Abstract:
The present invention discloses a system structure for supporting Evolved Multimedia Broadcast/Multicast Service (Evolved MBMS), comprising: a Broadcast/Multicast Service Center (BM-SC) for initiating control signaling and bearer services for Multimedia Broadcast/Multicast Service (MBMS); a System Architecture Evolved Gateway (SAE GW) for receiving MBMS service data and MBMS control signaling or service data from another network, and forwarding the received service data and control signaling; a Broadcast/Multicast Management Entity (BME) for receiving, processing and forwarding the MBMS control signaling, and determining, for each item of the service data for MBMS, an enhanced Node B (eNB) which needs to receive the control signaling; and an multicast User Plane Entity (mUPE) for receiving the MBMS service data, processing the received MBMS service data in Evolved Packet System Architecture Evolution, and forwarding the processed MBMS service data to a downstream node.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an architecture system for supporting EMBMS (Evolved Multimedia Broadcast/Multicast Service) in a core network of wireless communication system, and in particular to a core network architecture for supporting EMBMS in System Architecture Evolution/Long-Term Evolution (SAE/LTE) of 3GPP (the Third Generation Partnership Project) and method of using this architecture system. 
     BACKGROUND OF THE INVENTION 
     The project of Long Term Evolution was started by 3GPP in 2005, aiming to provide supports for increasing demands of operators and subscribers with a higher data throughput and an improved network performance. 
     Multimedia Broadcast/Multicast Service (MBMS), introduced by 3GPP Rel6, is a point-to-point service for transmitting data from one data source to a plurality of subscribers so as to share network (including core network and access network) resources and provide services to a possibly largest number of multimedia subscribers having identical demands at the expense of resources as less as possible. In a radio access network, MBMS service uses a common transmission channel and a common radio bearer to implement both lower-rate message-type multicast and broadcast in pure text and higher-rate multicast and broadcast of multimedia services, such as mobile phone having television function. 
       FIG. 1  schematically shows an example of a mobile communication network as WCDMA system. As shown in  FIG. 1 , a plurality of NodeBs, such as NodeBs  11 ,  12  and  13 , are connected to a NodeB controller, such as RNC (Radio Network Controller)  10  in the mobile communication network. A single RNC  10  manages several NodeBs. Each of the NodeBs is connected with RNC via a wired transmission, and the interface between them is defined as Iub interface. RNC  10  may also be connected to SGSN (Serving Gateway Support Node) of a System Architecture Evolution network (CN) via Iu interface. 
       FIG. 2  schematically shows a diagram of MBMS network structure in 3GPP Rel6 version. Network cells supporting MBMS includes BM-SC (Broadcast/Multicast Service Center), GGSN (GPRS Gateway Support Node), SGSN, access network (UTRAN) comprising NodeB and RNC, and UE (User Equipment). BM-SC is an entrance for content providers and adapted for authorization, initiating MBMS bearer service in PLMN (Public Landline Mobile Communication Network) and transmitting MBMS data in accordance with a predefined schedule. RNC performs allocation and control of radio resources on the MBMS bearer service and transmits MBMS service data to the NodeB, which is responsible for transmitting efficiently MBMS service data and control signaling via air interface. 
     Specification of SAE/LTE was defined by 3GPP since Rel7 version. In order to simplify network architecture and reduce delay, SAE/LTE cancels RNC as a network cell. The functions of RNC are distributed into NodeB (eNodeB) and core network. The current SAE/LTE-based network architecture is flatter than that before evolution. The portion of radio access network is reduced from the original structure of two network nodes (NodeB+RNC) to a structure of a single network (enhance NodeB, also simplified as eNB). MBMS is called EMBMS (Evolved MBMS) in the SAE/LTE-based network architecture. 
     The current version of Specification defines only an architecture supporting unicast service in terms of system architecture evolved networks. No proposal is given to an architecture supporting MBMS in system architecture evolved networks. There is a need for a system architecture evolved network entity for supporting MBMS in System Architecture Evolution. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a system structure and method for supporting EMBMS, which can support EMBMS in System Architecture Evolution and enable an efficient transmission of EMBMS control signaling and service data to eNBs. 
