Abstract:
Disclosed are methods for transmitting and receiving multimedia service data, base station and user equipment. The method for transmitting multimedia service data comprises steps of: receiving transmission order information representing the order in which a plurality of multimedia services is to be transmitted; generating schedule information including the beginning indices of the plurality of multimedia services; and transmitting data of the plurality of multimedia services based on the transmission order information and the schedule information. With the methods and equipment of the present invention, dynamic scheduling for MBMS service can be implemented in a SFN network so that power preservation of user equipment can be achieved in the case of discontinuous transmission and statistical multiplexing can be performed easily.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to multimedia service data transmitting and receiving technology, and in particular to methods for transmitting and receiving multimedia service data, base station (NodeB equipment) and user equipment which enable dynamic scheduling of MBMS (Multimedia broadcast/Multicast Service) service in SFN (Single Frequency Network) transmission. 
       BACKGROUND OF THE INVENTION 
       [0002]    The 3GPP (3 rd  Generation Partnership Project) launched LTE (Long Term Evolution) in 2005, which aims to provide support for increasing requirements from operators and subscribers with higher data throughput and better network performance. 
         [0003]    The 3GPP Rel. 6 has introduced MBMS which is a point-to-multipoint service for transmitting data from a single data source to multiple users, so as to achieve sharing of network (including core network and access network) resources and to provide services for more multimedia users of identical requirements with fewer resources. In a wireless access network, by using public transmission channel and public wireless carrier, MBMS service can implement not only message-type multicast and broadcast of pure text and lower rate, but also multimedia service multicast and broadcast of higher rate, such as mobile phone television. 
         [0004]    Under the LTE, the existing MBMS service has evolved into E-MBMS (Evolved MBMS). Several services are multiplexed on a single Multicast CHannel (MCH) in a time division manner. Such MCH generally occupies only a portion of all system resources, and those resources occupied by the MCH are represented by MSAP (MBMS Subframe Allocation Pattern). MSAP comprises a series of subframes which may be discontinuous. Generally, MSAP rarely has any change during an overall session, and thus can be simply called as static schedule information. 
         [0005]    If UE knows only MSAP, the UE may have to receive all services on the MCH, because the UE cannot learn exactly which suhframes should be received. It is thus desirable to further indicate to the UE how to receive only those subframes associated with the UE so as to preserve power of the UE. 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the present invention is to provide methods for transmitting and receiving multimedia service data, NodeB equipment and user equipment which enable dynamic scheduling of MBMS service in SFN transmission. 
         [0007]    An aspect of the present invention provides a method for transmitting multimedia service data, comprising steps of: receiving transmission order information representing the order in which a plurality of multimedia services is to be transmitted; generating schedule information including the beginning indices of the plurality of multimedia services; and transmitting data of the plurality of multimedia services based on the transmission order information and the schedule information. 
         [0008]    Another aspect of the present invention provides a method for receiving multimedia service data, comprising steps of: receiving transmission order information representing the order in which a plurality of multimedia services is to be transmitted; receiving schedule information including the beginning indices of the plurality of multimedia services; and receiving data of particular ones of the multimedia services based on the transmission order information and the schedule information. 
         [0009]    A further aspect of the present invention provides a base station comprising: means for receiving transmission information representing the order in which a plurality of multimedia services is to be transmitted, generation means for generating schedule information including the beginning indices of the plurality of multimedia services; and transmission means for transmitting data of the plurality of multimedia services based on the transmission order information and the schedule information. 
         [0010]    A still further aspect of the present invention provides a user equipment comprising: reception means for receiving transmission order information representing the order in which a plurality of multimedia services is to be transmitted and for receiving schedule information including the beginning indices of the plurality of multimedia services; and reception control means for receiving data of particular ones of the multimedia services based on the transmission order information and the schedule information. 
         [0011]    With the methods and equipment of the present invention, dynamic scheduling for MBMS service can be implemented in a SFN network so that power preservation of user equipment can be achieved in the case of discontinuous transmission and statistical multiplexing can be performed feasibly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The above and other objects, features and advantages of the present invention will be more apparent from the following description of preferred embodiments with reference to the drawings, in which: 
           [0013]      FIG. 1  is a schematic diagram of a communication system in which the methods, NodeB equipment and user equipment according to embodiments of the present invention are applied; 
           [0014]      FIG. 2  shows a schematic block diagram of NodeB equipment according to embodiments of the present invention. 
