KR100480799B1 - Method for Reverse Supplemental Channel Handoff in CDMA Mobile Communication System - Google Patents

Abstract

The present invention relates to a handoff method of a reverse supplemental channel caused by a mobile station and a change in radio environment when supporting a packet data service using a reverse normal channel in a CDMA mobile communication system.

In the conventional CDMA mobile communication system, since the handoff of the reverse SCH is performed using the forward pilot strength, it is impossible to immediately adapt to the fast fading of the reverse link, so that the handoff can be performed at an optimal moment. There is a problem that there is no.

The present invention, by performing a handoff to the reverse SCH by requesting handoff control to the handoff control station according to the reverse pilot strength received in the SDU of the control station receiving the reverse pilot strength from the base station to which the FCH is assigned, Handoff can be performed by adapting immediately to the fast fading of the reverse link.

After the SDU filters the reverse pilot strength transmitted from the base station, the handoff control is requested to the handoff control station, thereby suppressing the overhead of the handoff control unit.

Description

Method for Reverse Supplemental Channel Handoff in CDMA Mobile Communication System

The present invention relates to a reverse supplemental channel handoff method in a CDMA mobile communication system. In particular, the present invention relates to a reverse supplemental channel supporting medium speed and high speed packet data services when a handoff occurs due to a change in a mobile environment or a mobile station. The present invention relates to a reverse supplemental channel handoff method in a CDMA mobile communication system.

The existing code division multiple access (CDMA) mobile communication system mainly supports voice communication, but has been developed to support high-capacity data communication with the development of technology.

That is, by adding a supplemental channel (hereinafter referred to as SCH) for processing high-speed packet data to the primary communication channel (hereinafter referred to as FCH), the CDMA mobile communication system can be additionally used. Increased the amount of data that can be transmitted in the network improves the communication speed.

Here, the supplemental channel is further divided into a forward channel used for transmitting data from the base station to the terminal and a reverse channel used for uploading data from the mobile terminal to the base station.

Meanwhile, in the CDMA mobile communication system, when the mobile terminal in a busy state moves out of the base station service area to the adjacent base station service area to ensure the mobility of the mobile terminal, the mobile terminal automatically tunes to the new call channel of the neighboring base station and continues. It provides a handoff function so that a call state can be maintained.

As described above, in a CDMA mobile communication system, a call channel may be classified into an FCH, a forward SCH, and a reverse SCH. In the related art, a FCH and a forward SCH are used by using a forward pilot strength. Handoff for the reverse SCH.

Thus, the FCH, which is closely related to the forward pilot strength, and the forward SCH perform handoffs using the forward pilot strength, thereby enabling immediate adaptation to the fast fading of the forward link, so that the hand is at the optimal moment. The off can be performed to improve the quality of service.

However, if the reverse SCH is handed off using forward pilot strength, it cannot immediately adapt to fast fading of the reverse link, and thus cannot perform handoff at an optimum moment, thereby degrading service quality. There is a problem that is thrown away.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and is a reverse supplemental channel handoff method in a CDMA mobile communication system capable of providing an enhanced service by performing a handoff on a reverse SCH using reverse pilot strength. The purpose is to provide.

In the CDMA mobile communication system according to the present invention for achieving the above object, the method of the reverse supplemental channel handoff, when the mobile terminal is in a traffic state with the base station for the packet data service processing of the medium speed or higher, the handoff control unit of the control station Transmitting an RSCH parameter message to an SDU; An FCH handoff process of allocating an FCH to a target base station that will serve the mobile terminal according to a PSMM received according to a movement of a service area from the mobile terminal in packet data service through the assigned FCH and RSCH; From the set of base stations to which FCH and RSCH is allocated in the SDU (hereinafter referred to as 'RSCH active set') and the set of base stations to which FCH is allocated through the FCH handoff process (hereinafter referred to as 'RSCH candidate set') Periodically receiving reverse pilot strength; Transmitting a reverse pilot strength measurement message to the handoff controller according to whether a reverse pilot strength included in the RSCH parameter message satisfies a reverse pilot strength reporting rule; A handoff process of performing a handoff by analyzing the reverse pilot strength measurement message by the handoff controller; And performing an RSCH active set update in the SDU based on the RSCH active set update message received from the handoff control unit which has performed the handoff process.

