Title of Invention	A METHOD FOR PERFORMING CHANNEL ASSIGNMENT IN A BASE STATION FOR A MOBILE COMMUNICATION SYSTEM
Abstract	The invention relates to a a method for performing channel assignment in a base station for a mobile communication system. Upon receipt of a request for assigning a channel to a mobile station, a base station transceiver system (BTS) generates a connect message including channel information, which indicates a Walsh code,out of 256 Walsh codes to be used for a channel to be assigned to the mobile station, and a quasi-orthogonal function (QOF) index . The BTS transmits the generated connect message to a base station controller (BSC). The BSC generates a connect ACK message for acknowledging the channel assignment—related information included in the connect message and transmits the generated connect ACK message to the BTS. Upon receipt of the connect ACK message, in the BTS assigns the channel that was acknowledged by the BSC to the mobile station.

Title of Invention

A METHOD FOR PERFORMING CHANNEL ASSIGNMENT IN A BASE STATION FOR A MOBILE COMMUNICATION SYSTEM

Abstract

The invention relates to a a method for performing channel assignment in a base station for a mobile communication system. Upon receipt of a request for assigning a channel to a mobile station, a base station transceiver system (BTS) generates a connect message including channel information, which indicates a Walsh code,out of 256 Walsh codes to be used for a channel to be assigned to the mobile station, and a quasi-orthogonal function (QOF) index . The BTS transmits the generated connect message to a base station controller (BSC). The BSC generates a connect ACK message for acknowledging the channel assignment—related information included in the connect message and transmits the generated connect ACK message to the BTS. Upon receipt of the connect ACK message, in the BTS assigns the channel that was acknowledged by the BSC to the mobile station.