     To achieve the above object, in an aspect of the invention, the invention provides a system structure for supporting Evolved Multimedia Broadcast/Multicast Service (Evolved MBMS), comprising: 
     a Broadcast/Multicast Service Center (BM-SC) for initiating control signaling and bearer services for Multimedia Broadcast/Multicast Service (MBMS); 
     a System Architecture Evolved Gateway (SAE GW) for receiving MBMS service data and MBMS control signaling or service data from another network, and forwarding the received service data and control signaling; 
     a Broadcast/Multicast Management Entity (BME) for receiving, processing and forwarding the MBMS control signaling, and determining, for each item of the service data for MBMS, an enhanced Node B (eNB) which needs to receive the control signaling; and 
     an multicast User Plane Entity (mUPE) for receiving the MBMS service data, processing the received MBMS service data in Evolved Packet System Architecture Evolution, and forwarding the processed MBMS service data to a downstream node. 
     In another aspect of the invention, the invention provides a method for supporting Multimedia Broadcast/Multicast Service (MBMS) in system architecture evolution, comprising the steps of: 
     initiating, by a Broadcast/Multicast Service Center (BM-SC), MBMS bearer services and forwarding the services to a System Architecture Evolved Gateway (SAE GW), or sending service data by another network to the SAE GW; 
     forwarding, by the SAE GW, the received MBMS service data or the service data from the another network to an multicast User Plane Entity (mUPE) after the SAE GW receives the MBMS service data or the service data from the another network; 
     performing, by the mUPE, a core-network processing on the received MBMS service data in Evolved Packet Core Network and forwarding the processed MBMS service data to a downstream node after the mUPE receives the MBMS service data. 
     In yet another aspect of the invention, the invention provides a method for transmitting Multimedia Broadcast/Multicast Service (MBMS) in system architecture evolution, comprising the steps of: 
     initiating, by a Broadcast/Multicast Service Center (BM-SC), an MBMS Session Start message and forwarding the MBMS Session Start message to a corresponding System Architecture Evolved Gateway (SAE GW); 
     forwarding, by the SAE GW, the received MBMS Session Start message to a corresponding Broadcast/Multicast Management Entity (BME) after the SAE GW receives the MBMS Session Start message; 
     sending, by the SAE GW, a response message back to the BM-SC in response to the reception of the MBMS Session Start message, so as to acknowledge the reception of the message; 
     receiving, by the BME, the MBMS Session Start message forwarded from the SAE GW, and forwarding the received MBMS Session Start message to each of enhance Node Bs (eNBs) which are connected to the BME and located in the service area covered by the MBMS; 
     sending, by the BME, a response message back to the SAE GW in response to the reception of the MBMS Session Start message, so as to acknowledge the reception of the message; 
     sending, by each of the eNBs, a response message back to the BME in response to the reception of the MBMS Session Start message, so as to acknowledge the reception of the message. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and advantages of the invention can be more apparent from the following detailed descriptions with reference to the accompanying drawings in which, 
         FIG. 1  is a schematic diagram showing a system structure of WCDMA radio access network; 
         FIG. 2  is a schematic diagram showing a network topology structure for MBMS in Rel6 version; 
         FIG. 3  is a schematic diagram of a MBMS-supporting System Architecture Evolution according to an embodiment of the present invention; and 
         FIG. 4  is a flowchart showing a process of transmitting service data in the MBMS-supporting System Architecture Evolution according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings. For the sake of simple, the detailed description of the known function and structure incorporated herein will be omitted, which would otherwise weaken the subject of the invention. 
     Now, reference is made to  FIG. 3  which shows a schematic diagram of a MBMS-supporting system architecture in evolved packet System Architecture Evolution according to an embodiment of the present invention. 
     In  FIG. 3 , bold lines denote newly added function elements and interfaces, and thin lines denote existing function elements and interfaces in the conventional structure. The architecture has a mobile network as its center and thus can support mobility between fixed access and 3GPP. 
     The embodiment shown in  FIG. 3  provides a structure supporting EMBMS in an evolved packet core network with separate user plane and control plane. 
     As shown in  FIG. 3 , the system architecture of the present embodiment comprises BM-SC  41 , Serving SAE GW  42 , PDN (Packet Data Network) SAE GW  43 , BME  44 , eNB  45 , UE  46 , MME (Mobility Management Entity)  47 , PCRF (Policy and Charge Rule Function)  48 , HSS (Home Subscriber Server)  49 , SGSN (Serving Gateway Support Node)  50  and operators&#39; IP service. 
     The present invention supports both a configuration where Serving SAE GW and PDN (Packet Data Network) SAE GW are located at the same physical node and a configuration where Serving SAE GW and PDN SAE GW are located at different physical nodes. In other words, Serving SAE GW and PDN SAE GW can be separated from each other. For the purpose of conciseness, the present invention is described by exemplifying the configuration where Serving SAE GW and PDN SAE GW are located at the same physical node. 
     In the present embodiment, BM-SC  41  is connected with SAE GW via logical interfaces SGmb and SGi. The logical interface SGmb can be an evolved interface as one of Gmb interfaces for Rel6 MBMS, and SGi can be an evolved interface as one of Gi interfaces for Rel6 core network. It should be noted that the present invention is not limited to this, and the logical interfaces SGmb and SGi can also be called “reference point” as defined in the conventional protocol. The logical interfaces SGmb and SGi are reference points for user plane and control plane, respectively. 3GPP network is connected with PDN via the reference point SGi, which corresponds to the reference points Gi and Wi and incorporates their functions, as compared to networks in versions before SAE/LET. The reference point Gi supports 3GPP network access PDN, and the reference point Wi supports non-3GPP network access PDN. Further, the interface SGmb corresponds to the old interface Gmb before SAE/LET, and the two interfaces are a reference point dedicated to EMBMS service. Because evolution of network reduces control signaling in the core network, the interface SGmb may not support certain signaling such as subscription and authentication of users, as compared to the interface Gmb. 
     Logical interface Sx connecting BM-SC  41  with operator IP service is adapted to support, for example, IMS (IP Multimedia System) subscriber service through MBMS bearer service. BME  44  is connected with Serving SAE GW  42  via logical interface S 12 , and is further connected with eNB  45  via logical interface S 1 _BME. 
     The separate logical function entities for MBMS in the present invention are different from those for unicast service in which MME is for control plane and UPE (User Plane Entity) is for user plane. In the present embodiment, separate logical function entities are adopted. That is, EMBMS BME is responsible for control plane functions related to EMBMS, and mUPE (multicast UPE) is responsible for user plane functions related to EMBMS. 
     Further referring to  FIG. 3 , Serving SAE GW  42  can be connected to eNB  45  via interface S 1 _U, and also be connected with MME  47  and SGSN  50  via interfaces S 11 , S 4 , respectively. PDN SAE GW  43  can be connected with operator IP service via SGi, and also be connected with PCRF  48  via interface S 7 . PCRF  48  can be connected with operator IP service via interface Rx. eNB  45  can be connected with MME  47  via logical interface S 1 _MME, and MIME  47  can be connected with SGSN  50  and HSS  49  via interfaces S 3 , S 6   a , respectively. UE  46  can be connected with eNB via LTE_Uu, and GERAN network and UTRAN network can be connected with SGSN via interfaces Gb and Iu, respectively. 
     BM-SC  41  has functions identical to those of BM-SC in 3GPP Rel6. BM-SC  41  serves as an entrance for content providers, initiates EMBMS bearer service and MBMS Session Start message, and transmits MBMS service data in a predefined schedule. BM-SC  41 , as the beginning point of service provision to mobile terminals, transmits EMBMS service content in a broadcast or multicast protocol. SAE GW and BM-SC  41  exchange signaling via the logical interfaces SGmb and SGi. It should be noted that BM-SC  41  can also transmit messages and data in any other appropriate protocol. BM-SC  41  should also guarantee network security. 
     PDN SAE GW  43  receives MBMS service data and control signaling from BM-SC  41  or service data and control signaling from other network device, and stores service parameters locally. PDN SAE GW  43  forwards the received service data to Serving SAE GW  42 , which receives the MBMS service data and control signaling, subsequently performs a core network processing on the data and sends the processed service data to a downstream node. SAE GW also has a function of EMBMS distribution tree management. When there are a plurality of eNBs and a plurality of gateways in a network, subscriber data is passed downwards in a tree-shape structure. In this case, SAE GW, cooperating with eNB  45 , selects a specific route for passing subscriber data downwards in a tree-shape structure. 
     PDN SAE GW also receives MBMS service data and control signaling from BW-SC or other network, stores service parameters locally and forwards the received service data and control signaling to Serving SAE GW. 
     BME 44  receives, processes and forwards control signaling for MBMS such as MBMS Session Start message sent from BM-SC, and other control signaling, such as MBMS Session Update/Stop messages, and determines which eNBs need to receive these messages, with respect to each item of the MBMS service. BME  44  also stores context for MBMS service, and stores a mapping relationship from service area to eNBs, with respect to each item of the MBMS service. BME  44  further has a function of EMBMS distribution tree management. 
     It should be noted that BME  44  can be embodied as an individual network cell or can be provided in MCE or MME. 
     BME  44  can be an individual network as a control plane boundary cell of access network and core network in EMBMS architecture. Further, BMC  44  can be placed within MME if the future network evolution supports enhanced MME, that is, MME can support not only the currently defined unicast service but also EMBMS service. For operation of Single Frequency Network (SFN), a Multi-Cell/Multicast Coordination Entity (MCE) is specifically defined by 3GPP to address the problem of radio resource allocation for EMBMS. Also, BME  44  can be placed within MME if the future network evolution enhances the functions of MCE, that is, MCE can not only handle control plane processing for SFN operation on EMBMS service, but also support processing of EMBMS control signaling (e.g., MBMS Session Start) on the interface S 1 , setup and release of MBMS bearer, and other necessary control plane functions. 
     The number of BME depends on operator&#39;s configuration in Evolved Packet Core. SAE network is flatter than Rel6 network, and a single SAE GW can be connected with thousands of eNBs. If each SAE GW has only one BME, it is necessary to duplicate the received MBMS Session Start message for thousands of times and to transmit the duplicated MBMS Session Start messages to respective eNBs. In this case, BME suffers from heavy workload, and it is worse when several MBMS Session Start messages are ongoing at the same time. To avoid the potential problem with transmission of MBMS Session Start message, a plurality of BMEs  44  can be provided in the coverage of a single SAE GW. As an example, for broadcast service, one BME can be provided per maximum SFN area according to operator&#39;s static deployment. 
     mUPE in Serving SAE GW  42  receives MBMS service data sent from BM-SC  41  and processes the data in Evolved Packet SAE. mUPE also allocates the received MBMS service data to downstream nodes. For each Serving SAE GW, only one mUPE is provided per item of MBMS service. 
     In a situation of mobile terminal roaming, MME/UPE acts as mobile entity in access network, while PDN SAE GW acts as a function entity in network. An efficient mapping is required between MME/UPE and PDN SAE GW to implement Fixed Mobile Combination (FMC) control. 
       FIG. 4  is a flowchart showing a process of transmitting service data in the MBMS-supporting System Architecture Evolution according to the embodiment of the present invention. 
     Referring to  FIG. 4 , a process of transmitting MBMS service data in System Architecture Evolution is described by taking transmission of MBMS Session Start message as example. At step S 601 , BM-SC  41  first initiates MBMS Session Start message and transmits it to a corresponding SAE GW. The MBMS Session Start message carries attributes and parameters about the message such as ID, QoS, service area for a service. At step S 602 , SAE GW, after receiving MBMS Session Start message, stores locally the parameters contained in the message, and forwards MBMS Session Start message to a corresponding EMC  44 . At step S 603 , SAE GW sends a response message back to BM-SC to acknowledge reception of MBMS Session Start message. 
     At step S 604 , BME  44  receives MBMS Session Start message forwarded from SAE GW, stores parameters contained in the message, and forwards the received MBMS Session Start message to each of eNBs which are connected to BME  44  and located within MBMS service area. Then, at step S 605 , BME  44  sends a response message back to SAE GW to acknowledge reception of MBMS Session Start message. According to the present invention, BME  44  can sends the response message back to SAE GW before it receives from any involved eNB a response for reception of MBMS Session Start message at the eNB. It should be noted, in the present invention, no compulsive time limit is imposed on the transmission of the response message from BME to SAE GW. BME  44  can also send the response message to SAE GW after it receives a response message from eNBs. Finally, at step S 606 , each of the eNBs sends a response message to BME to acknowledge reception of MBMS Session Start message at the eNB. 
     Although the foregoing description is given by taking as example a process of BME starting MBMS Session, BME can also handle other control plane signaling such as MBMS Session Update or Stop. 
     In the foregoing description, means for implementing respective logical functions are called “entities”. It should be noted that the term “entity” covers cells, means and devices having respective logical functions as well as any other term having similar meaning. The above-mentioned functions can be realized in hardware, while the present invention is not limited to this. These functions can also be implemented in software executed in a computer. 
     The present invention provides a system structure for supporting MBMS service data in 3GPP SAE and a method for applying the system structure to transmission of MBMS control signaling and service data so that they can arrive eNBs in an efficient way. 
     While exemplary embodiments of the present invention have been described hereinabove, it should be clear to those skilled in the art that any variations and/or modifications of the basic inventive concepts will still fall within the scope of the present invention, as defined in the appended claims.