Here, the RSCH parameter message may include an RSCH add threshold value used to determine whether to request RSCH allocation; And an RSCH drop threshold value and an RSCH drop timer value used to determine whether to release the allocated RSCH.

The reverse pilot strength measurement message indicates the number of base stations for reporting the measured reverse pilot, the base station identification ID for measuring the reverse pilot, the reverse pilot strength, and an RSCH drop timer state for the base station for measuring the reverse pilot. And a reverse pilot hold indication value.

Further, in the process of transmitting a reverse pilot strength measurement message to the handoff control unit, if the reverse pilot strength received in the RSCH candidate set is equal to or greater than an RSCH add threshold, the reverse pilot strength is required to request RSCH allocation of the RSCH candidate set. Setting a measurement message and transmitting the measurement message to the handoff controller; If the reverse pilot strength received in the RSCH active set is less than or equal to the RSCH drop threshold and the RSCH drop timer expires, the reverse pilot strength measurement message is set to release the RSCH assigned to the RSCH active set and the handoff is performed. Characterized in that it comprises the step of transmitting to the control unit.

The handoff process may be configured to release an RSCH physical channel allocated to an RSCH active set and to perform an RSCH if a request for releasing an RSCH allocated to an RSCH active set is requested as a result of analyzing the reverse pilot strength measurement message. Recovering resources; When the RSCH allocation of the RSCH candidate set is requested, the step of assigning the RSCH resource to the RSCH candidate set and setting the RSCH physical channel is characterized in that it comprises.

The RSCH active set update message includes a reverse Walsh ID; RSCH rate; The number of base stations in the RSCH active set; And an RSCH active set identification ID.

The updating may include transmitting an RSCH active set update message including information on a base station changed to an RSCH active set through the handoff process to the SDU; Performing an RSCH active delay update based on RSCH active set information included in the RSCH active set update message in the SDU; And transmitting a RSCH active set update confirmation message to the handoff controller.

Hereinafter, a reverse supplemental channel handoff method in a CDMA mobile communication system according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 illustrates a road, base stations 20-1, 20-2, and 20-3, a selection and distribiute unit (SDU), and a configuration of a CDMA mobile communication system to which a reverse supplemental channel handoff method according to the present invention is applied. And a handoff control unit 40.

In such a configuration, an interface for handoff control and a control signal transmission / reception path exist between the handoff control unit 40 and the SDU 30 implemented in the control station, and the base stations 20-1, 20-2, Between 20-3) and the SDU 30, there is a traffic path and a frame protocol processing unit capable of exchanging traffic.

2 and 3 are diagrams for explaining a reverse supplemental channel handoff method in a CDMA mobile communication system according to the present invention.

First, a base station A 20-1 in which the mobile terminal 10 transmits an outgoing message to a base station serving an area in which the mobile terminal 10 is located by using an access channel, for example, base station A 20-1. When a connection with the base station A 20-1 is successfully established and the mobile terminal 10 is in a traffic state according to an attempted connection with the mobile station 10, the handoff control unit 40 performs an SDU ( In order to perform a reverse pilot strength report procedure in 30), as shown in Table 1, an RSCH parameter message including an RSCH (Reverse SCH) handoff related parameter is transmitted to the SDU 30. (S10).

Field Comments T_RSCHADD RSCH Add Threshold T_RSCHDROP RSCH Drop Threshold T_TRSCHDROP RSCH Drop Timer Value

In step S10, the handoff control unit 40 transmits an RSCH parameter message to the SDU 30 only when the connected mobile terminal 10 sets a call to a packet data service using a supplemental channel.

In step S10, the mobile station 10 which is in a traffic state with the base station A 20-1 is allocated an FCH and an RSCH (S12), and the mobile terminal 10 receives the RSCH from the base station A 20-1. In order to be allocated, the system transmits a supplemental channel request message (SCRM) including information on the size of data to be uploaded, and the handoff control unit 40 includes a request rate included in the SCRM received from the mobile terminal 10. RSCH is allocated according to the

As described above, after the FCH and the initial reverse SCH configuration are normally performed, the mobile terminal 10 moves out of the service area of the base station A 20-1 and the base station A 20-1 and the base station B 20-2 are performed. When entering a jointly serviced area, the handoff control unit 40 performs an FCH handoff process using a Pilot Strength Measurement Report message (PSMM) received from the mobile terminal 10 as the service area moves ( S14).

When the FCH handoff is performed through the process S14, the RSCH and the FCH are allocated to the base station A 20-1, and the FCH is allocated to the base station B 20-2.

Accordingly, the base station A 20-1 exchanges the FCH frames (FCHFwdData, FCHRevData) with the SDU 30 through the allocated FCH at 20 ms intervals, and simultaneously transmits the RSCH data (SSCH) to the SDU 30 through the allocated RSCH. SCHRevData is transmitted, and the base station B 20-2 also exchanges FCH frames (FCHFwdData, FCHRevData) at intervals of 20 ms with the SDU 30 through the FCH allocated through FCH handoff (S16).

Here, the FCH frame (FCHRevData) transmitted from the base station A / B 20-1 / 20-2 to the SDU 30 includes reverse pilot strength.

As described above, as the base station A / B 20-1 / 20-2 transmits the FCH frame (FCHRevData) every 20 ms to the SDU 30 through the assigned FCH, the SDU 30 every 20 ms. The FCH data (FCHRevData) is received from the base station A / B 20-1 / 20-2, and the FCH data (FCHRevData) is received from the base station A / B 20-1 / 20-2 every 20 ms. The SDU 30 compares the backward pilot strength included in the FCH data FCHRevData with the RSCH parameter included in the RSCH parameter message received from the handoff control unit 40 in step S10 (S18).

SDU 30 comparing the reverse pilot strength included in the FCH data (FCHRevData) received in step S16 with the RSCH parameter included in the RSCH parameter message received from the handoff control unit 40 in step S10. When the reverse pilot strength included in the FCH data FCHRevData satisfies the reverse pilot strength report rule, RPSMM (Reverse) as shown in Table 2 by the handoff control unit 40 is shown. The pilot strength measurement message) is transmitted to report the reverse pilot strength (S20 to S28).

Field Comments NUM_REPORT_BTS Number of BTS related in Reverse Pilot SOFT_LEG_ID Soft Handoff Leg Id PILOT_STRENGTH Reverse pilot strength KEEP Keep Reverse Pilot Indication

That is, if the reverse pilot strength received by the RSCH Candidate Set (the set of base stations to which FCH is allocated) is equal to or greater than the RSCH add threshold value T_RSCHADD that may request RSCH allocation, the SDU 30 sets the RSCH candidate set. The RSCH candidate set identification ID is set in the base station identification ID (SOFT_LEG_ID) field in which the reverse pilot of the RPSMM is measured so that the RSCH can be allocated to the base station B 20-2, and the RSCH drop for the base station measuring the reverse pilot The Reverse Pilot Keep Indication value indicating the timer state is set to '1' and transmitted to the handoff control unit 40 (S20 and S28).

In addition, if the reverse pilot strength received in the RSCH Active Set (set of base stations to which the reverse SCH is allocated) is equal to or less than the RSCH drop threshold value T_SCHDROP, the SDU 30 drops the RSCH handoff for the base station. When the timer is started and the RSCH handoff drop timer expires, the base station ID (SOFT_LEG_ID) field to perform handoff of the RPSMM is released so that the RSCH allocated to the base station A 20-1, which is the RSCH active set, can be released. The RSCH active set identification ID is set, and the reverse pilot retention indication value is set to '0' and transmitted to the handoff control unit 40 (S22, S24, and S26).

As described above, the reverse pilot strength received in the RSCH active set is equal to or lower than the RSCH drop threshold value (T_SCHDROP), and the reverse pilot strength received in the RSCH active set after driving the RSCH handoff drop timer for the corresponding base station. When the RSCH add threshold value (T_RSCHADD) or more again, the SDU 30 initializes the RSCH handoff drop timer for the corresponding base station.

