Patent Publication Number: US-2016249183-A1

Title: Method of selectively transmitting mbms service level information in wireless communication system and apparatus therefor

Description:
TECHNICAL FIELD 
     The present invention relates to a wireless communication system, more particularly to a method of selectively transmitting service level information with respect to a specific Multimedia Broadcast/Multicast Service (MBMS) in a wireless communication system for supporting the MBMS. 
     BACKGROUND ART 
     Mobile communication systems have been developed to provide voice services, while guaranteeing user activity. Service coverage of mobile communication systems, however, has extended even to data services, as well as voice services, and currently, an explosive increase in traffic has resulted in shortage of resource and user demand for a high speed services, requiring advanced mobile communication systems. 
     The requirements of the next-generation mobile communication system may include supporting huge data traffic, a remarkable increase in the transfer rate of each user, the accommodation of a significantly increased number of connection devices, very low end-to-end latency, and high energy efficiency. To this end, various techniques, such as small cell enhancement, dual connectivity, massive Multiple Input Multiple Output (MIMO), in-band full duplex, non-orthogonal multiple access (NOMA), supporting super-wide band, and device networking, have been researched. 
     SUMMARY OF INVENTION 
     Technical Problem 
     An object of the present invention is to provide a method of transmitting MBMS service level information with respect to a specific MBMS to a network in a wireless communication system for supporting the MBMS. 
     The technical problems solved by the present invention are not limited to the above technical problems and those skilled in the art may understand other technical problems from the following description. 
     Solution to Problem 
     According to an aspect of the present invention, there is provided a method of transmitting MBMS service level information in a wireless communication system for supporting a Multimedia Broadcast/Multicast Service (MBMS), the method including: determining, by User Equipment (UE), whether a received or reception interested MBMS is an MBSB necessary to be reported to a network; and transmitting, by the UE, service level information on the received or reception interested MBMS to the network through a MBMS interest indication message when the MBMS which is received or having interest in reception is the MBMS necessary to be reported to the network. 
     According to another aspect of the present invention, there is provided a User Equipment (UE) for transmitting MBMS service level information in a wireless communication system for supporting a Multimedia Broadcast/Multicast Service (MBMS), the UE including: a radio frequency (RF) unit to transmit/receive a wireless signal; and a processor, wherein the processor determines whether a received or reception interested MBMS is an MBSB necessary to be reported to a network; and transmits service level information on the received or reception interested MBMS to the network through a MBMS interest indication message by the UE when the MBMS which is received or having interest in reception is the MBMS necessary to be reported to the network. 
     Preferably, the service level information may include at least one of a Temporary Mobile Group Identity (TMGI), a service identity, or a session identity with respect to the MBMS. 
     Preferably, the method may further include receiving, by the UE, information on the MBMS necessary to be reported to the network. 
     Preferably, the information on the MBMS necessary to be reported to the network may be transmitted through a User Service Description (USD) or an RRC message on a Multicast Control Channel (MCCH). 
     Preferably, the MBMS necessary to be reported to the network may include a public safety service or a group communication service. 
     Advantageous Effects of Invention 
     According to an embodiment of the present invention, the network may know how many UEs in a specific cell are included in a specific MBMS by transmitting the MBMS service level information with respect to a specific MBMS service to the network through a MBMS Interest Indication message. 
     The effects of the present invention are not limited to the above-described effects and other effects which are not described herein will become apparent to those skilled in the art from the following description. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. 
         FIG. 1  is a diagram schematically illustrating an Evolved Packet System (EPS) according to the present invention. 
         FIG. 2  illustrates a schematic structure a network structure of an evolved universal mobile telecommunication system (E-UMTS) to which the present invention can be applied. 
         FIG. 3  illustrates architecture of a typical E-UTRAN and a typical EPC to which the present invention can be applied. 
         FIG. 4  illustrates the configurations of a control plane and a user plane of a radio interface protocol between the E-UTRAN and a UE in the wireless communication system to which the present invention can be applied. 
         FIG. 5  illustrates a downlink subframe and physical channels in the wireless communication system to which the present invention can be applied. 
         FIG. 6  illustrates definitions of MBMS in the wireless communication system to which the present invention can be applied. 
         FIG. 7  illustrates logical architecture of MBMS in the wireless communication system to which the present invention can be applied. 
         FIG. 8  illustrates Change of MCCH Information in the wireless communication system to which the present invention can be applied. 
         FIG. 9  illustrates MBMS session start procedure in the wireless communication system to which the present invention can be applied. 
         FIG. 10  illustrates MBMS session stop procedure in the wireless communication system to which the present invention can be applied. 
         FIG. 11  illustrates an MCCH information acquisition procedure in the wireless communication system to which the present invention can be applied. 
         FIG. 12  illustrates an MBMS interest indication procedure in the wireless communication system to which the present invention can be applied. 
         FIG. 13  illustrates an MBMS Counting procedure in the wireless communication system to which the present invention can be applied. 
         FIG. 14  illustrates GCSE architecture in the wireless communication system to which the present invention can be applied. 
         FIG. 15  is a diagram illustrating a method of selectively transmitting service information according to an embodiment of the present invention. 
         FIG. 16  is a diagram illustrating a structure of a TMGI according to an embodiment of the present invention. 
         FIG. 17  is a diagram illustrating a method of selectively transmitting service information according to an embodiment of the present invention. 
         FIG. 18  illustrates information on the MBSM necessary to report the service level information to a network an embodiment of the present invention. 
         FIG. 19  illustrates a block diagram of a wireless communication apparatus according to an embodiment of the present invention. 
     
    
    
     MODE FOR THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The detailed description set forth below in connection with the appended drawings is a description of exemplary embodiments and is not intended to represent the only embodiments through which the concepts explained in these embodiments can be practiced. The detailed description includes details for the purpose of providing an understanding of the present invention. However, it will be apparent to those skilled in the art that these teachings may be implemented and practiced without these specific details. 
     In some instances, known structures and devices are omitted, or are shown in block diagram form focusing on important features of the structures and devices, so as not to obscure the concept of the present invention. 
     In the embodiments of the present invention, the enhanced Node B (eNode B or eNB) may be a terminal node of a network, which directly communicates with the terminal. In some cases, a specific operation described as performed by the eNB may be performed by an upper node of the eNB. That is, it is apparent that, in a network comprised of a plurality of network nodes including an eNB, various operations performed for communication with a terminal may be performed by the eNB, or network nodes other than the eNB. The term ‘eNB’ may be replaced with the term ‘fixed station’, ‘base station (BS)’, ‘Node B’, ‘base transceiver system (BTS),’, ‘access point (AP)’, etc. The term ‘user equipment (UE)’ may be replaced with the term ‘terminal’, ‘mobile station (MS)’, ‘user terminal (UT)’, ‘mobile subscriber station (MSS)’, ‘subscriber station (SS)’, ‘Advanced Mobile Station (AMS)’, ‘Wireless terminal (WT)’, ‘Machine-Type Communication (MTC) device’, ‘Machine-to-Machine (M2M) device’, ‘Device-to-Device (D2D) device’, wireless device, etc. 
     In the embodiments of the present invention, “downlink (DL)” refers to communication from the eNB to the UE, and “uplink (UL)” refers to communication from the UE to the eNB. In the downlink, transmitter may be a part of eNB, and receiver may be part of UE. In the uplink, transmitter may be a part of UE, and receiver may be part of eNB. 
     Specific terms used for the embodiments of the present invention are provided to aid in understanding of the present invention. These specific terms may be replaced with other terms within the scope and spirit of the present invention. 
     The embodiments of the present invention can be supported by standard documents disclosed for at least one of wireless access systems, Institute of Electrical and Electronics Engineers (IEEE) 802, 3rd Generation Partnership Project (3GPP), 3GPP Long Term Evolution (3GPP LTE), LTE-Advanced (LTE-A), and 3GPP2. Steps or parts that are not described to clarify the technical features of the present invention can be supported by those documents. Further, all terms as set forth herein can be explained by the standard documents. 
     Techniques described herein can be used in various wireless access systems such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-Frequency Division Multiple Access (SC-FDMA), ‘non-orthogonal multiple access (NOMA)’, etc. CDMA may be implemented as a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented as a radio technology such as Global System for Mobile communications (GSM)/General Packet Radio Service (GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented as a radio technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Evolved-UTRA (E-UTRA) etc. UTRA is a part of Universal Mobile Telecommunication System (UMTS). 3GPP LTE is a part of Evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA for downlink and SC-FDMA for uplink LTE-A is an evolution of 3GPP LTE. 
     For clarity, this application focuses on the 3GPP LTE/LTE-A system. However, the technical features of the present invention are not limited thereto. 
     General System to which the Present Invention can be Applied 
       FIG. 1  is a diagram schematically illustrating an Evolved Packet System (EPS) according to the present invention. 
     A configuration diagram of  FIG. 1  is obtained by schematically reconfiguring a structure of an Evolved Packet System (EPS) including an Evolved Packet Core (EPC). 
     The EPC is a core element of a System Architecture Evolution (SAE) for improving performances of 3GPP techniques. The SAE represents a research subject to determine a network structure to support mobility between various types of networks. For example, the SAE is aimed at providing a packet-based system for supporting various wireless access techniques based on an IP and providing more improved data transmission capability. 
     In detail, the EPC is a core network of an IP mobile communication system for a 3GPP LTE system. In an existing mobile communication system (that is, second or third generation mobile communication system), a function of a core network is implemented through two distinguished sub-domains including Circuit-Switched (CS) for a sound and Packet-Switched (PS) for data. However, in the 3GPP LTE system being an evolved version of the third generation mobile communication system, sub-domains of a CS and a PS is unified as one IP domain. That is, in the 3GPP LTE system, connection between UEs having IP capability may be configured by a base station (for example, evolved Node B (eNodeB)), EPC, and application domain (for example, IMS). That is, the EPC is an essential configuration to implement an end-to-end IP service. 
     The EPC may include various constituent elements.  FIG. 1  illustrates some of the various constituent elements, that is, a Serving Gateway (SGW), a Packet Data Network Gateway (PDN GW), a Mobility Management Entity (MME), a Home Subscriber Ser (HSS), and a Policy Control and Charging Rules Function (PCRF). 
     The SGW is operated as a boundary point between a radio access network (RAN) and a core network, and is an element to perform a function for maintaining a data path between the eNodeB and a PDN GW. Further, when the UE moves through a serving zone by an eNodeB, the SGW serves as a local mobility anchor point. That is, packets may be routed through the SGW for mobility in an E-UTRAN (Universal Mobile Telecommunications System (Evolved-UMTS) Terrestrial Radio Access Network defined after 3GPP release-8). In addition, the SGW may function as an anchor point for mobility with another 3GPP network (RAN defined before a 3GPP release-8, for example, UTRAN or GERAN (GSM (Global System for Mobile Communication)/EDGE (Enhanced Data rates for Global Evolution) Radio Access Network). 
     The PDN GW represents a termination point of a data interface toward a packet data network. The PDN GW may support policy enforcement features, packet filtering, charging support, and the like. Further, the PDN GW may serve as an anchor for mobility management with a 3GPP network and a non-3GPP network (for example, a non-reliable network such as an Interworking Wireless Local Area Network (I-WLAN), and a reliable network such as a Code Division Multiple Access (CDMA) network or a Wimax). 
     Although  FIG. 1  illustrates an example of a network structure where the SGW and the PDN GW are configured as a separate gateway, two gateways may be realized according to single gateway configuration Option. 
     The MME is an element to perform signaling and control functions for supporting access with respect to network connection of the UE, allocation of a network resource, tracking, paging, roaming, and handover. The MME controls control plane functions associated with a subscriber and session management. The MME manages a great number of eNodeBs, and performs signaling to select a gateway of the related art for handover with respect to other 2G/3G networks. Further, the MME performs functions such as Security Procedures, Terminal-to-network Session Handling, and Idle Terminal Location Management. 
     A Home Subscriber Server (HSS) manages subscriber subscription information (or subscription data or subscription record)). 
     A Policy Control and Charging Rules Function (PCRF) is a node which a Policy to be applied to the UE, and Policy decision applying Quality of Service (QoS)) as dynamic. A Policy and Charging Control (PCC) rule generated from the PCRF is transferred to the PDN GW. 
     Referring to  FIG. 1 , UE having IP capability may access an IP service network (for example, IMS) provided from (that is, an operator) through various elements in an EPC based on 3GPP access and non-3GPP access. 
     Further,  FIG. 1  illustrates various reference points (for example, S1-U, S1-MME, or the like). In the 3GPP system, a conceptual link connecting two functions existing in different functional entities of the E-UTRAN and the EPC is defined as a reference point. Table 1 lists a reference point shown in  FIG. 1  and a usable protocol option. There may be various reference points according to a network structure except for examples of table 1. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Reference 
                   
