Abstract:
The present invention proposes a method for preventing, when two types of subframes (first subframe and second subframe) exist in a wireless communication system, a high version terminal from performing unnecessary operation for the second subframe. Through the present invention, the high version terminal skips unnecessary operation, resulting in reduction of unnecessary power consumption.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a wireless communication system and, in particular, to an operation method and apparatus of a high version (Rel-10) terminal in case of existence of MBSFN subframe supporting unicast in the high version (Rel-10) network of Long Term Evolution (LTE) system in which terminals with different versions (Releases 8, 9, 10, etc.) coexist. 
     2. Description of the Related Art 
     With the rapid advance of the wireless communication technology, the communication systems have evolved to the 4 th  Generation mobile communication system represented by LTE system. In the LTE system, the data is transmitted in unit of frame having a length of 10 msec, a frame consisting of 10 subframes. 
       FIG. 1  is a diagram illustrating a structure of a downlink frame used in the LTE system. 
     In  FIG. 1 , the frame  101  consists of 10 subframes  103  including normal subframes  150  carrying normal data and Multimedia Broadcast multicast service Single Frequency Network (MBSFN) subframes  107 . The normal and MBSFN subframes differ from each other in number of Orthogonal Frequency Division Multiplexing (OFDM) symbols, length of Cyclic Prefix (CP), and structure and number of Cell-specific Reference Signal (CRS), and the MBMS subframe is used only for the purpose of transmitting broadcast and multicast data in Rel-8 and Rel-9 systems. As the system evolves, however, the MBSFN subframe can be used for the purpose of unicast transmission to a specific terminal as well as broadcast/multicast in the LTE Rel-10 or later. 
     For unicast data transmission/reception, the resource allocation information indicating the resource allocated for transmission/reception is carried on the Physical Downlink Control Channel (PDCCH) and the real data is carried on the Physical Downlink Shared Channel (PDSCH). The terminal determines whether there is any resource allocation information addressed thereto on the PDCCH before attempt receiving real data. 
     In this case, the LTE Rel-10 terminal has to check the PDCCH carrying the resource allocation information for the MBSFN subframe in order to receive PDSCH through even the MBSFN subframe. However, if the LTE Rel-10 terminal has to check PDCCH in every MBSFN subframe, this may cause unnecessary operation depending on whether the MBSFN subframe carries terminal-specific unicast data or multicast/broadcast data. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     The present invention has been made in an effort to solve this problem, and it is an object of the present invention to provide a method for a terminal to receive data in a situation where different type subframes exist in the wireless communication system including networks operating with different versions of LTE. 
     Solution to Problem 
     In the case that the new version (Rel-10 or later) terminal is in a new version network, the terminal receives information on whether PDSCH reception over MBSFN subframe through broadcast or unicast is supportable from the new version network and, if supportable, takes operation for interpreting PDCCH for receiving PDSCH over MBSFN subframe and, otherwise if not supportable, skips corresponding operation in MBSFN subframe. 
     Advantageous Effects 
     In the proposed method, the new version terminal operating in a new version network reduces unnecessary operation for data reception when unicast data transmission is not supported in the network, depending on whether the network supports unicast data transmission in MBSFN subframe, resulting in reduction of power consumption. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a structure of a downlink frame used in the LTE system; 
         FIG. 2  is a flowchart illustrating the new terminal procedure in the method according to an embodiment of the present invention; and 
         FIG. 3  is a block diagram illustrating the configuration of the terminal according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In the following, detailed description of well-known functions and structures incorporated herein may be omitted to avoid obscuring the subject matter of the present invention. Exemplary embodiments of the present invention are described with reference to the accompanying drawings in detail. 
     In the present invention, the description is directed to the LTE system for convenience purpose. 
     There are several releases of LTE and among them the legacy Rel-8 and Rel-9 do not support PDSCH reception in MBSFN subframe. Accordingly, the legacy terminal does not attempt decoding PDCCH for receiving Downlink Control Information (DCI) including PDSCH scheduling information for receiving PDSCH in MBSFN subframe. 