Full Text	CHANNEL ASSIGNMENT METHOD FOR A BASE STATION IN A MOBILE COMMUNICATION SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a CDMA (Code Division Multiple Access) mobile communication system, and in particular, to a method for providing 4 quasi-orthogonal functions (QOF), which are used in association with 256 Walsh codes in a forward link, in a base station transceiver system (BTS) and a base station controller (BSC). 2. Description of the Related Art Existing IS-95A/B CDMA communication systems spread a radio channel with a Walsh function. However, as the 1S-2000 standard introduces new channels to the forward and reverse links, the existing conventional communication system lacks the necessary amount of Walsh codes to maintain orthogonality between channels Accordingly, there is a need for a method for increasing the number of the channels, without decreasing the orthogonality between the existing channels. For the IS-2000 forward link, several methods have been proposed. One method is to define a quasi-orthogonal function (QOF) necessary for the mobile station thereby to assign 4 times the channels as compared with the case when the existing Walsh function is used, and another method is to expand the existing Walsh function which can generate 64 Walsh codes, so as to generate 256 Walsh codes. The quasi- orthogonal function (QOF) is commonly applied to IS-2000 forward channels, such as the fundamental channel (FCH), the dedicated control channel (DCCH) and the supplemental channel (SCH). However, existing base stations can only support 64 Walsh code channels. Now, reference will be made to the types of the channels used in the IMT- 2000 standard . Every channel is divided into a physical channel and a logical channel. The logical channel is established over the physical channel, and several logical channels can be established on a single physical channel. If the physical channel is released, the logical channel established over the physical channel is automatically released. It is not necessary to establish another physical channel in order to establish a certain logical channel. When a physical channel to be established for a logical channel is already established for another logical channel, the only required operation is to assign this logical channel to the previously established physical channel. The physical channel can be divided into dedicated channels and common channels according to its characteristics. Dedicated channels are exclusively used for communication between the BTS and a particular mobile station (MS), and include a fundamental channel (FCH), a dedicated control channel (DCCH) and a supplemental channel (SCH). The fundamental channel is used to transmit voice, data and signaling signals. Such a fundamental channel is compatible with TIA/EIA-95-B. The dedicated control channel is used to transmit data and signaling signals. The dedicated control channel supports a discontinuous transmission (DTX) mode in which data is only transmitted when the upper layer generates transmission data. Because of this property, the dedicated control channel is suitable for effectively providing a packet service. The supplemental channel is used to transmit large amounts of data. In addition to the dedicated channels stated above, the physical channel includes a common channel which is used in common by the base station and several mobile stations. A physical channel for the forward link transmitted from the BTS to the MS is called a paging channel, and a physical channel for the reverse link transmitted form the MS to the BTS is called an access channel. These common channels are compatible with IS-95B. The logical channels to be assigned on the above physical channels include a dedicated signaling channel (dsch) and a dedicated traffic channel (dtch). The dedicated signaling channel can be assigned to the fundamental channel and the dedicated control channel, which are physical channels. The dedicated traffic channel can be assigned to the fundamental channel, the dedicated control channel and the supplemental channel. The dedicated signaling channel is used when the base station and the mobile station exchange a control signal. The dedicated traffic channel is used when the base station and the mobile station exchange user data. The common logical channel to be assigned on the common physical channel is divided into a common signaling channel (csch) used to transmit control signal, and a common traffic channel (ctch) use to transmit user data. The common logical channels are assigned on the paging channel for the forward link, and are assigned on the access channel for the reverse link. FIG. i shows a structure of a general mobile communication system. More specifically, FIG. 1 shows a reference model of a 3G IOS (Interoperability Specifications) for a digital air interface between a mobile switching center (MSC) and a base station, and between base stations in the common mobile communication system. Referring to FIG. 1, between MSC 20 and BSC 32, a signal is defined as an Al interface and user information is defined as an A2/A5 (circuit data) interface. An A3 interface is defined to connect a target BS 40 to a frame selection/distribution unit (SDU) function block 34 of a source BS 30 for soft/softer handoff between base stations. The signaling and user traffic between the target BS 40 and the SDU function block 34 of the source BS 30 are transmitted through the A3 interface. An A7 interface is defined for signal exchange between the target BS 40 and the source BS 30, for soft/softer handoff between the base stations. In the CDMA mobile communication system, a wired communication link between the base station 30 and the base station 40, and between the base station 30 and the MSC 20, is comprised of a forward link transmitted from the MSC 20 to the base station 30, a reverse link transmitted from the base station 30 to the MSC 20 and a line connected between the MSC 20 and the base station 30.The MSC 20 includes a call control and mobility management block 22 and a switching block 24. Further, the MSC 20 is connected to a data network such as the Internet through an interworking function (IWF) block 50. FIG. 2 shows a procedure for exchanging signals between the BTS and the BSC (more specifically, the SDU function block in the BSC, BSC-SDU) according to the prior art. The operation can be performed either between the BSC 32 (or BSC-SDU 34) and the BTS 36 in the source BS 30, or between the BSC 42 and the BTS 44 in the target BS 40. FIG.2 is independent of types of the required physical channel, i.e., DCCH, FCH, SCH and whatever. That is, the invention in this document can be applied to all types of physical channels. Referring to FIG. 2, the BTS determines forward and reverse channels to be established with the MS and then generates a signaling message (more specifically, a connect message) necessary for channel establishment, in step 201. The generated signaling message includes a frame selector (or channel type) and channel information. The detailed operation of step 201 will be described later with reference to FIG. 3. The BTS sends the generated connect message to the BSC in step 203. Upon receipt of the connect message, the BSC analyzes the received connect message to check the channel assigned to the MS, and generates a connect ACK message to be transmitted to the BTS, in step 205. The detailed operation of receiving the connect message will be described later with reference to FIG. 4. The BSC sends the generated connect ACK message to the BTS in step 207. The connect ACK message includes information for acknowledging establishment of the channel requested by the BTS. The BTS then assigns the acknowledged channel to the MS in step 209. Summarizing the operation of FIG. 2, the BTS generates the connect message including information about a channel to be assigned to the MS and sends the generated connect message to the BSC. Upon receipt of the connect message, the BSC processes the received connect message, generates the connect ACK message for acknowledging channel assignment and sends the generated connect ACK message to the BTS. The BTS then assigns the acknowledged channel to the MS. FIG. 3 shows a detailed procedure for transmitting the connect message according to the prior art. This operation is performed when the BTS transmits the connect message to the BSC-SDU when it is required to assign a channel to the MS. The structures of the connect message transmitted from the BTS to the BSC- SDU are shown in FIGS. 5A and 5B. Referring to FIG. 3, the BTS determines in step 301 whether the channel to be assigned to the MS is a supplemental code channel (SCCH). SCCH is the IS- 2000 defined name corresponding to IS-95B SCH(Supplemental Channel). [As I said earlier,] IS-2000 is on the evolution path of IS-95A/B. IS-2000 also has the IS-95 A/B channels for maintaining the backward compatibility. It is determined in step 301 that the channel to be assigned to the MS is SCCH, the BTS sets (designates) in step 303 the frame selector (or channel type) in the connect message, whose structure is shown in FIGS. 5A and 5B, to 1S-95B SCCH, so as to enable the BSC to recognize that the channel to be assigned is an IS-95B channel, and then designates a Walsh code with 6-bit channel information. Thereafter, in step 305, the BTS ignores an information element overlapped due to establishment of the IS-95 A/B fundamental channel in the connect message, whose structure is shown in FIGS. 5A and 5B, Cell Information, Extended Handoff Parameters in A3 Connect Information element are overlapped with those in the same Connect message used when IS-95 A/B FCH was newly established. IS-95B SCCH establishment procedure follows the IS-95 A/B FCH establishment procedure. IS- 95B SCCH have to be established in parallel to IS-95 A/B FCH under the same cell fills all other information elements to complete the connect message, and then transmits the connect message to the BSC. Here, in a handoff (HO) situation, the BTS fills all the handoff-related information element. If it is determined in step 301 that the channel to be assigned to the MS is not SCCH, the BTS designates in step 307 the frame selector (or channel type) in the connect message shown in FIGS. 5A and 5B to the fundamental channel, so as to enable the BSC to recognize that the channel to be assigned is an IS-95B fundamental channel, and then designates a Walsh code with 6-bit channel information. Thereafter, in step 309, the BTS fills all the information elements in the connect message of FIGS. 5A and 5B to complete the connect message, and then transmits the connect message to the BSC. Here, in the handoff (HO) situation, the BTS fills all the handoff-related information element. FIG. 4 shows a procedure for receiving the connect message according to the prior art. This operation is performed when the BSC-SDU receives the connect message for requesting channel assignment, transmitted from the BTS, and generates a connect ACK message for the connect message. Referring to FIG. 4, the BSC-SDU receives the connect message for requesting channel assignment from the BTS in step 401. In step 401, the BSC- SDU analyzes the received connect message, and examines the establishment- requested channel in the message of FIGS. 5A and 5B and an identifier of a traffic channel between the BTS and BSC. The BSC-SDU assigns the traffic channel between the BSC and BTS, corresponding to the radio channel, in step 403. As a result, channel connection among BSC-BTS-MS is completed. Further, in step 405, the BTS-SDU fills all the information elements of the connect ACK message shown in FIG. 6 and transmits it to the BTS. A simplified structure of the connect ACK message shown in FIG. 6 will be described with reference to Table 1 below. The connect message shown in Table 1 is an A3 message transmitted when the target BS 40 initiates or adds one or more A3 user traffic connections to the SDU 34 of the source BS 30. The A3 message includes the following information. - Message Type II : an information element indicating A3/A7 message type - Call Connection Reference : an information element for uniquely dividing call connection over all zones. This value is always maintained during call connection over every handoff. - Correlation ID : an information element used to correlate a request message with a response message for the request message - SDU ID : an information element for identifying a specific SDU instance in one SDU node A3 Connect Information : an information element used to add one or more cells to one new A3 connection or existing A3 connection. This information element field is shown in Table 2 below, and 4th to (j-1)th octets of Table 2 include Cell Information Record fields of Table 3 below. Table 3 shows a message including air interface channel information for the cells attached to one call leg, and each field is defined as follows. - Length : the number of octets of the elements following a Length field - Cell Identification Discriminator : a value used to describe the formats following a Cell Identification field according to cells - Cell Identification : identification of the cells relating to A3 connection - Reserved : this value is set to '00000'. - New Cell Indicator : a field indicating whether a corresponding cell is a cell newly added to A3 traffic connection in the present procedure or a cell which previously exists in A3 connection. - PWRComb lnd : a power control symbol combining indicator. The BTS sets this field to ' 1', if a forward traffic channel relating to the corresponding pilot transmits the same bits as closed-loop power control subchannel bits of a previous pilot in this message. Otherwise, the BTS sets this field to '0'. When this record occurs first in this element, the BTS sets this field to '0'. - PilotPN : this field includes a PN sequence offset corresponding to the related cell and is set in a unit of 64 PN chips. - CodeChan : this field includes a code channel index corresponding to the related cell. The BTS sets a value used on the forward traffic channel in connection with a designated pilot to one of 0 to 63. A simplified structure of the connect ACK. message shown in FIG. 6 will be described with reference to Table 4 below. The connect ACK message of Table 4 is an A3 message for transmitting A3-CDMA Long Code Transition Directive results performed on the A3 signaling interface from the target BS 40 to the SDU 34 of the source BS 30. Further, an A3 CDMA Long Code Transition Directive Ack message for the A3 CDMA Long Code Transition Directive of Table 4 is shown in Table 5 below. The A3 CDMA Long Code Transition Directive Ack message of Table 5 includes the following information elements. - Message Type II : an information element indicating an A3/A7 message type - Call Connection Reference : an information element for uniquely dividing call connection over all zones. This value is always maintained during call connection over every handoff. - SDU ID : an information element for identifying a specific SDU instance in one SDU node - PMC Cause : an information element indicating failed results of A3/A7 message - Cell Information Record (Committed, Uncommitted) : a Cell Information Record field of Table 3 is used, as it is. This is an information element including air interface channel information for the cells attached to one call leg. When successful, this field is set to 'Committed', and when failed, this field is set to 'Uncommitted'. This field is used together with the PMC Cause field. Problems of the existing channel assignment method will be described based on the foregoing descriptions. As described with reference to Tables 1 to 5, in the conventional 3G IOS radio channel information, the quasi-orthogonal function (QOF) specified in the CDMA-2000 standard is not defined. Further, only 64 Walsh codes of 0 to 63 are supported for the code channels. Thus, when the base station does not support the quasi-orthogonal function (QOF) which is necessary for the mobile station, the 3G forward radio channel cannot be assigned in the mobile station. Therefore, it is necessary to define a message field which can support the quasi-orthogonal function (QOF) and 256 Walsh codes for the radio channel information in the existing 3G IOS. SUMMARY OF THE TNVENTION It is, therefore, an object of the present invention to provide a method for expanding existing 64 supportable Walsh codes to 256 Walsh codes and supporting a quasi-orthogonal function (QOF) for a forward channel in a base station of a mobile communication system. To achieve the above objects, there is provided a method for performing channel assignment in a base station for a mobile communication system. Upon receipt of a request for assigning a channel to a mobile station, a base station transceiver system (BTS) generates a connect message including channel information indicating a Walsh code to be used for a channel to be assigned to the mobile station, out of 256 Walsh codes, and information indicating a quasi- orthogonal function (QOF) index, and transmits the generated connect message to a base station controller (BSC). The BTS generates a connect ACK message for acknowledging the channel assignment-related information included in the connect message and transmits the generated connect ACK message to the BSC. Upon receipt of the connect ACK message, in the BTS assigns a channel acknowledged by the BSC to the mobile station. , BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: FIG. 1 is a diagram illustrating a reference model of a 3G IOS (Interoperability Specifications) for a digital air interface between a mobile switching center (MSC) and a base station (BS), and between the base stations in a common mobile communication system; FIG. 2 is a flow diagram illustrating a procedure for exchanging signals between a base station transceiver system (BTS) and a base station controller (BSC) for radio channel assignment according to the prior art; FIG. 3 is a flow chart illustrating a procedure for transmitting a connect message according to the prior art, wherein the BTS transmits the connect message to the BSC-SDU when it is necessary to assign a channel to a mobile station (MS); FIG. 4 is a flow chart illustrating a procedure for receiving the connect message according to the prior art, wherein the BSC-SDU receives the connect message for requesting channel assignment, transmitted from the BTS, and generates a connect ACK message for the connect message; FIGS. 5A and 5B are diagrams illustrating the connect message transmitted from the BTS to the BSC according to the prior art; FIG. 6 is a diagram illustrating the connect ACK message transmitted from the BSC to the BTS according to the prior art; and FIG. 7 is a flow chart illustrating a procedure for transmitting a connect message according to a preferred embodiment of the present invention, wherein the BTS transmits the connect message to the BSC-SDU when it is necessary to assign a channel to the MS. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. In an exemplary embodiment of the invention, a base station supports a quasi-orthogonal function (QOF), defined by IS-2000, necessary for the mobile station and 256 Walsh codes, in addition to the maximum 64 code channels defined by the existing IS-95A/B. FIG. 7 shows a procedure for transmitting a connect message according to a preferred embodiment of the present invention. In this procedure, the BTS transmits the connect message to BSC-SDU when it is necessary to assign a channel to the MS. A detailed structure of the Cell Information Record included in the connect message transmitted from the BTS to the BSC-SDU will be described later with reference to FIG. 6. Referring to FIG. 7, the BTS determines in step 701 whether a channel to be assigned to the MS is SCCH. If it is determined in step 701 that the channel to be assigned is SCCH, the BTS designates in step 713 the frame selector (or channel type) shown in FIG. 6 to 'IS-95B SCCH' so as to enable the BSC to recognize that the channel to be assigned is an IS-95B channel, and designates a Walsh code with 6-bit channel information. Then, in step 715, the BTS ignores the information elements overlapped due to establishment of IS-2000 FCH RC 1/2 in the connect message shown in FIG. 5, fills all the remaining elements to generate (or complete) the connect message, and transmits the generated connect message to the BSC. Here, in the handoff situation, the BTS fills the handoff-related information elements to complete the connect message, and transmits the connect message to the BSC. If it is determined in step 701 that the channel to be assigned is not SCCH, the BTS determines in step 703 whether the channel to be assigned is a supplemental channel (SCH). If it is determined in step 703 that the channel to be assigned is the supplemental channel, the BTS determines in step 707 whether to perform QOF masking on the channel to be assigned. If it is determined in step 707 that QOF masking should be performed on the channel, the BTS designates in step 717 the frame selector (or channel type) shown in FIG. 6 to 'SCH' so as to enable the BSC to recognize that the channel to be assigned is a supplemental channel. Further, the BTS designates the channel information indicating a Walsh code to be assigned to the channel bit (8 bits or 11 bits) of IS-2000, 8 bits can support up to 256 Walsh Codes. However, 1S-2000 is describing 11 bits for specifying Walsh Codes even if the present IS-2000 can support up to 256 Walsh Codes. The remaining 3 bits are prepared for the future extension. For the compliance with IS-2000, 11 bits is O.K. But, just 8 bits are sufficient to the present need and then designates a QOF mask index (=01,10,11) corresponding to the Quasi orthogonal function codes to be assigned. Then, in step 719, the BTS ignores the information elements overlapped due to establishment of the fundamental channel (FCH) and the dedicated control channel (DCCH) in the connect message shown in FIG. 5, fills all the remaining elements to complete the connect message, and transmits the connect message to the BSC. Here, in the handoff situation, the BTS fills the handoff-related information elements of the message shown in FIG. 5 to complete the connect message, and transmits the connect message to the BSC. If it is determined in step 707 that QOF masking should not be performed on the channel to be assigned, the BTS designates in step 721 the frame selector (or channel type) to 'SCH' so as to enable the BSC to recognize that the channel