Patent Publication Number: US-RE46709-E

Title: Method and apparatus for providing location based service in wireless communication system

Description:
PRIORITY 
     The present application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Aug. 16, 2010, and assigned Serial No. 10-2010-0078707, the entire disclosure of which is hereby incorporated by reference. 
     The present application is a reissue application of U.S. Pat. No. 9,063,216, which issued on Jun. 23, 2015 from application Ser. No. 13/210,649 filed on Aug. 16, 2011.  
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method and an apparatus for providing a location used service in a wireless communication system. More particularly, the present invention relates to a method and an apparatus for providing a location-based service using a reference signal in an 802.16m system. 
     2. Description of the Related Art 
     Current mobile communication systems are advancing to provide the existing voice communication to various services, such as a multimedia broadcast, multimedia video, and multimedia message. Such a next-generation mobile communication system includes Institute of Electrical and Electronics Engineers (IEEE) 802.16e system recently commercialized, 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) being standardized, IEEE 802.20 Ultra Mobile Broadband (UMB), and IEEE 802.16m system. 
     Recently, those next-generation mobile communication systems offer a Location Based Service (LBS) for providing various services based on a location of a mobile station. 
     Techniques for estimating the location of the mobile station can be classified into a network based technique and a mobile station based technique. The mobile station based technique includes a method for estimating the location of the mobile station using well-known Global Positioning System (GPS). The method using the GPS exhibits high accuracy of the location estimation, but its accuracy is low in a downtown area and it is inoperable indoors. The network based technique includes a method for estimating a location of a base station and a signal delay time between the mobile station and the base station, or an angle of arrival of the signal using a reference signal of the base station in the wireless communication network, and thus estimating the location of the mobile station. Disadvantageously, the method using the reference signal can raise the location estimation accuracy only when the Reference Signal (RS) is normally sent and received. 
     Meanwhile, the next-generation mobile communication system studies and develops a distributed base station architecture. The distributed base station architecture is constructed by separating Radio Frequency (RF) transceivers from the base station and relocating them near antennas so that the antennas can function with minimum loss of transmission power. That is, in the distributed base station architecture, a plurality of RF transceivers (hereafter, referred to as Remote Radio Heads or RF Remote Heads (RRHs)) is dispersed in one cell. The RRHs are installed at quite a distance from the base station and connected using optical fiber cables. 
     In the distributed base station architecture with the RRHs dispersed in one cell or in the wireless communication system based on a relay station, when the base station transmits the RS for the LBS, the RS is sent to the mobile station via the RRHs or the relay stations. However, when the RRHs or the relay stations transmit the RS for the LBS, the mobile station cannot distinguish which RRH or relay station transmits the received RS, and accordingly cannot accurately measure the distance between the base station and the mobile station. 
     Therefore, a need exists for a method for a mobile station to efficiently receive an RS and to determine which device sends the received RS. 
     SUMMARY OF THE INVENTION 
     Aspects of the present invention are 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 a method and an apparatus for providing a location based service using a reference signal in a wireless communication system. 
     Another aspect of the present invention is to provide a method and an apparatus for indicating a transmission location of a reference signal at a base station of a wireless communication system. 
     Yet another aspect of the present invention is to provide a method and an apparatus for indicating whether a reference signal is transmitted using a System Configuration Descript (SCD) message at a base station of a wireless communication system. 
     Still another aspect of the present invention is to provide a method and an apparatus for identifying a transmission device of a reference signal in a wireless communication system. 
     According to an aspect of the present invention, a method of a Base Station (BS) for a Location Based Service (LBS) in a wireless communication system is provided. The method includes allocating identifiers to a plurality of transmission devices in a service coverage area of the BS, generating a Reference Signal (RS) including the identifier of the corresponding transmission device and an identifier of the BS with respect to each of the transmission devices, and transmitting the RS generated for each of the transmission devices, to a Mobile Station (MS) via the corresponding transmission device. 
     According to another aspect of the present invention, a method of an MS for an LBS in a wireless communication system is provided. The method includes receiving RSs from a plurality of transmission devices, obtaining identification information of a transmission device and identification information of a BS corresponding to the transmission device with respect to each of the received RSs, generating a report message for the LBS based on the obtained identification information of the transmission device, and transmitting the report message to a serving BS of the MS. 
     According to yet another aspect of the present invention, an apparatus of a BS for an LBS in a wireless communication system is provided. The apparatus includes a controller for allocating identifiers to a plurality of transmission devices in a service coverage area of the BS, and for generating an RS including the identifier of the corresponding transmission device and an identifier of the BS with respect to each of the transmission devices, and a transceiver for transmitting the RS generated for each of the transmission devices, to an MS via the transmission devices. 
     According to still another aspect of the present invention, an apparatus of an MS for an LBS in a wireless communication system is provided. The apparatus includes a receiver for receiving RSs from a plurality of transmission devices, a controller for obtaining identification information of a transmission device and identification information of a BS corresponding to the transmission device with respect to each of the received RSs, and for generating a report message for the LBS based on the obtained identification information of the transmission device, and a transmitter for transmitting the report message to a serving BS of the MS. 
     Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a system for transmitting and receiving a reference signal to provide a Location Based Service (LBS) according to an exemplary embodiment of the present invention; 
         FIG. 2  illustrates a Time Division Duplex (TDD) frame structure in an Institute of Electrical and Electronics Engineer (IEEE) 802.16m system according to an exemplary embodiment of the present invention; 
         FIG. 3  illustrates a reference signal using a Secondary Advanced (SA) preamble in an IEEE 802.16m system according to an exemplary embodiment of the present invention; 
         FIG. 4  illustrates a reference signal using a midamble in an IEEE 802.16m system according to an exemplary embodiment of the present invention; 
         FIG. 5  illustrates a system including a relay station and a Remote Radio Heads or RF Remote Heads (RRH) according to an exemplary embodiment of the present invention; 
         FIG. 6  illustrates a frame including a reference signal based on an LBS zone in an IEEE 802.16m system according to an exemplary embodiment of the present invention; 
         FIG. 7  illustrates a frame including a reference signal based on a superframe in an IEEE 802.16m system according to an exemplary embodiment of the present invention; 
         FIG. 8  illustrates operations of a base station in a wireless communication system according to an exemplary embodiment of the present invention; 
         FIG. 9  illustrates operations of a mobile station in a wireless communication system according to an exemplary embodiment of the present invention; 
         FIG. 10  illustrates operations of a base station in a wireless communication system according to an exemplary embodiment of the present invention; 
         FIG. 11  illustrates operations of a mobile station in a wireless communication system according to an exemplary embodiment of the present invention; 
         FIG. 12  is a block diagram of a base station in a wireless communication system according to an exemplary embodiment of the present invention; and 
         FIG. 13  is a block diagram of a mobile station in a wireless communication system according to an exemplary embodiment of the present invention. 
     