                   
               
               
                 point 
                 Protocol 
                 Description 
               
               
                   
               
             
            
               
                 S1-MME 
                 S1-AP 
                 Reference point with respect to a control plane protocol 
               
               
                   
                   
                 between the E-UTRAN and the MME 
               
               
                 S1-U 
                 GTP-U 
                 Reference point between the E-UTRAN and the SGW 
               
               
                   
                   
                 with respect to Path switching between eNBs and a user 
               
               
                   
                   
                 plane tunneling per bearer during handover 
               
               
                 S6a 
                 Diameter 
                 Reference point with respect to a control plane protocol 
               
               
                   
                   
                 between the HSS and the MME 
               
               
                 S5 
                 GTP, PMIP 
                 Reference point providing user plane tunneling and tunnel 
               
               
                   
                   
                 management between the SGW and the PDN GW. G5 is 
               
               
                   
                   
                 used for SGW rearrangement due to UE mobility and 
               
               
                   
                   
                 when there is a need for connection to PDN GW which is 
               
               
                   
                   
                 not located together with SGW for required PDN connectivity 
               
               
                 S11 
                 GTP-C 
                 Reference point with respect to a control plane protocol 
               
               
                   
                   
                 between the MME and the SGW 
               
               
                 Gx 
                 Diameter 
                 Reference point with respect to a control plane protocol 
               
               
                   
                   
                 between the PCRF and the P-GW 
               
               
                 SGi 
                 IP 
                 Reference point between the PDN GW and the PDN. In 
               
               
                   
                   
                 this case, the PDN may correspond to operator external 
               
               
                   
                   
                 public or private PDN or operator-inside PDN (for 
               
               
                   
                   
                 example, IMS service) 
               
               
                   
               
            
           
         
       
     