to be assigned is a supplemental channel. Further, the BTS designates the channel information indicating a Walsh code to be assigned to the channel bit number (8 bits or 11 bits) of IS-2000, and then sets the QOF mask index '00',. Here, the QOF mask index is set to '00', since QOF masking should not be performed. Then, in step 723, the BTS ignores the information elements overlapped due to establishment of the fundamental channel (FCH) and the dedicated control channel (DCCH) in the connect message shown in FIG. 5, fills all the remaining elements to complete the connect message, and transmits the connect message to the BSC. Here, in the handoff situation, the BTS fills the handoff-related information elements of the message shown in FIG. 5 to complete the connect message, and transmits the connect message to the BSC. Meanwhile, if it is determined in step 703 that the channel to be assigned is not the supplemental channel, the BTS determines in step 705 whether the channel to be assigned is a fundamental channel (FCH). If it is determined in step 705 that the channel to be assigned is a fundamental channel, the BTS examines in step 709 whether QOF masking should be performed on the channel to be assigned. If it is determined in step 709 that QOF masking should be performed on the channel, the BTS designates in step 725 the frame selector (or channel type) shown in FIG. 6 to 'FCH' so as to enable the BSC to recognize that the channel to be assigned is a fundamental channel. Further, the BTS designates the channel information indicating a Walsh code to be assigned to the channel bit number (8 bits or 11 bits) of IS-2000, and then designates a QOF mask index (=01,10,11) corresponding to the Quasi orthogonal function codes to be assigned. Then, in step 727, the BTS fills all the information elements included in the connect message shown in FIG. 5 to complete the connect message, and transmits the connect message to the BSC. Here, in the handoff situation, the BTS fills the handoff- related information elements of the message shown in FIG. 5 to complete the connect message, and transmits the connect message to the BSC. If it is determined in step 709 that QOF masking should not be performed on the channel to be assigned, the BTS designates in step 729 the frame selector (or channel type) to 'FCH' so as to enable the BSC to recognize that the channel to be assigned is a fundamental channel. Further, the BTS designates the channel information indicating a Walsh code to be assigned to the channel bit number (8 bits or 11 bits) of IS-2000, and then sets the QOF mask index to '00'. Here, the QOF mask index is set to '00', since QOF masking should not be performed. Then, in step 731, the BTS fills all the information elements included in the connect message shown in FIG. 5 to complete the connect message, and transmits the connect message to the BSC. Here, in the handoff situation, the BTS fills the handoff-related information elements of the message shown in FIG. 5 to complete the connect message, and transmits the connect message to the BSC. However, if it is determined in step 705 that the channel to be assigned is not the fundamental channel, the BTS determines in step 711 whether QOF masking should be performed on the channel to be assigned. If it is determined in step 711 that QOF masking should be performed on the channel, the BTS designates in step 733 the frame selector (or channel type) shown in FIG. 6 to 'DCCH' so as to enable the BSC to recognize that the channel to be assigned is a dedicated control channel. Further, the BTS designates the channel information indicating a Walsh code to be assigned to the channel bit number (8 bits or 11 bits) of IS-2000, and then designates a QOF mask index (=01,10,11) corresponding to the Quasi orthogonal function codes to be assigned. Then, in step 735, the BTS fills all the information elements included in the connect message shown in FIG. 5 to complete the connect message, and transmits the connect message to the BSC. Here, in the handoff situation, the BTS fills the handoff-related information elements of the message shown in FIG. 5 to complete the connect message, and transmits the connect message to the BSC. If it is determined in step 711 that QOF masking should not be performed on the channel to be assigned, the BTS designates in step 737 the frame selector (or channel type) to 'DCCH' so as to enable the BSC to recognize that the channel to be assigned is a dedicated control channel. Further, the BTS designates the channel information indicating a Walsh code to be assigned to the channel bit number (8 bits or 11 bits) of IS-2000, and then sets the QOF mask index '00'. Here, the QOF mask index is set to '00', since QOF masking should not be performed. Then, in step 739, the BTS fills all the information elements included in the connect message shown in FIG. 5 to complete the connect message, and transmits the connect message to the BSC. Here, in the handoff situation, the BTS fills the handoff-related information elements of the message shown in FIG. 5 to complete the connect message, and transmits the connect message to the BSC. Table 6 below shows the detailed structure of Cell Information Record for supporting the quasi-orthogonal function (QOF) and the 256 Walsh codes. The Cell Information Record includes a QOF_MASK field for recording the QOF mask index according to the present invention and a Code_Chan field for designating 256 Walsh codes. Upon receipt of the connect message including the above fields, the BSC analyzes the channel assignment-related information recorded in the above fields, and then transmits a connect ACK message including ACK information for the connect message. Upon receipt of the connect ACK message, the BTS assigns the channel to the MS. As described above, the present invention provides a signaling message and a procedure for processing the signaling message such that the base station can support the quasi-orthogonal function (QOF) necessary for the mobile station. In this manner, the base station and the mobile switching center can assign 256 Walsh codes for the radio channels. While the invention has been shown and described with reference to a certain preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. WE CLAIM: 1. A method for performing channel assignment in a base station for a mobile communication system, comprising the steps of: transmitting, from a base station transceiver system (BTS) to a base station controller (BSC), a connect message upon receipt of a request for assigning a channel to a mobile station, said connect message including channel information indicating a Walsh code, out of 256 Walsh codes, to be used for a channel to be assigned to the mobile station, and a quasi-orthogonal function (QOF) index; transmitting, from the BSC to the BTS, a connect ACK (acknowledge) message for acknowledging channel assignment-related information included in the connect message; and assigning, in the BTS, a channel to the mobile station, said channel having been acknowledged by the BSC, upon receipt of the connect ACK message. 2. The method as claimed in claim 1, wherein four quasi-orthogonal functions are provided. 3., The method as claimed in claim 1, wherein the channel information is comprised of 8 or 11 bits. 4. The method as claimed in claim 1, wherein the connect message is an A3 interface message transmitted when a target base station initiates or adds one or more A3 interface user traffic connections to a SDU (Selection/Distribution Unit) of the source base station. 5. The method as claimed in claim 1, further comprising the steps of: designating a frame selector (or channel type) in the connect message to indicate a supplemental code channel (SCCH) and designating a Walsh code with 6-bit channel information, if the channel to be assigned to the mobile station is a supplemental code channel (SCCH); and ignoring overlapped information elements due to establishment of a fundamental channel in the connect message and filling in the remaining information fields in the connect message. 6. The method as claimed in claim 1, further comprising the steps of: determining whether to perform QOF masking on the channel to be assigned to the mobile station; designating, if it is determined that QOF masking should be performed, the channel information indicating a Walsh code, out of 256 Walsh codes, to be used for a channel to be assigned to the mobile station, and designating the QOF index indicating a quasi-orthogonal function to be used for QOF masking; filling in the remaining information fields of the connect message; and transmitting the connect message to the BSC. 7. The method as claimed in claim 1, further comprising the steps of: determining whether to perform QOF masking on the channel to be assigned to the mobile station; designating, if it is determined that QOF masking should not be performed, the channel information indicating the Walsh code, out of 256 Walsh codes, to be used for a channel to be assigned to the mobile station, and setting the QOF index to '00'; filling in the remaining information fields of the connect message; and transmitting the connect message to the BSC. 8. An apparatus for performing channel assignment in a base station for a mobile communication system, comprising: base station transceiver system (BTS), transmitting to a base station controller (BSC), a connect message upon receipt of a request for assigning a channel to a mobile station, said connect message including channel information indicating a Walsh code, out of 256 Walsh codes, to be used for a channel to be assigned to the mobile station, and a quasi-orthogonal function (QOF) index; BSC, transmitting to BTS, a connect ACK (acknowledge) message for acknowledging channel assignment-related information included in the connect message; and BTS, assigning a channel to the mobile station, said channel having been acknowledged by the BSC, upon receipt of the connect ACK message. 9. The apparatus as claimed in claim 8, wherein four quasi-orthogonal functions are provided. 10. The apparatus as claimed in claim 8, wherein the channel information is comprised of 8 or 11 bits. 11. The apparatus as claimed in claim 8, wherein the connect message is an A3 interface message transmitted when a target base station initiates or adds one or more A3 interface user traffic connections to a SDU (Selection/Distribution Unit) of the source base station. The invention relates to a a method for performing channel assignment in a base station for a mobile communication system. Upon receipt of a request for assigning a channel to a mobile station, a base station transceiver system (BTS) generates a connect message including channel information, which indicates a Walsh code,out of 256 Walsh codes to be used for a channel to be assigned to the mobile station, and a quasi-orthogonal function (QOF) index . The BTS transmits the generated connect message to a base station controller (BSC). The BSC generates a connect ACK message for acknowledging the channel assignment—related information included in the connect message and transmits the generated connect ACK message to the BTS. Upon receipt of the connect ACK message, in the BTS assigns the channel that was acknowledged by the BSC to the mobile station.