    
    
     Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the 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. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness. 
     The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention is provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
     It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
     By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide. 
     Exemplary embodiments of the present invention provide a method and an apparatus for transmitting and receiving a Reference Signal (RS) for a Location Based Service (LBS) and identifying a transmission device of the RS in an Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system. Herein, the RS indicates a downlink RS sent from a Base Station (BS) to a Mobile Station (MS) for the LBS in an Institute of Electrical and Electronics Engineers (IEEE) 802.16m system. 
     Hereinafter, exemplary embodiments of the present invention are equally applicable to OFDM wireless communication systems, and the IEEE 802.16m system is described below by way of example. 
       FIGS. 1 through 13 , described below, and the various exemplary embodiments of the present invention provided are by way of illustration only and should not be construed in any way that would limit the scope of the present invention. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged communications system. The terms used to describe various exemplary embodiments of the present invention provided to merely aid the understanding of the description, and that their use and definitions in no way limit the scope of the invention. Terms first, second, and the like are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order, unless where explicitly state otherwise. A set is defined as a non-empty set including at least one element. 
       FIG. 1  illustrates a system for transmitting and receiving an RS to provide an LBS according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 1 , a plurality of BS 1   110 - 1  through BS 7   110 - 7  transmits the RS for the LBS. Thereafter, an MS  100  having a BS 1   110 - 1  as its serving BS receives RSs from the BSs  110 - 1  through  110 - 7 , estimates distances to the corresponding BSs based on the RSs received from at least three BSs, and reports the result to the serving BS  110 - 1 . 
     The serving BS  110 - 1  estimates the location of the MS  100  based on the distance information of the corresponding BSs as received from the MS  100 . 
     Alternatively, when the BSs  110 - 1  through  110 - 7  transmit the RS, the MS  100  receives the RSs from the BSs  110 - 1  through  110 - 7 , estimates a reception time of the RS, and identifies the BS transmitting the RS using a unique preamble allocated as a BS identifier in the RS. Thereafter, the MS  100  reports the BS transmitting the RS and the corresponding reception time to the serving BS  110 - 1 . 
     The serving BS  110 - 1  estimates the location of the MS  100  using the time when each BS transmits the RS and the information reported from the MS  100 . 
       FIG. 2  illustrates a Time Division Duplex (TDD) frame structure in an IEEE 802.16m system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 2 , to transmit and receive the RS for the LBS, the TDD frame structure of the IEEE 802.16m system sets four superframes as one LBS zone duration  200 . Each superframe  202  includes four frames. A preamble lies in the first symbol of each frame  204 . The preamble of the last frame of the superframe is used as the RS  210  for the LBS. Accordingly, one LBS zone duration  200  can contain four RSs. At this time, the RS can be constructed as illustrated in  FIG. 3  or  FIG. 4 . 
       FIG. 3  illustrates an RS using a Secondary Advanced (SA) preamble in an IEEE 802.16m system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 3 , an SA preamble is used as the RS. The SA preamble is uniquely allocated to each BS and used as a BS identifier (or a cell identifier). The RS using the SA preamble includes 288 subcarriers and eight sub-blocks, and is modulated with Quadrature Phase Shift Keying (QPSK). 
     A first sub-block  301  of the RS indicates transmission device information of the RS or location information of the RS, and the other seven sub-blocks indicate information (e.g., BS identification information) for the LBS as known in the method of the related art. 
     According to an exemplary embodiment of the present invention, the first sub-block  301  of the RS indicating the transmission device information of the RS is described below. 
       FIG. 5  illustrates a system including a relay station and a Remote Radio Heads or Radio Frequency (RF) Remote Heads (RRH) according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 5 , a service coverage area includes more than one relay station  520 , the RS is transmitted from the BS  500  connected to a plurality of RRHs  510 - 1  through  510 - 3  using optical fiber cables, to the MS  520 . As the first sub-block  301  of the RS contains RRH IDentification (ID) or relay station ID, it is possible to indicate which RRH or relay station transmits the RS. In the method of the related art, a plurality of relay stations or a plurality of RRHs equally transmits the unique SA preamble of the BS in the service coverage area of a particular BS. Hence, the MS cannot identify which relay station or RRH transmits the RS, and cannot precisely estimate the location of the MS since it merely recognizes that the RS is sent from the BS. In contrast, in exemplary embodiments of the present invention, since the sub-block  301  of the RS contains the RRH or relay station ID transmitting the RS, the MS, which receives the RS, can identify which relay station or RRH transmits the corresponding RS. 
     In so doing, the first sub-block  301  can indicate the transmission device information of the RS in various manners. For example, when each sub-block includes nine hexacodes, the transmission device information of the RS can include four bits to repeat nine times in the sub-block  301 . In this case, the RRH ID and relay station ID can be allocated a value 0˜15. 
     According to another exemplary embodiment of the present invention, the first sub-block  301  of the RS indicating the location information of the RS is described below. 
     Using the first sub-block  301 , the RS can indicate the LBS zone or the superframe carrying the RS. For example, the first sub-block  301  may indicate whether the RS is transmitted in the next LBS zone, and to which LBS zone from the next LBS zone do not carry the RS. 
       FIG. 6  illustrates a frame including a reference signal based on an LBS zone in an IEEE 802.16m system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 6 , assuming that the first sub-block  301  carries 4-bit RS location information, the 4-bit information of the first sub-block  301  can be set to ‘0000’  600  to indicate that the RS is transmitted in the next LBS zone, and to ‘0001’  602  to indicate that the next LBS zone does not carry the RS and an LBS zone after the next LBS zone carries the RS. According to the RS location information, the MS may wait to receive the RS of the next LBS zone, or perform other operation, rather than waiting to receive the RS of the next LBS zone, because the next LBS zone does not carry the RS. 
     In addition, the first sub-block  301  can indicate whether the next superframe carries the RS, and to which superframe from the next superframe do not carry the RS. 
       FIG. 7  illustrates a frame including a reference signal based on a superframe in an IEEE 802.16m system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 7 , assuming that the first sub-block  301  carries 4-bit RS location information, the 4-bit information of the first sub-block  301  can be set to ‘0000’  700  to indicate that the RS is transmitted in the next superframe, and to ‘0001’  702  to indicate that the next superframe does not carry the RS but a superframe after the next superframe carries the RS. Based on the RS location information, the MS may wait to receive the RS of the next superframe, or perform other operation, rather than waiting to receive the RS of the next superframe, because the next superframe does not carry the RS. 
     Herein, the first sub-block  301  can indicate the location information of the RS in various manners. For example, when each sub-block includes nine hexacodes, the location information of the RS can include four bits to repeat nine times within the sub-block  301 . The information is repeated nine times in the sub-block  301  in order to minimize error, and the nine repetitions can achieve boosting effect of 9.54 decibels (dB). 
     According to another exemplary embodiment of the present invention, a System Configuration Descript (SCD) message broadcast by the BS to indicate overall information of the system can indicate whether the BS transmits the RS. That is, in the IEEE 802.16 system, the MS, after receiving the SCD message from the BS, can receive the RS for the LBS. Hence, the location of the initially transmitted RS can be indicated using the SCD message. 
     Table 1 shows information contained in the SCD message. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                   
                   
                 Size 
                   
               
            
           
           
               
               
               
               
               
            
               
                 M/O 
                 Attributes 
                 (bits) 
                 Value/Note 
                 conditions 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 O 
                 E-LBS 
                 DLBS 
                 1 
                 Indicates: the 
                 Present 
               
               
                   
                 Configuration 
                   
                   
                 E-LBS 
                 when E-LBS is 
               
               
                   
                 Parameters 
                   
                   
                 configuration 
                 configured 
               
               
                   
                   
                   
                   
                 0b0: No 
                   
               
               
                   
                   
                   
                   
                 E-LBS zone 
                   
               
               
                   
                   
                   
                   
                 0b1: E-LBS 
                   
               
               
                   
                   
                   
                   
                 zone exists 
               
               
                   
               
            
           
         
       
     
     DLBS, which is a parameter for the LBS, indicates whether the RS is transmitted. That is, DLBS ‘0’ implies that no RS is transmitted until the next SCD message is received, and DLBS ‘1’ implies that the RS is transmitted in the next superframe. 
     While the RS using the SA preamble has been illustrated, the RS may be formed using a midamble as shown in  FIG. 4 . 
       FIG. 4  illustrates an RS using a midamble in an IEEE 802.16m system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 4 , a midamble is used as the RS. The midamble uses 2048-bit Golay sequence. Since one sub-block in the Golay sequence includes four hexacodes, the RS includes 18 sub-blocks in total. 
     First and second sub-blocks  401  and  403  of the RS, respectively, indicate transmission device information of the RS or location information of the RS, and the other six sub-blocks indicate information (e.g., BS identification information) for the LBS as known in the method of the related art. Herein, the RS transmission device information or the RS location information can include one or more sub-blocks and employ a Binary Phase Shift Keying (BPSK) modulation scheme. How many sub-blocks of the midamble are used to indicate the RS transmission device information or the RS location information can determine the boosting effect achieved severalfold. For example, assuming that the RS transmission device information or the RS location information is 4 bits, when one sub-block of the midamble is used to indicate the information, the 4-bit information is repeated four times and thus 6 dB boosting effect can be achieved. When two sub-blocks of the midamble are used to indicate the information, the 4-bit information is repeated eight times and thus 9 dB boosting effect can be achieved. Notably, the bits indicating the information may be increased according to the radio channel environment and the QPSK modulation scheme may be adopted. 
       FIG. 8  illustrates operations of a BS in a wireless communication system according to an exemplary embodiment of the present invention. Herein, it is assumed that the service coverage area of the BS includes one or more relay stations or the plurality of the RRHs is connected to the BS via the optical fiber cables. 
     Referring to  FIG. 8 , the BS determines whether it is necessary to transmit the RS in step  801 . Whether it is necessary to transmit the RS can be determined according to a preset scheme of the BS like the known scheme of the related art. 
     If it is determined in step  801  that it is necessary to transmit the RS, the BS generates a plurality of RSs including identification information of the BS and identification information of the relay stations or the RRHs in the service coverage area of the BS, based on the SA preamble or the midamble, and transmits the generated RS to the MS via the corresponding relay station or the corresponding RRH in step  803 . Referring back to  FIG. 5 , when the service coverage area of the BS  500  includes one relay station  520  and the three RRHs  510 - 1  through  510 - 3 , the BS  500  generates four RSs including the identification information pre-allocated to the relay station  520  and the three RRHs  510 - 1  through  510 - 3  respectively and the identification information of the BS, and transmits the generated RS to the MS via the corresponding relay station  520  or RRH  510 - 1 ,  510 - 2 , or  510 - 3 . For example, the BS of  FIG. 5  generates the RS of  FIG. 3  or  FIG. 4  using the identification information of the RRH 1   510 - 1  and the identification information of the BS and transmits the RS to the MS via the RRH 1   510 - 1 . 
     Thereafter, the BS returns to step  801 . 
       FIG. 9  illustrates operations of an MS in a wireless communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 9 , the MS determines whether the RS is received in step  901 . Upon receiving the RS, the MS extracts and analyzes the information bits from at least one preset sub-block in step  903 , and obtains the ID indicating the transmission device of the RS in step  905 . For example, the MS obtains the identification information indicating which relay station or RRH transmits the corresponding RS, from the first sub-block of the SA preamble or the first and second sub-blocks of the midamble used as the RS. 
     In step  907 , the MS generates and transmits a report message for the LBS based on the obtained ID. For example, the MS can generate the report message including the reception time of the RS and the ID obtained from the RS, and transmits the report message to its serving BS. 
     The MS stands by until the next RS is transmitted in step  909  and goes back to step  901 . 
       FIG. 10  illustrates operations of a BS in a wireless communication system according to an exemplary embodiment of the present invention. The operations of  FIG. 10  are applicable even when the service coverage area of the BS does not cover the relay station or the RRH. 
     Referring to  FIG. 10 , the BS generates and broadcasts the SCD message indicating whether or not the RS is transmitted in step  1001 . The SCD message can indicate that the RS is not transmitted until the next SCD message is sent or that the next superframe carries the RS by additionally setting the parameter indicative of whether the RS is transmitted as shown in Table 1. The SCD message can be broadcast periodically. 
     In step  1003 , the BS determines whether it is necessary to transmit the RS before broadcasting the next SCD message. If it is determined in step  1003  that it is not necessary to transmit the RS before broadcasting the next SCD message, the BS stands by to transmit the next SCD message and repeats step  1001 . 
     In contrast, if it is determined in step  1003  that it is necessary to transmit the RS before broadcasting the next SCD message, the BS transmits the RS including its identification information at preset intervals in step  1005 . In so doing, the BS generates the RS including the information indicating the transmission location of the next RS as shown in  FIG. 3  or  FIG. 4 . 
     Thereafter, the BS returns to step  1001 . 
       FIG. 11  illustrates operations of an MS in a wireless communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 11 , the MS receives the SCD message indicating the presence or absence of the RS, from the BS in step  1101 . 
     In step  1103 , the MS determines whether the RS is transmitted before the next SCD message is received by analyzing the parameter indicating whether the RS is sent, in the SCD message. If it is determined in step  1103  that the RS is not transmitted until the next SCD message is received according to the parameter analysis result (i.e., absence of RS is determined), the MS waits to receive the next SCD message in step  1115  and returns to step  1101 . 
     In contrast, if it is determined in step  1103  that the RS is transmitted before the next SCD message is received according to the parameter analysis result (i.e., presence of RS is determined), the MS receives the RS in the next superframe in step  1105 , extracts and analyzes the information bits from at least one preset sub-block in step  1107 , and acquires the location information carrying the next RS in step  1109 . For example, the MS obtains the identification information indicating whether the next superframe or LBS zone carries the RS, from the first sub-block of the SA preamble or the first and second sub-blocks of the midamble used as the RS. 
     Thereafter, the MS receives the RS at the transmission location of the next RS in step  1111  and determines whether the next SCD message is received in step  1113 . If it is determined in step  1113  that the next SCD message is not received, the MS goes back to step  1107 . In contrast, if it is determined in step  1113  that the next SCD message is received, the MS goes back to step  1103 . 
       FIG. 12  is a block diagram of a BS in a wireless communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 12 , the BS includes a controller  1200 , an OFDM transceiver  1210 , and a plurality of RRHs  1220 - 1  through  1220 -N. 
     The controller  1200  controls operations of the BS and the LBS. For example, the controller  1200  broadcasts overall information of the system and the information indicating whether the RS is transmitted using the SCD message. 
     More particularly, the controller  1200  may include an RS manager  1202 , determines the RS transmission time according to a preset manner, and generates the RS including the identification information of the BS. When the service coverage area of the BS includes a plurality of relay stations or a plurality of RRHs  1220 - 1  through  1220 -N, the RS manager  1202  allocates identification information for the LBS to each of the relay stations or the RRHs  1220 - 1  through  1220 -N, and generates a plurality of RSs including the identification information of the BS and the identification information of the relay stations or the RRHs based on the SA preamble or the midamble. More specifically, when the service coverage area of the BS includes the N-ary RRHs  1220 - 1  through  1220 -N, the RS manager  1202  generates N-ary RSs including the identification information pre-allocated to the N-ary RRHs  1220 - 1  through  1220 -N and the identification information of the BS, and controls to transmit the generated RS to the MS via the corresponding RRH  1220 - 1  through  1220 -N. For example, the RS manager  1202  generates the RS of  FIG. 3  or  FIG. 4  using the identification information of the RRH 1   1220 - 1  and the identification information of the BS, and controls to transmit the generated RS to the MS via the RRH 1   1220 - 1 . Furthermore, the controller  1200  controls to transmit a report message about the RS from the MS, and estimates a location of the MS based on the report message. 
     In addition, the RS manager  1202  can generate the RS including the information indicating the transmission location of the next RS as shown in  FIG. 3  or  FIG. 4 . 
     The OFDM transceiver  1210  OFDM-modulates and transmits data and control information output from the controller  1200  over an antenna, and OFDM-demodulates and provides data and information received over the antenna to the controller  1200 . For example, the OFDM transceiver  1210  OFDM-modulates and transmits the SCD message and the RS output from the controller  1200  over the antenna, and OFDM-demodulates and provides the report message received from the MS over the antenna to the controller  1200 . 
     The RRHs  1220 - 1  through  1220 -N each are allocated the identification information for the LBS from the controller  1200 , and transmit the generated RS of  FIG. 3  or  FIG. 4  to the MS under control of the controller  1200 . 
       FIG. 13  is a block diagram of an MS in a wireless communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 13 , the MS includes a controller  1300  and an OFDM transceiver  1310 . 
     The controller  1300  controls operations of the MS. In addition, the controller  1300  analyzes the RS for the LBS and generates and transmits the report message. More particularly, the controller  1310  may include an RS analyzer  1302 , determines whether the RS is transmitted by analyzing the SCD message received from the BS, and controls and processes to receive the RS. More specifically, when the SCD message includes the parameter indicative of the RS transmission as shown in Table 1, the RS analyzer  1302  processes to receive the RS in the next superframe. When the SCD message includes the parameter indicative of no transmission of the RS, the RS analyzer  1302  does not wait to receive the RS until the next SCD message is received. 
     The RS analyzer  1302  obtains the transmission device information of the corresponding RS or the location information of the next RS from the preset sub-block of the received RS. Upon obtaining the transmission device information of the corresponding RS from the preset sub-block of the received RS, the RS analyzer  1302  generates the report message including the reception time of the corresponding RS and the transmission device information. For example, the report message includes at least one of the identification information of the transmission device, the identification information of the BS, a distance between the MS and the transmission device, and a reception time of the RS. Upon obtaining the location information of the next RS from the preset sub-block of the received RS, the RS analyzer  1302  waits to receive the next RS based on the obtained location information. 
     The OFDM transceiver  1310  OFDM-demodulates and provides data and information received over an antenna to the controller  1300 , and OFDM-modulates and transmits the data and the control information output from the controller  1300  over the antenna. For example, the OFDM transceiver  1310  OFDM-demodulates and provides the SCD message and the RS received over the antenna to the controller  1300 , and OFDM-modulates and transmits the report message output from the controller  1300  to the BS over the antenna. 
     While the transmission location of the next RS or the transmission device of the corresponding RS is indicated using the certain sub-block of the SA preamble or the midamble used as the RS, the sub-block can indicate both of the transmission location information of the next RS and the transmission device information of the corresponding RS. 
     As the BS of the wireless communication system indicates whether or not the RS is transmitted using the SCD message for the LBS and indicates the transmission location of the next RS, the MS can efficiently receive the RS. As the BS indicates the transmission device identification information of the corresponding RS in the RS, the MS can determine which device transmits the RS and thus accurately estimate the location of the MS. 
     While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.