       FIG. 2  illustrates a schematic structure a network structure of an evolved universal mobile telecommunication system (E-UMTS) to which the present invention can be applied. 
     An E-UMTS system is an evolved version of the UMTS system. For example, the E-UMTS may be also referred to as an LTE/LTE-A system. The E-UMTS is also referred to as a Long Term Evolution (LTE) system. 
     The E-UTRAN consists of eNBs, providing the E-UTRA user plane and control plane protocol terminations towards the UE. The eNBs are interconnected with each other by means of the X2 interface. The X2 user plane interface (X2-U) is defined between eNBs. The X2-U interface provides non guaranteed delivery of user plane packet data units (PDUs). The X2 control plane interface (X2-CP) is defined between two neighbour eNBs. The X2-CP performs following functions: context transfer between eNBs, control of user plane tunnels between source eNB and target eNB, transfer of handover related messages, uplink load management and the like. Each eNB is connected to User Equipments (UEs) through a radio interface and is connected to an Evolved Packet Core (EPC) through an S1 interface. The S1 user plane interface (S1-U) is defined between the eNB and the serving gateway (S-GW). The S1-U interface provides non guaranteed delivery of user plane PDUs between the eNB and the S-GW (Serving Gateway). The S1 control plane interface (S1-MME) is defined between the eNB and the MME (Mobility Management Entity). The S1 interface performs following functions: EPS (Enhanced Packet System) Bearer Service Management function, NAS (Non-Access Stratum) Signaling Transport function, Network Sharing Function, MME Load balancing Function and the like. The S1 interface supports a many-to-many relation between MMEs/Serving Gateways and eNBs. 
       FIG. 3  illustrates architecture of a typical E-UTRAN and a typical EPC to which the present invention can be applied. 
     Referring to the  FIG. 3 , the eNB may perform functions of selection for the gateway (for example, MME), routing toward the gateway during a radio resource control (RRC) activation, scheduling and transmitting of paging messages, scheduling and transmitting of broadcast channel (BCH) information, dynamic allocation of resources to the UEs in both uplink and downlink, configuration and provisioning of eNB measurements, radio bearer control, radio admission control (RAC), and connection mobility control in LTE_ACTIVE state. In the EPC, and as stated above, the gateway may perform functions of paging origination, LTE_IDLE state management, ciphering of the user plane, System Architecture Evolution (SAE) bearer control, and ciphering and integrity protection of NAS signaling. 
       FIG. 4  illustrates the configurations of a control plane and a user plane of a radio interface protocol between the E-UTRAN and a UE in the wireless communication system to which the present invention can be applied. 
       FIG. 4( a )  shows the respective layers of the radio protocol control plane, and  FIG. 4( b )  shows the respective layers of the radio protocol user plane. 
     Referring to the  FIG. 4 , the protocol layers of a radio interface protocol between the E-UTRAN and a UE can be divided into an L1 layer (first layer), an L2 layer (second layer), and an L3 layer (third layer) based on the lower three layers of the Open System Interconnection (OSI) reference model widely known in communication systems. The radio interface protocol is divided horizontally into a physical layer, a data link layer, and a network layer, and vertically into a user plane for data transmission and a control plane for signaling. 
     The control plane is a passage through which control messages that a UE and a network use in order to manage calls are transmitted. The user plane is a passage through which data (e.g., voice data or Internet packet data) generated at an application layer is transmitted. The following is a detailed description of the layers of the control and user planes in a radio interface protocol. 
     The physical layer, which is the first layer, provides an information transfer service to an upper layer using a physical channel. The physical layer is connected to a Media Access Control (MAC) layer, located above the physical layer, through a transport channel. Data is transferred between the MAC layer and the physical layer through the transport channel. Data transfer between different physical layers, specifically between the respective physical layers of transmitting and receiving sides, is performed through the physical channel. The physical channel is modulated according to the Orthogonal Frequency Division Multiplexing (OFDM) method, using time and frequencies as radio resources. 
     The MAC layer of the second layer provides a service to a Radio Link Control (RLC) layer, located above the MAC layer, through a logical channel. The MAC layer plays a role in mapping various logical channels to various transport channels. And, the MAC layer also plays a role as logical channel multiplexing in mapping several logical channels to one transport channel. A set of logical channel types is defined for different data transfer services offered by MAC. Each logical channel type is defined according to the type of information transferred. 
     The RLC layer of the second layer supports reliable data transmission. The RLC layer performs segmentation and concatenation on data received from an upper layer to play a role in adjusting a size of the data to be suitable for a lower layer to transfer the data to a radio section. And, the RLC layer provides three kinds of RLC modes including a transparent mode (TM), an unacknowledged mode (UM) and an acknowledged mode (AM) to secure various kinds of QoS demanded by each radio bearer (RB). In particular, the AM RLC performs a retransmission function through automatic repeat and request (ARQ) for the reliable data transfer. The functions of the RLC layer may also be implemented through internal functional blocks of the MAC layer. In this case, the RLC layer need not be present. 
     A packet data convergence protocol (PDCP) layer of the second layer performs a header compression function for reducing a size of an IP packet header containing relatively large and unnecessary control information to efficiently transmit such an IP packet as IPv4 and IPv6 in a radio section having a small bandwidth. This enables a header part of data to carry mandatory information only to play a role in increasing transmission efficiency of the radio section. Moreover, in the LTE/LTE-A system, the PDCP layer performs a security function as well. This consists of ciphering for preventing data interception conducted by a third party and integrity protection for preventing data manipulation conducted by a third party. 
     A Radio Resource Control (RRC) layer located at the bottom of the third layer is defined only in the control plane and is responsible for control of logical, transport, and physical channels in association with configuration, re-configuration, and release of Radio Bearers (RBs). The RB is a logical path that the second layer provides for data communication between the UE and the E-UTRAN. To accomplish this, the RRC layer of the UE and the RRC layer of the network exchange RRC messages. To Configure of Radio Bearers means that the radio protocol layer and the characteristic of channels are defined for certain service and that each of specific parameters and operating method are configured for certain service. The radio bearer can be divided signaling radio bearer (SRB) and data radio bearer (DRB). The SRB is used as a path for transmission RRC messages in the control plane, and the DRB is used as a path for transmission user data in the user plane. 
     A Non-Access Stratum (NAS) layer located above the RRC layer performs functions such as session management and mobility management. 
     One cell of the eNB is set to use a bandwidth such as 1.25, 2.5, 5, 10 or 20 MHz to provide a downlink or uplink transmission service to UEs. Here, different cells may be set to use different bandwidths. 
     Downlink transport channels for transmission of data from the network to the UE include a Broadcast Channel (BCH) for transmission of system information, a Paging Channel (PCH) for transmission of paging messages, and a downlink Shared Channel (DL-SCH) for transmission of user traffic or control messages. User traffic or control messages of a downlink multicast or broadcast service may be transmitted through DL-SCH and may also be transmitted through a downlink multicast channel (MCH). The BCH is used for transmitting system information. The DL-SCH supports HARQ, dynamic link adaptation by varying the modulation, coding and transmit power, and both dynamic and semi-static resource allocation. The DL-SCH also may enable broadcast in the entire cell and the use of beamforming. The PCH is used for paging a UE. The MCH is used for multicast or broadcast service transmission. 
     Uplink transport channels for transmission of data from the UE to the network include a Random Access Channel (RACH) for transmission of initial control messages and an uplink SCH (UL-SCH) for transmission of user traffic or control messages. The UL-SCH supports HARQ and dynamic link adaptation by varying the transmit power and potentially modulation and coding. The UL-SCH also may enable the use of beamforming. The RACH is normally used for initial access to a cell. 
     Logical channels, which are located above the transport channels and are mapped to the transport channels. Logical channels are generally classified into two groups. The two groups are control channels for the transfer of control plane information and traffic channels for the transfer of user plane information. 
     Control channels are used for transfer of control plane information only. The control channels provided by MAC include a Broadcast Control Channel (BCCH), a Paging Control Channel (PCCH), a Common Control Channel (CCCH), a dedicated control channel (DCCH), a Multicast Control Channel (MCCH). The BCCH is a downlink channel for broadcasting system control information. The PCCH is a downlink channel that transfers paging information and is used when the network does not know the location cell of a UE. The CCCH is used by UEs having no RRC connection with the network. The MCCH is a point-to-multipoint downlink channel used for transmitting MBMS control information from the network to a UE. The DCCH is a point-to-point bidirectional channel used by UEs having an RRC connection that transmits dedicated control information between a UE and the network. 
     Traffic channels are used for the transfer of user plane information only. The traffic channels provided by MAC include a dedicated traffic channel (DTCH), and a Multicast Traffic Channel (MTCH). The DTCH is a point-to-point channel, dedicated to one UE for the transfer of user information and can exist in both uplink and downlink. The MTCH is a point-to-multipoint downlink channel for transmitting traffic data from the network to the UE. 
     Uplink connections between logical channels and transport channels include a DCCH that can be mapped to UL-SCH, a DTCH that can be mapped to UL-SCH and a CCCH that can be mapped to UL-SCH. Downlink connections between logical channels and transport channels include a BCCH that can be mapped to BCH or DL-SCH, a PCCH that can be mapped to PCH, a DCCH that can be mapped to DL-SCH, and a DTCH that can be mapped to DL-SCH, a MCCH that can be mapped to MCH, and a MTCH that can be mapped to MCH. 
     As an downlink physical channel for transmitting information forwarded on an downlink transport channel to a radio section between a network and a user equipment, there is a physical downlink shared channel (PDSCH) for transmitting information of DL-SCH, a physical control format indicator channel (PDFICH) for indicating the number of OFDM symbols used for transmitting a physical downlink control channel (PDCCH), a physical HARQ (hybrid automatic repeat request) indicator channel (PHICH) for transmitting HARQ ACK (Acknowledge)/NACK (Non-acknowledge) as response to UL transmission or a PDCCH for transmitting such control information, as DL grant indicating resource allocation for transmitting a Paging Channel (PCH) and DL-SCH, information related to HARQ, UL grant indicating resource allocation for transmitting a UL-SCH and like that. As an uplink physical channel for transmitting information forwarded on an uplink transport channel to a radio section between a network and a user equipment, there is a physical uplink shared channel (PUSCH) for transmitting information of UL-SCH, a physical random access channel (PRACH) for transmitting RACH information or a physical uplink control channel (PUCCH) for transmitting such control information, which is provided by first and second layers, as HARQ ACK/NACK (Non-acknowledge), scheduling request (SR), channel quality indicator (CQI) report and the like. 
     NAS Protocol States (EMM &amp; ECM) 
     The NAS state model is based on a two-dimensional model which consists of EPS Mobility Management (EMM) states and of EPS Connection Management (ECM) states. The EMM states describe the mobility management states that result from the mobility management procedures e.g., Attach and Tracking Area Update procedures. The ECM states describe the signaling connectivity between the UE and the EPC. 
     In detail, in order to manage mobility of a UE in NAS layers positioned in control planes of the UE and an MME, an EPS mobility management REGISTERED (EMM-REGISTERED) state and an EMM-DEREGISTERED state may be defined. The EMM-REGISTERED state and the EMM-DEREGISTERED state may be applied to the UE and the MME. 
     The UE is in the EMM deregistered state, like a state in which power of the UE is first turned on, and in order for the UE to access a network, a process of registering in the corresponding network is performed through an initial access procedure. When the access procedure is successfully performed, the UE and the MME transition to an EMM-REGISTERED state. 
     Also, in order to manage signaling connection between the UE and the network, an EPS connection management CONNECTED (ECM-CONNECTED) state and an ECM-IDLE state may be defined. The ECM-CONNECTED state and the ECM-IDLE state may also be applied to the UE and the MME. The ECM connection may include an RRC connection established between the UE and a BS and an S1 signaling connection established between the BS and the MME. The RRC state indicates whether an RRC layer of the UE and an RRC layer of the BS are logically connected. That is, when the RRC layer of the UE and the RRC layer of the BS are connected, the UE may be in an RRC_CONNECTED state. When the RRC layer of the UE and the RRC layer of the BS are not connected, the UE in an RRC_IDLE state. 
     Here, the ECM and EMM states are independent of each other and when the UE is in EMM-REGISTERED state this does not imply that the user plane (radio and S1 bearers) is established 
     In E-UTRAN RRC_CONNECTED state, network-controlled UE-assisted handovers are performed and various DRX cycles are supported. In E-UTRAN RRC_IDLE state, cell reselections are performed and DRX is supported. 
     The network may recognize the presence of the UE in the ECM-CONNECTED state by the cell and effectively control the UE. That is, when the UE is in the ECM-CONNECTED state, mobility of the UE is managed by a command from the network. In the ECM-CONNECTED state, the network knows about a cell to which the UE belongs. Thus, the network may transmit and/or receive data to or from the UE, control mobility such as handover of the UE, and perform cell measurement on a neighbor cell. 
     Meanwhile, the network cannot recognize the presence of the UE in the ECM-idle state and a core network (CN) manages the UE by the tracking area, a unit greater than cell. When the UE is in the ECM-idle state, the UE performs discontinuous reception (DRX) set by the NAS using an ID uniquely assigned in a tracking region. That is, the UE may monitor a paging signal at a particular paging opportunity in every UE-specific paging DRX cycle to receive broadcast of system information and paging information. Also, when the UE is in the ECM-idle state, the network does not have context information of the UE. 
     Thus, the UE in the ECM-idle state may perform a UE-based mobility-related procedure such as cell selection or cell reselection without having to receive a command from the network. When a location of the UE in the ECM-idle state is changed from that known by the network, the UE may inform the network about a location thereof through a tracking area update (TAU) procedure. 
     As described above, in order for the UE to receive a general mobile communication service such as voice or data, the UE needs to transition to an ECM-CONNECTED state. The UE is in the ECM-IDLE state like the case in which power of the UE is first turned on. When the UE is successfully registered in the corresponding network through an initial attach procedure, the UE and the MME transition to an ECM-CONNECTED state. Also, in a case in which the UE is registered in the network but traffic is deactivated so radio resource is not allocated, the UE is in an ECM-IDLE state, and when uplink or downlink new traffic is generated in the corresponding UE, the UE and the MME transition to an ECM-CONNECTED state through a service request procedure. 
       FIG. 5  illustrates a downlink subframe and physical channels in the wireless communication system to which the present invention can be applied. 
     Referring to  FIG. 5 , the downlink subframe includes a plurality of slots (e.g., two). The number of OFDM symbols included in one slot may be changed according to the length of a Cyclic Prefix (CP). For example, in case of a normal CP, the slot may include seven OFDM symbols. The downlink subframe is divided into a data region and a control region in a time domain. A maximum of three (or four) OFDM symbols located in the front part of a first slot of the subframe may correspond to a control region to which a control channel is allocated. The remaining OFDM symbols correspond to a data region to which a Physical Downlink Shared Channel (PDSCH) is allocated. 
     A variety of downlink control channels may be used in LTE/LTE-A, for example, a Physical Control Format Indicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH), a Physical hybrid ARQ indicator Channel (PHICH), etc. The PCFICH is transmitted on the first OFDM symbol of the subframe, and carries information about the number of OFDM symbols used for transmitting control channels within the subframe. The PHICH carries a Hybrid Automatic Repeat reQuest Acknowledgment/Negative-Acknowledgment (HARQ ACK/NACK) signal as a response to an uplink transmission signal. 
     Control information transmitted over a PDCCH is referred to as Downlink Control Information (DCI). DCI includes resource allocation information for either a UE or a UE group and other control information. For example, DCI includes UL/DL scheduling information, an UL transmission (Tx) power control command, etc. 
     The PDCCH carries a variety of information, for example, transmission format and resource allocation information of a DownLink Shared Channel (DL-SCH), transmission format and resource allocation information of an UpLink Shared Channel (UL-SCH), paging information transmitted over a Paging Channel (PCH), system information transmitted over the DL-SCH, resource allocation information of an upper-layer control message such as a random access response transmitted over PDSCH, a set of Tx power control commands of each UE contained in a UE group, a Tx power control command, activation indication information of Voice over IP (VoIP), and the like. A plurality of PDCCHs may be transmitted within a control region. A UE can monitor a plurality of PDCCHs. A PDCCH is transmitted as an aggregate of one or more contiguous Control Channel Elements (CCEs). The CCE is a logical allocation unit that is used to provide a coding rate based on a radio channel state to a PDCCH. The CCE may correspond to a plurality of Resource Element Groups (REGs). The format of PDCCH and the number of PDCCH bits may be determined according to the number of CCEs. 
     A eNB decides a PDCCH format according to DO to be sent to the UE, and adds a Cyclic Redundancy Check (CRC) to control information. The CRC is masked with an identifier (e.g., Radio Network Temporary Identifier (RNTI)) according to a PDCCH owner or a purpose of the PDCCH. For example, provided that the PDCCH is provided for a specific UE, a CRC may be masked with an identifier of the corresponding UE (e.g., cell-RNTI (C-RNTI)). If PDCCH is provided for a paging message, a CRC may be masked with a paging identifier (e.g., Paging-RNTI (P-RNTI)). If a PDCCH is provided for system information (e.g., System Information Block (SIB)), a CRC may be masked with system information RNTI (SI-RNTI). If PDCCH is provided for a random access response, a CRC may be masked with Random Access-RNTI (RA-RNTI), For example, CRC masking (or scrambling) may be performed using an exclusive OR (XOR) operation between CRC and RNTI at a bit level. 
     MBMS (Multimedia Broadcast/Multicast Service) 
     For MBMS, the following definitions may be introduced.
         Multicast broadcast single frequency network (MBSFN) synchronization area: an area of the network where all eNBs can be synchronized and perform MBSFN transmissions. MBSFN synchronization areas are capable of supporting one or more MBSFN areas. On a given frequency layer, an eNB can only belong to one MBSFN synchronization area. MBSFN synchronization areas are independent from the definition of MBMS service areas   MBSFN transmission or a transmission in MBSFN mode: a simulcast transmission technique realized by transmission of identical waveforms at the same time from multiple cells. An MBSFN transmission from multiple cells within the MBSFN area is seen as a single transmission by a UE.   MBSFN area: an MBSFN area consists of a group of cells within an MBSFN synchronization area of a network, which are coordinated to achieve an MBSFN transmission. Except for the MBSFN area reserved cells, all cells within an MBSFN area contribute to the MBSFN transmission and advertise its availability. The UE may only need to consider a subset of the MBSFN areas that are configured, i.e. when it knows which MBSFN area applies for the service(s) it is interested to receive.   MBSFN area reserved cell: A cell within a MBSFN area which does not contribute to the MBSFN transmission. The cell may be allowed to transmit for other services but at restricted power on the resource allocated for the MBSFN transmission.   Synchronization sequence: Each synchronization protocol data unit (SYNC PDU) contains a time stamp which indicates the start time of the synchronization sequence. For an MBMS service, each synchronization sequence has the same duration which is configured in the broadcast/multicast service center (BM-SC) and the MBMS coordination entity (MCE).   Synchronization Period: The synchronization period provides the time reference for the indication of the start time of each synchronization sequence. The time stamp which is provided in each SYNC PDU is a relative value which refers to the start time of the synchronization period. The duration of the synchronization period is configurable.       

       FIG. 6  illustrates definitions of MBMS in the wireless communication system to which the present invention can be applied. 
     Referring to  FIG. 6 , an MBMS service area may consists of one or more MBSFN area. The MBMS Service Area (MBMS SA) comprises of one or more MBMS Service Area Identities (MBMS SAIs), in any case each MBMS SA shall not include more than 256 MBMS SAIs. An MBMS SAI shall identify a group of cells within a PLMN, that is independent of the associated Location/Routing/Service Area and the physical location of the cell(s). A cell shall be able to belong to one or more MBMS SAs, and therefore is addressable by one or more MBMS SAIs. 
     In each MBSFN area, a plurality of cells, including a plurality of MBSFN area reserved cells, may exist. 
     Architecture of MBMS 
     In E-UTRAN, MBMS is only supported in a carrier shared with unicast traffic. Cells performing MBMS transmissions are referred to as MBMS/Unicast-mixed cells. 
     For the MBMS/Unicast mixed cells, MTCH and MCCH are mapped on MCH for point-to-multipoint transmission, and transmission of both unicast and MBMS in the cell is done in a co-ordinated manner. 
     MBMS reception is possible for UEs in RRC_CONNECTED or RRC_IDLE states. Whenever receiving MBMS services, a user shall be notified of an incoming call, and originating calls shall be possible. ROHC is not supported for MBMS. 
       FIG. 7  illustrates logical architecture of MBMS in the wireless communication system to which the present invention can be applied. 
     Multi-cell/multicast Coordinating Entity (MCE) is a logical entity—this does not preclude the possibility that it may be part of another network element—whose functions are:
         the admission control and the allocation of the radio resources used by all eNBs in the MBSFN area for multi-cell MBMS transmissions using MBSFN operation. The MCE decides not to establish the radio bearer(s) of the new MBMS service(s) if the radio resources are not sufficient for the corresponding MBMS service(s) or may pre-empt radio resources from other radio bearer(s) of ongoing MBMS service(s) according to Allocation and Retention Priority (ARP). Besides allocation of the time/frequency radio resources this also includes deciding the further details of the radio configuration e.g. the modulation and coding scheme.   counting and acquisition of counting results for MBMS service(s).   resumption of MBMS session(s) within MBSFN area(s) based on e.g. the ARP and/or the counting results for the corresponding MBMS service(s).   suspension of MBMS session(s) within MBSFN area(s) based e.g. the ARP and/or on the counting results for the corresponding MBMS service(s).       

     In case of distributed MCE architecture, the MCE manages the above functions for a single eNB of a MBSFN. The coordination of the functions between MCEs is provided by OAM, if needed. 
     The MCE is involved in MBMS Session Control Signalling. The MCE does not perform signaling between UE and MCE. 
     Multimedia Broadcast Multicast Services Gateway (MBMS GW) is a logical entity—this does not preclude the possibility that it may be part of another network element—that is present between the Broadcast/Multicast Service Center (BMSC) and eNBs whose principal functions is the sending/broadcasting of MBMS packets to each eNB transmitting the service. The MBMS GW uses IP Multicast as the means of forwarding MBMS user data to the eNB. The MBMS GW performs MBMS Session Control Signalling (Session start/update/stop) towards the E-UTRAN via MME. 
     A Broadcast/Multicast Service Center (BM-SC) schedules the MBMS service, reports the MBMS service to the UE, and allocates bearer service identification. Further, the BM-SC starts or terminates an MBMS bearer resource (i.e., MBMS session). A BM-SC entity may function as an interface point for contents provider. The BM-SC may function as a termination point of an SYNC protocol through M1 interface. 
     The SYNC protocol is defined as a protocol to carry additional information that enable eNBs to identify the timing for radio frame transmission and detect packet loss. Every E-MBMS service uses its own SYNC entity. The SYNC protocol is applicable to DL and is terminated in the BM-SC. 
     The eNB, for supporting eMBMS, supports SYNC protocol with the BM-SC. The eNB joins IP multicast group for the user plane data delivery, and terminates the MCCH and indicates MBMS session start and stop to UE. 
     The MME provides the signaling path between the BM-SC and eNBs. That is, The BM-SC signals to the eNB through MME. 
     An Application Part is defined for M3 interface between MME and MCE. This application part allows for MBMS Session Control Signalling on E-RAB level (i.e. does not convey radio configuration data). The procedures comprise e.g. MBMS Session Start and Stop. SCTP is used as signalling transport i.e. Point-to-Point signalling is applied. 
     An Application Part is defined for M2 interface between the MCE and the eNB, which conveys at least radio configuration data for the multi-cell transmission mode eNBs and Session Control Signalling. SCTP is used as signalling transport i.e. Point-to-Point signalling is applied. 
     The M1 interface is a pure user plane interface between the MBMS GW and the eNB. Consequently no Control Plane Application Part is defined for this interface. IP Multicast is used for point-to-multipoint delivery of user packets. 
     The Sm is the control plane interface between MME and MBMS GW. 
     The SGmb/SGimb is the control plane/user plane interfaces between BMSC and MBMS GW. 
     Radio Channels for MBSFN 
     In general the control rmation relevant only for UEs supporting MBMS is separated as much as possible from unicast control rmation. Most of the MBMS control rmation is provided on a logical channel specific for MBMS common control rmation: the MCCH. 
     E-UTRA employs one MCCH logical channel per MBSFN area. In case the network configures multiple MBSFN areas, the UE acquires the MBMS control rmation from the MCCHs that are configured to identify if services it is interested to receive are ongoing. 
     The MCCH carries the MBSFNAreaConfiguration message, which indicates the MBMS sessions that are ongoing as well as the (corresponding) radio resource configuration. The MCCH may also carry the MBMSCountingRequest message, when E-UTRAN wishes to count the number of UEs in RRC_CONNECTED that are receiving or interested to receive one or more specific MBMS services. 
     A limited amount of MBMS control rmation is provided on the BCCH. This primarily concerns the rmation needed to acquire the MCCH(s). This rmation is carried by means of a single MBMS specific SystemInformationBlock: SystemInformationBlockType13. An MBSFN area is identified solely by the mbsfn-AreaId in SystemInformationBlockType13. At mobility, the UE considers that the MBSFN area is continuous when the source cell and the target cell broadcast the same value in the mbsfn-AreaId. 
     The MCCH rmation is transmitted periodically, using a configurable repetition period. Scheduling rmation is not provided for MCCH i.e. both the time domain scheduling as well as the lower layer configuration are semi-statically configured, as defined within SystemInformationBlockType13. 
     For MBMS user data, which is carried by the MTCH logical channel, E-UTRAN periodically provides MCH scheduling rmation (MSI) at lower layers (MAC). This MCH rmation only concerns the time domain scheduling i.e. the frequency domain scheduling and the lower layer configuration are semi-statically configured. The periodicity of the MSI is configurable and defined by the MCH scheduling period. 
       FIG. 8  illustrates Change of MCCH Information in the wireless communication system to which the present invention can be applied. 
     Referring to the  FIG. 8 , change of MCCH information only occurs at specific radio frames, i.e. the concept of a modification period is used. Within a modification period, the same MCCH rmation may be transmitted a number of times, as defined by its scheduling (which is based on a repetition period). The modification period boundaries are defined by subframe number (SFN) values for which SFN mod m=0, where m is the number of radio frames comprising the modification period. The modification period is configured by means of SystemInformationBlockType13. 
     When the network changes (some of) the MCCH rmation, it notifies the UEs about the change during a first modification period. In the next modification period, the network transmits the updated MCCH rmation. 
     Different hatching of boxes in  FIG. 8  indicates different MCCH information. Upon receiving a change notification, a UE interested to receive MBMS services acquires the new MCCH rmation immediately from the start of the next modification period. The UE applies the previously acquired MCCH rmation until the UE acquires the new MCCH rmation. 
     Indication of an MBMS specific RNTI, the M-RNTI, on PDCCH is used to rm UEs in RRC_IDLE and UEs in RRC_CONNECTED about an MCCH rmation change. When receiving an MCCH rmation change notification, the UE knows that the MCCH rmation will change at the next modification period boundary. The notification on PDCCH indicates which of the MCCHs will change, which is done by means of an 8-bit bitmap. Within this bitmap, the bit at the position indicated by the field notificationIndicator is used to indicate changes for that MBSFN area: if the bit is set to “1”, the corresponding MCCH will change. No further details are provided e.g. regarding which MCCH rmation will change. The MCCH rmation change notification is used to rm the UE about a change of MCCH rmation upon session start or about the start of MBMS counting. 
     The MCCH rmation change notifications on PDCCH are transmitted periodically and are carried on MBSFN subframes only. These MCCH rmation change notification occasions are common for all MCCHs that are configured, and configurable by parameters included in SystemInformationBlockType13: a repetition coefficient, a radio frame offset and a subframe index. These common notification occasions are based on the MCCH with the shortest modification period. 
     E-UTRAN may modify the MBMS configuration rmation provided on MCCH at the same time as updating the MBMS configuration rmation carried on BCCH i.e. at a coinciding BCCH and MCCH modification period. Upon detecting that a new MCCH is configured on BCCH, a UE interested to receive one or more MBMS services should acquire the MCCH, unless it knows that the services it is interested in are not provided by the corresponding MBSFN area. 
     A UE that is receiving an MBMS service shall acquire the MCCH information from the start of each modification period. A UE that is not receiving an MBMS service, as well as UEs that are receiving an MBMS service but potentially interested to receive other services not started yet in another MBSFN area, shall verify that the stored MCCH rmation remains valid by attempting to find the MCCH rmation change notification at least notificationRepetitionCoeff times during the modification period of the applicable MCCH(s), if no MCCH rmation change notification is received. 
     In case the UE is aware which MCCH(s) E-UTRAN uses for the service(s) it is interested to receive, the UE may only need to monitor change notifications for a subset of the MCCHs that are configured, referred to as the ‘applicable MCCH(s)’ in the above. 
     MBMS Session Start/Stop Procedures 
     In general, network provides an MBMS service to one or more UEs in accordance with the following sequence:
         When a session of the MBMS service starts, the eNB joins the MBMS service and then transmits MBMS data to one or more UEs.   When the session starts, the UE receives MCCH information related to the MBMS service and then establishes a radio bearer related to the MBMS service called an MBMS Point-to-Multipoint Radio Bearer (MRB).   While the eNB is transmitting the session to one or more UEs, the session may be updated, for example, with an update of the service area.   When the session of the MBMS service stops, the eNB leaves the MBMS service and stops transmitting MBMS data to one or more UEs.   When the session of the MBMS service stops, the UE receives updated MCCH information and then releases the MRB related to the MBMS service.       

