Patent Publication Number: US-2007105592-A1

Title: Apparatus and method for providing neighbor node information in cellular communication system

Description:
PRIORITY  
      This application claims priority under 35 U.S.C. §119 to an application filed in the Korean Intellectual Property Office on Nov. 9, 2005 and assigned Serial No. 2005-107208, the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention generally relates to a cellular communication system, and in particular, to an apparatus and method for providing neighbor node information in a cellular communication system, such as a multi-hop relay Broadband Wireless Access (BWA) system in consideration of an Institute of Electrical and Electronics Engineers (IEEE) 802.16e communication terminal.  
      2. Description of the Related Art  
      Extensive research is being conducted to provide various Quality of Service (QoS) features with a data rate of about 100 Mbps in an advanced fourth-generation (4G) communication system. 4G communication systems are evolving to provide mobility, high data rate transmission, and high QoS in a BWA system, such as a Local Area Network (LAN) system and a Metropolitan Area Network (MAN) system. Typical examples of 4G communication systems are identified in IEEE 802.16d and IEEE 802.16e system standards.  
      IEEE 802.16d systems and BWA systems use an Orthogonal Frequency Division Multiplexing (OFDM)/Orthogonal Frequency Division Multiple Access (OFDMA) scheme. An IEEE 802.16d system considers only a fixed Subscriber Station (SS) and a single cell structure (i.e., the mobility of an SS is not considered). An IEEE 802.16e system considers the mobility of an SS. When the mobility of an SS is considered, the SS is referred to as a Mobile Station (MS).  
       FIG. 1  shows a conventional IEEE 802.16e system with a multi-cell structure. The conventional IEEE 802.16e system includes a cell  100 , a cell  150 , a Base Station (BS)  110  managing the cell  100 , a BS  140  managing the cell  150 , and a plurality of MSs  111 ,  113 ,  130 ,  151  and  153 . The signal exchange between the BSs  110  and  140  and the MSs  111 ,  113 ,  130 ,  151  and  153  is performed using an OFDM/OFDMA scheme. The MS  130  is located in a boundary region (i.e., a handover region) between the cells  100  and  150 . When the MS  130  moves from the cell  100  of the BS  110  into the cell  150  of the BS  140  while communicating with the BS  110 , the serving BS of the MS  130  is changed from the BS  110  to the BS  140 .  
      The MS may receive information about neighbor BSs from its own serving BS and acquire, from the received neighbor BS information, information about a neighbor BS suitable to perform a handover. Alternatively, the MS may perform a handover to one of the neighbor BSs and then acquire information for network re-entry.  
       FIG. 2  shows a procedure for exchanging the information about neighbor BSs between an MS and a serving BS in a conventional IEEE 802.16e system. A serving BS  210  and an 802.16e mode MS  240  communicate with each other in step  211 . In step  213 , the serving BS  210  checks the transmit (TX) period of a mobile neighbor advertisement (MOB_NBR-ADV) message including neighbor BS information during the communication.  
      Table 1 below shows a format of an MOB_NBR-ADV message according to the prior art.  