           [0015]      FIG. 3  shows an exemplary structure of MSAP according to embodiments of the present invention; 
           [0016]      FIG. 4  is a specific chart illustrating a method for transmitting multimedia service data according to embodiments of the present invention; 
           [0017]      FIG. 5  shows a schematic block diagram of user equipment according to embodiments of the present invention; and 
           [0018]      FIG. 6  is a specific flow chart illustrating a method for receiving multimedia according to embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    A detailed description of preferred embodiments of the present invention will be given below in conjunction with the drawings. In the description, any detail and function unnecessary to the present invention are omitted so that the above objects, features and advantages of the present invention will not be obscured. 
         [0020]      FIG. 1  shows the network architecture of a communication system according embodiments of the present invention. As shown in  FIG. 1 , only one evolved cBM-SC (evolved Broadcast/Multicast Service Center), one MBMS GW (GateWay), two NodeBs, eNB 1  and eNB 2 , located in the same SFN region, and user equipment UE 1 , UE 2 , UE 3  are shown for the purpose of illustration, while any other devices like routers are omitted. 
         [0021]    Under the LTE, a user plane interface between MBMS GW and the base stations eNBs is called as M1 interface, and an interface between the base stations eNB 1  and eNB 2  is called as X2 interface. 
         [0022]    Further, in the user plane, data is sent from MBMS GW directly to the eNBs, and the interface between them is called as M1 interface. In a control plane, signaling is first sent from the MBMS GW to MCE (MBMS Control Entity), and then sent from MCE to the respective eNBs via M2 interface(s). The duration scheduling period and static scheduling information are both configured by MCE. 
         [0023]    Obviously, the network architecture shown in  FIG. 1  intended to illustrate the embodiments of the present invention and should not be construed as limiting any network architecture applied in any actual applications. One skilled in the art can employ several MBMS gateways and more NodeBs and add other auxiliary devices. 
         [0024]    According to an embodiment of the present invention, in addition to the static scheduling information, dynamic scheduling information is introduced into MSAP to indicate to user equipment the positions of respective services to be received by the user equipment. The subframes used for representing dynamic scheduling information are part of MSAP, and these subframes can be called as dynamic scheduling information. Dynamic scheduling is critical to support statistical multiplexing, and is very beneficial for power saving in case of DRX (Discontinuous RX). As mentioned above, a single MCH may carry a number of services, and a large amount of power will be wasted if UE receives its desired services by receiving all subframes indicated by MSAP. 
         [0025]    MSAP is valid for the session until MCE changes it. In other words, MSAP may vary with change of the session. Suppose there are N f  subframes in one MSAP (N f  is a natural number), these subframes can be indexed from 1 to N f  according to the transmission timing relationship of the subframes. This is useful to indicate the transmission occasions for a specific service, which avoids an exact indication of the position of a subsequent subframe and thus reduces signaling overhead. According to the present embodiment, for certain E-MBMS service, it is only required to indicate to the UE the indices of the subframes to be transmitted by a specific MTCH (MBMS point-to-multipoint Traffic CHannel). 
         [0026]    According to an embodiment of the present invention, data of an individual in MSAP are transmitted with consecutive indices, that is, indices for same service are set to be consecutive, so as to simplify composition of dynamic scheduling information. In this case, for example, dynamic scheduling information provided in MSAP needs to indicate only the beginning index of a service and the number of the indices. This would be beneficial for UE power saving, especially in case the UE does not receive the scheduling information correctly. Since all the eNBs should guarantee the same scheduling information, packets to be scheduled must be received and buffered first. So, it is feasible to record and transmit data of the same service the consecutive indices of MSAP subframe set. 
         [0027]      FIG. 2  shows a schematic block diagram of base station (NodeB equipment) according to embodiments of the present invention. As shown in  FIG. 2 , the NodeB equipment comprises a buffer unit  110 , a paketization unit  130 , a scheduling information generation unit  120  and a transmitting unit  140 . 
         [0028]    The buffer unit  110  stores temporarily multimedia service data, such as MBMS data, received by a receiving unit (not shown) from MBMS gateway. 