     1) MBMS Session Start Procedure 
     The purpose of the MBMS Session Start procedure is to request the E-UTRAN to notify UEs about an upcoming MBMS Session of a given MBMS Bearer Service and to establish an MBMS E-RAB for this MBMS Session. The MBMS Session Start procedure is triggered by the EPC. 
       FIG. 9  illustrates MBMS session start procedure in the wireless communication system to which the present invention can be applied. 
     Step  1 ) The MME sends MBMS session start request message to the MCE(s) controlling eNBs in the targeted MBMS service area. The message includes the IP multicast address, session attributes and the minimum time to wait before the first data delivery. 
     Step  2 ) MCE checks whether the radio resources are sufficient for the establishment of new MBMS service(s) in the area it controls. If not, MCE decides not to establish the radio bearers of the MBMS service(s) and does not forward the MBMS session start request message to the involved eNBs, or may pre-empt radio resources from other radio bearer(s) of ongoing MBMS service(s) according to ARP. The MCE confirms the reception of the MBMS Session Start request to the MME. This message can be transmitted before the step  4 . Only in case of distributed MCE architecture radio resource setup is scheduled according to the parameter “time of MBMS data transfer” which indicates an absolute start time of data delivery, otherwise according to the “minimum time to MBMS data transfer” parameter. 
     Step  3 ) MCE sends the MBMS Session Start message to the eNBs in the targeted MBMS service area. If the MBMS Session Start message includes the MBMS Service Area Identity with value 0, the MCE shall consider that all the eNBs are involved. The MCE then determines in which MBSFN area(s) the service should be delivered. 
     When to send the MBMS Session Start message from MCE to eNB according to the minimum time to wait indication is an MCE implementation issue. 
     Step  4 ) eNB confirms the reception of the MBMS Session Start message. 
     Step  5 ) MCE sends the MBMS Scheduling Information message to the eNB including the updated MCCH information which carries the MBMS service&#39;s configuration information. The MBMS service&#39;s configuration information may includes configuration of an MRB corresponding to the session and the MCCH update time indicating when the eNB should apply the updated MCCH information. This message can be transmitted before the step  3 . 
     Step  6 ) eNB confirms the reception of the MBMS Scheduling Information message. 
     Step  7 ) eNB indicates MBMS session start to UEs by MCCH change notification and updated MCCH information which carries the MBMS service&#39;s configuration information. Indication of an MBMS specific RNTI, the M-RNTI, on PDCCH is used to notify UEs in RRC_IDLE and UEs in RRC_CONNECTED about an MCCH information change. 
     In detail, when the MBMS Scheduling Information message is received for the session start, the eNBs indicated the M-RNTI on the PDCCH in order to pass information to UEs in an MCCH modification period. Then, the eNBs update the MCCH information broadcast on the MCCH in the next MCCH modification period, according to the MCCH update time indicated by the MCE. 
     Step  8 ) eNB joins the IP multicast group to receive the MBMS User Plane data. 
     Step  9 ) eNB sends the MBMS data to radio interface at the determined time. 
     In detail, if a UE supporting the MBMS is interested in the MBMS service, it keeps monitoring the PDCCH using the configuration contained in SIB 13. When the PDCCH indicates a change in MCCH information in the MBSFN area concerning the MBMS service, the UE receives the MCCH to acquire the updated MCCH information for the MBSFN area. 
     Then, the UE establishes an MRB corresponding to the session with the updated MCCH information. When the MRB is established, the MTCH and the Physical Multicast Channel (PMCH) corresponding to the MRB are also configured. 
     After MRB establishment, the UE may receive MBMS user data from the MTCH. While the UE is moving across cells within the MBSFN area, the UE can continue to receive MBMS user data via the established MRB. 
     2) MBMS Session Stop Procedure 
     The MBMS Session Stop procedure is to request the E-UTRAN to notify UEs about the end of a given MBMS Session and to release the corresponding MBMS E-RAB this MBMS Session. The MBMS Session Stop procedure is triggered by the EPC. 
       FIG. 10  illustrates MBMS session stop procedure in the wireless communication system to which the present invention can be applied. 
     Step  1 ) The MME sends MBMS session stop request message to the MCE(s) controlling eNBs in the targeted MBMS service area. 
     Step  2 ) MCE confirms the reception of the MBMS Session stop request to the MME. 
     Step  3 ) MCE forwards the MBMS Session stop message to the eNBs in the targeted MBMS service area. 
     Step  4 ) eNB confirms the reception of the MBMS Session stop message. 
     Step  5 ) MCE sends the MBMS Scheduling Information message to the eNB including the updated MCCH information which carries the MBMS service&#39;s configuration information. This message can be transmitted before the step  3 . 
     Step  6 ) eNB confirms the reception of the MBMS Scheduling Information message. 
     Step  7 ) eNB indicates MBMS session stop to UEs by removing any service configuration associated with the stopped session from the updated MCCH message. 
     In detail, when the MBMS Scheduling Information message is received, the eNB updates the MCCH information for the concerned MBSFN area and stops MBSFN transmission for the MRB corresponding to the session. 
     Step  8 ) The corresponding E-RAB (i.e., MRB) is released, and eNB leaves the IP multicast group. 
     While a session of the MBMS service is ongoing, the interested UE periodically receives the MCCH information from the MBSFN area concerning the MBMS service. The UE can recognize the Session Stop from the updated MCCH information. 
     MCCH Information Acquisition 
     The UE applies the MCCH information acquisition procedure to acquire the MBMS control information that is broadcasted by the E-UTRAN. The procedure applies to MBMS capable UEs that are in RRC_IDLE or in RRC_CONNECTED. 
     A UE interested to receive MBMS services shall apply the MCCH rmation acquisition procedure upon entering the corresponding MBSFN area (e.g. upon power on, following UE mobility) and upon receiving a notification that the MCCH rmation has changed. A UE that is receiving an MBMS service shall apply the MCCH rmation acquisition procedure to acquire the MCCH, that corresponds with the service that is being received, at the start of each modification period. 
       FIG. 11  illustrates an MCCH information acquisition procedure in the wireless communication system to which the present invention can be applied. 
     Referring to the  FIG. 11 , an MBMS capable UE shall: 
     1&gt; if the procedure is triggered by an MCCH rmation change notification: 
     2&gt; start acquiring the MBSFNAreaConfiguration message and the MBMSCountingRequest message if present, from the beginning of the modification period following the one in which the change notification was received; 
     The UE continues using the previously received MCCH rmation until the new MCCH rmation has been acquired. 
     1&gt; if the UE enters an MBSFN area: 
     2&gt; acquire the MBSFNAreaConfiguration message and the MBMSCountingRequest message if present, at the next repetition period; 
     1&gt; if the UE is receiving an MBMS service: 
     2&gt; start acquiring the MBSFNAreaConfiguration message and the MBMSCountingRequest message if present, that both concern the MBSFN area of the service that is being received, from the beginning of each modification period; 
     MBMS Interest Indication Procedure 
     In MBSFN area, a specific eNB may use multiple frequencies at the same time. For using radio resources efficiently, the network may provide the MBMS on only one frequency among the multiple frequencies, and may provide dedicated bearers to each UE on all multiple frequencies. In this case, if the UE, which receives a service using the dedicated bearer in a frequency not providing the MBMS, wants to receive the MBMS, the UE may have to be handed over to a frequency providing the MBMS. 
     For this, a network control option may be adopted as a basic architecture for handling the MBMS. The network may be informed about UE&#39;s interest in the MBMS by the UE, and then the network tries to ensure that the UE is able to receive the MBMS. 
       FIG. 12  illustrates an MBMS interest indication procedure in the wireless communication system to which the present invention can be applied. 
     The purpose of this procedure is to inform the E-UTRAN that the UE is receiving or is interested to receive MBMS via an MBMS Point to Multipoint Radio Bearer (MRB), and if so, to inform the E-UTRAN about the priority of MBMS versus unicast reception. 
     Referring to  FIG. 12 , at step S 1201 , the UE acquires a system information block 15 (SIB 15) from the E-UTRAN. 
     The UE may obtain the information on the frequency providing the MBMS that the UE wants to receive, by receiving a system information block (SIB)-15 from a serving cell. 
     If the UE would like to receive the MBMS, at step S 1203 , the UE transmits an MBMS interest indication (MBMSInterestIndication) to the eNB. 
     The MBMS interest indication may indicate that the UE wants to receive the MBMS. The MBMS interest indication may include information on the frequency which provides the MBMS that the UE wants to receive. That is, the MBMS interest indication provides MBMS interest information at the level of a frequency rather than of an individual service, and indicates UE&#39;s interest in MBMS frequency reception. 
     The UE may transmit the MBMS interest indication whenever the UE&#39;s interest changes. 
     Upon receiving the MBMS interest indication from the UE, the eNB acknowledges that the UE wants to receive the MBMS, and makes the UE move to a frequency providing the MBMS. 
     MBMS continuity is described. The UE who wants to receive a specific MBMS acknowledges information on frequency and time on which the specific MBMS is provided. When the MBMS is on air or is going to be broadcast soon, the UE sets a priority of a frequency providing the MBMS to the highest priority. The UE in the RRC_IDLE can move to a cell providing the MBMS and receive the MBMS by performing a cell reselection procedure using the frequency priority information which is set. 
     The MBMS interest indication procedure will be described in more detail hereinafter. 
     An MBMS capable UE in RRC_CONNECTED may initiate the procedure in several cases including 1) upon successful connection establishment, 2) upon entering or leaving the service area, 3) upon session start or stop, upon change of interest, 4) upon change of priority between MBMS reception and unicast reception or 5) upon change to a PCell broadcasting SystemInformationBlockType15, etc. 
     Upon initiating the procedure, the UE shall: 
     if SystemInformationBlockType15 is broadcast by the PCell: 
     1&gt; ensure having a valid version of SystemInformationBlockType15 for the PCell; 
     2&gt; if the UE did not transmit an MBMSInterestIndication message since last entering RRC_CONNECTED state; or 
     2&gt; if since the last time the UE transmitted an MBMSInterestIndication message, the UE connected to a PCell not broadcasting SystemInformationBlockType15: 
     3&gt; if the set of MBMS frequencies of interest is not empty: 
     4&gt; initiate transmission of the MBMSInterestIndication message; 
     2&gt; else: 
     3&gt; if the set of MBMS frequencies of interest has changed since the last transmission of the MBMSInterestIndication message; or 
     3&gt; if the prioritisation of reception of all indicated MBMS frequencies compared to reception of any of the established unicast bearers has changed since the last transmission of the MBMSInterestIndication message: 
     4&gt; initiate transmission of the MBMSInterestIndication message; 
     The UE may send an MBMSInterestIndication even when it is able to receive the MBMS services it is interested in i.e. to avoid that the network allocates a configuration inhibiting MBMS reception. 
     The procedure for determination of MBMS frequencies of interest will be described in more detail hereinafter. 
     The UE shall: 
     1&gt; consider a frequency to be part of the MBMS frequencies of interest if the following conditions are met: 
     2&gt; at least one MBMS session the UE is receiving or interested to receive via an MRB is ongoing or about to start; and 
     The UE may determine whether the session is ongoing from the start and stop time indicated in the USD. 
     2&gt; for at least one of these MBMS sessions SystemInformationBlockType15 acquired from the PCell includes for the concerned frequency one or more MBMS SAIs as indicated in the USD for this session; and 
     The UE considers a frequency to be part of the MBMS frequencies of interest even though E-UTRAN may (temporarily) not employ an MRB for the concerned session. That is, the UE does not verify if the session is indicated on MCCH. 
     2&gt; the UE is capable of simultaneously receiving the set of MBMS frequencies of interest, regardless of whether a serving cell is configured on each of these frequencies or not; and 
     2&gt; the supportedBandCombination the UE included in UE-EUTRA-Capability contains at least one band combination including the set of MBMS frequencies of interest; 
     Indicating a frequency implies that the UE supports SystemInformationBlockType13 acquisition for the concerned frequency. That is, the indication should be independent of whether a serving cell is configured on that frequency. 
     When evaluating which frequencies it can receive simultaneously, the UE does not take into account the serving frequencies that are currently configured. That is, it only considers MBMS frequencies it is interested to receive. 
     The above stated the term ‘frequency’ does not indicate a physical frequency but covers the associated band(s), noting that additional bands may be indicated in SystemInformationBlockType1 (serving frequency) or SystemInformationBlockType15 (neighbouring frequencies). 
     The procedure for setting the contents of the MBMSInterestIndication message will be described in more detail hereinafter. 
     The UE shall set the contents of the MBMSInterestIndication message as follows: 
     1&gt; if the set of MBMS frequencies of interest is not empty: 
     2&gt; include mbms-FreqList and set it to include the MBMS frequencies of interest, using the E-UTRA Absolute Radio Frequency Channel Number (EARFCN) corresponding with freqBandIndicator included in SystemInformationBlockType1, if applicable, and the EARFCN(s) as included in SystemInformationBlockType15; 
     The mbms-FreqList merely indicates the physical frequencies the UE is interested to receive and does not imply the UE supports the associated band. 
     2&gt; include mbms-Priority if the UE prioritises reception of all indicated MBMS frequencies above reception of any of the unicast bearers; 
     If the UE prioritises MBMS reception and unicast data cannot be supported because of congestion on the MBMS carrier(s), E-UTRAN may initiate release of unicast bearers. It is up to E-UTRAN implementation whether all bearers or only Guaranteed Bit Rate (GBR) bearers are released. E-UTRAN does not initiate re-establishment of the released unicast bearers upon alleviation of the congestion. 
     The UE shall submit the MBMSInterestIndication message to lower layers for transmission. 
     MBMS Counting Procedure 
     The MBMS Counting procedure is used by the E-UTRAN to count the number of RRC_CONNECTED mode UEs which are receiving via an MRB or interested to receive via an MRB the specified MBMS services. 
     The UE determines interest in an MBMS service that is identified by the TMGI, by interaction with upper layers. 
       FIG. 13  illustrates an MBMS Counting procedure in the wireless communication system to which the present invention can be applied. 
     Referring to  FIG. 13 , at step S 1301 , E-UTRAN initiates the procedure by sending an MBMSCountingRequest message. 
     Upon receiving the MBMSCountingRequest message, at step S 1303 , the UE in RRC_CONNECTED mode shall: 
     1&gt; if the SystemInformationBlockType1, that provided the scheduling information for the systemInformationBlockType13 that included the configuration of the MCCH via which the MBMSCountingRequest message was received, contained the identity of the Registered PLMN; and 
     1&gt; if the UE is receiving via an MRB or interested to receive via an MRB at least one of the services in the received countingRequestList: 
     2&gt; if more than one entry is included in the mbsfn-AreaInfoList received in the SystemInformationBlockType13 that included the configuration of the MCCH via which the MBMSCountingRequest message was received: 
     3&gt; include the mbsfn-AreaIndex in the MBMSCountingResponse message and set it to the index of the entry in the mbsfn-AreaInfoList within the received SystemInformationBlockType13 that corresponds with the MBSFN area used to transfer the received MBMSCountingRequest message; 
     2&gt; for each MBMS service included in the received countingRequestList: 
     3&gt; if the UE is receiving via an MRB or interested to receive via an MRB this MBMS service: 
     4&gt; include an entry in the countingResponseList within the MBMSCountingResponse message with countingResponseService set it to the index of the entry in the countingRequestList within the received MBMSCountingRequest that corresponds with the MBMS service the UE is receiving or interested to receive; 
     2&gt; submit the MBMSCountingResponse message to lower layers for transmission upon which the procedure ends; 
     UEs that are receiving an MBMS User Service by means of a Unicast Bearer Service (i.e. via a DRB), but are interested to receive the concerned MBMS User Service via an MBMS Bearer Service (i.e. via an MRB), respond to the counting request. 
     If ciphering is used at upper layers, the UE does not respond to the counting request if it cannot decipher the MBMS service for which counting is performed. 
     The UE treats the MBMSCountingRequest messages received in each modification period independently. In the unlikely case E-UTRAN would repeat an MBMSCountingRequest (i.e. including the same services) in a subsequent modification period, the UE responds again. 
     Service Continuity 
     Service continuity procedures (or Mobility procedures) for MBMS reception allow the UE to start or continue receiving MBMS service(s) via MBSFN when changing cell(s). E-UTRAN procedures provide support for service continuity with respect to mobility within the same MBSFN area. Within the same geographic area, MBMS services can be provided on more than one frequency and the frequencies used to provide MBMS services may change from one geographic area to another within a PLMN. 
     UEs that are receiving MBMS service(s) in RRC_IDLE state performing cell reselection or are in RRC_CONNECTED state obtain target cell MTCH information from the target cell MCCH. Mechanisms to deliver MCCH to UE via handover command are not supported. 
     To avoid the need to read MBMS related system information and potentially MCCH on neighbour frequencies, the UE is made aware of which frequency is providing which MBMS services via MBSFN through the combination of the following MBMS assistance information:
         user service description (USD): in the USD, the application/service layer provides for each service the Temporary Mobile Group Identity (TMGI), the session start and end time, the MBMS frequencies and the MBMS service area identities (e.g., MBMS SAIs) belonging to the MBMS service area;   system information: MBMS and non-MBMS cells indicate in SystemInformationBlockType15 the MBMS SAIs of the current frequency and of each neighbour frequency.       

     The MBMS SAIs of the neighbouring cell may be provided by X2 signaling (i.e. X2 Setup and eNB Configuration Update procedures) or/and OAM. 
     When applying the procedures described below for UEs in RRC_IDLE and RRC_CONNECTED state:
         the UE does not need to verify that a frequency is providing a MBMS service by acquiring MCCH and may apply these procedures even though a MBMS service is not provided via MBSFN;   the UE may consider that a service is provided if a session of this service is ongoing as derived from the session start and end times indicated for this service in the USD and if a frequency provides this service;   the UE determines the frequency on which a service is provided according to the following:   if the serving cell provides SystemInformationBlockType15, the UE considers that a frequency is providing the MBMS service via MBSFN if and only if one of the MBMS SAI(s) of this frequency as indicated in SystemInformationBlockType15 of the serving cell is indicated for this MBMS service in the USD;   if the serving cell does not provide SystemInformationBlockType15, the UE in RRC_IDLE state may consider that a frequency included in the USD for the MBMS service is providing this MBMS service as long as the UE reselects cells where SystemInformationBlockType13 is provided.       

     1) In RRC_IDLE, the UE applies the normal cell reselection rules with the following modifications:
         the UE which is receiving MBMS service(s) via MBSFN and can only receive these MBMS service(s) via MBSFN while camping on the frequency providing these MBMS service(s) is allowed to make this frequency highest priority;   the UE which is interested in receiving MBMS service(s) via MBSFN and can only receive these MBMS service(s) via MBSFN while camping on the frequency providing these MBMS service(s) is allowed to make this frequency highest priority when it intends to receive these MBMS service(s) and a session is already available or about to start via MBSFN;   when the MBMS service(s) which the UE is interested in are no longer available (after the end of the session) or the UE is no longer interested in receiving the service(s), the UE no longer prioritises the frequency providing these MBMS service(s);       

     2) In RRC_CONNECTED, the UE that is receiving or interested to receive MBMS via MBSFN informs the network about its MBMS interest via a RRC message and the network does its best to ensure that the UE is able to receive MBMS and unicast services subject to the UE&#39;s capabilities:
         the UE indicates the frequencies which provide the service(s) that the UE is receiving or is interested to receive simultaneously, and which can be received simultaneously in accordance with the UE capabilities.   the UE indicates its MBMS interest at RRC connection establishment (the UE does not need to wait until AS security is activated), and whenever the set of frequencies on which the UE is interested in receiving MBMS services has changed compared with the last indication sent to the network (e.g. due to a change of user interest or of service availability).   the UE may only indicate its interest when the PCell provides SystemInformationBlockType15 and after having acquired SystemInformationBlockType15 of the current PCell.   the UE may indicate its MBMS interest even if the current configured serving cell(s) do not prevent it from receiving the MBMS services it is interested in.   the UE indicates with a single bit whether it prioritises MBMS reception over unicast. This priority indication applies to all unicast bearers and all MBMS frequencies. It is sent whether the MBMS frequencies are congested or not.   the E-UTRAN reuses the SupportedBandCombination IE to derive the UEs MBMS related reception capabilities, i.e. the E-UTRAN tries to ensure that the UE is able to receive MBMS and unicast bearers by providing them on the frequencies indicated in SupportedBandCombination IE signalled by the UE. The UE shall support MBMS reception on any serving cell and on any cell that may be additionally configured as serving cell according to the UE capabilities for unicast reception.   for handover preparation, the source eNB transfers the MBMS interest of the UE, if available, to the target eNB. After handover, the UE reads SystemInformationBlockType15 before updating its MBMS interest. If SystemInformationBlockType15 is provided on the target cell but not on the source cell, the UE indicates its MBMS interest after handover.       

     If MBMS is prioritised and the unicast connection cannot be maintained because of congestion on the MBMS carrier then the E-UTRAN releases unicast bearers. The E-UTRAN does not trigger re-establishment of the released unicast bearers. For congestion control, the E-UTRAN can rely on existing access control mechanisms. 
     The E-UTRAN may take into account the UE priority for MBMS or unicast reception when receiving an indication of proximity to a CSG cell from a UE which also indicated interest in MBMS reception (or vice-versa). 
     Group Communication Service 
     For Group communication service, the following definitions may be introduced.
         Group Member: A user assigned to a Group Communication System Enabler (GCSE) Group.   GCSE Group: A set of Group Members.   Receiver Group Member: A Group Member of a GCSE Group that has interest expressed in receiving ongoing or future Group Communications of that GCSE Group.   Transmitter Group Member: A Group Member of a GCSE Group that is authorized to transmit an ongoing or future Group Communications for that GCSE Group.   Group Communication: Communication from Transmitter Group Members to Receiver Group Members.   Group Communication System Enabler (GCSE): A 3GPP feature enabling an application layer functionality to provide Group Communication over E-UTRAN.   Multipoint Service: A service used to distribute the same content to many UEs in a resource efficient way.       

     A Group Communication Service is intended to provide a fast and efficient mechanism to distribute the same content to multiple users in a controlled manner. As an example, the concept of group communications is used extensively in the operation of classical Land Mobile Radio (LMR) systems used for, but not limited to, Public Safety organizations. At the moment, the primary use of a Group Communication Service in LMR is to provide “Push to Talk” (PTT) functionality, so a Group Communication Service based on 3GPP architecture, using LTE radio technology, should enable PTT voice communications with comparable performance. 
     The service should allow flexible modes of operation as the users and the environment they are operating in evolves. For example, the capabilities of LTE allow for broadband communication, so Group Communication Service is expected to support, voice, video or, more general, data communication. Also LTE can allow users to communicate to several groups at the same time in parallel e.g. voice to one group, different streams of video or data to several other groups. 
     The users of Group Communication Service are organised into groups; a user can be member of more than one group. 
     Functional Requirements 
     High Level Requirements 
     The ability to make use of the Group Communication System Enabler provided by the 3GPP system shall be enabled on a Group Member basis. 
     The system shall provide a mechanism to indicate network support of Group Communication System Enabler to the UE. 
     The UE shall have the ability to indicate the network support of Group Communication System Enabler to the user. 
     Group Communication System Enabler shall support various media such as conversational type communication (e.g. voice, video) or streaming (e.g. video) or data (e.g. messaging) or a combination of them. 
     The system shall be able to uniquely identify a GCSE group. The system shall be able to uniquely identify a Group Member within a GCSE group 
     The system shall provide a mechanism to send a Group Communication to all Receiver Group Members. 
     Only Receiver Group Members of the GCSE Group shall be able to receive from that GCSE Group via Group Communication. 
     The system shall be able to authorise a Group Member to become a Transmitter Group Member. 
     A Transmitter Group Member shall be able to transmit to a GCSE Group that it is a member of, with or without being a Receiver Group Member of that GCSE Group. 
     The interface between the GCSE client on the UE and the network shall be an open interface. 
     The network shall provide a third party interface for Group Communication. This implies that the interface supports e.g. charging and authentication/authorisation. 
     The system shall provide a mechanism for a Group Member that is not connected via a 3GPP network, to communicate in a Group Communication for a GCSE Group that it is a member of. 
     Performance) The system shall be optimized to minimize the time intervals related to the use of Group Communication. 
     The recommended time intervals specified below are for consideration in the development of detailed RAN/CN requirements, and the evaluation of architecture solutions. 
     The system should provide a mechanism to support a Group Communication end-to-end setup time less than or equal to 300 ms. It is assumed that this value is for an un-contended network, where there is no presence checking and no acknowledgements requested from Receiver Group Member(s). The end-to-end setup time is defined as the time between when a Group Member initiates a Group Communication request on a UE and the point when this Group Member can start sending start sending a voice or data communication. 
     The time from when a UE requests to join an ongoing Group Communication to the time that it receives the Group Communication should be less than or equal to 300 ms. 
     The end to end delay for media transport for Group Communications should be less than or equal to 150 ms. 
     Service Continuity 
     When UEs are moving among cells during Group Communication, service continuity shall be supported. 
     Resource Efficiency 
     The system shall provide a mechanism to efficiently distribute data for Group Communication. 
     Scalability 
     The number of Receiver Group Members in any area may be unlimited. 
     The system shall support multiple distinct Group Communications in parallel to any one UE that is capable of supporting that number of distinct Group Communications in parallel. The mechanisms defined shall allow future extension of the number of distinct Group Communications supported in parallel. 
     This includes both multiple Group Communications within the same GCSE Group, and multiple Group Communications associated with multiple GCSE Groups. The actual number of such Group Communications achievable and desirable will depend on the type of media. 
     Security Requirements for Group Communication 
     The system shall support at least the same security level for Group Communication (e.g. for Authentication, Integrity, Confidentiality and Privacy) as a 3GPP LTE packet data bearer. 
     Charging Requirements for Group Communication 
     The system shall support the collection of resource and service usage rmation for Group Communication. 
     Roaming and Network Interworking Requirements 
     The system shall support the transmitting and/or receiving of Group Communication by Group Members that are roaming. 
     Subject to operator agreement, the system shall be able to support Group Communications where Group Members are attached to different PLMNs. 
     An interface shall be provided to enable Group Communication interworking between a network offering GCSE-based Group Communication Services with either or both of:
         another 3GPP network offering GCSE-based Group Communication Services,   a non-3GPP network offering group communication services.       

