Patent Publication Number: US-2004058696-A1

Title: Radio communication system, mobile station and radio network controller

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. P2002-274128, filed on Sep. 19, 2002; the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] The present invention relates to a radio communication system performing multicast communication, a mobile station and a radio network controller.  
       [0004] 2. Description of the Related Art  
       [0005] As shown in FIG. 1, broadcast communication whereby a plurality of base stations  11  to  17  transmit common information to unspecified mobile stations  101  to  112  in predetermined areas is known in a conventional radio communication system.  
       [0006] As shown in FIG. 2, multicast communication whereby a plurality of base stations  11  to  17  transmit common information to specific mobile stations joining in (belonging to) a specific group is known in a conventional radio communication system.  
       [0007] In the multicast communication, a plurality of mobile stations forms one multicast group. In order to start the multicast communication, one PICH (Paging indicator channel) is transmitted to each multicast group, and each mobile station returns a response signal to the received PICH.  
       [0008] However, there is a problem in that a plurality of response signals are transmitted to the radio network controller RNC at approximately the same time even though the multicast communication can be started with one response signal, so that the load on receiving control of the radio network controller RNC is increased in the conventional multicast communication.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009] In viewing of the foregoing, it is an object of the present invention to provide a radio communication system which can reduce the load on the radio network controller during multicast communication, a mobile station and a radio network controller which can be used in the above radio communication system.  
       [0010] A first aspect of the present invention is summarized as a radio communication system having a radio network controller, base stations and mobile stations, to perform multicast communication.  
       [0011] The radio network controller comprises a control signal transmitter configured to divide a multicast group into subgroups, to divide a control signal for the multicast group into control signals for the subgroups and to transmit the control signals for the subgroups to the base station.  
       [0012] The mobile station comprises a response signal creator configured to create a response signal to the control signal for at least one subgroup, a transmission timing detector configured to detect a transmission timing of the response signal from the control signal for at least one subgroup, and a response signal transmitter configured to transmit the response signal to the base station with the transmission timing.  
       [0013] A second aspect of the present invention is summarized as a mobile station supporting multicast communication. The mobile station comprises a response signal creator configured to create a response signal to a control signal for at least one subgroup into which a control signal for multicast group is divided, a transmission timing detector configured to detect a transmission timing of the response signal from the control signal for at least one subgroup, and a response signal transmitter configured to transmit the response signal to a base station with the transmission timing.  
       [0014] A third aspect of the present invention is summarized as a radio network controller supporting multicast communication. The radio network controller comprises a control signal transmitter configured to divide a multicast group into subgroups, to divide a control signal for the multicast group into control signals for the subgroups, and to transmit the control signals for the subgroups to a base station.  
       [0015] In the third aspect, the radio network controller may perform a predetermined processing on a predetermined number of response signals. The predetermined number of response signals respond to the control signal for the multicast group, and are transmitted from mobile stations joining in the multicast group. And the radio network controller may perform processing on the only the predetermined number of response signals. Any following response signal is unprocessed by the radio network controller. The following response signals are transmitted from the mobile stations joining in the multicast group. The predetermined number may be one. 
     
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
     [0016]FIG. 1 is a diagram for explaining broadcast communication according to the prior art.  
     [0017]FIG. 2 is a diagram for explaining multicast communication according to the prior art.  
     [0018]FIG. 3 is a diagram showing the entire configuration of a radio communication system according to one embodiment of the present invention.  
     [0019]FIG. 4 is a functional block diagram of a mobile station in the radio communication system according to the embodiment.  
     [0020]FIG. 5 is a functional block diagram of a radio network controller in the radio communication system according to the embodiment.  
     [0021]FIG. 6 is a sequence diagram illustrating the operation of the radio communication system according to the embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0022] &lt;A Configuration of a Radio Communication System According to an Embodiment of the Present Invention&gt; 
     [0023]FIG. 3 shows the entire configuration of a radio communication system according to an embodiment of the present invention.  
     [0024] As shown in FIG. 3, the radio communication system according to the embodiment comprises four base stations  10 ,  20 ,  30  and  40  under a radio network controller  50 .  
     [0025] In the radio communication system according to the embodiment, the base station  10  manages mobile stations  11  to  13 , the base station  20  manages mobile stations  21  and  22 , the base station  30  manages mobile stations  31  and  32 , and the base station  40  manages mobile stations  41  to  43 . The mobile stations  11 ,  12 ,  21 ,  41 ,  42  and  43  join in the same multicast group A in the embodiment.  
     [0026] The radio network controller  50  divides the multicast group A into three subgroups A 1  to A 3  in the embodiment. The radio network controller  50  allocates each of six mobile stations  11 ,  12 ,  21 ,  41 ,  42  and  43  joining in the multicast group A to one of the subgroups A 1  to A 3 .  
     [0027] For example, the radio network controller  50  allocates the mobile station  11  and  12  to the subgroup A 1 , allocates the mobile station  21  and  41  to the subgroup A 2 , and allocates the mobile station  42  and  43  to the subgroup A 3 .  
     [0028]FIG. 4 shows a functional block diagram of the mobile station used in the radio communication system according to the embodiment. Functions of a plurality of mobile stations  11  to  43  are basically the same, so that the function of the mobile station  11  will be explained as follows.  
     [0029] As shown in FIG. 4, the mobile station  11  is configured with a control signal receiver  11   a , a response signal transmitter  11   b , a response signal creator  11   c  and a transmission timing detector  11   d.    
     [0030] The control signal receiver  11   a  is configured to receive a control signal for the multicast group A and a control signal for the subgroup A 1  which are transmitted from the base station  10 .  
     [0031] The response signal creator  11   c  is configured to create a response signal to the control signal for the multicast group A or the control signal for the subgroup A 1 .  
     [0032] The transmission timing detector  11   d  is configured to detect a transmission timing of the response signal in the subgroup A 1  from the received control signal for the subgroup A 1 .  
     [0033] For example, the transmission timing detector  11   d  can detect 100 ms as the transmission timing of the response signal in the subgroup A 1 , detect 200 ms as the transmission timing of the response signal in the subgroup A 2 , detect 300 ms as the transmission timing of the response signal in the subgroup A 3 .  
     [0034] And the transmission timing detector  11   d  can detect a time X (for example, 19:00) as the transmission timing of the response signal in the subgroup A 1 , detect a time Y (for example, 19:01) as the transmission timing of the response signal in the subgroup A 2 , detect a time Z (for example, 19:02) as the transmission timing of the response signal in the subgroup A 3 .  
     [0035] The response signal transmitter  11   b  is configured to transmit the created response signal to the base station  10  with the detected transmission timing.  
     [0036] For example, the response signal transmitter  11   b  transmits the response signal to the base station  10  100 ms after receiving the control signal for the subgroup A 1  (or at the time X), transmits the response signal to the base station  10  200 ms after receiving the control signal for the subgroup A 3  (or at the time Y), and transmits the response signal to the base station  10  300 ms after receiving the control signal for the subgroup A 3  (or at the time Z).  
     [0037]FIG. 5 shows a functional block diagram of the radio network controller  50  used in the radio communication system according to the embodiment.  
     [0038] As shown in FIG. 5, the radio network controller  50  is configured with a response signal receiver  50   a , a control signal transmitter  50   b  and a subgroup divider  50   c.    
     [0039] The subgroup divider  50   c  is configured to divide the multicast group A into the subgroups A 1  to A 3 , and to divide a control signal for the multicast group A into control signals for the subgroups A 1  to A 3 .  
     [0040] The control signal transmitter  50   b  is configured to transmit the control signals for the subgroups A 1  to A 3  to the base station  10 .  
     [0041] For example, the control signal transmitter  50   b  may transmit the control signals for the subgroups A 1  to A 3  to the base stations  10 ,  20  and  40 .  
     [0042] The control signal transmitter  50   b  may transmit the control signals for the subgroups A 1  to the base stations  10 , transmit the control signals for the subgroups A 2  to the base stations  20  and  40 , and transmit the control signals for the subgroups A 3  to the base stations  40 .  
     [0043] The response signal receiver  50   a  is configured to receive the response signal to the control signal for the multicast group A from the mobile stations  11  and  12  at a different time.  
     [0044] &lt;An Operation of the Radio Communication System According to the Embodiment&gt; 
     [0045] Referring to FIG. 6, the operation where the radio network controller  50  performs predetermined processing (for example, a service notice processing, or an authentication processing) on the mobile stations  11 ,  12 ,  21 ,  41 ,  42 ,  43  joining in the multicast group A in the radio communication system according to the embodiment will be described.  
     [0046] As shown in FIG. 6, in step  1001 , the radio network controller  50  allocates each of six mobile stations  11 ,  12 ,  21 ,  41 ,  42  and  43  joining in the multicast group A to one of the subgroups A 1  to A 3 .  
     [0047] In step  1002 , the radio network controller  50  transmits a control signal such as a service notice signal and an authentication signal (a control signal for each of the subgroups A 1  to A 3 ) to three base stations  10 ,  20  and  40 .  
     [0048] In step  1003 , each of the base stations  10 ,  20  and  40  receives the control signal transmitted from the radio network controller  50 . The control signals transmitted by each of the base stations  10 ,  20  and  40  reach the mobile stations  11 ,  12 ,  21 ,  41 ,  42  and  43  joining in the multicast group A under the base stations  10 ,  20  and  40 .  
     [0049] In step  1004 , each of the mobile stations  11 ,  12 ,  21 ,  41 ,  42  and  43  receives the control signal from each of the base stations  10 ,  20  and  40 , and detects transmission timing of a response signal in the subgroup A 1 , A 2  or A 3  in which each of the mobile stations  11 ,  12 ,  21 ,  41 ,  42  and  43  is joining.  
     [0050] In step  1005 , each of the mobile stations  11 ,  12 ,  21 ,  41 ,  42  and  43  creates the response signal to the control signal for the each of the subgroups A 1  to A 3 , and transmits the response signal to the base stations  10 ,  20  and  40  with the detected transmission timing.  
     [0051] In step  1006 , each of the base stations  10 ,  20  and  40  receives the response signal from each of the mobile stations  11 ,  12 ,  21 ,  41 ,  42  and  43 , and transmits the received response signal to the radio network controller  50 .  
     [0052] In step  1007 , the radio network controller  50  transmits a service data to the base stations  10 ,  20  and  40 , in accordance with the response signals received from each of the mobile stations  11 ,  12 ,  21 ,  41 ,  42  and  43 .  
     [0053] In step  1008 , each of the base stations  10 ,  20  and  40  transmits the received service data to each of the mobile stations  11 ,  12 ,  21 ,  41 ,  42  and  43 .  
     [0054] The radio network controller  50  can be configured to perform a predetermined processing on only a predetermined number of response signals (for example, a first response signal). The predetermined number of response signals are transmitted from each mobile station  11 ,  12 ,  21 ,  41 ,  42  or  43  joining in the multicast group A.  
     [0055] In other words, any response signal following the predetermined number of response signals is unprocessed by the radio network controller  50 . The following response signals are transmitted from the mobile stations  11 ,  12 ,  21 ,  41 ,  42  and  43  joining in the multicast group A.  
     [0056] The radio network controller  50  can determine any number (for example, one, two and so on) as the predetermined number.  
     [0057] &lt;Functions and Effects of the Radio Communication System According to the Embodiment&gt; 
     [0058] The radio communication system according to the embodiment can reduce the load on the radio network controller  50  caused by response signals which are transmitted from a plurality of mobile stations  11 ,  12 ,  21 ,  41   42  and  43 , and which reach the radio network controller  50  at approximately the same time, when common information are transmitted to a plurality of mobile stations like multicast communication or broadcast communication.  
     [0059] The present invention can provide a radio communication system which can reduce the load on the radio network controller during multicast communication, a mobile station and a radio network controller which can be used in the above radio communication system.  
     [0060] Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and the representative embodiment shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.