Abstract:
A method and apparatus for utilizing multicast services to enhance battery life and provide for more efficient use of radio resources. A UE is configured to receive messages indicating an assigned paging window from a plurality of paging windows. The receiver receives a notification messages in the assigned paging window, wherein notification messages include the group identifiers of multicast groups associated with the UE that have subsequent data messages to send. The UE powers down during paging windows to which it is not assigned.

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 10/325,794 filed Dec. 19, 2002 which claims the benefit of U.S. Provisional Patent Application No. 60/413,954, filed Sep. 26, 2002, which are incorporated by reference as if fully set forth. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention generally relates to efficient message transmission in cellular systems. More particularly, the present invention is related to efficient transmission of multicast and broadcast services to user equipment to conserve radio resources and extend battery life. 
       BACKGROUND 
       [0003]    Third generation (3G) cellular systems are continually being modified to improve the efficiency of transmission of multicast and broadcast services to user equipment (UE). There are various parameters that are desirable to optimize in these cellular systems and networks. Typically, when one of the parameters is optimized, the optimum for another parameter is sacrificed. One of the opposing sets of parameters comprises UE power consumption versus radio resource utilization. 
         [0004]    For minimum power consumption, UEs should actively search for signals as infrequently as possible. As shown in  FIG. 1 , when a UE is not searching for the paging window K or being used by the user for some purpose, it should preferably be in a sleep-mode to minimize power consumption. 
         [0005]    Additionally, for efficient radio resource utilization, the same message targeted to multiple UEs should ideally be sent only once. For example, referring to  FIG. 2 , a plurality of UEs  12 ,  14 ,  16  are shown. The UEs  12 ,  14 ,  16  are associated with a single group XYZ, which is identified by a single group identifier ID XYZ . The terminology “group identifier” as used hereinafter may refer to a group, a service or any other type of signal that may be associated with one or more recipients or services. The UEs are notified that the group identifier ID XYZ  will be transmitted within a certain paging window, for example paging window K shown in  FIG. 1 . All the UEs targeted for the transmission will then receive that single transmission of ID XYZ  in paging window K. 
         [0006]    An important consideration is how to satisfy opposing requirements of both the UE power consumption and radio resource utilization to an acceptable degree. It is desirable to optimize both UE power consumption and radio resource utilization so that the sacrifice in each is within an acceptable range. 
         [0007]    To satisfy the UE power requirements, the system can transmit multiple message notifications within a synchronized time period. Each broadcast service or message, or target group for a service is assigned an identifier. The UE can search for the identifier to know that a message it should receive is being transmitted. If the UE does not detect the appropriate identifier within a certain time period, the UE can go into a sleep-mode until the next cycle of the time period occurs. 
         [0008]    Prior methods of message transmission in cellular systems have had disadvantages which resulted in loss of UE battery life. Although a desirable approach would be to put the group identifiers for all of the different services expected by UE in the same time window, this approach requires that the UE must look for two or more identifiers, which are likely made up of different groups of UEs. While it may be possible to coordinate some of the recipients into the same search window, the majority will often still require multiple windows. 
         [0009]    For example, as shown in  FIG. 3 , a UE may be associated with several groups. As shown in Table 1 below, UE22 is associated with all three groups: ABC, DEF and GHI. Referring to  FIG. 4 , since ID ABC  is transmitted in paging window K, ID DEF  is transmitted in paging window L and ID GHI  is transmitted in paging window M, UE22 will have to be in a waking mode during paging windows K, L and M for each possible message identification. Likewise, UE34 will have to be in a waking mode during paging windows L and M. Accordingly, the number of group services a UE is enabled to receive will therefore dictate the number of awake-periods. This will multiply the battery consumption rate by the number of awake-periods. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 GROUP 
                 GROUP ID 
                 MEMBERS 
                 WINDOW 
               
               
                   
                   
               
             
             
               
                   
                 ABC 
                 ID ABC   
                 UE22, UE24, UE26 
                 K 
               
               
                   
                 DEF 
                 ID DEF   
                 UE22, UE34, UE36 
                 L 
               
               
                   
                 GHI 
                 ID GHI   
                 UE22, UE34, UE46 
                 M 
               
               
                   
                   
               
             
          
         
       
