Abstract:
An apparatus and a method for relay service in a wireless communication system are provided. A method for constituting a frame for a relay service in a wireless communication system includes configuring Downlink and Uplink subframes for a Base Station (BS) to transmit and receive signals to and from a Mobile Station via one or more relay stations over one or more communication zones. Thus, the frames for the multihop relay service can be constituted with ease, the multihop relay service can be provided not to drive the relay service data into a particular part of the frame, and the service coverage of the MS can be extended.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
       [0001]    The present application claims the benefit under 35 U.S.C. § 119(a) to a Korean patent application filed in the Korean Intellectual Property Office on Apr. 25, 2008 and assigned Serial No. 10-2008-0039039, a Korean patent application filed in the Korean Intellectual Property Office on Apr. 25, 2008 and assigned Serial No. 10-2008-0039040, the entire disclosure of which is hereby incorporated by reference. 
       TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to a wireless communication system which adopts a relay scheme. More particularly, the present invention relates to an apparatus and a method for constituting a frame to provide a multihop relay service in the wireless communication system. 
       BACKGROUND OF THE INVENTION 
       [0003]    A wireless communication system provides a relay service using a relay station in order to offer a good radio channel to a terminal in a cell boundary or in a shadow area. For example, the wireless communication system relays signals transmitted and received between a base station and a terminal via the relay station as shown in  FIG. 1 . 
         [0004]      FIG. 1  illustrates a conventional wireless communication system for providing the relay service. 
         [0005]    The wireless communication system of  FIG. 1  includes a Base Station (BS)  100 , a Relay Station (RS)  110 , and Mobile Stations (MSs)  101  and  111 . 
         [0006]    The BS  100  communicates directly with the first MS  101  traveling in its service coverage. 
         [0007]    The BS  100  services the second MS  111  traveling outside the service coverage via the RS  110 . More particularly, by way of the RS  110 , the BS  100  services MSs that travel outside the service coverage or in the shadow area and suffer a poor channel status. 
         [0008]    The wireless communication system provides the relay service using a frame of  FIG. 2 . 
         [0009]      FIG. 2  illustrates the frame structure for the relay service in the conventional wireless communication system. 
         [0010]    The frame of  FIG. 2  includes a DownLink (DL) subframe  200  and an UpLink (UL) subframe  210 . 
         [0011]    The DL subframe  200  of a BS frame  220  includes a DL access zone  202  for sending a signal from the BS to the MS connected through a direct link, and a DL relay zone  204  for sending a signal from the BS to the RS. 
         [0012]    The UL subframe  210  of the BS frame  220  includes a UL access zone  212  for receiving a UL signal from the MS to the BS, and a UL relay zone  214  for receiving a UL signal from the RS to the BS. 
         [0013]    The DL subframe  200  of an RS frame  230  includes an access zone  202  for sending a signal from the RS to the MS connected through a relay link, and a relay zone  204  for receiving a signal from the BS to the RS. 
         [0014]    The UL subframe  210  of the RS frame  230  includes an access zone  212  for receiving a UL signal from the MS to the RS, and a relay zone  214  for sending a UL signal from the RS to the BS. 
         [0015]    As stated above, the wireless communication system divides the subframe for the relay service into the access zone and the relay zone. 
         [0016]    In a case where the wireless communication system includes multiple hops, the wireless communication system splits the relay zone to a zone for the communication between the BS and the RS and a zone for the communication between the RSs. 
         [0017]    As the number of the RSs for relaying the signals between the BS and the MS increases, disadvantageously, the signals are driven into the relay zone. 
       SUMMARY OF THE INVENTION 
       [0018]    To address the above-discussed deficiencies of the prior art, it is a primary aspect of the present invention to address at least the above mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide an apparatus and a method for configuring a frame to offer a multihop relay service in a wireless communication system. 
         [0019]    Another aspect of the present invention is to provide an apparatus and a method for configuring a downlink subframe to offer a multihop relay service in a wireless communication system. 
         [0020]    Yet another aspect of the present invention is to provide an apparatus and a method for configuring an uplink subframe to offer a multihop relay service in a wireless communication system. 
         [0021]    Still another aspect of the present invention is to provide an apparatus and a method for distributing data for a relay link service in a wireless relay communication system 
         [0022]    A further aspect of the present invention is to provide an apparatus and a method for configuring a frame to distribute data for a relay link service in a wireless relay communication system. 
         [0023]    According to one aspect of the present invention, a method for configuring a frame for a relay service in a wireless communication system includes configuring a DL subframe for at a BS to transmit a signal to an MS over a first zone of the DL subframe and to transmit a signal to the MS or a lower RS over a second zone; configuring an UpLink (UL) subframe to receive a signal from the MS over a first zone of the UL subframe and to receive a signal from the MS or the lower RS over a second zone; configuring a DL subframe for an odd-hop RS to transmit a signal to an MS or a lower even-hop RS over a first zone of the DL subframe and to receive a signal from an upper node over a second zone; configuring a UL subframe to receive a signal from an MS or a lower even-hop RS over a first zone of the UL subframe and to transmit a signal to an upper node over a second zone; configuring a DL subframe for an even-hop RS to receive a signal from an upper node over a first zone of the DL subframe and to transmit a signal to an MS or a lower odd-hop RS over a second zone; and configuring a UL subframe to transmit a signal to an upper node over a first zone of the UL subframe and to receive a signal from an MS or a lower odd-hop RS over a second zone. 