Full Text

CHANNEL ASSIGNMENT METHOD FOR A BASE STATION IN A
MOBILE COMMUNICATION SYSTEM
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a CDMA (Code Division
Multiple Access) mobile communication system, and in particular, to a method for
providing 4 quasi-orthogonal functions (QOF), which are used in association with
256 Walsh codes in a forward link, in a base station transceiver system (BTS) and
a base station controller (BSC).
2. Description of the Related Art
Existing IS-95A/B CDMA communication systems spread a radio channel
with a Walsh function. However, as the 1S-2000 standard introduces new channels
to the forward and reverse links, the existing conventional communication system
lacks the necessary amount of Walsh codes to maintain orthogonality between
channels
Accordingly, there is a need for a method for increasing the number of the
channels, without decreasing the orthogonality between the existing channels. For
the IS-2000 forward link, several methods have been proposed. One method is to
define a quasi-orthogonal function (QOF) necessary for the mobile station thereby
to assign 4 times the channels as compared with the case when the existing Walsh
function is used, and another method is to expand the existing Walsh function
which can generate 64 Walsh codes, so as to generate 256 Walsh codes. The quasi-
orthogonal function (QOF) is commonly applied to IS-2000 forward channels,
such as the fundamental channel (FCH), the dedicated control channel (DCCH)
and the supplemental channel (SCH). However, existing base stations can only
support 64 Walsh code channels.
Now, reference will be made to the types of the channels used in the IMT-
2000 standard .
Every channel is divided into a physical channel and a logical channel.
The logical channel is established over the physical channel, and several logical
channels can be established on a single physical channel. If the physical channel is
released, the logical channel established over the physical channel is automatically
released. It is not necessary to establish another physical channel in order to
establish a certain logical channel. When a physical channel to be established for a
logical channel is already established for another logical channel, the only required
operation is to assign this logical channel to the previously established physical
channel.
The physical channel can be divided into dedicated channels and common
channels according to its characteristics. Dedicated channels are exclusively used
for communication between the BTS and a particular mobile station (MS), and
include a fundamental channel (FCH), a dedicated control channel (DCCH) and a
supplemental channel (SCH). The fundamental channel is used to transmit voice,
data and signaling signals. Such a fundamental channel is compatible with
TIA/EIA-95-B. The dedicated control channel is used to transmit data and
signaling signals. The dedicated control channel supports a discontinuous
transmission (DTX) mode in which data is only transmitted when the upper layer
generates transmission data. Because of this property, the dedicated control
channel is suitable for effectively providing a packet service. The supplemental
channel is used to transmit large amounts of data.
In addition to the dedicated channels stated above, the physical channel
includes a common channel which is used in common by the base station and
several mobile stations. A physical channel for the forward link transmitted from
the BTS to the MS is called a paging channel, and a physical channel for the
reverse link transmitted form the MS to the BTS is called an access channel. These
common channels are compatible with IS-95B.
The logical channels to be assigned on the above physical channels include
a dedicated signaling channel (dsch) and a dedicated traffic channel (dtch). The
dedicated signaling channel can be assigned to the fundamental channel and the
dedicated control channel, which are physical channels. The dedicated traffic
channel can be assigned to the fundamental channel, the dedicated control channel
and the supplemental channel. The dedicated signaling channel is used when the
base station and the mobile station exchange a control signal. The dedicated traffic
channel is used when the base station and the mobile station exchange user data.
The common logical channel to be assigned on the common physical
channel is divided into a common signaling channel (csch) used to transmit control
signal, and a common traffic channel (ctch) use to transmit user data. The common
logical channels are assigned on the paging channel for the forward link, and are
assigned on the access channel for the reverse link.
FIG. i shows a structure of a general mobile communication system. More
specifically, FIG. 1 shows a reference model of a 3G IOS (Interoperability
Specifications) for a digital air interface between a mobile switching center (MSC)
and a base station, and between base stations in the common mobile
communication system.
Referring to FIG. 1, between MSC 20 and BSC 32, a signal is defined as
an Al interface and user information is defined as an A2/A5 (circuit data) interface.
An A3 interface is defined to connect a target BS 40 to a frame
selection/distribution unit (SDU) function block 34 of a source BS 30 for
soft/softer handoff between base stations. The signaling and user traffic between
the target BS 40 and the SDU function block 34 of the source BS 30 are
transmitted through the A3 interface. An A7 interface is defined for signal
exchange between the target BS 40 and the source BS 30, for soft/softer handoff
between the base stations. In the CDMA mobile communication system, a wired
communication link between the base station 30 and the base station 40, and
between the base station 30 and the MSC 20, is comprised of a forward link
transmitted from the MSC 20 to the base station 30, a reverse link transmitted from
the base station 30 to the MSC 20 and a line connected between the MSC 20 and
the base station 30.The MSC 20 includes a call control and mobility management
block 22 and a switching block 24. Further, the MSC 20 is connected to a data
network such as the Internet through an interworking function (IWF) block 50.
FIG. 2 shows a procedure for exchanging signals between the BTS and the
BSC (more specifically, the SDU function block in the BSC, BSC-SDU) according
to the prior art. The operation can be performed either between the BSC 32 (or
BSC-SDU 34) and the BTS 36 in the source BS 30, or between the BSC 42 and the
BTS 44 in the target BS 40. FIG.2 is independent of types of the required physical
channel, i.e., DCCH, FCH, SCH and whatever. That is, the invention in this
document can be applied to all types of physical channels.
Referring to FIG. 2, the BTS determines forward and reverse channels to
be established with the MS and then generates a signaling message (more
specifically, a connect message) necessary for channel establishment, in step 201.
The generated signaling message includes a frame selector (or channel type) and
channel information. The detailed operation of step 201 will be described later
with reference to FIG. 3. The BTS sends the generated connect message to the
BSC in step 203. Upon receipt of the connect message, the BSC analyzes the
received connect message to check the channel assigned to the MS, and generates
a connect ACK message to be transmitted to the BTS, in step 205. The detailed
operation of receiving the connect message will be described later with reference
to FIG. 4. The BSC sends the generated connect ACK message to the BTS in step
207. The connect ACK message includes information for acknowledging
establishment of the channel requested by the BTS. The BTS then assigns the
acknowledged channel to the MS in step 209.
Summarizing the operation of FIG. 2, the BTS generates the connect
message including information about a channel to be assigned to the MS and sends
the generated connect message to the BSC. Upon receipt of the connect message,
the BSC processes the received connect message, generates the connect ACK
message for acknowledging channel assignment and sends the generated connect
ACK message to the BTS. The BTS then assigns the acknowledged channel to the
MS.
FIG. 3 shows a detailed procedure for transmitting the connect message
according to the prior art. This operation is performed when the BTS transmits the
connect message to the BSC-SDU when it is required to assign a channel to the
MS. The structures of the connect message transmitted from the BTS to the BSC-
SDU are shown in FIGS. 5A and 5B.
Referring to FIG. 3, the BTS determines in step 301 whether the channel
to be assigned to the MS is a supplemental code channel (SCCH). SCCH is the IS-
2000 defined name corresponding to IS-95B SCH(Supplemental Channel). [As I
said earlier,] IS-2000 is on the evolution path of IS-95A/B. IS-2000 also has the
IS-95 A/B channels for maintaining the backward compatibility. It is determined in
step 301 that the channel to be assigned to the MS is SCCH, the BTS sets
(designates) in step 303 the frame selector (or channel type) in the connect
message, whose structure is shown in FIGS. 5A and 5B, to 1S-95B SCCH, so as to
enable the BSC to recognize that the channel to be assigned is an IS-95B channel,
and then designates a Walsh code with 6-bit channel information. Thereafter, in
step 305, the BTS ignores an information element overlapped due to establishment
of the IS-95 A/B fundamental channel in the connect message, whose structure is
shown in FIGS. 5A and 5B, Cell Information, Extended Handoff Parameters in A3
Connect Information element are overlapped with those in the same Connect
message used when IS-95 A/B FCH was newly established. IS-95B SCCH
establishment procedure follows the IS-95 A/B FCH establishment procedure. IS-
95B SCCH have to be established in parallel to IS-95 A/B FCH under the same cell
fills all other information elements to complete the connect message, and then
transmits the connect message to the BSC. Here, in a handoff (HO) situation, the
BTS fills all the handoff-related information element.
If it is determined in step 301 that the channel to be assigned to the MS is
not SCCH, the BTS designates in step 307 the frame selector (or channel type) in
the connect message shown in FIGS. 5A and 5B to the fundamental channel, so as
to enable the BSC to recognize that the channel to be assigned is an IS-95B
fundamental channel, and then designates a Walsh code with 6-bit channel
information. Thereafter, in step 309, the BTS fills all the information elements in
the connect message of FIGS. 5A and 5B to complete the connect message, and
then transmits the connect message to the BSC. Here, in the handoff (HO) situation,
the BTS fills all the handoff-related information element.
FIG. 4 shows a procedure for receiving the connect message according to
the prior art. This operation is performed when the BSC-SDU receives the connect
message for requesting channel assignment, transmitted from the BTS, and
generates a connect ACK message for the connect message.