     In the Rel-10 or later system, however, it is allowed to transmit PDSCH in MBSFN subframe. In this case, unlike the legacy terminal which takes no action for MBSFN subframe because it cannot receive PDSCH in MBSFN subframe, the new terminal has to take an action for receiving PDSCH to acquire DCI including scheduling information for receiving PDSCH in MBSFN subframe. In the following description, new terminal denotes an LTE Rel-10 terminal, i.e. the terminal capable of receiving PDSCH in MBSFN subframes. 
       FIG. 2  is a flowchart illustrating the new terminal procedure in the method according to an embodiment of the present invention. 
     The new version terminal receives a downlink frame structure in System Information Block broadcast by a base station at step  203 . The downlink frame structure is transmitted in the form of a bitmap indicating positions of MBSFN subframes. 
     Next, the terminal receives information on whether the base station supports PDSCH over MBSFN subframe at step  205 . The PDSCH over MBSFN subframe supportability can be broadcasted in the system information of the base station or transmitted to the individual terminals through respective control messages. The PDSCH over MBSFN subframe supportability information can be transmitted in a Radio Resource Control (RRC) message explicitly with a newly defined indicator or implicitly with a legacy information (e.g. predefined channel configuration information, transmission mode information, etc.). Steps  203  and  250  can be performed in opposite order. In the case of legacy network or legacy base station, the supportability information on PDSCH over MBSFN is not transmitted. If no supportability information on PDSCH over MBSFN is received, the UE assumes that the base station does not support PDSCH of MBSFN. 
     If it is determined at step  207  that PDSCH over MBSFN subframe is supported, the UE receives PDCCH including DCI, at step  209 , for receiving PDSCH in MBSFN subframes based on the information received at step  205 . 
     If it is determined at step  207  that PDSCH over MBSFN subframe is not supported or if no supportability information on PDSCH over MBSFN subframe is received, the terminal takes no action for receiving PDSCH in MBSFN subframe. In this case, the terminal does not perform any operation for receiving PDSCH. 
       FIG. 3  is a block diagram illustrating the configuration of the terminal according to an embodiment of the present invention. 
     The terminal communicates data with higher layer  305  and transmits/receives control messages through a control message processor  207 . The terminal multiplexes the control signals or data by means of the multiplexer/demultiplexer  303  and transmits the multiplex result by means of the transceiver  301  under the control of the controller  309 . The terminal demultiplexes the physical signal received by the transceiver  301 , by means of the multiplexer/demultiplexer  303 , and transfers the demultiplexed signals to the higher layer  305  or control message processor  307  under the control of the controller  309 . 
     In the present invention, the terminal receives MBSFN subframe configuration information broadcasted by the base station and receives the supportability information on PDSCH over MBSFN subframe through broadcast or unicast. Such a control message is received, the control message processor  307  transfers to the controller  309  the information on whether each subframe is normal or MBSFN subframe and whether PDSCH over MBSFN subframe is supported in order to determine whether to receive PDCCH for receiving PDSCH at every subframe. That is, if PDSCH over MBSFN subframe is supported, the terminal performs operation for receiving PDSCH even in MBSFN subframes and, otherwise PDSCH over MBSFN subframe is not supported, performs no action for receiving PDSCH in MBSFN subframes. 
     Although the block diagram of the terminal is directed to the case where the function blocks are responsible for different functions, the present invention is not limited thereto. For example, the controller  309  may perform the functions of the control message processor  307 . 
     In the proposed method, the network notifies the new version terminal whether it supports PDSCH over MBSFN subframe so as to avoid unnecessary reception operation for receiving PDSCH over MBSFN subframe, resulting in reduction of power consumption. 
     Although exemplary embodiments of the present invention have been described in detail hereinabove with specific terminology, this is for the purpose of describing particular embodiments only and not intended to be limiting of the invention. While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention.