KR20060091163A - Method for provide multimedia broadcast/multicast service using high speed downlink packet data channel in a mobile communication system - Google Patents

Abstract

The present invention provides a method for providing a multimedia broadcast / multicast service using a downlink high speed packet data channel in a mobile communication system, and sets a high speed forward common channel (HS-DSCH) and a multicast ID for a multicast service, and performs the multicast service. Setting a list of IDs for each user of the user; and generating multicast data for the multicast service, collecting channel quality information (CQI) of users using the multicast service, and obtaining the lowest CQI. A process of selecting, allocating an optimal transmission amount and transmission power according to the selected CQI, transmitting the multicast data through HS-DSCH according to the allocated transmission amount and transmission power, and the HS-DSCH The control information for the multicast data transmitted through the multicast ID Use it characterized in that it comprises the step of transmitting over a high-speed forward common control channel (HS-SCCH) corresponding to the HS-DSCH.

MBMS, HSDPA, HS-DSCH Multicast RNTI, HS-SCCH

Description

METHOD FOR PROVIDE MULTIMEDIA BROADCAST / MULTICAST SERVICE USING HIGH SPEED DOWNLINK PACKET DATA CHANNEL IN A MOBILE COMMUNICATION SYSTEM}

1 is a diagram illustrating a network configuration for a general MBMS service.

2 is a diagram illustrating an MBMS service procedure in a mobile communication system according to a preferred embodiment of the present invention.

3 shows the physical procedure of HS-SCCH in HSDPA.

4 is a flowchart illustrating a multicast service transmission procedure of a base station through HSDPA according to a preferred embodiment of the present invention.

5 is a flowchart illustrating a channel type change procedure for a multicast service according to a preferred embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio access network of a mobile communication system. In particular, the present invention relates to a multimedia broadcasting multicast service using a high speed downlink packet access (HSDPA), which is a high speed data transmission channel. (Multimedia Broadcast / Multicast Service, hereinafter referred to as "MBMS").

In a mobile communication system, radio resources are important resources for determining the capacity and efficiency of the system. Therefore, it is necessary to efficiently manage radio resources, improve system performance, and provide services appropriately and fairly to system users. The 3rd Generation Partnership Project (3GPP) standard Rel'5 supports HSDPA for transmitting high-speed packet data in the downlink. HSDPA is a technology for supporting high-speed downlink data service in the same frequency band as the existing UMTS Rel'99 and Rel'4, and the existing dedicated channel (DCH) and forward common channel ( It is expected to replace the Downlink Shared Channel (hereinafter referred to as "DSCH").

In case of the conventional DSCH for packet data service, since a channel allocation and scheduling process is performed in a radio network controller (hereinafter, referred to as "RNC"), a lot of delay may occur and efficiency may be reduced. have. In order to solve this problem, MAC-hs dedicated to HSDPA for packet data service is implemented in a base station Node-B to provide a packet service at a higher speed. HSDPA is a forward high-speed data transmission technology capable of having a throughput of up to 13.976 Mbps in peak data rate.

Fast Power Control and Variable Spreading Factor (VSF) features of Wideband Code Division Multiple Access (WCDMA) do not apply to HSDPA. The HSDPA performs high-speed packet data transmission through Adaptive Modulation & Coding (hereinafter referred to as "AMC"), Multi-Code Operation, and Fast & Efficient Retransmission. HSDPA can prevent performance degradation that can occur by using fast power control and VSF technology.

The main technologies used by HSDPA include AMC, Node B Fast Scheduling, Hybrid Automatic Repeat Request (hereinafter referred to as "H-ARQ"), and 2ms transmit time interval (TTI). . The AMC function is a technique that applies adaptive modulation and coding to the user's wireless environment. By performing the AMC function at a short time interval of 2ms TTI, it is possible to select and transmit the data modulation and coding method most suitable for the user's wireless environment, thereby maximizing the performance of the wireless network.

In addition, since the scheduling is performed at the base station instead of the RNC, the air environment can be known more accurately, thereby enabling optimal scheduling according to the air environment. Since the retransmission is performed between the base station and the user through the H-ARQ, the delay time is reduced compared to the existing retransmission between the RNC layer of the RNC and the RLC layer of the UE. The packet reception rate can be increased through chase combining and incremental redundancy. That is, there is an advantage that the delay is small and the packet reception rate can be increased compared to the retransmission method through the RLC of the RNC of the R'99 / R4.

Multicast service is a service that can transmit the same traffic to multiple users through one channel. The multicast service can provide services such as broadcasting, music, and movies to many users with a minimum of radio resources. The 3GPP standard provides a multicast service through a service called MBMS.

MBMS of 3GPP uses a Forward Access Channel (FACH) to provide a multicast service, and as a physical channel, a secondary common control physical channel (hereinafter referred to as "S-CCPCH"). Use Multicast services can be provided in a point-to-point and point-to-multipoint manner.

In the conventional multicast service method operating as described above, multicast data is transmitted through S-CCPCH. The S-CCPCH does not perform power control and is generally broadcasted throughout the cell. Therefore, when multicast service is transmitted through S-CCPCH, for example, when applying a selective combine technique to three radio links and allocating 70 to 80% of the power for MBMS, 1FA ( It is expected that up to 9 64kbps MBMS services can be supported for Frequency Assignment. Therefore, there is a problem that the radio resource usage efficiency is very low.

Accordingly, an object of the present invention, which was devised to solve the problems of the prior art operating as described above, is to provide a multimedia broadcasting multicast service using a high speed downlink packet access (HSDPA).

It is another object of the present invention to provide a method of increasing the efficiency of a radio resource and an average cell throughput by providing a multicast service through a high speed forward packet data channel.

In order to achieve the above object, an embodiment of the present invention provides a method for providing a multimedia broadcast / multicast service using a downlink high speed packet data channel in a mobile communication system. HS-DSCH) and a multicast ID, a user ID list for each user of the multicast service, and when multicast data for the multicast service is generated, the user who uses the multicast service. Collecting channel quality information (CQI), selecting the lowest CQI, allocating an optimal amount of transmission and transmission power according to the selected CQI, and multicasting according to the allocated amount of transmission and transmission power Transmitting data through the HS-DSCH, and transmitting the data through the HS-DSCH. It characterized in that it comprises the step of using the multicast ID the control information for the multicast data transmitted on the high speed forward common control channel (HS-SCCH) corresponding to the HS-DSCH.

Another embodiment of the present invention provides a method for providing a multimedia broadcasting / multicast service using a downlink high speed packet data channel in a mobile communication system, the method comprising: generating a multicast ID for a user who first uses a specific multicast service; Managing a list of users using the multicast service, providing a multicast service to a user included in the list of users using the multicast ID through a multicast service channel, and multi The process of calculating the latest CQI of each user by collecting the CQIs from the users receiving the cast service, and changing the channel type for the user having a significantly lower CQI value than the CQIs of other users to the dedicated channel. Requesting from the RNC and an instruction from the RNC. It depending characterized in that it comprises the step of performing the substantially lower change the channels of the type having a CQI value.

Hereinafter, the operating principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily flow the gist of the present invention, the detailed description thereof will be omitted. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

The present invention provides a multicast service using HSDPA. HSDPA has a maximum data rate of 14Mbps and averages about 3Mbps. Such a forward high speed packet channel can support streaming services as well as interactive and background services.

The channel structure of HSDPA is called downlink HS-DSCH, High Speed Shared Control Channel (hereinafter referred to as "HS-SCCH"), and Dedicated Physical Control Channel (hereinafter referred to as "DPCCH"). ) And an uplink High Speed Dedicate Physical Control Channel (hereinafter referred to as "HS-DPCCH"). The HS-DSCH may transmit a data frame every Tms of 2ms, and the HS-SCCH corresponds to a transport formant and resource related information (TFRI), which is a format of data, in response to a data frame transmitted from the HS-DSCH, and a UE to receive. A UE ID (equipment) that specifies equipment and hybrid ARQ (HARQ) information, which is retransmission state information, is transmitted.

1 is a diagram illustrating a network configuration for a general MBMS service.

Referring to FIG. 1, UEs 161, 162, 163, 171, and 172 refer to terminal equipment or subscribers capable of receiving MBMS service, and cell 1 160 and cell 2 170 are subscribers. It is controlled by a base station apparatus for wirelessly transmitting MBMS-related data to a mobile station. The RNC 140 controls the plurality of cells 160 and 170, selectively transmits multimedia data to a specific cell, and controls a radio channel configured to provide an MBMS service. The connection between the RNC 140 and the UEs 161, 162, 163, 171, and 172 is connected to a Radio Resource Control (RRC) interface.

The RNC 140 is a Packet Switched or Packet Service (PS) network such as the Internet by a Serving GPRS Support Node (SGSN) 130. Is connected to. Communication between the RNC 140 and the PS network is made by packet switched signaling (hereinafter referred to as 'PS signaling'). In particular, the connection between the RNC 140 and the SGSN 130 is called an Iu-PS interface. SGSN 130 controls the MBMS-related services of each subscriber. Representative examples of the role played by the SGSN 130 include managing a service related data of each subscriber and selectively transmitting multimedia data to a specific RNC 140.

Transit NW 120 provides a communication path between Broadcast Multicast Service Center (hereinafter referred to as BM-SC) 110 and SGSN 130, and provides a gateway packet radio. It may be connected to an external network through a Gateway GPRS Support Node (hereinafter referred to as 'GGSN') (not shown) The BM-SC 110 is responsible for scheduling MBMS data as a source of MBMS data. have.

The RNC 140 is connected to a Circuit Switched (CS) network by a Mobile Switching Center (MSC) 150. The CS network refers to a voice-based legacy communication network that is connection-based. Communication between the RNC 140 and the MSC 150 is performed by circuit switched signaling (CS signaling). In particular, the connection between the RNC 140 and the MSC 150 is called an Iu-CS interface.

MBMS data streams are delivered to UEs 161, 162, 163, 171 and 172 via the transport network 120, SGSN 130, RNC 140, base station and cells 160, 170.

Although not shown in FIG. 1, there may be multiple SGSNs for one MBMS service and multiple RNCs for each SGSN. Each SGSN is an RNC 140, and each RNC performs selective data transmission to each of a plurality of cells, and for this purpose, a list of nodes to which a data stream should be delivered (that is, SGSN is a list of RNCs, and the RNC is a cell). List) and the like and selectively perform MBMS data transmission only to the stored nodes later.

In order for UEs to access a network and receive a service, a context, which is a set of information required to provide a corresponding service between UEs and network nodes, must be created. Typically, the context includes a UE context and a mobility management (hereinafter referred to as 'MM') context.

First, the RNC creates a UE context for UEs after establishing an RRC connection. The UE context is composed of basic information such as UE identifier, UE location information, UE RRC status information, radio resource information allocated to the UE, and is managed by the RNC while the RRC connection is active.

The MM context is for managing the location of the UE in the core network (including SGSN 130 and GGSN). In order for the UE to receive the PS service, first, the MM context of the UE must be generated in the SGSN 130 and the GGSN through a GPRS attach procedure. In particular, the MM context of SGSN 130 may include international mobile subscriber identity (hereinafter referred to as IMSI), temporary mobile subscriber identity (hereinafter referred to as P-TMSI), and international mobility. UE identifiers such as device identification (International Mobile Equipment Identity, hereinafter referred to as 'IMEI'), Mobile Subscriber Integrated Switched Data Network (ISDN) Number (hereinafter referred to as 'MS-ISDN'), and routing Location information such as Routing Area (hereinafter referred to as RA) and Service Area Code (hereinafter referred to as "SAC"), authentication / encryption related information, billing information and discontinuous reception parameters (Discontinuous Reception Parameters) , Hereinafter referred to as 'DRX parameter', and the like.

2 is a diagram illustrating an MBMS service procedure in a mobile communication system according to a preferred embodiment of the present invention.

The BM-SC 206 communicates with the UE 202 via the RNC 204. The RNC 204 also communicates with the BM-SC 206 via SGSN (not shown). Although only one RNC 204 and only one UE 202 are shown here, the same procedure is of course applicable to multiple UEs and multiple RNCs wishing to receive MBMS service.

SUBSCRIPTION step 210 is a process in which a user who wants to receive MBMS service, that is, a UE 202, registers with a BM-SC 206 which is a service provider. In the service registration step 210, the BM-SC 206 and the UE 202 exchange basic information related to charging or service reception.

In the SERVICE ANNOUNCEMENT step 220, the UEs acquire basic information on the MBMS service. For example, service identifiers (MBMS IDs) for identifying MBMS services that can be provided by the BM-SC 206, service start time, and duration are recognized. Here, the MBMS service identifier is composed of a multicast address and an access point name (hereinafter, referred to as 'APN').

In the service announcement step 220, nodes located between the BM-SC 206 and the UE 202 (the RNC 204, SGSN, transport network, etc.) are connected to the UE 202 and the UE ( Recognize other nodes that are connected to 202. For example, the SGSN grasps a list of UEs that want to receive the MBMS service and a list of RNCs in which the UEs are located, and transmits MBMS data only to RNCs in which the UEs are located later with reference to the lists. do.

The UE 202 learning the MBMS service basic information performs a service joining step 230 to receive desired MBMS service data. In the service joining step 230, the UE 202 transmits the desired at least one MBMS service identifier among the MBMS service identifiers obtained through the service announcement step 220 to the BM-SC 206.

SESSION START step 240 uses a signaling procedure such as session initiation informing of data transmission on the HS-SCCH before MBMS notification. In addition, the high speed physical downlink shared channel (hereinafter referred to as "HS-PDSCH") is a common channel that can be shared by several users and used through the HS-SCCH.

HSDPA MBMS NOTIFICATION step 260 calls the UE 202 to inform that the MBMS service using the HSDPA requested by the UE 202 in the service joining step 230 will start soon. to be. In the service notification step 240, group paging is performed for a plurality of UEs participating in the MBMS service using the HSDPA.

In a data transfer step 260, actual MBMS data is transmitted to the UE 202 via the RNC 204. In step 260, for example, if there is a need to change a ciphering key for the MBMS service, the RNC 204 sends a new encryption key to all UEs receiving the MBMS service. To pass.

When the MBMS service is terminated, the session stop signaling step 270 uses a session stop signaling message indicating that the data transmission through the HS-SCCH is finished. Although not shown, the UE 202 may voluntarily stop receiving the MBMS service and stop receiving the MBMS service while receiving the MBMS service (ie, at step 260).

In the living step 280, the MBMS service is released and the MBMS service signaling procedure using the HSDPA is completed.

3 is a diagram illustrating a physical procedure of the HS-SCCH in the general HSDPA.

3 is a HS-SCCH transmission procedure for transmitting control information such as code information and a transport block size for a high speed physical downlink shared channel (HS-PDSCH) that is a physical channel to which an HS-DSCH is mapped. Indicates. However, a CRC (Cyclic Redundancy Checks) value is transmitted using a CRC related to multicast.

In step 312, Xccs (Channelization-Code-Set information) and Xms (Modulation-Scheme information) are input and multiplexed to output X1, and in step 302, an additional version is added. (redundancy version) variables r and s and constellation version (b) variables are input and Xrv (additional version information) output through random variable (RV) coding and Xtbs (transport block size information ( Transport Block Size information)), Xhap (Hybrid ARQ Processing Information), and Xnd (New Data Indicator) are multiplexed in step 304 to output X2. In step 306, X1 and X2 are combined with a multicast CRC indicating Xue (a UE identity, using a multicast group identity for an MBMS service), and outputs Y. X1 and Y are converted into Z1 and Z2 through channel coding 1 in step 314 and channel coding 2 in step 308, respectively, and Z1 and Z2 are rate matching in step 316 and rate matching in step 310. Convert to R1 and R2 through 2.

In step 318, the R1 is converted to S1 through multicast specific masking using Xue, and in step 320, the S1 and R2 are physical channel mapped to generate HS-SCCH information.

In this way, since multiple users should be able to receive simultaneously using HSDPA, the user ID for transmitting a data frame is not a specific user ID (HS-DSCH Radio Network Temporary Identity) but a multicast ID (HS-D). DSCH Multicast RNTI). That is, a multicast group ID that can be distinguished by a service is used rather than an ID that can be distinguished by subscriber so that users who subscribe to a specific multicast service can simultaneously receive the same channel. Accordingly, the multicast group ID is used in the same manner to inform HS-SCCH information indicating whether traffic is transmitted during the next transmission period to inform the user of the presence of HS-PDSCH data. However, in order for the base station to refer to channel quality information (called "CQI") of each user belonging to the multicast group and to manage the multicast group, the base station together with the terminal ID information from the RNC to the Iub. Receive the HS-DSCH Multicast RNTI. When the base station receives both the terminal ID and the HS-DSCH Multicast RNTI, the base station may recognize that it is a multicast service through HSDPA.

Here, the RNC does not assign individual flow IDs for each user in the same service for the multicast service, and performs flow control for each multicast service in the Iub using the same flow ID. In addition, CQI transmitted through uplink for each user is managed for each multicast service. That is, the format to be transmitted during the next TTI is determined in consideration of the lowest CQI among the CQIs transmitted by users belonging to the same multicast service, and the transmit power is determined. However, if the CQI of a specific user is too bad, that is, if the channel environment is very poor in a cell boundary area of a specific user, the channel type switching may be performed so that the specific user can be configured in an end-to-end manner. It is a structure that can be.

4 is a flowchart illustrating a multicast service transmission procedure of a base station through HSDPA according to a preferred embodiment of the present invention.

In step 410, the base station sets the HS-DSCH and the multicast ID for each service, and sets the ID list for each user of the service. In step 420, the base station transmits a flow control message to the RNC to perform flow control between the RNC and the base station.

In step 430, if the multicast data to be transmitted is received from the RNC, the base station performs scheduling by the MAC-hs object. Here, the MAC-hs object in the base station exists for each multicast service and separately manages user IDs belonging to each multicast service.

If it is determined in step 440 to transmit a new packet proceeds to step 450, MAC-hs collects the channel quality information (CQI) transmitted by the user using the same multicast service through the uplink, the lowest Select the CQI of the value.

Select CQI = Min (CQI1, CQI2, ..., CQI1), where CQIi is the CQI value sent by user i who is given a particular multicast service.

If it is determined in step 440 that the retransmission packet is transmitted due to a terminal reception error, the process proceeds to step 460 where the MAC-hs requests retransmission among CQI values transmitted through uplink by each user using the same multicast service. After collecting only the CQI values of the users, select the lowest CQI among the CQI values of the users requesting retransmission, and proceeds to step 470.

In step 470, the MAC-hs allocates the most optimal transmission amount and transmission power according to the selected CQI.

In step 480, the MAC-hs entity transmits an HS-DSCH data frame including the multicast data according to the allocated transmission amount and transmission power through HS-DSCH flow control. In this case, however, only one transmission is performed for each multicast service using the HS-DSCH Multicast RNTI.

On the other hand, the MAC-hs informs the terminal that there is data transmitted through the HS-PDSCH through the HS-SCCH. Here, the information is informed using the HS-DSCH Multicast RNTI allocated to each multicast service instead of the ID assigned to each terminal.

The terminal receiving the multicast service uses the HS-DSCH Multicast RNTI as a CRC checking procedure when the HS-SCCH demodulates. In case that there is no CRC error in the HS-SCCH data, each UE transmits HS-PDSCH information on the modulation scheme, HS-PDSCH physical channel information, transport block size, etc. of data to be transmitted through HS-PDSCH. Obtain from SCCH data.

The terminal receives the data frame through the HS-PDSCH using the HS-PDSCH information. If there is no error in the data frame, the data frame is transmitted to a higher layer. If there is an error in the data frame, the HARQ operation is performed to transmit a NACK. The base station receiving the NACK retransmits the data frame according to the retransmission procedure defined in the standard.

There is a need to perform channel and user management when providing multicast services over HSDPA. In other words, when a user's CQI is continuously significantly bad or is located in a soft handoff area during multicast service through HSDPA, the user does not provide a multicast service through HSDPA. It is efficient to transmit by using. The procedure of the base station and RNC for this purpose is as follows.

5 is a flowchart illustrating a channel type change procedure for a multicast service according to an embodiment of the present invention.

If a user who wants a multicast service occurs, the base station determines whether the user is the first user of the multicast service in step 510. If the first user of the multicast service, the flow proceeds to step 520, and if the existing user, the flow proceeds to step 530. In step 520, the base station generates an HS-DSCH Multicast RNTI for each service and proceeds to step 530.

In step 530, the base station updates the user ID and the CQI value to manage the list of users included in the multicast service. In step 540, CQI information is collected from a user corresponding to the multicast service to manage a recent CQI value of each user. Specifically, the base station measures and compares the average CQI value of each user with the average CQI value of all users.

For example, the addition average value calculated as follows can be used.

CQI_i_avg = W1 * CQI_i_now + W2 * CQI_i_ (now-1) + ... + Wk * CQI_i_ (now-k + 1)

At this time, Wk is a weighting factor for each measurement time point and has the characteristic of W1> W2> ...> Wk. CQI_i_k means the CQI value measured by the user i at the kth previous time.

The base station compares the average CQI values of the various users and checks whether the average CQI value of a specific user is significantly lower than the CQI values of other users in step 550. In this case, a method using average and variance may be used, or the following method may be used, but the present invention does not limit the particular method.

Ex) CQI_i is less than average (CQI_1, CQI_2, ..., CQI_k) * Weighting_Factor.

The base station proceeds to step 530 if the CQI value of a specific user is not significantly lower than the CQI of other users belonging to the multicast service through the check of step 550, and proceeds to step 560 if the CQI of the other user is significantly lower than the CQI of other users. Request the RNC including the HS-DSCH Multicast RNTI and the user ID to change the channel type for the user to the dedicated channel, and perform the channel type change procedure according to the instruction from the RNC. At this time, the base station may transmit the request information through a modified Radio Link Parameter Update message or may transmit the request information through a new message.

The RNC performs a series of procedures for performing a service through a dedicated channel for a corresponding UE. Specifically, the RNC instructs the base station and the terminal to configure a dedicated channel for the multicast service. Thereafter, the terminal receives the multicast data through the dedicated channel. If no user receives the multicast service after changing the channel type, the multicast service channel is terminated.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention can increase the number of services that can be provided per cell by using the HSDPA channel instead of the FACH channel which is less efficient in using a multicast service. Therefore, since more services can be provided in the same frequency band from the operator's point of view, there is a benefit of maximizing wireless efficiency, and when changing the channel type of a specific user when providing a multicast service through HSDPA, By performing the transmission power can be reduced. In addition, by providing a multicast service using HSDPA, there is an effect that can provide a more reliable service through fast retransmission and HARQ.

Claims (8)

A method for providing a multimedia broadcasting / multicast service using a downlink high speed packet data channel in a mobile communication system, Setting a high speed forward common channel (HS-DSCH) and a multicast ID for a multicast service, and setting an ID list for each user of the multicast service; When the multicast data for the multicast service is generated, collecting channel quality information (CQI) of users using the multicast service and selecting the lowest CQI; Allocating an optimal transmission amount and transmission power according to the selected CQI; Transmitting the multicast data through HS-DSCH according to the allocated transmission amount and transmission power; And transmitting control information on the multicast data transmitted through the HS-DSCH through a high speed forward common control channel (HS-SCCH) corresponding to the HS-DSCH using the multicast ID. Characterized in that the method. The method as claimed in claim 1, wherein the multicast ID is an HS-DSCH multicast Radio Network Temporary Identity (RNTI). The method of claim 1, wherein the selecting of the multicast data comprises requesting retransmission due to a reception error of the multicast data. And selecting the lowest CQI among the CQI values of users requesting retransmission. A method for providing a multimedia broadcasting / multicast service using a downlink high speed packet data channel in a mobile communication system, Creating a multicast ID for users who are new to a specific multicast service; Managing a list of users using the multicast service; Providing a multicast service through a multicast service channel to users included in the list of users using the multicast ID; Calculating the latest CQI of each user by collecting CQIs from users receiving the multicast service; Requesting a radio network controller (RNC) to change a channel type for a user having a CQI value significantly lower than that of other users to a dedicated channel; And performing a channel type change of a user having the significantly low CQI value according to the instruction from the RNC. The method as claimed in claim 4, wherein the multicast ID is a HS-DSCH multicast Radio Network Temporary Identity (RNTI). The method of claim 4, wherein the managing of the list of users comprises: And updating the user IDs of the users who use the multicast service and the CQI values of each user. The method of claim 4, wherein the requesting process comprises: And requesting information including a multicast ID of the multicast service and a user ID of a user having the significantly low CQI value to the RNC. 5. The method of claim 4, further comprising the step of releasing the multicast service channel for the multicast service when the user receiving the multicast service no longer exists.

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