                       TABLE 1                           Size           Syntax   (bits)   Notes                                        MOB_NBR-           ADV_Message_format( ) {                                 Management Message Type   8                         = 53                                     Skip-optional-fields bitmap   8   Bit[0]: if set to 1, omit Operator                                 Identification (ID) field               Bit[1]: if set to 1, omit NBR BS               ID field               Bit[2]: if set to 1, omit Handover               (HO) process optimization field               Bit[3]: if set to 1, omit Quality               of Service (QoS) related fields               Bit[4]-[7]: reserved                                 If   (Skip-optional-fields-                         [0]=0) {                                     Operator ID   24   Unique ID assigned to the operator                             }                                     Configuration Change Count   8   Incremented each time the                                 information for the associated               neighbor BS has changed.                                 Fragmentation Index   4   Indicates the current fragmentation                                 index.                                 Total Fragmentation   4   Indicates the total number of                                 fragmentations.                                 N_NEIGHBORS   8                                     For   (j=0;                         j&lt;N_NEIGHBORS; j++) {                                     Length   8   Length of message information                                 within the iteration of               N_NEIGHBOR in bytes.                                 PHY Profile ID   8   Aggregated IDs of Co-located                                 Frequency Assignment (FA)               indicator, FA Configuration               Indicator, Fast Fourier Transform               (FFT) size, Bandwidth, Operation               Mode of the starting sub-               channelization of a frame, and               Channel Number                             if (FA Index Indicator ==                         1) {                                     FA Index   8   This field, FA Index, is present                                 only if the FA Index Indicator               in Physical (PHY) Profile ID               is set. Otherwise, the neighbor               BS has the same FA Index or the               center frequency is indicated               using the Type/Length/Value               (TLV) encoded information.                             }               if (BS Effective Isotropic                     Radiated Power (EIRP)           Indicator == 1) {                                 BS EIRP   8   Signed Integer from −128 to 127                                 in unit of dBm. This field is               present only if the BS EIRP               indicator is set in PHY Profile               ID. Otherwise, the BS has the               same EIRP as the serving BS.                             }                                     If   (Skip-optional-                         fields[1]=0) {                                     Neighbor BSID   24   This is an optional field for                                 OFDMA PHY and it is omitted               or skipped if Skip optional               fields Flag = 1                             }                                     Preamble Index/Subchannel   8   For the Sub-Channel (Sca) and                         Index       OFDMA PHY this parameter                                 defines the PHY specific               preamble. For the OFDM PHY               the 5 Least Significant Bit               (LSB) contain the active DL               subchannel index. The 3 Most               Significant Bit (MSB) shall be               Reserved and set to ‘0b00’.                                 if   (Skip-optional-                         fields[2]=0) {                                     HO Process Optimization   8   HO process Optimization is provided                                 as part of this message is               indicative only. HO process               requirements may change at time of               actual HO. For each Bit location,               a value of 0 indicates the               associated reentry management               messages shall be required, a value               of 1 indicates the reentry               management messages may be omitted.               Regardless of the HO Process               Optimization TLV settings, the               target BS may send unsolicited               Subscriber station&#39;s Basic               Capability SBC-RSP and/or               REQ-RSP management messages               Bit#0: Omit SBC-REQ/RSP               management messages during re-entry               processing               Bit#1: Omit Privacy Key Management               (PKM) Authentication phase               except Traffic Encryption Key               (TEK) phase during current               re-entry processing               Bit#2: Omit PKM TEK creation               phase during re-entry processing               Bit#3: Omit REG-REQ/RSP               management messages during current               re-entry processing               Bit#4: Omit Network Address               Acquisition management messages               during current reentry processing               Bit#5: Omit Time of Day               Acquisition management during               current reentry processing               Bit#6: Omit Trivial File Transfer               Protocol (TFTP) management               messages during current re-entry               processing               Bit#7: Full service and               operational state transfer or               sharing between serving BS and               target BS (Automatic Repeat               reQuest (ARQ), timers, counters,               Medium Access Control (MAC) state               machines, etc)                             }                                     if   (Skip-optional-fields-                         [3]=0) {                                         Scheduling   Service   8   Bitmap to indicate if BS supports                         Supported       a particular scheduling service. 1                                 indicates support, 0 indicates no               support:               bit 0: Unsolicited Grant Service               (USG)               bit 1: Real-time Polling service               (rtPS)               bit 2: Non-real-time Polling               service (nrtPS)               bit 3: Best Effort               bit 4: Extended real-time Polling               Service (ertPS)               If the value of bit 0 through bit               4 is 0b00000, it indicates no               information on service available.               bits 5-7: reserved; shall be set               to zero                                 Reserved   4   Shall be set to zero                             }                                     DCD Configuration Change   4   This represents the 4 Least                                 Significant                         Count       Bits (LSBs) of the Neighbor BS                                 current Downlink Channel               Description (DCD) configuration               change count                                 UCD Configuration Change   4   This represents the 4 LSBs of the                         Count       Neighbor BS current Uplink Channel                                 Description (UCD) configuration               change count                                         TLV   Encoded   Neighbor   vari-   TLV specific                         Information   able                                 }                         }                  
 
      As shown in Table 1, the MOB_NBR-ADV message includes the type of a TX message (Management Message Type), the number of neighbor BSs (N_NEIGHBORS), IDs of the neighbor BSs, the preamble indexes of the neighbor BSs (Preamble Index), the information about physical channel profile (e.g., physical channel frequency) for the neighbor BSs (PHY Profile ID), handover process optimization information for the neighbor BSs (HO Process Optimization), and other neighbor BS information (TLV Encoded Neighbor Information).  
      As a result of the check operation in step  213 , when the TX period of the MOB_NBR-ADV message begins, the serving BS  210  broadcasts the MOB_NBR-ADV message to 802.16e mode MSs in its cell area, in step  215 . Upon receipt of the MOB_NBR-ADV message, the MS  240  acquires the neighbor BS information from the received MOB_NBR-ADV message.  
      Because a signaling communication between a stationary BS and an MS is performed through a direct link, as shown in  FIG. 1 , a conventional IEEE 802.16e system can easily establish a highly reliable wireless link between the BS and the MS. However, because the BS is stationary, a conventional IEEE 802.16e system has a low flexibility in constructing a wireless network. Accordingly, the use of a conventional IEEE 802.16e system makes it difficult to provide an efficient communication service in a radio environment where traffic distribution or call parameters change frequently.  
      In order to overcome this problem, a stationary relay station (RS), a mobile RS or general MSs can be used to apply a multi-hop relay data transmission scheme to a general cellular communication system, such as an IEEE 802.16e system. The use of a multi-hop relay wireless communication system makes it possible to reconfigure a network in rapid response to a change in the communication environment, and to operate the entire wireless network more efficiently. For example, a multi-hop relay wireless communication system can expand a cell coverage area and increase a system capacity. When channel conditions between a BS and an MS are poor, an RS is installed between the BS and the MS to establish a multi-hop relay link therebetween, thereby making it possible to provide the MS with a radio channel having better channel conditions. In addition, a multi-hop relay scheme is used in a cell boundary region with poor channel conditions, thereby making it possible to provide a high-rate data channel and to expand the cell coverage area.  
       FIG. 3  shows a BWA system that uses a multi-hop relay scheme to expand a BS coverage area according to the prior art. The multi-hop relay BWA system has a multi-cell structure, and includes a cell  300 , a cell  340 , a BS  310  managing the cell  300 , a BS  350  managing the cell  340 , a plurality of MSs  311  and  313  located within the cell  300 , a plurality of MSs  321  and  323  located in a region  330  outside the cell  300  of the BS  310  and communicating with the BS  310 , an RS  320  providing a multi-hop relay path between the BS  310  and the MSs  321  and  323  located in the region  330 , a plurality of MSs  351 ,  353  and  355  located in the cell  340 , a plurality of MSs  361  and  363  located in a region  370  outside the cell  340  of the BS  350  and communicating with the BS  350 , and an RS  360  providing a multi-hop relay path between the BS  350  and the MSs  361  and  363  located in the region  370 . An OFDM/OFDMA scheme is used for communication among the BSs  310  and  350 , the RSs  320  and  360 , and the MSs  311 ,  313 ,  321 , 323 ,  351 ,  353 ,  355 ,  361 , and  363 .  
      The MSs  311  and  313  located in the cell  300  and the RS  320  can directly communicate with the BS  310 , but the MSs  321  and  323  located in the region  330  cannot directly communicate with the BS  310 . Therefore, the RS  320  covers the region  330  to relay signals between the BS  310  and the MSs  321  and  323 . That is, the MSs  321  and  323  can communicate with the BS  310  through the RS  320 . Likewise, the RS  360  and the MSs  351 ,  353 , and  355  located in the cell  340  can directly communicate with the BS  350 , but the MSs  361  and  363  located in the region  370  cannot directly communicate with the BS  350 . Therefore, the RS  360  covers the region  370  to relay signals between the BS  350  and the MSs  361  and  363 . That is, the MSs  361  and  363  can communicate with the BS  350  through the RS  360 .  
       FIG. 4  is shows a BWA system that uses a multi-hop relay scheme to increase the system capacity according to the prior art. The multi hop relay BWA system includes a BS  410 , a plurality of MSs  411 ,  413 ,  421 ,  423 ,  431 , and  433 , and RSs  420  and  430  providing multi-hop paths between the BS  410  and the MSs  411 ,  413 ,  421 ,  423 ,  431 , and  433 . The BS  410 , the MSs  411 ,  413 ,  421 ,  423 ,  431 , and  433 , and the RSs  420  and  430  communicate with one another by an OFDM/OFDMA scheme. The BS  410  manages a cell  400 . The RSs  420  and  430  and the MSs  411 ,  413 ,  421 ,  423 ,  431 , and  433  that are in the cell  400  directly communicate with the BS  410 .  
      When some MSs  421 ,  423 ,  431 , and  433  are in a boundary region of the cell  400 , Signal to Noise Ratios (SNRs) of direct links between the BS  410  and the MSs  421 ,  423 ,  431 , and  433  can be low. In this case, the RS  420  relays unicast traffic between the BS  410  and the MSs  421  and  423 . The MSs  421  and  423  make unicast communication with the BS via the RS  420 . Likewise, the RS  430  relays unicast traffic between the BS  410  and the MSs  431  and  433 . The MSs  431  and  433  make unicast communication with the BS via the RS  430 . That is, the RSs  420  and  430  provide high-rate data paths to the MSs  421 ,  423 ,  431 , and  433 , thereby increasing the effective transfer rates of the MSs  421 ,  423 ,  431 , and  433  and the capacity of the multi-hop relay BWA system.  
      In the multi-hop relay BWA systems of  FIGS. 3 and 4 , the RSs  320 ,  360 ,  420 , and  430  may be infrastructure RSs that are installed by a service provider and managed by the BSs  310 ,  350 , and  410  or may be client RSs that operate as SSs, MSs, or RSs according to situations. In addition, the RSs  320 ,  360 ,  420 , and  430  may be stationary RSs, nomadic RSs, such as notebooks, or mobile RSs having mobility like an MS.  
      In such a multi-hop relay wireless communication system, a BS managing each cell must transmit to MSs of the cell not only information about neighbor BSs but also information about RSs for expanding/increasing the area/capacity of the cell. Moreover, an MS performing a conventional IEEE 802.16e communication mode and another MS performing a multi-hop relay communication mode may coexist in the cell managed by the BS.  
      Accordingly, a BS must transmit not only neighbor BS information but also neighbor RS information using the MOB_NBR-ADV message (defined in Table 1). What is therefore needed is a method that enables an MS performing a conventional IEEE 802.16e communication mode and an MS performing a multi-hop relay communication mode to discriminate between neighbor BS information and neighbor RS information based on an MOB_NBR-ADV message.  
     SUMMARY OF THE INVENTION  
      An object of the present invention is to substantially solve at least the above problems and/or disadvantages and to provide at least the advantages below. Accordingly, an object of the present invention is to provide an apparatus and method for providing neighbor node information in a cellular communication system. The present invention also provides an apparatus and method for discriminatively processing neighbor BS information and neighbor RS information, which are contained in a received neighbor advertisement message, in a multi-hop relay BWA system.  
      Another object of the present invention is to provide an apparatus and method for providing neighbor node information in a multi-hop relay BWA system in consideration of an 802.16e mode MS.  
      According to one aspect of the present invention, there is provided a method for transmitting a neighbor advertisement message in a cellular communication system using a multi-hop relay scheme, the method including generating a neighbor advertisement message including neighbor BS information and neighbor RS information; and processing and broadcasting the generated neighbor advertisement message in accordance with a transport protocol.  
      According to another aspect of the present invention, there is provided a method for processing a neighbor advertisement message in a cellular communication system using a multi-hop relay scheme, the method including receiving a neighbor advertisement message broadcast by a BS, and discriminatively processing neighbor BS information and neighbor RS information that are included in the neighbor advertisement message.  
      According to a further aspect of the present invention, there is provided a BS apparatus for a cellular communication system using a multi-hop relay scheme, the BS apparatus including a message generator for generating a neighbor advertisement message including neighbor BS information and neighbor RS information, and a transmitter for processing and broadcasting the generated neighbor advertisement message in accordance with a transport protocol.  
      According to still another aspect of the present invention, there is provided a node apparatus for a cellular communication system using a multi-hop relay scheme, the node apparatus including a receiver for receiving a neighbor advertisement message broadcast by a BS, and a message processor for discriminatively processing neighbor BS information and neighbor RS information that are included in the received neighbor advertisement message.  
      According to yet another aspect of the present invention, there is provided a method for communicating a neighbor advertisement message in a cellular communication system using a multi-hop relay scheme, the method including generating and broadcasting, at a BS, a neighbor advertisement message including neighbor base station BS information and neighbor RS information, and discriminatively processing, at a node, the neighbor BS information and the neighbor RS information that are included in the neighbor advertisement message received from the BS. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:  
       FIG. 1  is a block diagram of a conventional IEEE 802.16e system;  
       FIG. 2  is a flow diagram illustrating a procedure for exchanging the information about neighbor BSs between an MS and a serving BS in a conventional IEEE 802.16e system;  
       FIG. 3  is a block diagram illustrating a BWA system that uses a multi-hop relay scheme to expand a BS coverage area according to the prior art;  
       FIG. 4  is a block diagram illustrating a BWA system that uses a multi-hop relay scheme to increase the system capacity according to the prior art;  
       FIG. 5  is a flowchart illustrating a procedure for receiving and processing a neighbor advertisement message in a multi-hop relay BWA system according to a first embodiment of the present invention;  
       FIG. 6  is a flowchart illustrating a procedure for receiving and processing a neighbor advertisement message in a multi-hop relay BWA system according to a second embodiment of the present invention;  
       FIG. 7  is a flowchart illustrating a procedure for receiving and processing a neighbor advertisement message in a multi-hop relay BWA system according to a third embodiment of the present invention;  
       FIG. 8  is a flowchart illustrating a procedure for receiving and processing a neighbor advertisement message in a multi-hop relay BWA system according to a fourth embodiment of the present invention; and  
       FIG. 9  is a block diagram of an 802.16e mode MS (a relay mode MS, an RS, or a BS) in a multi-hop relay BWA system according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Preferred embodiments of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Also, the terms used herein are defined according to the functions of the present invention. Thus, the terms may vary depending on user&#39;s or operator&#39;s intension and usage. That is, the terms used herein must be understood based on the descriptions made herein.  
      The present invention provides an apparatus and method for providing neighbor node information in a cellular communication system. The present invention also provides an apparatus and method for discriminatively processing neighbor Base Station (BS) information and neighbor Relay Station (RS) information, which are contained in a received neighbor advertisement message, in a multi-hop relay Broadband Wireless Access (BWA) system.  
      A multi-hop relay BWA system uses an Orthogonal Frequency Division Multiplexing (OFDM) scheme or an Orthogonal Frequency Division Multiple Access (OFDMA) scheme, for example. Accordingly, a multi-hop relay BWA system can transmit physical channel signals using a plurality of subcarriers, thereby enabling high-rate data transmission. In addition, a multi-hop relay BWA system supports a multi-cell structure, thereby supporting the mobility of a mobile station (MS).  
      An RS for a multi-hop relay BWA system may be a stationary node, a mobile node, a specific system installed for a BS, or a general subscriber terminal. Such a node may be selected as an RS through an RS capability negotiation process in accordance with a standard for expansion of the cell coverage or capacity of a BS.  
      Although a multi-hop relay BWA system is taken as an example in the following description, the present invention can be applied to any cellular communication system that uses a multi-hop relay scheme.  
       FIG. 5  shows an example of a procedure for receiving and processing a neighbor advertisement message in a multi-hop relay BWA system according to the present invention. A node receiving the neighbor advertisement message may be an RS, an MS capable of performing relay communication (hereinafter referred to as “relay mode MS”), or an MS communicating directly with a BS (hereinafter referred to as “802.16e mode MS”). The 802.16e mode MS is incapable of performing relay communication.  
      Referring to  FIG. 5 , a node receives a neighbor advertisement (MOB_NBR-ADV) message broadcast by a BS, in step  511 . For example, the MOB_NBR-ADV message has the same format as that defined in Table 1, and may include not only neighbor BS information but also neighbor RS information to support a multi-hop relay communication mode according to the present invention. The neighbor RS information of the MOB_NBR-ADV message may be included in the Type/Length/Value (TLV) Encoded Neighbor information (defined in Table 1) in the TLV format so the 802.16e mode MS can acquire the neighbor BS information from the MOB_NBR-ADV message and can disregard the neighbor RS information for the multi-hop relay communication mode.  
      Table 2 below shows an example of RS information TLV in which the RS information is recorded according to the present invention.  
                       TABLE 2                           Length           Type   (byte)   Value                  Neighbor Node (NN) (RS Info)   variable   RS information       NN. 1 (RS identification info)   1   RS identification information       NN. 2 (PHY synchronization   1   PHY synchronization       info 1)       information #1       NN. 3 (PHY synchronization   1   PHY synchronization       info 2)       information #2       . . .       NN.xx (scheduling info)   1   RS scheduling information       . . .       NN.yy (DCD info)   1   RS&#39;s DCD information       . . .                  
 
      As shown in Table 2, the RS information TLV includes TLV type Neighbor Node (NN), TLV length, and a variety of RS information. The RS information may include information about RSs managed by a corresponding BS, information about the respective RS identifications (IDs). For each RS, the RS information may include RS ID information, RS PHY synchronization information (e.g., RS frequency information, and physical channel profile information), RS scheduling information supported by the RS, and information about an RS Downlink Channel Description (DCD) message or an RS Uplink Channel Description (UCD) message transmitted by the RS. Although only a portion of the RS information is shown in Table 2, the RS information may include a variety of other information like the BS information defined in Table 1.  
      In step  513 , the node starts to process information about each NEIGHBOR of the MOB_NBR-ADV message including the RS information TLV as described above. A plurality of NEIGHBORs included in the MOB_NBR-ADV message may be sequentially processed. The subsequent process for each type of node will now be described in detail.  
      A case where the node receiving the MOB_NBR-ADV message is an RS supporting a multi-hop relay communication mode will be described first.  
      In step  517 , the node (RS) processes neighbor BS information included in a corresponding NEIGHBOR.  
      In step  519 , the node (RS) processes TLV encoding information included in the corresponding NEIGHBOR (Encoded Neighbor Information) and determines if the TLV encoding information includes RS information TLV as defined in Table 2. If so, the procedure proceeds to step  521 ; and if not, the procedure proceeds directly to step  523 . In step  521 , the node (RS) processes the RS information TLV included in the corresponding NEIGHBOR.  
      In step  523 , the node (RS) determines if processing of information about all NEIGHBORS included in the received MOB_NBR-ADV message is completed. If so, the procedure proceeds to step  525 ; and if not, the procedure returns to step  517  to process information about the next NEIGHBOR. In step  525 , the node (RS) reconstructs the neighbor BS/RS information in the received MOB_NBR-ADV message to generate a neighbor node information message, and transmits the generated neighbor node information message to lower nodes managed by the node (RS).  
      A case where the node receiving the MOB_NBR-ADV message is an MS supporting a multi-hop relay communication mode will now be described.  
      In step  529 , the node (relay mode MS) processes neighbor BS information included in a corresponding NEIGHBOR.  
      In step  531 , the node (relay mode MS) processes TLV encoding information included in the corresponding NEIGHBOR (Encoded Neighbor Information) and determines if the TLV encoding information includes RS information TLV as defined in Table 2. If so, the procedure proceeds to step  533 ; and if not, the procedure proceeds directly to step  535 . In step  533 , the node (relay mode MS) processes the RS information TLV included in the corresponding NEIGHBOR.  
      In step  535 , the node (relay mode MS) determines if processing of information about all NEIGHBORS included in the MOB_NBR-ADV message is completed. If so, the procedure proceeds to step  537 ; and if not, the procedure returns to step  529  to process information about the next NEIGHBOR. In step  537 , the node (relay mode MS) completes processing of neighbor node information.  
      A case where the node receiving the MOB_NBR-ADV message is an MS supporting a conventional IEEE 802.16e communication mode will now be described.  
      In step  541 , the node (802.16e mode MS) processes neighbor BS information included in a corresponding NEIGHBOR.  
      In step  543 , the node (802.16e mode MS) processes TLV encoding information included in the corresponding NEIGHBOR (Encoded Neighbor Information) and determines if the TLV encoding information includes RS information TLV as defined in Table 2. If so, the procedure proceeds to step  545 ; and if not, the procedure proceeds directly to step  547 . At this point, the node (802.16e mode MS) does not know a type value NN corresponding to the RS information TLV. Therefore, the node (802.16e mode MS) cannot process the RS information TLV even when the type value NN is included in the TLV encoding information (Encoded Neighbor Information).  
      Accordingly, in step  545 , the node (802.16e mode MS) disregards (or discards) the RS information TLV and processes only recognizable TLV encoding information.  
      In step  547 , the node (802.16e mode MS) determines if processing of information about all NEIGHBORS included in the MOB_NBR-ADV message is completed. If so, the procedure proceeds to step  547 ; and if not, the procedure returns to step  541  to process information about the next NEIGHBOR. In step  547 , the node (802.16e mode MS) completes processing of neighbor node information.  
      As described above, this example uses the format of the MOB_NBR-ADV message (defined in Table 1) as it is. That is, the 802.16e mode MS can acquire the neighbor BS information in the same manner as conventional art, without recognizing the neighbor RS information (defined in Table 2) added to a conventional MOB_NRB-ADV message (defined in Table 1).  
      Unlike a conventional MOB_NBR_ADV message defined in Table 1, an MOB_NBR-ADV message according to the present invention includes neighbor RS information for a multi-hop relay communication mode, as well as neighbor BS information for a conventional IEEE 802.16e communication mode. In this case, an indicator is used to indicate whether the NEIGHBOR information is RS information or BS information. This will be described below.  
       FIG. 6  shows another example of a procedure for receiving and processing a neighbor advertisement message in a multi-hop relay BWA system according to the present invention. A node receiving the neighbor advertisement message may be an RS, a relay mode MS, or an 802.16e mode MS.  
      Referring to  FIG. 6 , a node receives a neighbor advertisement (MOB_NBR-ADV) message broadcast by a BS, in step  611 . The MOB_NBR-ADV message may include neighbor RS information for supporting the multi-hop relay communication mode, as well as the neighbor BS information defined in Table 1. In addition, the MOB_NBR-ADV message may further include a relay station indicator for indicating the existence of the neighbor RS information, so the RS, the 802.16e mode MS, or the relay mode MS can detect that the neighbor RS information as well as the neighbor BS information is included in the MOB_NBR-ADV message.  
      Table 3 below shows an example of a format of the MOB_NBR-ADV message including an RS indicator according to the present invention. An MOB_NBR-ADV message according to this example includes not only the information defined in Table 1 but also an RS indicator for indicating whether corresponding NEIGHBOR information is RS information.  
                       TABLE 3                          ...   . . .   . . .       N_NEIGHBORS   8   Number of neighbor RSs                                 and BSs                         For(i=0;   i&lt;N_NEIGHBORS                         i++) {                                     Relay station indicator   1   0: base station                                 1: relay station                                 Reserved   7   Shall be set to zero           Length   8   Length of message                                 information within the               iteration of               N_NEIGHBORS in bytes.                                 PHY synchronization info   TBD   Information for physical                                 synchronization                                 Neighbor station info   TBD   Information of this                                 neighbor station                                 TLV encoded neighbor   Vari-   TLV specific                         information   able           }                  
 
      As shown in Table 3, the MOB_NBR-ADV message includes a relay station indicator that is added to each NEIGHBOR information in a conventional MOB_NBR-ADV message (defined in Table 1) to indicate whether the NEIGHBOR is a neighbor BS or a neighbor RS. When the RS indicator is ‘0’, it indicates that a corresponding NEIGHBOR is a neighbor BS. When the RS indicator is ‘1’, it indicates that a corresponding NEIGHBOR is a neighbor RS. If the RS indicator ‘1’ indicating a neighbor RS, a portion of the information included in a conventional MOB_NBR-ADV message (defined in Table 1) may be omitted.  
      In step  613 , the node starts to process information about each NEIGHBOR of the MOB_NBR-ADV message including an RS indicator. A plurality of NEIGHBORs included in the MOB_NBR-ADV message may be sequentially processed. The subsequent process for each type of node will now be described in detail.  
      A case where the node receiving the MOB_NBR-ADV message is an RS supporting a multi-hop relay communication mode will be described first.  
      In step  617 , the node (RS) determines if the RS indicator in the corresponding NEIGHBOR information is ‘1’. If not, the procedure proceeds to step  619 ; and if so, the procedure proceeds to step  621 . In step  619 , the node (RS) processes BS information corresponding to the NEIGHBOR information. In step  621 , the node (RS) processes RS information corresponding to the NEIGHBOR information.  
      In step  623 , the node (RS) determines if processing of information about all NEIGHBORS included in the MOB_NBR-ADV message is completed. If so, the procedure proceeds to step  625 ; and if not, the procedure returns to step  617  so as to process information about the next NEIGHBOR. In step  625 , the node (RS) reconstructs neighbor BS/RS information included in the MOB_NBR-ADV message to generate a neighbor node information message, and transmits the generated neighbor node information message to lower nodes managed by the node (RS).  