Referring to FIG. 4, the BSC-SDU receives the connect message for
requesting channel assignment from the BTS in step 401. In step 401, the BSC-
SDU analyzes the received connect message, and examines the establishment-
requested channel in the message of FIGS. 5A and 5B and an identifier of a traffic
channel between the BTS and BSC. The BSC-SDU assigns the traffic channel
between the BSC and BTS, corresponding to the radio channel, in step 403. As a
result, channel connection among BSC-BTS-MS is completed. Further, in step 405,
the BTS-SDU fills all the information elements of the connect ACK message
shown in FIG. 6 and transmits it to the BTS.
A simplified structure of the connect ACK message shown in FIG. 6 will
be described with reference to Table 1 below.
The connect message shown in Table 1 is an A3 message transmitted when
the target BS 40 initiates or adds one or more A3 user traffic connections to the
SDU 34 of the source BS 30. The A3 message includes the following information.
- Message Type II : an information element indicating A3/A7 message
type
- Call Connection Reference : an information element for uniquely
dividing call connection over all zones. This value is always maintained during call
connection over every handoff.
- Correlation ID : an information element used to correlate a request
message with a response message for the request message
- SDU ID : an information element for identifying a specific SDU instance
in one SDU node
A3 Connect Information : an information element used to add one or
more cells to one new A3 connection or existing A3 connection. This information
element field is shown in Table 2 below, and 4th to (j-1)th octets of Table 2 include
Cell Information Record fields of Table 3 below.
Table 3 shows a message including air interface channel information for
the cells attached to one call leg, and each field is defined as follows.
- Length : the number of octets of the elements following a Length field
- Cell Identification Discriminator : a value used to describe the formats
following a Cell Identification field according to cells
- Cell Identification : identification of the cells relating to A3 connection
- Reserved : this value is set to '00000'.
- New Cell Indicator : a field indicating whether a corresponding cell is a
cell newly added to A3 traffic connection in the present procedure or a cell which
previously exists in A3 connection.
- PWRComb lnd : a power control symbol combining indicator. The
BTS sets this field to ' 1', if a forward traffic channel relating to the corresponding
pilot transmits the same bits as closed-loop power control subchannel bits of a
previous pilot in this message. Otherwise, the BTS sets this field to '0'. When this
record occurs first in this element, the BTS sets this field to '0'.
- PilotPN : this field includes a PN sequence offset corresponding to the
related cell and is set in a unit of 64 PN chips.
- CodeChan : this field includes a code channel index corresponding to
the related cell. The BTS sets a value used on the forward traffic channel in
connection with a designated pilot to one of 0 to 63.
A simplified structure of the connect ACK. message shown in FIG. 6 will
be described with reference to Table 4 below.
The connect ACK message of Table 4 is an A3 message for transmitting
A3-CDMA Long Code Transition Directive results performed on the A3 signaling
interface from the target BS 40 to the SDU 34 of the source BS 30. Further, an A3
CDMA Long Code Transition Directive Ack message for the A3 CDMA Long
Code Transition Directive of Table 4 is shown in Table 5 below.
The A3 CDMA Long Code Transition Directive Ack message of Table 5
includes the following information elements.
- Message Type II : an information element indicating an A3/A7 message
type
- Call Connection Reference : an information element for uniquely
dividing call connection over all zones. This value is always maintained during call
connection over every handoff.
- SDU ID : an information element for identifying a specific SDU instance
in one SDU node
- PMC Cause : an information element indicating failed results of A3/A7
message
- Cell Information Record (Committed, Uncommitted) : a Cell Information
Record field of Table 3 is used, as it is. This is an information element including
air interface channel information for the cells attached to one call leg. When
successful, this field is set to 'Committed', and when failed, this field is set to
'Uncommitted'. This field is used together with the PMC Cause field.
Problems of the existing channel assignment method will be described
based on the foregoing descriptions.
As described with reference to Tables 1 to 5, in the conventional 3G IOS
radio channel information, the quasi-orthogonal function (QOF) specified in the
CDMA-2000 standard is not defined. Further, only 64 Walsh codes of 0 to 63 are
supported for the code channels. Thus, when the base station does not support the
quasi-orthogonal function (QOF) which is necessary for the mobile station, the 3G
forward radio channel cannot be assigned in the mobile station. Therefore, it is
necessary to define a message field which can support the quasi-orthogonal
function (QOF) and 256 Walsh codes for the radio channel information in the
existing 3G IOS.
SUMMARY OF THE TNVENTION
It is, therefore, an object of the present invention to provide a method for
expanding existing 64 supportable Walsh codes to 256 Walsh codes and supporting
a quasi-orthogonal function (QOF) for a forward channel in a base station of a
mobile communication system.
To achieve the above objects, there is provided a method for performing
channel assignment in a base station for a mobile communication system. Upon
receipt of a request for assigning a channel to a mobile station, a base station
transceiver system (BTS) generates a connect message including channel
information indicating a Walsh code to be used for a channel to be assigned to the
mobile station, out of 256 Walsh codes, and information indicating a quasi-
orthogonal function (QOF) index, and transmits the generated connect message to
a base station controller (BSC). The BTS generates a connect ACK message for
acknowledging the channel assignment-related information included in the connect
message and transmits the generated connect ACK message to the BSC. Upon
receipt of the connect ACK message, in the BTS assigns a channel acknowledged
by the BSC to the mobile station. ,
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above and other objects, features and advantages of the present
invention will become more apparent from the following detailed description when
taken in conjunction with the accompanying drawings in which:
FIG. 1 is a diagram illustrating a reference model of a 3G IOS
(Interoperability Specifications) for a digital air interface between a mobile
switching center (MSC) and a base station (BS), and between the base stations in a
common mobile communication system;
FIG. 2 is a flow diagram illustrating a procedure for exchanging signals
between a base station transceiver system (BTS) and a base station controller
(BSC) for radio channel assignment according to the prior art;
FIG. 3 is a flow chart illustrating a procedure for transmitting a connect
message according to the prior art, wherein the BTS transmits the connect message
to the BSC-SDU when it is necessary to assign a channel to a mobile station (MS);
FIG. 4 is a flow chart illustrating a procedure for receiving the connect
message according to the prior art, wherein the BSC-SDU receives the connect
message for requesting channel assignment, transmitted from the BTS, and
generates a connect ACK message for the connect message;
FIGS. 5A and 5B are diagrams illustrating the connect message
transmitted from the BTS to the BSC according to the prior art;
FIG. 6 is a diagram illustrating the connect ACK message transmitted
from the BSC to the BTS according to the prior art; and
FIG. 7 is a flow chart illustrating a procedure for transmitting a connect
message according to a preferred embodiment of the present invention, wherein
the BTS transmits the connect message to the BSC-SDU when it is necessary to
assign a channel to the MS.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A preferred embodiment of the present invention will be described herein
below with reference to the accompanying drawings. In the following description,
well-known functions or constructions are not described in detail since they would
obscure the invention in unnecessary detail.
In an exemplary embodiment of the invention, a base station supports a
quasi-orthogonal function (QOF), defined by IS-2000, necessary for the mobile
station and 256 Walsh codes, in addition to the maximum 64 code channels defined
by the existing IS-95A/B.
FIG. 7 shows a procedure for transmitting a connect message according to
a preferred embodiment of the present invention. In this procedure, the BTS
transmits the connect message to BSC-SDU when it is necessary to assign a
channel to the MS. A detailed structure of the Cell Information Record included in
the connect message transmitted from the BTS to the BSC-SDU will be described
later with reference to FIG. 6.
Referring to FIG. 7, the BTS determines in step 701 whether a channel to
be assigned to the MS is SCCH. If it is determined in step 701 that the channel to
be assigned is SCCH, the BTS designates in step 713 the frame selector (or
channel type) shown in FIG. 6 to 'IS-95B SCCH' so as to enable the BSC to
recognize that the channel to be assigned is an IS-95B channel, and designates a
Walsh code with 6-bit channel information. Then, in step 715, the BTS ignores the
information elements overlapped due to establishment of IS-2000 FCH RC 1/2 in
the connect message shown in FIG. 5, fills all the remaining elements to generate
(or complete) the connect message, and transmits the generated connect message
to the BSC. Here, in the handoff situation, the BTS fills the handoff-related
information elements to complete the connect message, and transmits the connect
message to the BSC.
If it is determined in step 701 that the channel to be assigned is not SCCH,
the BTS determines in step 703 whether the channel to be assigned is a
supplemental channel (SCH). If it is determined in step 703 that the channel to be
assigned is the supplemental channel, the BTS determines in step 707 whether to
perform QOF masking on the channel to be assigned.
If it is determined in step 707 that QOF masking should be performed on
the channel, the BTS designates in step 717 the frame selector (or channel type)
shown in FIG. 6 to 'SCH' so as to enable the BSC to recognize that the channel to
be assigned is a supplemental channel. Further, the BTS designates the channel
information indicating a Walsh code to be assigned to the channel bit (8 bits or 11
bits) of IS-2000, 8 bits can support up to 256 Walsh Codes. However, 1S-2000 is
describing 11 bits for specifying Walsh Codes even if the present IS-2000 can
support up to 256 Walsh Codes. The remaining 3 bits are prepared for the future
extension. For the compliance with IS-2000, 11 bits is O.K. But, just 8 bits are