As described above, the SDU 30 manages the state of the handoff drop timer for all base stations belonging to the RSCH active set.

Table 3 shows the expiration time of the RSCH handoff drop timer.

T_TRSCHDROP Timer Expiration T_TRSCHDROP Timer Expiration 0 0 4 2000 One 500 5 2500 2 1000 6 3000 3 1500 7 3500

Meanwhile, the handoff control unit 40 receiving the RPSMM transmitted from the SDU 30 through step S28 performs RSCH handoff control based on the reverse pilot strength (S30), and the SDU 30. As a result of analyzing the RPSMM received from the RPSMM, if the base station to perform the soft handoff is the RSCH active set and the KEEP is '0', the RSCH physical channel set in the base station is released and the RSCH resource is recovered. do.

For example, as a result of analyzing the RPSMM received from the SDU 30, if the SOFT_LEG_ID indicates the base station A 20-1, and KEEP is '0', the RSCH physical channel set in the base station A 20-1. Is released, and the RSCH resource is recovered.

If the base station to which the soft handoff should be performed is an RSCH candidate set rather than an RSCH active set, and KEEP is '1', the RSCH resource is allocated to the corresponding base station and the RSCH physical channel is set.

For example, as a result of analyzing the RPSMM received from the SDU 30, if SOFT_LEG_ID indicates the base station B 20-2, and KEEP is '1', the RSCH resource is allocated to the base station B 20-2. Sets the RSCH physical channel.

When the RSCH allocation is completed to the base station B 20-2 through the RSCH handoff control process, the handoff control unit 40 may perform the RSCH active set update according to the changed RSCH active set. In operation S32, an RSCH active set update message as shown in Table 3 including information on a base station changed to an RSCH active set is transmitted to the SDU 30 through an RSCH handoff control process.

Field Comments REV_WALSH_ID Reverse Walsh Id. (See IS-2000 Standard) RSCH_RATE Reverse SCH Rate. (See IS-2000 Standard) NUM_ACTIVE_BTS Number of BTS in the RSCH Active Set SOFT_LEG_ID Soft Handoff Leg Id (RSCH Active Base Station Identification ID) Soft Handoff Leg Id is designated at the time of FCH handoff and becomes an index for identifying a base station receiving an RSCH frame. Therefore, the base station receiving the RSCH frame and the Soft Handoff Leg Id have a one-to-one mapping relationship.

The SDU 30 that has received the RSCH active set update message from the handoff control unit 40 through the above-described process S32 is used as the RSCH active set information included in the RSCH active set update message received from the handoff control unit 40. The RSCH active set is updated to maintain the RSCH active set in the same manner as the handoff controller 40 (S34).

The SDU 30 having updated the RSCH active set through the process S34 transmits an RSCH active set update confirmation message to the handoff control unit 40 to inform the handoff control unit 40 that the RSCH active set update has been normally performed. (S36).

The handoff control unit 40 receiving the RSCH active set update confirmation message transmitted by the SDU 30 in step S36 may apply to the changed RSCH active set based on the RSCH active set update confirmation message received from the SDU 30. It is recognized that the SDU 30 and the handoff control unit 40 maintain the same information.

The SDU 30 that has performed the RSCH active set update through steps S32 to S36 receives data from the RSCH active set through the RSCH (S38), and the SDU 30 receives the received data from each RSCH active set. The selection process is performed through Frame Quality Indication of the RSCH data (SCHRevData), and the selected RSCH data (SCHRevData) is transmitted to the PCF / PDSN.

The reverse supplemental channel handoff method in the CDMA mobile communication system of the present invention is not limited to the above-described embodiment, and can be implemented in various modifications within the range allowed by the technical idea of the present invention.

According to the reverse supplemental channel handoff method in the CDMA mobile communication system of the present invention as described above, the handoff is performed according to the reverse pilot strength received by the SDU of the control station that receives the reverse pilot strength from the base station to which the FCH is allocated. By requesting handoff control to the control station to perform a handoff for the reverse SCH, the handoff can be immediately adapted to reverse fast fading.

After the SDU filters the reverse pilot strength transmitted from the base station, the handoff control is requested to the handoff control station, thereby suppressing the overhead of the handoff control unit.

1 is a block diagram of a CDMA mobile communication system to which a reverse supplemental channel handoff method according to the present invention is applied.

2 and 3 are diagrams for explaining a reverse supplemental channel handoff method in a CDMA mobile communication system according to the present invention;

*** Explanation of symbols for the main parts of the drawing ***

10. Mobile terminal 20-1, 20-2, 20-3. Base Station,

30. SDU, 40. Handoff Control

Claims (7)

Transmitting, by the handoff control unit of the control station, the RSCH parameter message to the SDU when the mobile station is in a traffic state with the base station for the packet data service processing of medium speed or higher; An FCH handoff process of allocating an FCH to a target base station that will serve the mobile terminal according to a PSMM received according to a movement of a service area from the mobile terminal in packet data service through the assigned FCH and RSCH; From the set of base stations to which FCH and RSCH is allocated in the SDU (hereinafter referred to as 'RSCH active set') and the set of base stations to which FCH is allocated through the FCH handoff process (hereinafter referred to as 'RSCH candidate set') Periodically receiving reverse pilot strength; Transmitting a reverse pilot strength measurement message to the handoff controller according to whether a reverse pilot strength included in the RSCH parameter message satisfies a reverse pilot strength reporting rule; A handoff process of performing a handoff by analyzing the reverse pilot strength measurement message by the handoff controller; An uplink supplementary channel handoff in a CDM mobile communication system including an update process of performing an RSCH active set update in the SDU based on an RSCH active set update message received from the handoff control unit performing the handoff process Way. The method of claim 1, wherein the RSCH parameter message, An RSCH add threshold value used for determining whether to request RSCH allocation; And a RSCH drop threshold value and an RSCH drop timer value used to determine whether to release the allocated RSCH. 2. The method of claim 1, wherein the reverse pilot strength measurement message, The number of base stations reporting the measured reverse pilot, The base station identification ID measuring the reverse pilot, Reverse pilot strength, And a reverse pilot hold indication value indicating an RSCH drop timer state for a base station measuring a reverse pilot. The method of claim 1, wherein the transmitting of the reverse pilot strength measurement message to the handoff controller comprises: If the reverse pilot strength received in the RSCH candidate set is equal to or greater than an RSCH add threshold, setting the reverse pilot strength measurement message to request RSCH allocation of the RSCH candidate set and transmitting the reverse pilot strength measurement message to the handoff controller; If the reverse pilot strength received in the RSCH active set is less than or equal to the RSCH drop threshold and the RSCH drop timer expires, the reverse pilot strength measurement message is set to release the RSCH assigned to the RSCH active set and the handoff is performed. The reverse supplemental channel handoff method in a CDA mobile communication system comprising the step of transmitting to a control unit. The method of claim 1, wherein the handoff process comprises: Releasing the RSCH physical channel allocated to the RSCH active set and recovering the RSCH resource when a request for releasing the RSCH allocated to the RSCH active set is determined as a result of analyzing the reverse pilot strength measurement message; When the RSCH allocation of the RSCH candidate set is requested, allocating the RSCH resource to the RSCH candidate set and configuring an RSCH physical channel, the reverse supplemental channel handoff in the CDA mobile communication system is performed. Way. The method of claim 1, wherein the RSCH active set update message, Reverse Walsh ID; RSCH rate; The number of base stations in the RSCH active set; A reverse supplemental channel handoff method in a CDA mobile communication system comprising an RSCH active set identification ID. The method of claim 1, wherein the updating process, Transmitting an RSCH active set update message including information on a base station changed to an RSCH active set through the handoff process to the SDU; Performing an RSCH active delay update based on RSCH active set information included in the RSCH active set update message in the SDU; And transmitting an RSCH active set update confirmation message to the handoff control unit.