     High availability of Group Communication) The system shall be capable of achieving high levels of availability for Group Communications utilising GCSE_LTE, e.g. by seeking to avoid single points of failure in the GCSE_LTE architecture and/or by including recovery procedures from network failures. 
     Group Handling 
     Creation, Modification, and Deletion of GCSE Groups 
     The system shall provide a mechanism for the dynamic creation, modification, and deletion of GCSE Groups. 
     Information additional to the set of Group Members shall be associated with a GCSE Group, to be used by the system to identify the GCSE Group and to specify attributes that determine how it is changed and used. This may be used to, e.g. define which Group Members are authorized for administrative functions, and whether the GCSE Group can be relayed via ProSe. 
     The system shall provide notification of the creation or deletion of a GCSE Group to its Group Members. 
     If authorised, a user shall be able to request and receive a list of all the GCSE Groups for which it is a Group Member. 
     A mechanism shall be provided such that, if authorized, a user may modify rmation associated with a GCSE Group, add or remove Group Members of a GCSE Group, or create/delete a GCSE Group. 
     If authorized, a user shall be able to request and receive a list of Group Members of a particular GCSE Group. 
     If authorized, a user shall be able to request a notification for when specific or any Group Member(s) is added to or removed from a particular GCSE Group. 
     The system shall provide a mechanism to remotely configure a UE with any GCSE related rmation. 
     Geographical Scope of GCSE Groups 
     GCSE Groups shall by definition be of system wide scope. Optionally, GCSE Groups may be geographically restricted. 
     The system shall provide a mechanism to restrict all Group Communications for a given GCSE Group to a defined geographic area. In this case Group Members shall be able to receive and/or transmit only within this geographic area. 
     The system shall provide a mechanism to redefine the geographic area for a GCSE Group that has a defined geographic area. 
     The system shall provide a mechanism to override geographic area restrictions for a GCSE Group for a particular Group Communication transmission. 
     The system shall provide a mechanism to restrict a particular Group Communication transmission to a defined geographic area within the geographical scope of that group. In this case only Receiver Group Members within the geographic area shall receive the Group Communication. 
     Group Communication 
     Group Communication Setup Requirements 
     A Transmitter Group Member shall be able to transmit a Group Communication for a GCSE Group without knowledge of the identities of other GCSE Group Members. 
     A Group Member shall be able to request to join or leave an established Group Communication. 
     The system shall provide a mechanism to setup, release, and modify a multipoint service with applicable parameters e.g. QoS, priority. 
     The system shall validate the parameters received in the request to setup or modify a Group Communication based on the policy specified by the group&#39;s subscription rmation, e.g. checks for QoS, priority. 
     The system shall provide the means to notify the requesting entity of any updates in the status of an on-going Group Communication. 
     The system shall provide notification to the requesting entity of the outcome of a request to setup, release, or modify a multipoint service. 
     Services to the Group Member 
     The system shall provide a mechanism to permit a Group Member to request notification when a Group Communication is initiated using that GCSE group. 
     The system shall provide notification of a Group Communication to Group Members that have requested notification for the GCSE Group. 
     Group Member Requests of the System 
     A Group Member shall be able to express interest to receive Group Communications when the GCSE Group is used for Group Communications. 
     The system shall provide a mechanism for a Receiver Group Member receiving a Group Communication to be able to accept, reject, or ignore the Group Communication. 
     The system shall provide a mechanism for a Receiver Group Member receiving a Group Communication to be required to accept the Group Communication. 
     Priority and Pre-Emption of GCSE Communication 
     The following requirements apply to the allocation and retention of system resources: 
     The system shall provide a mechanism to support at least n priority levels for Group Communication. 
     The system shall provide a mechanism to support reassignment of Group Communication priority level. 
     The network operator shall be able to configure each Group Communication priority level with the ability to pre-empt lower priority Group Communications and non-Group Communications traffic. 
     The system shall provide a mechanism to allow pre-emption of lower priority for Group Communications and non-Group Communications traffic. 
     Group Members within a GCSE Group shall be able to have different priorities from each other. 
     Services Provided During an on-Going Group Communication 
     For Group Communication services that require floor control (i.e. the ability to arbitrate who currently has the right to transmit)
         The Group Member shall be able to request the floor;   The system shall be able to arbitrate floor requests and grant permissions to Group Members.   A Transmitter Group Member shall be uniquely identified to the Receiver Group Members.       

     An entity shall be able to request a notification when a specific Group Member ceases to be a Receiver Group Member. 
     A Receiver Group Member ceases to be a Receiver Group Member of a certain group by:
         user decision   third party decision   after a service dependent amount of time   after a system configurable amount of time of unavailability.       

     A notification shall be provided to the requesting entity when a specific Group Member ceases to be a Receiver Group Member. 
     During the lifetime of a Group Communication the Receiver Group Members of the Group Communication may change. In the case where there are no Receiver Group Members, Transmitter Group Members would need to know that there are no other Receiver Group Members, and when another Receiver Group Member returns to the Group Communication. 
     A Transmitter Group Member ceases to be a Transmitter Group Member of a certain group by:
         user decision   third party decision   after a service dependent amount of time   after a system configurable amount of time of unavailability.       

     User Perception of Group Communication 
     All Receiver Group Members in a given area shall receive the Group Communication at the same time according to user perception. 
     All changes to the GCSE Group (e.g., adding or removing group members) shall take effect as soon as possible. 
     All changes to the set of Receiver Group Members shall take effect in the Group Communication as soon as possible. 
     Interaction with Other Services and Functions 
     Emergency Calling 
     The ability for a UE to make an emergency call shall be unaffected by being in a Group Communication. 
     Interaction with Proximity-Based Services (ProSe) 
     If EPC and E-UTRAN support ProSe, the EPC and E-UTRAN shall be able to make use of ProSe Group Communication and the public safety ProSe UE-to-Network Relay for Group Communication, subject to operator policies and UE capabilities or settings. 
     A public safety ProSe-enabled UE not served by E-UTRAN shall be able to support Group Communication based on ProSe Communication paths. A public safety ProSe-enabled UE shall be able to dynamically express its interest in receiving, via a public safety ProSe UE-to-Network Relay, the Group Communications of one or more GCSE Groups for which it is authorized. 
     A public safety ProSe UE-to-Network Relay shall be able to relay Group Communication to/from ProSe Communication paths, if the following conditions apply:
         the GCSE Group is allowed to be relayed; and   the public safety ProSe UE-to-Network Relay is allowed to relay Group Communication.       

     A public safety ProSe UE-to-Network Relay shall be able to restrict the relayed Group Communication on a per group basis. 
     The system shall support groups whose membership shall be the same irrespective of whether a Group Communication is made using ProSe Group Communication or GCSE Group Communication. 
     GCSE Group Members shall be able to access Group Communication services using ProSe Communication paths and/or by EPC Path. 
     Architecture of GCSE Service 
       FIG. 14  illustrates GCSE architecture in the wireless communication system to which the present invention can be applied. 
     This high-level architecture diagram consists of Application layer and 3GPP EPS layer. The Application layer consists of Group Communication Service Enabler Application Server (GCSE AS). The 3GPP EPS layer consists of a Multipoint Service (MuSe) function. The MuSe function interworks with the 3GPP EPS entities to provide the MuSe functionality. For example, MBMS GW and BM-SC ( FIG. 7 ) may provide the MuSe function. 
     The reference points related to the application server (e.g., GCSE application server) will be described hereinafter. 
     GC1: It is the reference point between the GCSE application in the UE and in the application server. It is used to define application level signalling requirement to enable Multipoint functionality for GCSE_LTE, and possibly for session establishment and floor control usages, etc. 
     GC2: It is the reference point between the GCSE AS and the MuSe function. It is used to define the interaction between and MuSe functionality provided by the 3GPP EPS layer. 
     GC3: It is the reference point between the E-UTRAN and MuSe function. It is used to define the interaction between E-UTRAN and MuSe function in order to achieve Multipoint functionality provided by the 3GPP EPS layer. 
     GC4: It is the reference point between the MME and MuSe function. It is used to define the interaction between MME and MuSe function in order to achieve Multipoint functionality provided by the 3GPP EPS layer. 
     GC5: It is the reference point between the P-GW and MuSe function. It is used to provide DL unicast service by MuSe. 
     Selective Service Level Information Indication 
     The network ability of switching between unicast and MBMS seems based on knowledge about what kind of MBMS service a specific UE is receiving and how many UEs are involved in a specific group communication. Unfortunately, the existing network does not know which MBMS service UE is receiving, regardless of RRC state. The network may only know a MBMS frequency that UE in RRC_CONNECTED is receiving, based on MBMS Interest Indication messages, because MBMS Interest Indication messages indicates the MBMS frequency only. 
     Even though counting function could be used to help the network know how many UEs in RRC_CONNECTED are receiving a specific MBMS service, the network would need to perform counting every modification period, in order to keep track of MBMS reception status in UEs, because MBMS reception status may change in UEs any time. However, using counting every period would result in significant uplink signalling burden in high load situation which group communication mainly concerns. 
     In this invention, we propose to add service level information in MBMS Interest Indication message for particular MBMS service, e.g. group communication, in order to help the network to evaluate how many UEs are involved in the particular MBMS service at a particular cell. 
     Hereinafter, in the specification, ‘service level information’ means information for specifying a corresponding MBMS service unlike reporting frequency information with respect to an MBMS which the UE receives or is interested to receive through mbms-FreqList included in an MBMS Interest Indication message. 
       FIG. 15  is a diagram illustrating a method of selectively transmitting service information according to an embodiment of the present invention. 
     Referring to  FIG. 15 , UE determines whether or not to indicate to the network about a specific MBMS service which the UE is receiving or interested to receive (S 1501 ). 
     In this case, when UE configures the MBMS Interest Indication message, the UE may determine whether a received or reception interested service is a service required to transmit service level information from the network. 
     As above stated, an MBMS capable UE in RRC_CONNECTED may initiate the procedure in several cases including 1) upon successful connection establishment, 2) upon entering or leaving the service area, 3) upon session start or stop, upon change of interest, 4) upon change of priority between MBMS reception and unicast reception or 5) upon change to a PCell broadcasting SystemInformationBlockType15, etc. 
     In this case, a service required to transmit the service level information to the network may mean a specific type of service. Desirably, the MBMS service corresponds to a public safety related service or a group call service such as GCSE service. 
     Further, for example, the service required to report the service level information to the network may include a service based on channel switching of the UE to the MBMS in unicast by the network. 
     Further, for example, the service required to report the service level information to the network may include service(s) indicated from an RRC message transmitted through User Service Description (USD) or MCCH. That is, by receiving an USD or an MCCH, the UE may know which MBSM service is a service required to report the service level information to the network. Accordingly, the UE may determine whether a currently received or reception interested service is a service included in an MBMS service list from an RRC message through the USD or the MCCH. 
     A detailed description thereof is as follows. 
     Desirably, UE determines whether the interested MBMS service is needed to be indicated to the network or not as follows: 
     Option 1: if the MBMS service corresponds to a specific type of service such as public safety service and/or a group call service such as GCSE service, the UE determines that the MBMS service needs to be indicated in MBMS Interest Indication message. 
     Option 2: if User Service Description (USD) indicates to the UE that the MBMS service corresponds to a specific type of service such as public safety service and/or a group call service such as GCSE service, or if USD indicates to the UE that the MBMS service needs to be indicated to the network, the UE determines that the MBMS service needs to be indicated in MBMS Interest Indication message. 
     Option 3: if a RRC message on MCCH indicates to the UE that the MBMS service corresponds to a specific type of service such as public safety service and/or a group call service such as GCSE service, or if a RRC message on MCCH indicates to the UE that the MBMS service needs to be indicated to the network, the UE determines that the MBMS service needs to be indicated in MBMS Interest Indication message. 
     In this way, the UE determines whether a corresponding MBSM service with respect to currently received MBMS service and/or an interested MBSB service to receive is a service required to transmit the service level information to the network. 
     For each interested MBMS services, if the UE determines that an interested service needs to be indicated to the network (in step S 1501 ), the UE transmits the service level information of the interested MBMS service to the network (S 1503 ). 
     In this case, the UE may transmit the service level information to the network through an MBMS interest indication message. 
     Desirably, the service level information is a MBMS service identity (or Temporary Mobile Group Identity (TMGI)), and/or a MBMS session identity. 
     That is, when there is a service necessary to transmit the service level information to the network among MBMS services which are received service or having interest in reception by the UE, the UE may transmit a service ID (or TMGI) with respect to a corresponding MBMS service to the network. 
     The service ID identifies uniquely the identity of an MBMS service within a PLMN. The service ID contains octet 3-5 of the IE Temporary Mobile Group Identity (TMGI). 
     TMGI is used within MBMS to uniquely identify Multicast and Broadcast bearer services. 
       FIG. 16  is a diagram illustrating a structure of a TMGI according to an embodiment of the present invention. 
     Referring to  FIG. 16 , the TMGI is composed of MBMS Service ID, Mobile Country Code and Mobile Network Code. 
     MBMS Service ID consisting of three octets. MBMS Service ID consists of a 6-digit fixed-length hexadecimal number between 000000 and FFFFFF. MBMS Service ID uniquely identifies an MBMS bearer service within a PLMN. 
     Mobile Country Code (MCC) consisting of three digits. The MCC identifies uniquely the country of domicile of the BM-SC. 
     Mobile Network Code (MNC) consisting of two or three digits (depending on the assignment to the PLMN by its national numbering authority). The MNC identifies the PLMN which the BM-SC belongs to. 
     The MBSFNAreaConfiguration message indicates the service ID (or TMGI) of MBMS services that are ongoing. 
     Further, the UE may receive the TMGI through the USD. As described above, the application/service layer provides for each service the Temporary Mobile Group Identity (TMGI), the session start and end time, the frequencies and the MBMS service area identities (e.g., MBMS SAIs) belonging to the MBMS service area in the USD. 
     In addition, when there is a service necessary to transmit the service level information to the network among MBMS services which are received or having interest in reception by the UE, the UE may transmit a session ID with respect to a corresponding MBMS service to the network. 
     MBMS session ID together with TMGI identifies a transmission or a possible retransmission of a specific MBMS session. The MBSFNAreaConfiguration message indicates the MBMS sessions that are ongoing. 
       FIG. 17  is a diagram illustrating a method of selectively transmitting service information according to an embodiment of the present invention. 
     Referring to  FIG. 17 , the UE receives information on the MBSM service necessary to report the service level information the network from the network (for example, EUTRAN) through the MCCH (S 1701 ). 
     In this case, the information on the MBSM service necessary to report the service level information to the network may be transmitted through an MBSFNAreaConfiguration message, a System Information Block Type 15 (SIB 15), and the like. 
     As described above, for example, the MBSM service necessary to report the service level information to the network may include a specific type of an MBMS service and/or a GCSE service such as a group call service. In this case, for example, UE may receive a GCSE service list or a list of specific type of service such as public safety service via MCCH. 
     Further, unlike an example of  FIG. 17 , the UE may receive information on the MBSM service necessary to report the service level information to the network from an application server ( FIG. 14 ) such as a GCSE application server or through a USD. 
     The information on the MBSM service necessary to report the service level information to the network will be described with reference to  FIG. 18 . 
       FIG. 18  illustrates information on the MBSM service necessary to report the service level information to a network an embodiment of the present invention. 
     As illustrated in  FIG. 18( a ) , the information on the MBSM service necessary to report the service level information to the network may include a list including both of the MBSM service necessary to report the service level information to the network and an MBSM service unnecessary to report the service level information to the network. 
     In this case, the UE may independently determine which type of service is the MBSM service necessary to report the service level information to the network. 
     For example, when a specific type of service such as public safety service and/or a group call service such as GCSE service is defined as the MBSM service necessary to report the service level information to the network, the UE may discriminate a type of service through contents of the MBMS service in a (particularly, by application layer). 
     Moreover, in a case of the MBSM service necessary to report the service level information to the network, a service ID (or TMGI) or a session ID may be allocated within a predetermined range. In addition, the UE may discriminate the MBSM service necessary to report the service level information to the network based on the service ID (or TMGI) or the session ID. 
     For example, it is assumed that the service ID (or TMGI) or the session ID is allocated within a predetermined range, that is, within the range of 000000 to 000FFF in the MBSM service necessary to report the service level information to the network shown in  FIG. 18( a ) . Accordingly, the UE may discriminate an MBMS service 1 (public safety service) and an MBMS service 3 (group call service) having the service ID (or TMGI) or the session ID of 000001 and 000002 as the MBSM service necessary to report the service level information to the network. 
     Further, as illustrated in  FIG. 18( b ) , the MBSM service necessary to report the service level information to the network may include only a MBSM service list necessary to report the service level information to the network. 
     In this case, the UE may determine an MBMS service included in received information (that is, a list) as the MBSM service necessary to report the service level information to the network. That is, the UE determines an MBMS service 1 (public safety service) and an MBMS service 3 (group call service) included in the list in an example of  FIG. 14( b )  as the MBSM service necessary to report the service level information to the network. 
     Although  FIG. 18  illustrates a case where only the service ID (or TMGI) or the session ID is included in the list, both of the service ID (or TMGI) or the session ID may be included by MBMS services. 
     Referring back to  FIG. 17 , the UE determines whether the received or reception interested MBMS service is the MBSM service necessary to report the service level information to the network based on the information on the MBSM service necessary to report the service level information to the network. 
     Further, when the MBMS service which is received or having interest in reception is the MBSM service necessary to report the service level information to the network, the UE transmits identifier information of a corresponding MBMS to the network (for example, EUTRAN) (S 1703 ). 
     In this case, the UE may transmit identifier information (for example, interest GCSE service identifier) with respect to the MBSB to the network through a MBMS interest indication message. 
     In this case, for example, the identifier information with respect to the MBSB may include a TMGI and/or session identity corresponding to the MBMS service. 
     In this case, if the UE is interested in MBMS service A and B, but if only the service B is included in the received list, the UE may indicate only MBMS service B in MBMS Interest Indication message. For example, since a reception interested MBMS service 4 (group call service) by the UE is not included in a list, identifier information with respect to the MBMS service 4 is not transmitted to the network. 
     That is, the UE may transmit only identifier information with respect to an MBMS service 1 and an MBMS service 3 (when the MBMS service 1 and the MBMS service 3 are an MBSM service which is interested in reception by the UE and is necessary to report the service level information to the network). 
     In this manner, by transmitting the service level information with respect to a specific MBMS service (for example, group communication service, public safety service) through an MBMS Interest Indication message, the network may know how many UEs in a specific cell are included in the specific MBMS service. 
     Apparatus for Implementing the Present Invention 
       FIG. 19  illustrates a block diagram of a wireless communication apparatus according to an embodiment of the present invention. 
     Referring to the UE includes a processor (or digital signal processor)  1910 , RF module (RF unit)  1935 , power management module  1905 , antenna  1940 , battery  1955 , display  1915 , keypad  1920 , memory  1930 , SIM card  1925  (which may be optional), speaker  1945  and microphone  1950 . The UE may include a single antenna or multiple antennas. 
     The processor  1910  may be configured to implement the functions, procedures and/or methods proposed by the present invention as described in  FIG. 1-18 . Layers of a wireless interface protocol may be implemented by the processor  1910 . 
     The memory  1930  is connected to the processor  1910  and stores information related to operations of the processor  1910 . The memory  1930  may be located inside or outside the processor  1910  and may be connected to the processors  1910  through various well-known means. 
     A user enters instructional information, such as a telephone number, for example, by pushing the buttons of a keypad  1920  or by voice activation using the microphone  1950 . The microprocessor  1910  receives and processes the instructional information to perform the appropriate function, such as to dial the telephone number. Operational data may be retrieved from the Subscriber Identity Module (SIM) card  1925  or the memory module  1930  to perform the function. Furthermore, the processor  1910  may display the instructional and operational information on the display  1915  for the user&#39;s reference and convenience. 
     The RF module  1935  is connected to the processor  1910 , transmits and/or receives an RF signal. The processor  1910  issues instructional information to the RF module  1935 , to initiate communication, for example, transmits radio signals comprising voice communication data. The RF module  1935  comprises a receiver and a transmitter to receive and transmit radio signals. An antenna  1940  facilitates the transmission and reception of radio signals. Upon receiving radio signals, the RF module  1935  may forward and convert the signals to baseband frequency for processing by the processor  1910 . The processed signals would be transformed into audible or readable information outputted via the speaker  1945 . 
     The aforementioned embodiments are achieved by combination of structural elements and features of the present invention in a predetermined manner. Each of the structural elements or features should be considered selectively unless specified separately. Each of the structural elements or features may be carried out without being combined with other structural elements or features. Also, some structural elements and/or features may be combined with one another to constitute the embodiments of the present invention. The order of operations described in the embodiments of the present invention may be changed. Some structural elements or features of one embodiment may be included in another embodiment, or may be replaced with corresponding structural elements or features of another embodiment. Moreover, it will be apparent that some claims referring to specific claims may be combined with another claims referring to the other claims other than the specific claims to constitute the embodiment or add new claims by means of amendment after the application is filed. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 
     INDUSTRIAL APPLICABILITY 
     Although the method of selectively transmitting an MBMS service level in the wireless communication system was described while focusing on the 3GPP LTE/LTE-A according the present invention, various wireless communication systems are applicable except for the 3GPP LTE/LTE-A system.