         [0024]    According to another aspect of the present invention, a method for a relay service at an RS in a wireless communication system includes confirming a frame structure to be used to provide a relay service by taking into account of the number of hops to a BS; transmitting, at an odd-hop RS, a signal to an MS or a lower even-hop RS over a first zone of a DL subframe and receiving a signal from an upper node over a second zone according to the confirmed frame structure; receiving a signal from an MS or a lower even-hop RS over a first zone of a UL subframe and transmitting a signal to an upper node over a second zone; receiving, at an even-hop RS, a signal from an upper node over a first zone of a DL subframe and transmitting a signal to an MS or a lower odd-hop RS over a second zone according to the confirmed frame structure; and transmitting a signal to an upper node over a first zone of the UL subframe and receiving a signal from the MS or the lower odd-hop RS over a second zone. 
         [0025]    According to yet another aspect of the present invention, a method for a relay service at a BS in a wireless communication system includes confirming frame structures to be used for RSs to provide the relay service by taking into account the number of hops of at least one RS; allocating resources for the RSs by taking into account the frame structures of the RSs; transmitting resource allocation information to the RSs; and communicating with an MS or the RS according to the resource allocation information. 
         [0026]    According to still another aspect of the present invention, an apparatus for a relay service at an RS in a wireless communication system includes a scheduler for controlling transmission and reception of signals according to a frame structure determined based on the number of hops to a BS; a receiver for, in an odd-hop RS, receiving a signal from an upper node over a second zone of a DL subframe and receiving a signal from an MS or a lower even-hop RS over a first zone of a UL subframe under control of the scheduler, and, in an even-hop RS, receiving a signal from an upper node over a first zone of the DL subframe and receiving a signal from the MS or a lower odd-hop RS over a second zone of the UL subframe under the control of the scheduler; and a transmitter for, in the odd-hop RS, transmitting a signal to the MS or the lower even-hop RS over the first zone of the DL subframe and transmitting a signal to the upper node over the second zone of the UL subframe under the control of the scheduler, and, in the even-hop RS, transmitting a signal to the MS or the lower odd-hop RS over the second zone of the DL subframe and transmitting a signal to the upper node over the first zone of the UL subframe under the control of the scheduler. 
         [0027]    According to a further aspect of the present invention, an apparatus for a relay service at a BS in a wireless communication system includes a frame determiner for confirming frame structures to be used for RSs to provide the relay service by taking into account the number of hops of at least one RS; a scheduler for allocating resources for the RSs by taking into account the frame structures of the RSs; a transmitter for transmitting resource allocation information to the RSs, and sending a signal to an MS or an RS according to the resource allocation information; and a receiver for receiving a signal from the MS or the RS according to the resource allocation information. 
         [0028]    Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
           [0030]      FIG. 1  illustrates a conventional wireless communication system for providing a relay service; 
           [0031]      FIG. 2  illustrates a frame structure for the relay service in the conventional wireless communication system; 
           [0032]      FIG. 3  illustrates a wireless multihop communication system according to an exemplary embodiment of the present invention; 
           [0033]      FIG. 4  illustrates downlink subframes for the relay service in the wireless communication system according to an exemplary embodiment of the present invention; 
           [0034]      FIG. 5  illustrates downlink subframes for the relay service in the wireless communication system according to another exemplary embodiment of the present invention; 
           [0035]      FIG. 6  illustrates uplink subframes for the relay service in the wireless communication system according to an exemplary embodiment of the present invention; 
           [0036]      FIG. 7  illustrates uplink subframes for the relay service in the wireless communication system according to another exemplary embodiment of the present invention; 
           [0037]      FIG. 8  illustrates operations of a base station for the relay service in the wireless communication system according to an exemplary embodiment of the present invention; 
           [0038]      FIG. 9  illustrates operations of a relay station for the relay service in the wireless communication system according to an exemplary embodiment of the present invention; 
           [0039]      FIG. 10  illustrates the base station in the wireless communication system according to an exemplary embodiment of the present invention; 
           [0040]      FIG. 11  illustrates the relay station in the wireless communication system according to an exemplary embodiment of the present invention; 
           [0041]      FIG. 12  illustrates relay station sets in the wireless multihop communication system according to an exemplary embodiment of the present invention; 
           [0042]      FIG. 13  illustrates downlink subframes according to the RS sets in the wireless communication system according to an exemplary embodiment of the present invention; 
           [0043]      FIG. 14  illustrates uplink subframes according to the RS sets in the wireless communication system according to an exemplary embodiment of the present invention; 
           [0044]      FIG. 15  illustrates operations of the base station for the relay service in the wireless communication system according to another exemplary embodiment of the present invention; and 
           [0045]      FIG. 16  illustrates operations of the relay station for the relay service in the wireless communication system according to another exemplary embodiment of the present invention. 
       
    
    
       [0046]    Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0047]      FIGS. 3 through 16 , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged wireless communication system. 
         [0048]    The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the present invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness. 
         [0049]    Exemplary embodiments of the present invention provide a technique for providing a multihop relay service in a wireless communication system. 
         [0050]    Hereinafter, the number of hops of a RS is determined by a distance between a BS and the RS. An RS directly communicating with the BS is referred to as a 1-hop RS and an RS communicating with the BS by connecting to the 1-hop RS is referred to as a 2-hop RS. When the wireless communication system includes three or more hops, the 1-hop RS, the 3-hop RS, the (2n−1)-hop RS, and so forth are referred to as odd-hop RSs, and 2-hop RS, the 4-hop RS, the 2n-hop RS, and so forth are referred to as even-hop RSs, where n is an integer greater than 1. 
         [0051]    A wireless communication system for providing a relay service can be established in multihop hops as shown in  FIG. 3 . 