sufficient to the present need and then designates a QOF mask index (=01,10,11)
corresponding to the Quasi orthogonal function codes to be assigned. Then, in step
719, the BTS ignores the information elements overlapped due to establishment of
the fundamental channel (FCH) and the dedicated control channel (DCCH) in the
connect message shown in FIG. 5, fills all the remaining elements to complete the
connect message, and transmits the connect message to the BSC. Here, in the
handoff situation, the BTS fills the handoff-related information elements of the
message shown in FIG. 5 to complete the connect message, and transmits the
connect message to the BSC.
If it is determined in step 707 that QOF masking should not be performed
on the channel to be assigned, the BTS designates in step 721 the frame selector
(or channel type) to 'SCH' so as to enable the BSC to recognize that the channel to
be assigned is a supplemental channel. Further, the BTS designates the channel
information indicating a Walsh code to be assigned to the channel bit number (8
bits or 11 bits) of IS-2000, and then sets the QOF mask index '00',. Here, the QOF
mask index is set to '00', since QOF masking should not be performed. Then, in
step 723, the BTS ignores the information elements overlapped due to
establishment of the fundamental channel (FCH) and the dedicated control channel
(DCCH) in the connect message shown in FIG. 5, fills all the remaining elements
to complete the connect message, and transmits the connect message to the BSC.
Here, in the handoff situation, the BTS fills the handoff-related information
elements of the message shown in FIG. 5 to complete the connect message, and
transmits the connect message to the BSC.
Meanwhile, if it is determined in step 703 that the channel to be assigned
is not the supplemental channel, the BTS determines in step 705 whether the
channel to be assigned is a fundamental channel (FCH). If it is determined in step
705 that the channel to be assigned is a fundamental channel, the BTS examines in
step 709 whether QOF masking should be performed on the channel to be assigned.
If it is determined in step 709 that QOF masking should be performed on
the channel, the BTS designates in step 725 the frame selector (or channel type)
shown in FIG. 6 to 'FCH' so as to enable the BSC to recognize that the channel to
be assigned is a fundamental channel. Further, the BTS designates the channel
information indicating a Walsh code to be assigned to the channel bit number (8
bits or 11 bits) of IS-2000, and then designates a QOF mask index (=01,10,11)
corresponding to the Quasi orthogonal function codes to be assigned. Then, in step
727, the BTS fills all the information elements included in the connect message
shown in FIG. 5 to complete the connect message, and transmits the connect
message to the BSC. Here, in the handoff situation, the BTS fills the handoff-
related information elements of the message shown in FIG. 5 to complete the
connect message, and transmits the connect message to the BSC.
If it is determined in step 709 that QOF masking should not be performed
on the channel to be assigned, the BTS designates in step 729 the frame selector
(or channel type) to 'FCH' so as to enable the BSC to recognize that the channel to
be assigned is a fundamental channel. Further, the BTS designates the channel
information indicating a Walsh code to be assigned to the channel bit number (8
bits or 11 bits) of IS-2000, and then sets the QOF mask index to '00'. Here, the
QOF mask index is set to '00', since QOF masking should not be performed. Then,
in step 731, the BTS fills all the information elements included in the connect
message shown in FIG. 5 to complete the connect message, and transmits the
connect message to the BSC. Here, in the handoff situation, the BTS fills the
handoff-related information elements of the message shown in FIG. 5 to complete
the connect message, and transmits the connect message to the BSC.
However, if it is determined in step 705 that the channel to be assigned is
not the fundamental channel, the BTS determines in step 711 whether QOF
masking should be performed on the channel to be assigned. If it is determined in
step 711 that QOF masking should be performed on the channel, the BTS
designates in step 733 the frame selector (or channel type) shown in FIG. 6 to
'DCCH' so as to enable the BSC to recognize that the channel to be assigned is a
dedicated control channel. Further, the BTS designates the channel information
indicating a Walsh code to be assigned to the channel bit number (8 bits or 11 bits)
of IS-2000, and then designates a QOF mask index (=01,10,11) corresponding to
the Quasi orthogonal function codes to be assigned. Then, in step 735, the BTS
fills all the information elements included in the connect message shown in FIG. 5
to complete the connect message, and transmits the connect message to the BSC.
Here, in the handoff situation, the BTS fills the handoff-related information
elements of the message shown in FIG. 5 to complete the connect message, and
transmits the connect message to the BSC.
If it is determined in step 711 that QOF masking should not be performed
on the channel to be assigned, the BTS designates in step 737 the frame selector
(or channel type) to 'DCCH' so as to enable the BSC to recognize that the channel
to be assigned is a dedicated control channel. Further, the BTS designates the
channel information indicating a Walsh code to be assigned to the channel bit
number (8 bits or 11 bits) of IS-2000, and then sets the QOF mask index '00'. Here,
the QOF mask index is set to '00', since QOF masking should not be performed.
Then, in step 739, the BTS fills all the information elements included in the
connect message shown in FIG. 5 to complete the connect message, and transmits
the connect message to the BSC. Here, in the handoff situation, the BTS fills the
handoff-related information elements of the message shown in FIG. 5 to complete
the connect message, and transmits the connect message to the BSC.
Table 6 below shows the detailed structure of Cell Information Record for
supporting the quasi-orthogonal function (QOF) and the 256 Walsh codes. The
Cell Information Record includes a QOF_MASK field for recording the QOF
mask index according to the present invention and a Code_Chan field for
designating 256 Walsh codes. Upon receipt of the connect message including the
above fields, the BSC analyzes the channel assignment-related information
recorded in the above fields, and then transmits a connect ACK message including
ACK information for the connect message. Upon receipt of the connect ACK
message, the BTS assigns the channel to the MS.
As described above, the present invention provides a signaling message
and a procedure for processing the signaling message such that the base station can
support the quasi-orthogonal function (QOF) necessary for the mobile station. In
this manner, the base station and the mobile switching center can assign 256 Walsh
codes for the radio channels.
While the invention has been shown and described with reference to a
certain preferred embodiment thereof, it will be understood by those skilled in the
art that various changes in form and details may be made therein without departing
from the spirit and scope of the invention as defined by the appended claims.
WE CLAIM:
1. A method for performing channel assignment in a base station for a mobile
communication system, comprising the steps of:
transmitting, from a base station transceiver system (BTS) to a base station controller
(BSC), a connect message upon receipt of a request for assigning a channel to a mobile station,
said connect message including channel information indicating a Walsh code, out of 256 Walsh
codes, to be used for a channel to be assigned to the mobile station, and a quasi-orthogonal
function (QOF) index;
transmitting, from the BSC to the BTS, a connect ACK (acknowledge) message for
acknowledging channel assignment-related information included in the connect message; and
assigning, in the BTS, a channel to the mobile station, said channel having been
acknowledged by the BSC, upon receipt of the connect ACK message.
2. The method as claimed in claim 1, wherein four quasi-orthogonal functions are
provided.
3., The method as claimed in claim 1, wherein the channel information is comprised of 8
or 11 bits.
4. The method as claimed in claim 1, wherein the connect message is an A3 interface
message transmitted when a target base station initiates or adds one or more A3 interface user
traffic connections to a SDU (Selection/Distribution Unit) of the source base station.
5. The method as claimed in claim 1, further comprising the steps of:
designating a frame selector (or channel type) in the connect message to indicate a
supplemental code channel (SCCH) and designating a Walsh code with 6-bit channel information,
if the channel to be assigned to the mobile station is a supplemental code channel (SCCH); and
ignoring overlapped information elements due to establishment of a fundamental channel
in the connect message and filling in the remaining information fields in the connect message.
6. The method as claimed in claim 1, further comprising the steps of:
determining whether to perform QOF masking on the channel to be assigned to the
mobile station;
designating, if it is determined that QOF masking should be performed, the channel
information indicating a Walsh code, out of 256 Walsh codes, to be used for a channel to be
assigned to the mobile station, and designating the QOF index indicating a quasi-orthogonal
function to be used for QOF masking;
filling in the remaining information fields of the connect message; and transmitting the
connect message to the BSC.
7. The method as claimed in claim 1, further comprising the steps of:
determining whether to perform QOF masking on the channel to be assigned to the
mobile station;
designating, if it is determined that QOF masking should not be performed, the channel
information indicating the Walsh code, out of 256 Walsh codes, to be used for a channel to be
assigned to the mobile station, and setting the QOF index to '00';
filling in the remaining information fields of the connect message; and
transmitting the connect message to the BSC.
8. An apparatus for performing channel assignment in a base station for a mobile
communication system, comprising:
base station transceiver system (BTS), transmitting to a base station controller (BSC), a
connect message upon receipt of a request for assigning a channel to a mobile station, said
connect message including channel information indicating a Walsh code, out of 256 Walsh codes,
to be used for a channel to be assigned to the mobile station, and a quasi-orthogonal function
(QOF) index;
BSC, transmitting to BTS, a connect ACK (acknowledge) message for acknowledging
channel assignment-related information included in the connect message; and
BTS, assigning a channel to the mobile station, said channel having been acknowledged
by the BSC, upon receipt of the connect ACK message.

9. The apparatus as claimed in claim 8, wherein four quasi-orthogonal functions are
provided.

10. The apparatus as claimed in claim 8, wherein the channel information is comprised of 8
or 11 bits.
11. The apparatus as claimed in claim 8, wherein the connect message is an A3 interface
message transmitted when a target base station initiates or adds one or more A3 interface user
traffic connections to a SDU (Selection/Distribution Unit) of the source base station.
The invention relates to a a method for performing channel
assignment in a base station for a mobile communication system.
Upon receipt of a request for assigning a channel to a mobile
station, a base station transceiver system (BTS) generates a
connect message including channel information, which indicates a
Walsh code,out of 256 Walsh codes to be used for a channel to be
assigned to the mobile station, and a quasi-orthogonal function
(QOF) index . The BTS transmits the generated connect message to a
base station controller (BSC). The BSC generates a connect ACK
message for acknowledging the channel assignment—related
information included in the connect message and transmits the
generated connect ACK message to the BTS. Upon receipt of the
connect ACK message, in the BTS assigns the channel that was
acknowledged by the BSC to the mobile station.

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Patent Number

225234

Indian Patent Application Number

IN/PCT/2001/00050/KOL

PG Journal Number

45/2008

Publication Date

07-Nov-2008

Grant Date

05-Nov-2008

Date of Filing

12-Jan-2001

Name of Patentee

SAMSUNG ELECTRONICS CO., LTD

Applicant Address

416 MAETAN-DONG, PALDAL-GU, SUWON-SHI, KYUNGKI-DO

Inventors:

#	Inventor's Name	Inventor's Address
1	HYNN-SEOK LEE	JUGONG APT. 4DANJI, #420-106, CHAMSHIL 3-DONG, SONGPA-GU 138-790, SEOUL
2	YOUNG CHANG	117, CHONGJA-DONG, PUNTANG-GU, SONGNAM-SHI, 463-010, KYONGGI-DO

PCT International Classification Number

H04B 7/26

PCT International Application Number

PCT/KR00/00452

PCT International Filing date

2000-05-12

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60 133 790	1999-05-12	U.S.A.