     
         [0010]    It would be desirable to provide a method for enabling multicast services and UE battery savings without the shortcomings of the prior art. 
       SUMMARY 
       [0011]    The present invention provides a method and apparatus for utilizing multicast services to enhance battery life and more efficiently use of radio resources. A UE is configured to receive messages indicating an assigned paging window from a plurality of paging windows. The receiver receives a notification messages in the assigned paging window, wherein notification messages include the group identifiers of multicast groups associated with the UE that have subsequent data messages to send. The UE powers down during paging windows to which it is not assigned. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    A more detailed understanding of the invention may be had from the following description of a preferred embodiment, given by way of example and to be understood in conjunction with the accompanying drawings: 
           [0013]      FIG. 1  is a signal diagram of a repeating paging. 
           [0014]      FIG. 2  is a block diagram of a single identifier for multiple UEs. 
           [0015]      FIG. 3  is a block diagram of multiple identifiers, each having multiple UEs. 
           [0016]      FIG. 4  is a signal diagram of several identifiers and associated pointers transmitted in several paging windows. 
           [0017]      FIG. 5  is a system made in accordance with the teachings of the present invention. 
           [0018]      FIG. 6  is a signal diagram of multiple paging windows, each paging window having a plurality of identifiers. 
           [0019]      FIG. 7  is a flow diagram of a procedure in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Referring to  FIG. 5 , the system  100  in accordance with the present invention comprises a network  102  having memory  103 . The network  102 , is associated with one or more Node Bs  104 ,  106 ,  108  or base stations (hereafter referred to as “Node Bs”) and is in communication with a plurality of UEs  110 ,  112 ,  114 ,  116 ,  118 . The UEs  110 - 118  may be associated with the network  102 , or may be associated with another network and can roam from one network to another. 
         [0021]    As will be explained in detail hereinafter, the network  102  maintains in memory  103  information regarding each of the UEs, the services and/or groups with which each UE is associated, and the paging windows each UE will access. Although the foregoing description will present the information in memory  103  as being a plurality of tables, this description is presented for convenience only. One skilled in the art would clearly realize that a plurality of tables may be utilized, or a single table having many different columns may be utilized in accordance with the present invention. The description regarding one or more tables is not intended to limit the present invention to requiring multiple tables. Referring to Table 2, the network  102  maintains in memory  103  a table having a group list comprising a listing of each group identifier and all of the members associated with each group identifier. The memory is accessible to the system administrator. This permits the system administrator to call up the group list and edit it when appropriate. When the group is edited, for example by adding or deleting a member UE, the affected UE is then informed as to its addition or deletion from the group as appropriate. 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 GROUP 
                 GROUP ID 
                 MEMBER UEs 
               
               
                   
                   
               
             
             
               
                   
                 ABC 
                 ID ABC   
                 UE22, UE24, UE26 
               
               
                   
                 DEF 
                 ID DEF   
                 UE22, UE34, UE36 
               
               
                   
                 GHI 
                 ID GHI   
                 UE22, UE34, UE46 
               
               
                   
                   
               
             
          
         
       
     
         [0022]    Referring to Table 3, the network  102  also maintains in memory  103  a data file comprising a list of all of the groups to which each UE belongs. This allows the network  102  to schedule transmissions for a given UE such that it can indeed handle more than one possible source of message for it. For example, as will be described in greater detail hereinafter, if a UE is scheduled to receive a data message at time X on channel A, the UE may not be able to simultaneously also receive a different message overlapping with time X, but on a different channel. 
         [0000]    
       
         
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 UEs 
                 ASSOCIATED GROUPS 
               
               
                   
               
             
             
               
                 22 
                 ABC, DEF, GHI 
               
               
                 24 
                 ABC 
               
               
                 26 
                 ABC 
               
               
                 34 
                 DEF, GHI 
               
               
                 36 
                 DEF 
               
               
                 46 
                 GHI 
               
               
                   
               
             
          
         
       
     
         [0023]    The network  102 , having the information from Tables 2 and 3, must then determine the most efficient manner for scheduling the group identifiers. It should be recognized that in order to save airtime, the “shortest” amount of airtime should be utilized. Since the data message is assumed to be many orders of magnitudes longer than the group identifiers with associated pointers, it is paramount to limit the number of times that messages are sent. In fact, it is assumed that the data message is only sent once unless the UE experiences a scheduling conflict whereby a data message may have to be re-transmitted or scheduled for more than one occurrence. 
         [0024]    A second scheduling factor is to attempt to transmit all of the group identifiers and associated pointers for a particular UE within a single paging window. Since the group identifier and associated pointers are assumed to be minimal in length, it is preferable to repeat the group identifiers and associated pointers in multiple paging windows as necessary in order to limit the number of paging windows each UE must access, and therefore limit the number of waking periods for each UE. 
         [0025]    Accordingly, referring to Table 4, the network maintains in memory  103  a listing of paging windows and the group identifiers that will be transmitted within each window. This table is derived from the information in Tables 2 and 3 which show the group, group identifier, the member UEs associated with each group and the groups associated with each UE. In essence, Table 4 sets forth the scheduling parameters for each paging window. As shown, each member UE is associated with a single paging window within which multiple group identifiers will be transmitted. Although shown in Table 4 as associated with paging window L, UE36 and UE46 may be associated with either paging window K or paging window L since UE36 needs only group identifier ID DEF  to be received and UE46 needs only ID GHI  to be received. Paging window K or L would be sufficient to provide an adequate message and pointer for both UE36 and UE46. 
         [0000]    
       