         [0052]      FIG. 3  illustrates a wireless multi-hop communication system according to an exemplary embodiment of the present invention. 
         [0053]    The wireless communication system of  FIG. 3  includes a BS  300 , RSs  310  and  320 , and MSs  311  and  321 . 
         [0054]    The BS  300  services the first MS  311  via the 1-hop RS  310 . The BS  300  services the second MS  321  via the 1-hop RS  310  and the 2-hop RS  320 . 
         [0055]    As mentioned earlier, when the wireless communication system includes multiple hops, the wireless communication system offers the relay service using a DL subframe of  FIG. 4 . 
         [0056]      FIG. 4  illustrates the DL subframes for the relay service in the wireless communication system according to an exemplary embodiment of the present invention. 
         [0057]    The DL subframe  400  of  FIG. 4  is divided to a first zone  402  and a second zone  404  using time resources. 
         [0058]    The BS sends a DL signal to an MS directly communicating therewith and a 1-hop RS over the first zone  402  of a BS frame  410 . 
         [0059]    The BS sends a DL signal to the MS directly communicating, over the second zone  404  of the BS frame  410 . 
         [0060]    The odd-hop RS receives a DL signal from the BS or an upper RS over the first zone  402  of an odd-hop RS frame  420 . For example, in the first zone  402 , the 1-hop RS receives a DL signal from the BS and the 3-hop RS receives a DL signal from the 2-hop RS. 
         [0061]    In the second zone  404  of the odd-hop RS frame  420 , the odd-hop RS sends a DL signal to an MS of the relay service or a lower RS. For example, over the second zone  404 , the 1-hop RS sends a DL signal to the 2-hop RS or the MS of the relay service. 
         [0062]    An even-hop RS sends a DL signal to the MS of the relay service or the lower RS over the first zone  402  of an even-hop RS frame  430 . For example, over the first zone  402 , the 2-hop RS sends the DL signal to the 3-hop RS or the MS of the relay service. 
         [0063]    The even-hop RS receives a DL signal from the upper RS in the second zone  404  of the even-hop RS frame  430 . For example, in the second zone  404 , the 2-hop RS receives the DL signal from the 1-hop RS. 
         [0064]    As such, the odd-hop RS and the even-hop RS switch their operation between the first zone  402  and the second zone  404 . A time gap for the operation transition of the RS is inserted between the first zone  402  and the second zone  404  of the odd-hop RS frame  420  and the even-hop RS frame  430 . 
         [0065]    When the wireless communication system is configured in the multiple hops, the wireless communication system may provide the relay service using DL subframes of  FIG. 5 . 
         [0066]      FIG. 5  illustrates DL subframes for the relay service in the wireless communication system according to another exemplary embodiment of the present invention. 
         [0067]    The DL subframe  500  of  FIG. 5  is divided into a first zone  502  and a second zone  504  using the time resources. 
         [0068]    The BS transmits a DL signal to the MS directly communicating, over the first zone  502  of a BS frame  510 . 
         [0069]    The BS transmits a DL signal to the MS of the direction communication and the 1-hop RS over the second zone  504  of the BS frame  510 . 
         [0070]    In the first zone  502  of an odd-hop RS frame  520 , the odd-hop RS sends a DL signal to the MS of the relay service or the lower RS. For example, in the first zone  502 , the 1-hop RS sends the DL signal to the 2-hop RS or the MS of the relay service. 
         [0071]    The odd-hop RS receives a DL signal from the BS or the upper RS over the second zone  504  of the odd-hop RS frame  520 . For example, in the second zone  504 , the 1-hop RS receives a DL signal from the BS and the 3-hop RS receives a DL signal from the 2-hop RS. 
         [0072]    The even-hop RS receives a DL signal from the upper RS in the first zone  502  of an even-hop RS frame  530 . For example, in the first zone  502 , the 2-hop RS receives a DL signal from the 1-hop RS. 
         [0073]    The even-hop RS sends a DL signal to the MS of the relay service or the lower RS in the second zone  504  of the even-hop RS frame  530 . For example, in the second zone  504 , the 2-hop RS sends the DL signal to the 3-hop RS or the MS of the relay service. 
         [0074]    As such, the odd-hop RS and the even-hop RS switch their operation between the first zone  502  and the second zone  504 . A time gap for the operation transition of the RS is interposed between the first zone  502  and the second zone  504  of the odd-hop RS frame  520  and the even-hop RS frame  530 . 
         [0075]    When the wireless communication system includes multiple hops, the wireless communication system offers the relay service using UL subframes of  FIG. 6 . 
         [0076]      FIG. 6  illustrates the UL subframes for the relay service in the wireless communication system according to an exemplary embodiment of the present invention. The UL subframe  600  of  FIG. 6  is divided into a first zone  602  and a second zone  604  using the time resources. 
         [0077]    The BS receives a UL signal from the MS of the direction communication and the 1-hop RS over the first zone  602  of a BS frame  610 . 
         [0078]    The BS receives a UL signal from the MS of the direction communication over the second zone  604  of the BS frame  610 . 
         [0079]    The odd-hop RS sends the UL signal to the BS or the upper RS over the first zone  602  of the odd-hop RS frame  620 . For example, in the first zone  602 , the 1-hop RS sends the UL signal to the BS and the 3-hop RS sends the UL signal to the 2-hop RS. 
         [0080]    Over the second  604  of the odd-hop RS frame  620 , the odd-hop RS receives a UL signal from the MS of the relay service or the lower RS. For example, in the second zone  604 , the 1-hop RS receives a UL signal from the MS of the relay service or the 2-hop RS. 
         [0081]    The even-hop RS receives a signal from the MS of the relay service or the lower RS in the first zone  602  of an even-hop RS frame  630 . For example, over the first zone  602 , the 2-hop RS receives a UL signal from the MS of the relay service or the 3-hop RS. 
         [0082]    The even-hop RS sends the UL signal to the upper RS in the second zone  604  of the even-hop RS frame  630 . For example, in the second zone  604 , the 2-hop RS sends the UL signal to the 1-hop RS. 
         [0083]    As such, the odd-hop RS and the even-hop RS switch their operation between the first zone  602  and the second zone  604 . A time gap for the operation transition of the RS is inserted between the first zone  602  and the second zone  604  of the odd-hop RS frame  620  and the even-hop RS frame  630 . 
         [0084]    When the wireless communication system includes multiple hops, the wireless communication system can offer the relay service using UL subframes of  FIG. 7 . 
         [0085]      FIG. 7  illustrates the UL subframes for the relay service in the wireless communication system according to another exemplary embodiment of the present invention. 
         [0086]    The UL subframe  700  of  FIG. 7  is divided into a first zone  702  and a second zone  704  using the time resources. 
         [0087]    The BS receives a UL signal from the MS of the direction communication over the first zone  702  of a BS frame  710 . 
         [0088]    The BS receives a UL signal from the MS of the direction communication and the 1-hop RS over the second zone  704  of the BS frame  710 . 
         [0089]    The odd-hop RS receives a signal from the MS of the relay service or the lower RS over the first zone  702  of the odd-hop RS frame  720 . For example, in the first zone  702 , the 1-hop RS receives a UL signal from the MS of the relay service or the 2-hop RS. 
         [0090]    Over the second  704  of the odd-hop RS frame  720 , the odd-hop RS sends the UL signal to the BS or the upper RS. For example, in the second zone  704 , the 1-hop RS sends the UL signal to the BS and 3-hop RS sends the UL signal to the 2-hop RS. 
         [0091]    The even-hop RS sends a UL signal to the upper RS over the first zone  702  of an even-hop RS frame  730 . For example, in the first zone  702 , the 2-hop RS sends the UL signal to the 1-hop RS. 
         [0092]    The even-hop RS receive a UL signal from the MS of the relay service or the lower RS over the second zone  704  of the even-hop RS frame  730 . For example, in the second zone  704 , the 2-hop RS receives a UL signal from the MS of the relay service or the 3-hop RS. 
         [0093]    As such, the odd-hop RS and the even-hop RS switch their operation between the first zone  702  and the second zone  704 . A time gap for the operation transition of the RS is inserted between the first zone  702  and the second zone  704  of the odd-hop RS frame  720  and the even-hop RS frame  730 . 
         [0094]    Now, operations of the BS for the relay service in the wireless multihop communication system are described. 
         [0095]      FIG. 8  is a flowchart of the operations of the BS for the relay service in the wireless communication system according to an exemplary embodiment of the present invention. 
         [0096]    In step  801 , the BS determines the frame structures for the relay service of the RSs based on the number of the hops of the RSs. For example, the frame structures of the even-hop RS and the odd-hop RS are different from each other as shown in  FIGS. 4 through 7 . Accordingly, the BS confirms the frame structures to be used for the RSs to provide the relay service based on the number of the hops of the RSs. 
         [0097]    In step  803 , the BS allocates the resources to the RSs by taking into account the frame structures of the RSs. In so doing, the BS also allocates the resources to the serviced MSs. 
         [0098]    In step  805 , the BS transmits the resource allocation information to the MSs directly communicating with the RSs. 
         [0099]    In step  807 , the BS communicates in consideration of the resource allocation information. For instance, when the DL subframe is configured as shown in  FIG. 5 , the BS sends the DL signal to the MS through the resource allocated to the MS over the first zone and the second zone of the DL subframe. The BS sends the DL signal to the RS through the resource allocated to the RS over the second zone of the DL subframe. When the UL subframe is configured as shown in  FIG. 7 , the BS receives the UL signal from the MS through the resource allocated to the MS over the first zone and the second zone of the UL subframe. The BS receives the UL signal from the RS through the resource allocated to the RS over the second zone of the UL subframe. 
         [0100]    Next, the BS finishes this process. 
         [0101]    As above, the BS confirms the frame structure to be used for the corresponding RS to offer the relay service by taking into account the number of the hops of the RS. The BS can transmit the frame structure information confirmed based on the hops of the RS, to the RSs. For example, the BS transmits the frame structure information to the RSs using a Downlink Channel Descriptor (DCD) message or Uplink Channel Descriptor (UCD) message, or a separate control message. 
         [0102]    Now, operations of the RS for the relay service in the wireless multihop communication system are illustrated. 
         [0103]      FIG. 9  is a flowchart of the operations of the RS for the relay service in the wireless communication system according to an exemplary embodiment of the present invention. 
         [0104]    In step  901 , the RS confirms the frame structure to be used to provide the relay service based on the number of the hops to the BS. For example, the RS confirms the frame structure to be used for the relay service in consideration of its hops. Alternatively, the RS can confirm the frame structure to be used for the relay service using the control message received from the BS. 
         [0105]    In step  903 , the RS confirms the resource allocated from the upper node through the resource allocation information received from the upper node. Herein, the upper node represents the BS or the upper RS. 
         [0106]    In step  905 , the RS communicates through the resource allocated from the upper node in the frame structure confirmed in step  901 . 
         [0107]    Next, the RS finishes this process. 
         [0108]    A structure of the BS for the relay service in the wireless multihop communication system is now explained. 
         [0109]      FIG. 10  is a block diagram of the BS in the wireless communication system according to an exemplary embodiment of the present invention. 
         [0110]    The BS of  FIG. 10  includes a duplexer  1000 , a receiver  1010 , a transmitter  1020 , and a scheduler  1030 . 
         [0111]    The duplexer  1000  transmits a transmit signal output from the transmitter  1020  over an antenna, and provides a signal received over the antenna to the receiver  1010  in the duplex manner. The duplexer  1000  switches the transmission and the reception under the control of the scheduler  1030 . 
         [0112]    The receiver  1010  includes a Radio Frequency (RF) processor  1011 , an Analog/Digital Converter (ADC)  1013 , an Orthogonal Frequency Division Multiplexing (OFDM) demodulator  1015 , a decoder  1017 , and a message processor  1019 . 
         [0113]    The RF processor  1011  converts the RF signal output from the duplexer  1000  to a baseband analog signal. 
         [0114]    The ADC  1013  converts the analog signal output from the RF processor  1011  to digital sample data. 
         [0115]    The OFDM demodulator  1015  converts the digital sample data output from the ADC  1013  to frequency-domain data through a Fast Fourier Transform (FFT). 
         [0116]    The decoder  1017  demodulates and decodes the signal output from the OFDM demodulator  1015  at a preset modulation level (Modulation and Coding Scheme (MCS) level). 
         [0117]    The message processor  1019  processes the messages received from the lower nodes and outputs the processed messages to the scheduler  1030 . 
         [0118]    The scheduler  1030  schedules the resources to communicate with the MS in the service coverage and the RS. The scheduler  1030  schedules the resource for the corresponding RS according to the frame information of the RS provided from a frame determiner  1031 . For example, the frame structures of the even-hop RS and the odd-hop RS are different from each other as shown in  FIGS. 4 through 7 . Correspondingly, the scheduler  1030  schedules the resource for the corresponding RS by taking into account the frame structure of the RS to be assigned the resource. 
         [0119]    The frame determiner  1031  determines the frame structure of the RS to be used for the relay service by considering the number of the hops of the RSs. For example, the frame determiner  1031  determines the frame structure of the RS depending on the even hops or the odd hops of the RS for the relay service. 
         [0120]    The transmitter  1020  includes a message generator  1021 , an encoder  1023 , an OFDM modulator  1025 , a Digital/Analog Converter (DAC)  1027 , and an RF processor  1029 . 
         [0121]    The message generator  1021  generates the resource allocation message including the scheduling information provided from the scheduler  1030 . The message generator  1021  generates the message including the frame structure information determined by the frame determiner  1031 . For example, the message generator  1021  generates the DCD message, the UCD message, or the separate control message including the frame structure information of the RS. 
         [0122]    The encoder  1023  encodes and modulates the transmit signal or the message output from the message generator  1021  at the corresponding modulation level (MCS level). 
         [0123]    The OFDM modulator  1025  converts the encoded and modulated signal output from the encoder  1023  to time-domain sample data (OFDM symbols) through Inverse FFT (IFFT). 
         [0124]    The DAC  1027  converts the sample data output from the OFDM modulator  1025  to an analog signal. 
         [0125]    The RF processor  1029  converts the analog signal output from the DAC  1027  to an RF signal. 
         [0126]    The following explanation provides a structure of the RS for the relay service in the wireless multihop communication system. 
         [0127]      FIG. 11  is a block diagram of the RS in the wireless communication system according to an exemplary embodiment of the present invention. 
         [0128]    The RS of  FIG. 11  includes a duplexer  1100 , a receiver  1110 , a transmitter  1120 , and a scheduler  1130 . 
         [0129]    The duplexer  1100  transmits a transmit signal output from the transmitter  1120  over an antenna, and provides a signal received over the antenna to the receiver  1110  in the duplex manner. The duplexer  1100  switches the transmission and the reception under the control of the scheduler  1130 . 
         [0130]    The receiver  1110  includes an RF processor  1111 , an ADC  1113 , an OFDM demodulator  1115 , a decoder  1117 , and a message processor  1119 . 
         [0131]    The RF processor  1111  converts the RF signal output from the duplexer  1100  to a baseband analog signal. 
         [0132]    The ADC  1113  converts the analog signal output from the RF processor  1111  to digital sample data. 
         [0133]    The OFDM demodulator  1115  converts the digital sample data output from the ADC  1113  to frequency-domain data through the FFT. 
         [0134]    The decoder  1117  demodulates and decodes the signal output from the OFDM demodulator  1115  at a preset modulation level (MCS level). 
         [0135]    The message processor  1119  extracts the control information from the signal output from the decoder  1117  and outputs the extracted control information to the scheduler  1130 . For example, the message processor  1119  extracts the control message including the frame structure information and the resource allocation information from the signal output from the decoder  1117  and provides the extracted control message to the scheduler  1130 . 
         [0136]    The scheduler  1130  controls the RS to provide the relay service through the resource allocated from the upper node. For instance, the scheduler  1130  acquires the frame structure information to be used for the relay service and the resource information allocated from the upper node through the control messages fed from the message processor  1119 . Next, the scheduler  1130  controls the RS to provide the relay service through the resource allocated from the upper node in the acquired frame structure. Alternatively, the scheduler  1130  confirms the frame structure to be used for the relay service by taking into account the number of the hops of the BS. The scheduler  1130  acquires the resource information allocated from the upper node through the control message fed from the message processor  1119 . Next, the scheduler  1130  can control the RS to provide the relay service through the resource allocated from the upper node in the confirmed frame structure. 
         [0137]    The scheduler  1130  controls the duplexer  1100  according to the frame structure to be used for the relay service. 
         [0138]    The transmitter  1120  includes a message generator  1121 , an encoder  1123 , an OFDM modulator  1125 , a DAC  1127 , and an RF processor  1129 . 
         [0139]    The message generator  1121  generates the control message to be sent to the upper node or the lower node under the control of the scheduler  1130 . 
         [0140]    The encoder  1123  encodes and modulates the transmit signal or the control message output from the message generator  1121  at the corresponding modulation level (MCS level). 
         [0141]    The OFDM modulator  1125  converts the encoded and modulated signal output from the encoder  1123  to time-domain sample data (OFDM symbols) through the IFFT. 
         [0142]    The DAC  1127  converts the sample data output from the OFDM modulator  1125  to an analog signal. The RF processor  1129  converts the analog signal output from the DAC  1127  to an RF signal. 
         [0143]    In one embodiment, the wireless communication system configures the frames such that the even-hop RS and the odd-hop RS classified based on the number of the hops offer the relay service using the different frame structures. 
         [0144]    Alternatively, regardless of the number of the hops of the RSs, the wireless communication system can classify the RSs of the relay service to a first RS set and a second RS set. In this case, the wireless communication system configures the frames such that the first RS set and the second RS set provide the relay service using the different frame structures. For example, the wireless communication system can configure the same frame structures of the first RS set and the second RS set as the even-hop RS and the odd-hop RS. 
         [0145]    When the RS sets are used regardless of the number of the hops of the RSs as above, the wireless communication system can divide the RSs for the relay service to the first RS set and the second RS set as shown in  FIG. 12 . 
         [0146]      FIG. 12  illustrates the RS sets in the wireless multihop communication system according to an exemplary embodiment of the present invention. 
         [0147]    The wireless communication system of  FIG. 12  includes a BS  1200 , RSs  1210  through  1240 , and MSs  1211  through  1241 . 
         [0148]    The BS  1200  services the MSs  1211  through  1241  via the RSs  1210  through  1240 . 
         [0149]    The BS  1200  generates the first RS set  1202  with the first 1-hop RS  1210  connected to the BS  1200  and the first 2-hop RS  1220  connected to the first 1-hop RS  1210 . The BS  1200  generates the second RS set  1204  with the second 1-hop RS  1230  connected to the BS  1200  and the second 2-hop RS  1240  connected to the second 1-hop RS  1230 . 
         [0150]    With the RS sets as above, the wireless communication system offers the relay service using DL subframes of  FIG. 13 . 
         [0151]      FIG. 13  illustrates the DL subframes according to the RS sets in the wireless communication system according to an exemplary embodiment of the present invention. 
         [0152]    The DL subframe  1300  of  FIG. 13  is divided into a first zone  1302  and a second zone  1304  using the time resources. 
         [0153]    Over the first zone  1302  of the BS frame  1310 , the BS sends a DL signal to the MS of the direct communication and the 1-hop RS of the first RS set. That is, the BS sends the DL signals to the RSs of the first RS set in the first zone  1302 . 
         [0154]    Over the second zone  1304  of the BS frame  1310 , the BS sends DL signals to the MS of the direct communication and the 1-hop RS of the first RS set. That is, the BS sends DL signals to the RSs of the second RS set over the second zone  1304 . 
         [0155]    As in  FIG. 4  or  FIG. 5 , the odd-hop RS and the even-hop RS of the first RS set provide the relay service using different DL subframes. 
         [0156]    The odd-hop RS of the first RS set receives a DL signal from the BS or the upper RS over the first zone  1302  of the odd-hop RS frame  1320 . For example, in the first zone  1302 , the 1-hop RS receives the DL signal from the BS and the 3-hop RS receives the DL signal from the 2-hop RS. 
         [0157]    Over the second zone  1304  of the odd-hop RS frame  1320 , the odd-hop RS sends the DL signal to the MS of the relay service or the lower RS. For example, in the second zone  1304 , the 1-hop RS sends the DL signal to the 2-hop RS or the MS of the relay service. 
         [0158]    In the first zone  1302  of the even-hop RS frame  1330 , the even-hop RS of the first RS set sends a DL signal to the MS of the relay service or the lower RS. For example, in the first zone  1302 , the 2-hop RS sends the DL signal to the 3-hop RS or the MS of the relay service. 
         [0159]    In the second zone  1304  of the even-hop RS frame  1330 , the even-hop RS receives a DL signal from the upper RS. For example, over the second zone  1304 , the 2-hop RS receives a DL signal from the 1-hop RS. 
         [0160]    The odd-hop RS and the even-hop RS of the second RS set offer the relay service using different DL subframes as in  FIG. 4  or  FIG. 5 . 
         [0161]    The odd-hop RS of the second RS set sends a DL signal to the MS of the relay service or the lower RS over the first zone  1302  of the odd-hop RS frame  1320 . For example, in the first zone  1302 , the 1-hop RS sends a DL signal to the 2-hop RS or the MS of the relay service. 
         [0162]    Over the second zone  1304  of the odd-hop RS frame  1320 , the odd-hop RS receives a DL signal from the BS or the upper RS. For example, in the second zone  1304 , the 1-hop RS receives the DL signal from the BS and the 3-hop RS receives the DL signal from the 2-hop RS. 
         [0163]    Over the first zone  1302  of the even-hop RS frame  1330 , the even-hop RS of the second RS set receives a DL signal from the upper RS. For example, in the first zone  1302 , the 2-hop RS receives a DL signal from the 1-hop RS. 