         [0029]    In the scenario of transmitting data of several services, the NodeB equipment needs to transmit the transmission order of the respective services in MSAP which is determined by MCE. For example, the transmitting unit  140  transmits over MCCH (MBMS point-to-multipoint Control CHannel) the MSAP received via the receiving unit, with the MSAP containing the transmission order of data for the respective services. 
         [0030]    It is unnecessary to transmit the transmission order information at each scheduling process. Instead, its transmission is generally repeated at a lower frequency, such as every 640 ms. Scheduling may be conducted in a granularity of only 160 ms. Typically, upon the beginning of a service session, the order information of the individual services has been determined. The order information is transmitted repeatedly to the UE until another session starts, during which the possibility of change is not excluded. Thereafter, the data arrive, and the eNBs perform scheduling. 
         [0031]    As given above, the transmission order can be pre-configured by MCE, and can be determined with some priority information. In this way, the scheduling information would be simpler and has less signaling overhead. For example, there are three services, service A, service B and service C, multiplexed on the same MCH. If there are the numbers of 3, 2, 4 subframes allocated to the three services, respectively, the scheduling information could be just as {3, 2, 4}, and no service ID is required. Hence, it is required to send the transmission order information, which is a list of services multiplexed onto the MCH, to the UE via MCCH in the same order as that of scheduling. 
         [0032]    As such, the indices for each of the MBMS services are consecutive, so that the scheduling information can have a simpler structure. As an example, the scheduling information generation unit  120  can generate scheduling information comprising the beginning index of the service. 
         [0033]    Further, according to an embodiment of the present invention, the dynamic scheduling information for the individual services can be added into the first subframe in MSAP, and be sent to the user equipment by the transmitting unit  140  via L3 logic channel like MSCH or via L1/L2 signaling in respective scheduling update periods. In the case of transmitting the scheduling information via L1/L2 signaling, the scheduling information can be transmitted as part of MAC header transmitted via MAC control element. 
         [0034]    In another embodiment, the scheduling information can be distributed among subframes of a specific MTCH and transmitted. In this case, the scheduling information could be distributed among different MAC PDUs as part of MAC PDUs. 
         [0035]    In another embodiment, the scheduling information can be transmitted over MCCH, unlike the above description of transmitting the scheduling information as multiplexed with service data. 
         [0036]      FIG. 3  shows an exemplary structure diagram of MSAP of MCH according to embodiments of the present invention. As shown in  FIG. 3 , service A and service B are multiplexed on the MCH. There are a total of 8 subframes in the MSAP subframe set. In the current scheduling period, service A is to be transmitted in subframe indices {1, 2, 3, 4}, and service B is to be transmitted in subframe indices {4, 5, 6, 7, 8}. In subframe  4 , the two services are concatenated in the same MAC PDU. The scheduling information is transmitted via the MAC control element in the transmitting unit  140 . For example, the scheduling information can be arranged in the first subframe of the MSAP. 
         [0037]    Then, the packetization unit  130  packetizes the data of the services stored temporarily in the buffer unit  110  according to the transmission order information determined before the start of the session as well as the dynamic scheduling information generated by the scheduling information generation unit  120 , such that the indices for each service in the MSAP are consecutive, and the data packets of different services are concatenated together. 
         [0038]    During the data transmitting period, the transmitting nit  140  groups the data of the services and transmits them one by one in timing order, according to the transmission order information and the scheduling information determined by the scheduling information generation unit  120 . 
         [0039]    According to an embodiment the present invention, the scheduling information can be updated periodically by MCE, usually before transmission of data. 
         [0040]      FIG. 4  is a specific flow chart illustrating a method for transmitting multimedia service data according to embodiments of the present invention. As shown in  FIG. 4 , at step S 11  the transmitting unit  140  receives the transmission order information configured by MCE and forwards it to the user equipment. 
         [0041]    At step S 12  after the start of the session, the buffer unit  110  stores temporarily multimedia service data, such as MBMS data, received from MBMS gateway. 
         [0042]    Then, at step S 13 , the indices for each MBMS service are consecutive in the MSAP, so that the scheduling information can have a simple structure. For example, the scheduling information generation unit  120  can generate scheduling information comprising the beginning index of the service. 
         [0043]    As described above, the scheduling information can comprise beginning position information, and it can additionally comprise other information. If the scheduling information comprises only beginning position information, the UE needs to conduct blind detection upon reception of the information. That is, if the UE receives data of another service or receives the last index in the MSAP during a certain scheduling period, the reception for the service during the current scheduling period is completed. 
         [0044]    At step S 14 , the packetization unit  130  packetizes the data of the services stored temporarily in the buffer unit  110  according to the transmission order information determined before the start of the session as well as the dynamic scheduling information generated by the scheduling information generation unit  120 , such that the indices for each service in the MSAP are consecutive, and the data packets of different services are concatenated together. 
         [0045]    During the data transmitting period, the transmitting unit  140  groups the data of the services and transmits them one by one in timing order, according to the transmission order information and the scheduling information determined by the scheduling information generation unit  120 . 
         [0046]      FIG. 5  shows a schematic block diagram of user equipment according to embodiments of the present invention. As shown in  FIG. 5 , the user equipment comprises a receiving unit  210 , a reception control unit  240 , a transmission order information extraction unit  220 , a scheduling information extraction unit  230 , an MBMS data storage unit  250 , an MBMS data processing unit  260  and a presentation unit  270 . 
         [0047]    The receiving unit  210  first receives all of the data transmitted from the NodeB equipment including the transmission order information on MCCH channel. Then, the transmission order information extraction unit  220  extracts the transmission order information configured by MCE from the data received by the receiving unit  210 . As given previously, it is unnecessary to transmit the transmission order information at each scheduling process. Instead, its transmission is generally repeated at a lower frequency, such as every 640 ms. Scheduling may be conducted in a granularity of only 160 ms. Typically, upon the beginning of a service session, the order information of the individual services has been determined. The order information is transmitted repeatedly to the UE until another session starts. 
         [0048]    After the start of the session, the scheduling information extraction unit  230  extracts the scheduling information from the data received by the receiving unit  210 . The scheduling information comprises, for example, the beginning index of a service in the MSAP. 
         [0049]    Then, according to the transmission order information and the scheduling information, the reception control unit  240  controls the receiving unit  210  to receive the MBMS data of a specific service, such as a mobile television program, and to store the data into the MBMS data storage unit  250 . 
         [0050]    Here, the receiving unit  210  needs to conduct blind detection when the UE is in the operation of reception. That is, if the receiving unit receives data of another service or receives the last index in the MSAP during a certain scheduling period, the reception for the service during the current scheduling period is completed. 
         [0051]    The MBMS data processing unit  260  performs processing, such as decoding and decompression, on the MBMS data stored in the MBMS data storage unit  250  so as to restore them to content data to be presented. Then, the content data are presented by the presentation unit  270 , such as displaying the mobile television program. 
         [0052]    In addition, if the user wants to receive a new program, the receiving unit  240  can receive MBMS data corresponding to such new program. 
         [0053]      FIG. 6  is a specific flow chart illustrating a method for receiving multimedia service data according to embodiments of the present invention. As shown in  FIG. 6 , the receiving unit  210  first receives all of the data including the transmission order information. Then, at step S 21 , the transmission order information extraction unit  220  extracts the transmission order information configured by MCE from the data by the receiving unit  210 . 
         [0054]    At step S 22  after the start of the session, the scheduling information extraction unit  230  extracts the scheduling information from the data received by the receiving unit  210 . The scheduling information comprises, for example, the beginning index of a service in the MSAP. 
         [0055]    Then, at step S 23 , according to the transmission order information and the scheduling information, the reception control unit  240  controls the receiving unit  210  to receive the MBMS data of a specific service, such as a mobile television program, and to store the data in the MBMS data storage unit  250 . 
         [0056]    At step S 24 , the MBMS data processing unit  260  performs processing, such as decoding and decompression, on the MBMS data stored in the MBMS data storage unit  250  so as to restore them to content data to be presented. Then, the content data are presented by the presentation unit  270 , such as displaying the mobile television program. 
         [0057]    The present invention has been disclosed above with the preferred embodiments. Those skilled in the art can make various variations, replacements and additions to the present invention within the scope of the present invention. Therefore, the scope of the present invention is not limited to the above specific embodiments, but should be defined by the appended claims.