parameters, status parameters, timers, etc. In the AM RLC layer, PDUs used to
control transmission of data such as status report or status PDU will be referred to as
control PDUs, and PDUs used to transfer user data will be referred to as data PDUs.
As described above, the AM RLC entity of the transmitting side includes two
buffers, i.e., a transmission buffer and a retransmission buffer. Data which have not yet
been included in RLC PDU, among data transferred from an upper entity, are stored in
the transmission buffer. RLC PDU transferred to a lower entity is stored in the
retransmission buffer until the receiving side acknowledges that the RLC PDU has been
successfully received therein.
FIG. 4 is a diagram illustrating an example of a functional block of the RLC
AM entity.
Referring to FIG 4, an RLC SDU (Service Data Unit) transferred from the
upper layer (RRC layer or PDCP sub-layer) is stored in a transmission buffer 41. A
segmentation/concatenation module 42 performs segmentation and/or concatenation for
at least one RLC SDU transferred from the transmission buffer 41. Segmentation and/or
concatenation is performed at a specific transmission opportunity in accordance with a
transport block size reported from the lower layer. As a result, the RLC PDU generated
by the RLC AM entity can have a size desired by the lower layer. An RLC header
adding module 43 adds an RLC header to a data block transferred from the
segmentation/concatenation module 42. An RLC AMD PDU is generated as the RLC
PDU header is added to the data block.
FIG. 5 is a diagram illustrating a basic structure of the AMD PDU. The AMD
PDU includes a PDU header part and a data field part. The header can include a fixed
part and an extended part, wherein the fixed part exists in every AMD PDU and the
extended part is included in the AMD PDU only if necessary. The extended part is
included in the AMD PDU if one or more data field elements exist in the AMD PDU.
The fixed part includes a D/C field, a re-segmentation flag (RF) field, a polling
(P) field, a framing info (Fl) field, an extension bit (E) field and a sequence number
(SN) field. The D/C field includes information identifying whether a corresponding
AMD PDU is a data PDU or a control PDU. The RF field includes information
indicating whether a corresponding RLC PDU is a single perfect AMD PDU or a part of
another AMD PDU. The polling field includes information indicating whether the AM
RLC entity of the transmitting side will request the peer AM RLC entity of the receiving
side to transmit status report. The Fl field includes information indicating that the RLC
SDU included in the AMD PDU has been segmented from a start part and/or an end part
of the data field. The E field includes information indicating whether the data field starts
behind the fixed part or whether additional E field and LI field follow behind the fixed
part. The SN field includes a sequence number of the AMD PDU.
Referring to FIG. 4 again, the AMD PDU generated as the header is added by
the RLC header adding module 43 is transferred to the lower layer, for example, a MAC
layer. Before the AMD PDU is transferred to the lower layer, additional procedure such
as ciphering can be performed for the AMD PDU if necessary. The AMD PDU
transferred to the lower layer is stored in the retransmission buffer 44 to perform a
retransmission function.
If the RLC AM entity performs a receiving function, a routing module 46
performs routing for the received RLC PDU in accordance with a type of the RLC PDU,
so as to transfer a control PDU to an RLC control module 45 and an AMD PDU to a
receiving buffer/HARQ reordering module 47. The receiving buffer/HARQ reordering
module 47 stores AMD PDUs transferred from the routing module 46, and aligns them
in the order of SN if they are not received in the order of SN. An RLC header removing
module 48 removes the RLC header from the AMD PDU and transfers the resultant data
to an SDU reassembly module 49. The SDU reassembly module 49 reassembles at least
one or more RLC SDUs using the data transferred from the RLC header removing
module and then transfers the resultant data to the upper layer.
The RLC AM entity of the receiving side transfers the status report lo the
transmitting side through the status PDU to report whether the at least one or more RLC
PDUs transmitted from the transmitting side have been successfully received.
FIG. 6 is a flow chart illustrating a procedure according to one embodiment of
the present invention. The embodiment of FIG. 6 relates to an example of determining
whether the RLC AM entity performs a polling procedure in accordance with the
statuses of the transmission buffer and the retransmission buffer. Namely, if there are
no data to be transmitted to the receiving side in both the transmission buffer and the
retransmission buffer, the RLC AM entity performs the polling procedure to request the
receiving side to transmit the status report. When determining whether there are data to
be transmitted to the receiving side in the retransmission buffer, a data block for which
etransmission request information is not received from the receiving side is excluded.
Referring to FIG. 4 and FIG. 6, the AM RLC entity checks the status of the
ransmission buffer 41 [S61] and identifies whether data to be transmitted to the
receiving side are stored in the transmission buffer 4] [S62]. If the data to be
transmitted to the receiving side are stored in the transmission buffer 41, the AM RLC
entity does not perform the polling procedure. Namely, the AM RLC entity sets the P
field to "0," wherein the P field exists in a header of the AMD PDU to be transmitted to
the receiving side [S66]. If the P field receives the AMD PDU set to "0," the receiving
side regards that the transmitting side does not request transmission of the status report.
If the data to be transmitted to the receiving side are not stored in the
transmission buffer 41, i.e., if the transmission buffer 41 is empty, the AM RLC entity
checks the status of the retransmission buffer 44 [S63] to identify whether data to be
transmitted to the receiving side are stored in the retransmission buffer [S64]. When
determining whether the data to be transmitted to the receiving side are stored in the
retransmission buffer 44, a data block for which retransmission request information is
not received from the receiving side is excluded. In other words, even though at least
one RLC PDU is stored in the retransmission buffer 44, if the status report or
acknowledgement for the at least one RLC PDU is not received from the receiving side,
it is regarded that the retransmission buffer 44 is empty.
In step S64, if the data to be transmitted to the receiving side are stored in the
retransmission buffer 44, the AM RLC entity does not perform the polling procedure.
Namely, the AM RLC entity sets the P field to "0," wherein the P field exists in the
header of the AMD PDU to be transmitted to the receiving side [S66].
If the data to be transmitted to the receiving side are not stored in the
retransmission buffer 44, the AM RLC entity performs the polling procedure. Namely,
the AM RLC entity sets the P field to "1," wherein the P field exists in the header of the
AMD PDU to be transmitted to the receiving side [S65]. If the P field receives the AMD
PDU set to "1", the receiving side regards that the transmitting side requests
transmission of the status report, and transmits to the transmitting side the status report
for at least one RLC PDU received from the transmitting side.
In the embodiment of FIG. 6, although the status of the retransmission buffer
has been checked after the status of the transmission buffer is checked, this checking
order may be changed. Namely, the status of the transmission buffer may be checked
after the status of the retransmission buffer is checked. Also, the status of the
transmission buffer and the status of the retransmission buffer may simultaneously be
checked.
FIG. 7 is a diagram illustrating the embodiment of FIG. 6 in view of another
aspect. In FIG. 7, a horizontal axis is a lime axis, and a vertical axis represents the
amount of data stored in the transmission buffer and the retransmission buffer.
Although the transmission buffer is empty at a timing point "A," since data to be
transmitted to the receiving side are stored in the retransmission buffer, the polling
procedure is not triggered. The data to be transmitted to the receiving side will not
remain in the transmission buffer and the retransmission buffer at a timing point "B" At
this time, the AM RLC layer performs the polling procedure.
There are no data to be transmitted to the receiving side in the transmission
buffer at a timing point "C" but at least one RLC PDU is stored in the retransmission
buffer. However, if acknowledgements for the at least one RLC PDU stored in the
retransmission buffer is not received from the receiving side, it is regarded that there are
no data to be transmitted to the receiving side in the retransmission buffer. Accordingly,
the RLC AM entity performs the polling procedure even at the timing point "C."
Although the retransmission buffer is empty at a timing point "D," since data to be
transmitted to the receiving side are stored in the transmission buffer, the RLC AM
entity does not perform the polling procedure.
According to other embodiments of the present invention, it is considered that
the RLC AM entity performs the polling procedure considering the sequence number of
the RLC PDU in addition to the status of the transmission buffer and the status of the
retransmission buffer. Namely, in a state that data to be transmitted to the receiving side
do not remain in the transmission buffer and the retransmission buffer, the polling
procedure can be performed for each of the following cases:
1. When an AMD PDU stored in the retransmission buffer is transmitted, in
case where the AMD PDU has the highest sequence number among AMD PDUs to be
retransmitted;
2. When an AMD PDU stored in the retransmission buffer is transmitted, in
case where the AMD PDU has the highest sequence number among AMD PDUs for
which status report indicating that the receiving side has not received successfully the
AMD PDUs is received;
3. When an AMD PDU stored in the retransmission buffer is transmitted, in
case where the AMD PDU is generated most recently among AMD PDUs to be
retransmitted;
4. When an AMD PDU stored in the retransmission buffer is transmitted, in
case where the AMD PDU is generated most recently among AMD PDUs for which
NACKs have been received from the receiving side;
5. When an AMD PDU is transmitted from the transmission buffer, in case
where the AMD PDU is generated most recently;
6. When an AMD PDU is transmitted from the transmission buffer, in case
where data to be trancemitted to the receiving side do not remain in the transmission
buffer and the retransmission buffer any more;
7. When an AMD PDU is transmitted from the transmission buffer, in case
where neither data to be transmitted to the receiving side nor AMD PDU to be
retransmitted remain in the transmission buffer;
8. When an AMD PDU is transmitted from the transmission buffer, in case
where neither data to be transmitted to the receiving side nor AMD PDU waiting for
retransmission remain in the transmission buffer;
9. When an AMD PDU is transmitted from the transmission buffer, in case
where data to be transmitted to the receiving side do not remain in the transmission
buffer any more and at the same time an AMD PDU for which NACK has been received
from the receiving side does not remain in the retransmission buffer;
10. When an AMD PDU is transmitted from the retransmission buffer, in case
where the AMD PDU has the highest sequence number among the AMD PDUs to be
retransmitted, and data to be transmitted to the receiving side do not remain in the
transmission buffer;
11. When an AMD PDU is transmitted from the retransmission buffer, in case
where the AMD PDU has the highest sequence number among the AMD PDUs for
which NACKs have been received from the receiving side, and data to be transmitted to
the receiving side do not remain in the transmission buffer; and
12. When an AMD PDU is transmitted from the retransmission buffer, in case
where the AMD PDU is generated most recently among the AMD PDUs to be
retransmitted, and data to be transmitted to the receiving side do not remain in the
transmission buffer.
FIG 8 is a diagram illustrating another embodiment of the present invention. In
the embodiment of FIG. 8, an AM RLC entity performs a polling procedure at the time
when sum of data included in AMD PDUs transmitted to the receiving side reaches a
threshold value, which is previously set.
Referring to FIG 8, supposing that PDU 1 to PDU 5 are transmitted to the
receiving side in due order, sum of the data transmitted to the receiving side reaches a
threshold value or greater at the time when PDU 5 is transmitted. At this time, the AM
RLC entity performs the polling procedure. Namely, the AM RLC entity requests the
receiving side to transmit the status report by setting a P field included in a header of
PDU 5 to "1".
If the polling procedure is performed once, sum of data calculated to trigger the
polling procedure is calculated again from the beginning. Namely, in FIG 8, since sum
of data exceeds the threshold value at the time when PDU 6 to PDU 13 are transmitted
after the polling procedure is performed through PDU 5, the P field included in a header
of PDU 13 is set to "I" again.
The embodiment of FIG 8 can be achieved using a parameter named
BYTE_SENT. Namely, BYTE_SENT is initiated to 0, and the RLC AM entity adds a
size value of data included in an AMD PDU to BYTE_SENT whenever the AMD PDU
is transmitted. The RLC AM entity performs the polling procedure by selling the P field
included in the header of the AMD PDU transmitted at the time when BYTE_SENT
exceeds the threshold value to "1". If the polling procedure is performed, the RLC AM
entity resets BYTE_SENT to "0" and repeats the same procedure.
If the size of the data included in the AMD PDU transmitted to the receiving
. side is added to BYTE_SENT, various methods can be considered with respect to what
value is taken as the size of the data. As described above, an AMD PDU includes a
header part and a data field part, wherein the header part includes a fixed part and an
extended part. Accordingly, a total size of the AMD PDU, a size of the data field part, or
the size of the other part excluding the fixed part in the header could be the part added
to the value BYTE_SENT.
For example, if the size of the data included in the data field part of the AMD
PDU is only considered when sum of the size of the data is calculated, the data field is
aligned per 1 byte. Accordingly, a counter can be increased per 1 byte of the data field
included in each AMD PDU, and the polling procedure can be performed at the time
when the counter value calculated for the AMD PDUs transmitted to the receiving side
exceeds a predetermined threshold.
The aforementioned embodiments are achieved by combination of structural
elements and features of the present invention in a predetermined type. Each of the
structural elements or features should be considered selectively unless specified
separately. Each of the structural elements or features may be carried out without being
combined with other structural elements or features. Also, some structural elements
and/or features may be combined with one another to constitute the embodiments of the
present invention. The order of operations described in the embodiments of the
present invention may be changed. Some structural elements or features of one
embodiment may be included in another embodiment, or may be replaced with
corresponding structural elements or features of another embodiment. Moreover, it will
be apparent that some claims referring to specific claims may be combined with another
claims referring to the other claims other than the specific claims to constitute the
embodiment or add new claims by means of amendment after the application is filed.
The embodiments according to the present invention may be implemented by
various means, for example, hardware, firmware, software, or their combination. If the
embodiment according to the present invention is implemented by hardware, the
embodiment of the present invention may be implemented by one or more application
specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal
processing devices (DSPDs), programmable logic devices (PLDs), field programmable
gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc.
If the embodiment according to the present invention is implemented by
firmware or software, the method of transmitting and receiving data in the wireless
communication system according to the embodiment of the present invention may be
implemented by a type of a module, a procedure, or a function, which performs
functions or operations described as above. A software code may be stored in a memory
unit and then may be driven by a processor. The memory unit may be located inside or
outside the processor to transmit and receive data to and from the processor through
various means which are well known.
It will be apparent to those skilled in the art that the present invention can be
embodied in other specific forms without departing from the spirit and essential
characteristics of the invention. Thus, the above embodiments are to be considered in
ail respects as illustrative and not restrictive. The scope of the invention should be
determined by reasonable interpretation of the appended claims and all change which
comes within the equivalent scope of the invention are included in the scope of the
invention.
INDUSTRIAL APPLICABILITY
The present invention can be used in a wireless communication system such as
a mobile communication system or a wireless Internet system.
[CLAIMS]
1. A method of generating data blocks in a protocol layer performing a data
retransmission function in a wireless communication system, the method comprising:
receiving a first data block from an upper layer; and
generating a second data block which includes a polling field set in accordance
with statuses of a transmission buffer and a retransmission buffer and at least part of the
first data block,
wherein, in case that there are no data to be transmitted to a receiving side in
the transmission buffer and the retransmission buffer, the polling field includes a value
instructing the receiving side to transmit status report.
2. The method of claim 1, wherein a data block waiting for an
acknowledgement from the receiving side is excluded when determining whether there
are data to be transmitted to the receiving side in the retransmission buffer.
3. The method of claim 1, wherein the case where there are no data to be
transmitted to the receiving side in the retransmission buffer includes a case where all
data blocks for which retransmission request information has been received from the
receiving side are retransmitted.
4. The method of claim 1, wherein the protocol layer is a radio link control
(RLC) layer.
5. A method of transmitting data in a protocol layer performing a data
retransmission function in a wireless communication system, the method comprising:
receiving status report from a receiving side, the status report requesting
retransmission with respect to a data block stored in a retransmission buffer;
setting a polling field included in the data block in accordance with statuses of
a transmission buffer and a retransmission buffer of the protocol layer; and
transmitting the data block to the receiving side,
wherein, in case that there are no data to be transmitted to a receiving side in
the transmission buffer and the retransmission buffer after transmission of the data
block, the polling field includes a value instructing the receiving side to transmit status
report.
6. The method of claim 5, wherein a data block waiting for an
acknowledgement from the receiving side is excluded when determining whether there
are data to be transmitted to the receiving side in the retransmission buffer.
7. A method of performing a polling procedure in a protocol layer performing a
data retransmission function in a wireless communication system, the method
comprising:
checking statuses of a transmission buffer and a retransmission buffer of the
protocol layer; and
performing a polling procedure for requesting a receiving side to transmit
status report if there are no data to be transmitted to the receiving side in both the
transmission buffer and the retransmission buffer.
8. The method of claim 7, wherein performing the polling procedure
comprises:
setting a polling field of a data block to be transmitted to the receiving field to
a specific value; and
transmitting the data block to the receiving side.
9. The method of claim 8, wherein a data block waiting for an
acknowledgement from the receiving side is excluded when determining whether there
are data to be transmitted to the receiving side in the retransmission buffer.
10. A method of performing a polling procedure in a protocol layer performing
a data retransmission function in a wireless communication system, the method
comprising:
generating a data block including a header part and a data field part;
checking whether sum of a size of data included in at least one data block
transmitted to a receiving side and a size of data included in the generated data block
exceeds a predetermined threshold; and
performing a polling procedure if the sum of the sizes of the data exceeds the
threshold value.
11. The method of claim 10, wherein the size of data included in data field
parts of the at least one data block and the generated data block is only considered when
the sum of the sizes of the data is calculated.
12. The method of claim 10, wherein the polling procedure is performed by
setting a polling field included in a header of the generated data block to a specific
value.

A method of generating a data block for performing a polling procedure in a wireless communication system, a
method of transmitting data and a method of performing a polling procedure are disclosed. A protocol layer performs the polling
procedure for requesting a receiving side to transmit status report if there are no data to be transmitted to the receiving side in both a
transmission buffer and a retransmission buffer. When determining whether there are no data to be transmitted to the receiving side
in the retransmission buffer, it is preferable that a data block for which retransmission request information is not received from the
receiving side is excluded.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=6po/d/sDsscVc5UqTPLcNw==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

271564

Indian Patent Application Number

963/KOLNP/2010

PG Journal Number

09/2016

Publication Date

26-Feb-2016

Grant Date

25-Feb-2016

Date of Filing

15-Mar-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	PARK, SUNG JUN	LG INSTITUTE, HOGYE 1(IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO, 431-080 REPUBLIC OF KOREA
2	LEE, YOUNG DAE	LG INSTITUTE, HOGYE 1(IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO, 431-080 REPUBLIC OF KOREA
3	YI, SEUNG JUNE	LG INSTITUTE, HOGYE 1(IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO, 431-080 REPUBLIC OF KOREA
4	CHUN, SUNG DUCK	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/KR2008/005485

PCT International Filing date

2008-09-17

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/973,442	2007-09-18	U.S.A.
2	60/981,807	2007-10-22	U.S.A.
3	10-2008-0084996	2008-08-29	U.S.A.