         [0164]    Over the second zone  1304  of the even-hop RS frame  1330 , the even-hop RS sends the DL signal to the MS of the relay service or the lower RS. For example, in the second zone  1304 , the 2-hop RS sends the DL signal to the 3-hop RS or the MS of the relay service. 
         [0165]    There is a time gap for the operation transition of the RS between the first zone  1302  and the second zone  1304  of the odd-hop RS frame  1320  and the even-hop RS frame  1330 . 
         [0166]    As such, the RSs of the first RS set and the second RS set switch their operation between the first zone  1302  and the second zone  1304 . For doing so, there is a time gap for the operation transition of the RS between the first zone  1302  and the second zone  1304  of the odd-hop RS frame  1320  and the even-hop RS frame  1330 . 
         [0167]    In one embodiment, the RSs of the first RS set provide the relay service using the DL subframe structure of  FIG. 4  and the RSs of the second RS set provide the relay service using the DL subframe structure of  FIG. 5 . 
         [0168]    Alternatively, the RSs of the first RS set can offer the relay service using the DL subframe structure of  FIG. 5  and the RSs of the second RS set can offer the relay service using the DL subframe structure of  FIG. 4 . 
         [0169]    With the RS sets of  FIG. 12 , the wireless communication system provides the relay service using UL subframes of  FIG. 14 . 
         [0170]      FIG. 14  illustrates the UL subframes according to the RS sets in the wireless communication system according to an exemplary embodiment of the present invention. 
         [0171]    The UL subframe  1400  of  FIG. 14  is divided into a first zone  1402  and a second zone  1404  using the time resources. 
         [0172]    Over the first zone  1402  of the BS frame  1410 , the BS receives UL signals from the MS of the direct communication and the 1-hop RS of the first RS set. That is, the BS receives UL signals from the RSs of the first RS set over the first zone  1402 . 
         [0173]    Over the second zone  1404  of the BS frame  1410 , the BS receives UL signals from the MS of the direct communication and the 1-hop RS of the second RS set. That is, the BS receives UL signals from the RSs of the second RS set over the second zone  1404 . 
         [0174]    The odd-hop RS and the even-hop RS of the first RS set offer the relay service using different UL subframes as in  FIG. 6  or  FIG. 7 . 
         [0175]    Over the first zone  1402  of the odd-hop RS frame  1420 , the odd-hop RS of the first RS set sends a UL signal to the BS or the upper RS. For example, in the first zone  1402 , the 1-hop RS sends the UL signal to the BS and the 3-hop RS sends the UL signal to the 2-hop RS. 
         [0176]    Over the second zone  1404  of the odd-hop RS frame  1420 , the odd-hop RS receives a UL signal from the MS of the relay service or the lower RS. For example, in the second zone  1404 , the 1-hop RS receives the UL signal from the MS of the relay service or the 2-hop RS. 
         [0177]    Over the first zone  1402  of the even-hop RS frame  1430 , the even-hop RS of the first RS set receives a signal from the MS of the relay service or the lower RS. For example, in the first zone  1402 , the 2-hop RS receives the UL signal from the MS of the relay service or the 3-hop RS. 
         [0178]    Over the second zone  1404  of the even-hop RS frame  1430 , the even-hop RS sends the UL signal to the upper RS. For example, in the second zone  1404 , the 2-hop RS sends the UL signal to the 1-hop RS. 
         [0179]    The odd-hop RS and the even-hop RS of the second RS set offer the relay service using different UL subframe structures as in  FIG. 6  or  FIG. 7 . 
         [0180]    Over the first zone  1402  of the odd-hop RS frame  1420 , the odd-hop RS of the second RS set receives a signal from the MS of the relay service or the lower RS. For example, in the first zone  1402 , the 1-hop RS receives the UL signal from the MS of the relay service or the 2-hop RS. 
         [0181]    Over the second zone  1404  of the odd-hop RS frame  1420 , the odd-hop RS sends a UL signal to the BS or the upper RS. For example, in the second zone  1404 , the 1-hop RS sends the UL signal to the BS and the 3-hop RS sends the UL signal to the 2-hop RS. 
         [0182]    Over the first zone  1402  of the even-hop RS frame  1430 , the even-hop RS of the second RS set sends a UL signal to the upper RS. For example, in the first zone  1402 , the 2-hop RS sends the UL signal to the 1-hop RS. 
         [0183]    Over the second zone  1404  of the even-hop RS frame  1430 , the even-hop RS receives a UL signal from the MS of the relay service or the lower RS. For example, in the second zone  1404 , the 2-hop RS receives the UL signal from the MS of the relay service or the 3-hop RS. 
         [0184]    As such, the RSs of the first RS set and the second RS set switch their operation between the first zone  1402  and the second zone  1404 . For doing so, there is a time gap for the operation transition of the RS between the first zone  1402  and the second zone  1404  of the odd-hop RS frame  1420  and the even-hop RS frame  1430 . 
         [0185]    In one embodiment, the RSs of the first RS set provide the relay service using the DL subframe of  FIG. 6  and the RSs of the second RS set provide the relay service using the DL subframe of  FIG. 7 . 
         [0186]    Alternatively, the RSs of the first RS set can offer the relay service using the DL subframe of  FIG. 7  and the RSs of the second RS set can offer the relay service using the DL subframe of  FIG. 6 . 
         [0187]    Hereafter, the operations of the BS for the relay service are described using the RS sets of  FIG. 12 . It is assumed that the BS provides the relay service using the DL subframe of  FIG. 13  and the UL subframe of  FIG. 14 . 
         [0188]      FIG. 15  is a flowchart of the operations of the BS for the relay service in the wireless communication system according to another exemplary embodiment of the present invention. 
         [0189]    In step  1501 , the BS generates two or more RS sets by dividing a plurality of RSs. For example, the BS generates the RS sets by taking into account interference between the RSs or the data transmission amount of the RSs. The BS can determine the RS set at the point of the initial access of the RS, or generate a new RS set during the communication with the RS. 
         [0190]    In step  1503 , the BS confirms the frame structures for the relay services of the RSs according to the RS set of the RSs and the hops of the RSs. For instance, as shown in  FIGS. 13 and 14 , the frame structures of the even-hop RS and the odd-hop RS are different from each other, the frame structures of the odd-hop RSs of the first RS set and the second RS set are different from each other, and the frame structures of the even-hop RSs of the first RS set and the second RS set are different from each other. Depending on the RS set of the RSs and the hops of the RSs, the BS confirms the frame structures to be used for the RSs to provide the relay service. 
         [0191]    In step  1505 , the BS allocates the resources for the RSs by considering the frame structures of the RSs. The BS also allocates the resources for the serviced MSs. 
         [0192]    In step  1507 , the BS transmits the resource allocation information of the RSs to the MSs that communicate directly with the RSs. For instance, given the DL subframe of  FIG. 13 , the BS transmits the resource allocation information on the RS set basis. More specifically, the BS transmits the resource allocation information of the RSs of the first RS set over the first zone  1302  of the DL subframe  1300  and the resource allocation information of the RSs of the second RS set over the second zone  1304  of the DL subframe. 
         [0193]    In step  1509 , the BS communicates using the resources allocated to the RS sets. For example, given the DL subframe of  FIG. 13 , the BS transmits the DL signal to the MS through the resource allocated to the MS in the first zone and the second zone of the BS frame. In the first zone of the DL subframe, the BS transmits the DL signal to the corresponding RS through the resource allocated to the RS of the first RS set. In the second zone of the DL subframe, the BS transmits the DL signal to the corresponding RS through the resource allocated to the RS of the second RS set. Meanwhile, given the UL subframe of  FIG. 14 , the BS receives the UL signal from the MS through the resource allocated to the MS in the first zone and the second zone of the BS frame. Over the first zone of the UL subframe, the BS receives the UL signal from the corresponding RS through the resource allocated to the RS of the first RS set. Over the second zone of the UL subframe, the BS receives the UL signal from the corresponding RS through the resource allocated to the RS of the second RS set. 
         [0194]    Next, the BS finishes this process. 
         [0195]    In one embodiment, the BS confirms the frame structure used for the corresponding RS to provide the relay service by considering the RS set and the hops of the RS. The BS can transmit the confirmed frame structure information to the RSs. For instance, the BS transmits the frame structure information to the RSs using the DCD message, the UCD message, or the separate control message. 
         [0196]    Alternatively, the wireless communication system can confirm the frame structure to be used for the corresponding RS to provide the relay service by taking into account only the RS set according to the RS set constitution manner. 
         [0197]    Descriptions provide the operations of the RS for the relay service using the RS sets of  FIG. 12 . It is assumed that the RS offers the relay service using the DL subframe of  FIG. 13  and the UL subframe of  FIG. 14 . 
         [0198]      FIG. 16  is a flowchart of the operations of the RS for the relay service in the wireless communication system according to another exemplary embodiment of the present invention. 
         [0199]    In step  1601 , the RS confirms the frame structure to be used for the relay service determined based on the hops to the BS and its RS set. For example, the RS confirms the frame structure to be used for the relay service by considering the hops to the BS and its RS set information based on the control message received from the upper node. Alternatively, the RS can confirm the frame structure to be used for the relay service through the control message received from the upper node. 
         [0200]    In step  1603 , the RS confirms the resource allocated from the upper node through the resource allocation information received from the upper node. 
         [0201]    In step  1605 , the RS communicates through the resource allocated from the upper node in the frame structure confirmed in step  1601 . For example, using the DL subframe of  FIG. 13  and the UL subframe of  FIG. 14 , the odd-hop RS of the first RS set communicates with the upper node through the resource allocated from the upper node over the first zone of the UL/DL subframe. The even-hop RS of the first RS set communicates with the lower node through the resource allocated from the upper node over the second zone of the UL/DL subframe. Meanwhile, the odd-hop RS of the second RS set communicates with the upper node through the resource allocated from the lower node over the first zone of the UL/DL subframe. The even-hop RS of the second RS set communicates with the upper node through the resource allocated from the upper node over the second zone of the UL/DL subframe. 
         [0202]    Next, the RS finishes this process. 
         [0203]    With the RS sets as aforementioned, the BS of the wireless communication system further includes a set configurer in  FIG. 10  for configuring the RS set by taking into account the interference between the RSs and the data transmission amount of the RSs. In this situation, the frame determiner  1031  determines the frame structure of the RS for the relay service by considering the RS set and the hops. 
         [0204]    The scheduler  1130  of the RS in  FIG. 11  can confirm the frame structure to be used for the relay service by taking into account the RS set and the hops to the BS. 
         [0205]    So far, it has been assumed that the wireless communication system provides one communication service using the multihop. 
         [0206]    Alternatively, when the communication services of other standards can be provided, the wireless communication system can constitute the various communication services as different sets. At this time, each set can offer the service using the same frame structure as the RS set. 
         [0207]    In the light of the foregoing, the wireless communication system provides the multihop relay service by use of the different frame structures based on the number of the hops of the RS. Therefore, the frames for the multihop relay service can be constituted with ease, the multihop relay service can be provided not to drive the relay service data into a particular part of the frame, and the service coverage of the MS can be extended. 
         [0208]    Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims