Multicast communication method in a CDMA mobile communication system

Abstract

A multicast communication method in a CDMA mobile communication system which is capable of reducing a transmission power in a base station system, and is capable of performing an efficient multicast operation for a large number of mobile subscribers is provided. The starting of information distribution by a multicast operation and identification information indicating a content of the information thereof are notified through a broadcast channel to a mobile subscriber. Further, through the broadcast channel, information such as a spread code or the like to be used at this time, which is necessary for actual reception of communication data, is notified. Then, in the mobile subscriber, a surround environment of the mobile subscriber is checked to determine the possibility of simultaneous receiving from a plurality of other base station systems. If possible, similar notified information is also received from other base station systems. Thus, all kinds of information regarding the spread code or the like to be used for receiving distributed information are obtained.

What is claimed is:  
     
         1 . A multicast communication method in a CDMA mobile communication system, which comprises a plurality of mobile subscribers and a plurality of base station systems communicatively connected to said mobile subscribers by radio channels, said method comprising: 
 notifying, by each of said base stations to said mobile subscribers, multicast information necessary for receiving a multicast broadcast to be output from at least one of said base stations at a time of information transmission; and    transmitting multicast data from said at least one of said base stations to said mobile subscribers.    
     
     
         2 . The multicast communication method according to  claim 1 , wherein the multicast information necessary for receiving a multicast broadcast comprises multicast starting information and spread code information.  
     
     
         3 . The multicast communication method according to  claim 1 , wherein the multicast data is transmitted from a broadcast channel of said at least one of said base stations.  
     
     
         4 . The multicast communication method according to  claim 1 , further comprising: 
 receiving, by at least one of said mobile subscribers, said multicast data transmitted from at least two of said base stations; and    performing a RAKE combining process by said at least one of said mobile subscribers in order to extract the multicast data sent over the corresponding broadcast channel of said at least two of said base stations.    
     
     
         5 . A multicast communication method in a CDMA mobile communication system, which comprises a plurality of mobile subscribers and a plurality of base station systems including anchor base stations and branch base stations that are communicatively connected to said mobile subscribers by radio channels, said method comprising: 
 outputting information regarding a multicast transmission to be output, the information including a designated area in which the multicast transmission is to be broadcast;    transferring the information regarding the multicast transmission to one or more of said anchor base stations corresponding to the designated area;    informing, by said one or more anchor base stations to one or more of said branch base stations adjacent to said one or more anchor base stations, a starting of information transmission of the multicast transmission; and    notifying, by said one or more branch base stations to at least one of said mobile subscribers in a radio transmission range of said one or more branch base stations, a starting of information transmission of the multicast transmission; and    transmitting, over a multicast channel at a time corresponding to the starting of information transmission, multicast data to said at least one of said mobile subscribers.    
     
     
         6 . The multicast communication method according to  claim 5 , wherein the multicast information comprises multicast starting information and spread code information.  
     
     
         7 . The multicast communication method according to  claim 5 , further comprising: 
 receiving, by at least one of said mobile subscribers, said multicast data transmitted from at least two of said base stations; and    performing a RAKE combining process by said at least one of said mobile subscribers in order to extract said multicast data sent over the corresponding broadcast channel of said at least two of said base stations.    
     
     
         8 . A multicast communication system in a CDMA mobile communication system, which comprises a plurality of mobile subscribers and a plurality of base station systems communicatively connected to said mobile subscribers by radio channels, each of said station systems comprising: 
 notifying means for notifying multicast information necessary for receiving a multicast broadcast to be output at a time of information transmission; and    transmitting means for transmitting multicast data to said mobile subscribers.    
     
     
         9 . The multicast communication system according to  claim 8 , wherein the multicast information necessary for receiving a multicast broadcast comprises multicast starting information and spread code information.  
     
     
         10 . The multicast communication system according to  claim 8 , wherein the multicast data is transmitted from a broadcast channel of said at least one of said base stations.  
     
     
         11 . The multicast communication system according to  claim 8 , wherein each of said mobile subscribers comprises: 
 receiving means for receiving said multicast data transmitted from at least two of said base stations; and    means for performing a RAKE combining process to extract the multicast data transmitted from said at least two of said base stations.