         
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                 PAGING WINDOW 
                 GROUP ID 
                 MEMBER UEs 
               
               
                   
               
             
             
               
                 K 
                 ID ABC , ID DEF , ID GHI   
                 UE22, UE24, UE26 
               
               
                 L 
                 ID DEF , ID GHI   
                 UE34, UE36, UE46 
               
               
                   
               
             
          
         
       
     
         [0026]    Referring to  FIG. 6 , the group identifiers are added to the appropriate paging windows. As shown, the group identifiers are repeated as necessary. The network  102  then notifies each UE which paging window to look to for its group identifier. The UE then looks to this paging window (or windows) for its group identifiers. Accordingly, each UE need only look within its assigned paging window for its identifiers. This method permits each UE to only search a single paging window, or a vastly reduced set of paging windows as opposed to the prior art methods. 
         [0027]    As shown in  FIG. 6 , the UEs look in the appropriate paging window to search for its group identifiers. Each group identifier, as mentioned, includes a pointer which directs the UE to the location or address of a subsequent data message. Depending on the wireless network being utilized the pointer may indicate time, frequency channel, coding (eg. CDMA), and/or direction, (often called space encoding), as appropriate for the RF modulation scheme employed. In fact, the pointer may “point” from one RF network to another RF Network. For instance, the pointer may be delivered via GSM, but the actual data may arrive via a Wireless LAN, for UEs so equipped. The data message itself is scheduled to occur after the last pointer transmission occurs, in order to guarantee that all the member UEs have the pointer to the data and will be able to assume a state suitable to acquire the data prior to its actual transmission. The approach shown in  FIG. 6  is efficient with respect to air-time, if the one instance of the data message is relatively long compared to the multiple instances of the group identifiers and associated pointers to the data. 
         [0028]    Even in the event that scheduling of the UEs to certain paging windows is so complicated as to require a UE to search more than one paging window, the present invention still has several significant advantages over the prior art. First, if the UE searches multiple paging windows, it can avoid redundant receptions of the same data message by comparing the multiple pointers. Redundant pointers will be discarded. For each repeating cycle, there can only be one unique message per instance of the pointer. 
         [0029]    Second, although a UE may be forced to search multiple paging windows, the number of paging windows will be significantly reduced over that required by the prior art. Accordingly, the number of waking periods will be reduced and the expected UE battery life will be significantly increased. 
         [0030]    For example, the three group identifiers ID ABC , ID DEF , ID GHI  will be present in paging window K, which is now the only window UE22 needs to search. These identifiers may be repeated in one or more other paging windows, because the other members of the group only search those windows. All occurrences of the group identifications, however, point (by way of their associated pointer) to one unique instance of the actual data message. Although there is an increase in airtime usage because the group identifications are repeated, this increase is assumed to be insignificant compared to what would be required to repeat the data message. UE22 needs to awaken for only one paging window, so it saves significant battery life versus the scheme set forth in Table 1. 
         [0031]    Referring to  FIG. 7 , a flow diagram, of a method  100  in accordance with the present invention is shown. The method  100  begins with the network determining each group and the member UEs associated with each group in step  102 . As a result of the determination made in step  102 , the network will then determine all groups with which a UE is associated (step  104 ). It should be noted that steps  102  and  104  are essentially different views of the same information and may comprise a single step. The network then schedules group identifications and associated pointers within the paging windows such that each UE accesses only a single paging window (step  106 ). The network then determines if more than one paging window is necessary for each UE (step  108 ). If so, the network schedules an additional paging window for that particular UE (step  110 ) and then continues on with step  112 . If more than one paging window is not necessary as determined at  108 , the network proceeds directly to step  112  which determines whether there are any scheduling conflicts between data messages for a particular UE. If there are any data message conflicts (step  114 ) then network reschedules data messages as necessary (step  116 ). The network then determines if data message conflicts still exist (step  118 ). If so, duplicate data messages as necessary are scheduled (step  120 ). Step  118  is then repeated as necessary in order to resolve data message scheduling conflicts. Once it has been determined that no further conflicts still exists (step  118 ) the UEs are notified of their assigned paging window(s) (step  122 ). 
         [0032]    While the foregoing description represents a time line with a single physical carrier channel as an example, there can be multiple physical channels. For example, the paging information may exist on the same or a different physical channel from the data channel. Likewise, the invention is not intended to be limited to 3G cellular systems, even though 3G cellular systems have been referenced as an example. All such and other variations are envisaged to be within the purview and scope of the invention.