      A case where the node receiving the MOB_NBR-ADV message is an MS supporting a multi-hop relay communication mode will now be described.  
      In step  629 , the node (relay mode MS) determines if an RS indicator in the corresponding NEIGHBOR information is ‘1’. If not, the procedure proceeds to step  631 ; and if so, the procedure proceeds to step  633 . In step  631 , the node (relay mode MS) processes neighbor BS information corresponding to the NEIGHBOR information. In step  633 , the node (relay mode MS) processes neighbor RS information corresponding to the NEIGHBOR information.  
      In step  635 , the node (relay mode MS) determines if processing of information about all NEIGHBORS included in the MOB_NBR-ADV message is completed. If so, the procedure proceeds to step  637 ; and if not, the procedure returns to step  629  so as to process information about the next NEIGHBOR. In step  637 , the node (relay mode MS) completes processing of neighbor node information.  
      A case where the node receiving the MOB_NBR-ADV message is an MS supporting a conventional IEEE 802.16e communication mode will now be described.  
      In step  641 , the node (802.16e mode MS) determines if an RS indicator in the corresponding NEIGHBOR information is ‘1’. If not, the procedure proceeds to step  643 ; and if so, the procedure proceeds to step  645 . In step  643 , the node (802.16e mode MS) processes BS information corresponding to the NEIGHBOR information. In step  645 , the node (802.16e mode MS) disregards RS information corresponding to the NEIGHBOR information.  
      In step  647 , the node (802.16e mode MS) determines if processing of information about all NEIGHBORS included in the MOB_NBR-ADV message is completed. If so, the procedure proceeds to step  649 ; and if not, the procedure returns to step  641  so as to process information about the next NEIGHBOR. In step  649 , the node (802.16e mode MS) completes processing of neighbor node information.  
      According to this example, using an RS indicator added to a conventional MOB_NBR-ADV message, the 802.16e mode MS can determine whether the corresponding NEIGHBOR information is the neighbor BS information or information about other nodes.  
      Unlike a conventional MOB_NBR_ADV message defined in Table 1, an MOB_NBR-ADV message according to the present invention includes neighbor RS information for the multi-hop relay communication mode, as well as neighbor BS information for a conventional IEEE 802.16e communication mode. In this case, an indicator is used to indicate whether the NEIGHBOR information includes neighbor RS information. This will be described below.  
       FIG. 7  shows an example of a procedure for receiving and processing a neighbor advertisement message in a multi-hop relay BWA system according to the present invention. A node receiving the neighbor advertisement message may be an RS, a relay mode MS, or an 802.16e mode MS.  
      Referring to  FIG. 7 , a node receives a neighbor advertisement (MOB_NBR-ADV) message broadcast by a BS, in step  711 . The MOB_NBR-ADV message may include neighbor RS information for supporting a multi-hop relay communication mode, as well as the neighbor BS information defined in Table 1. In addition, the MOB_NBR-ADV message may further include a relay info indicator for indicating the existence of the neighbor RS information, so the RS, the 802.16e mode MS, or the relay mode MS can detect that the neighbor RS information as well as the neighbor BS information is included in the MOB_NBR-ADV message.  
      Table 4 below shows an example of a format of an MOB_NBR-ADV message including the relay info indicator according to the present invention. A MOB_NBR-ADV message according to this example includes not only the information defined in Table 1 but also the relay info indicator for indicating whether corresponding NEIGHBOR information includes neighbor RS information.  
                       TABLE 4                          ...   . . .   . . .       N_NEIGHBORS   8   Number of neighbor BSs       For(i=0; i&lt;N_NEIGHBORS       i++) {                                 Length   8   Length of BS information                                 within the iteration of               N_NEIGHBORS in bytes,               except RS information               within the iteration of               N_RS.                                 PHY synchronization info   TBD   Information for physical                                 synchronization                                 Neighbor station info   TBD   Information of this                                 neighbor station                                 TLV encoded neighbor   Variable   TLV specific                     information                                     Relay info indicator   1   0: RS information not                                 included               1: RS information included                                 Reserved   7   Shall be set to zero           N_RS   8   Number of neighbor RSs in                                 this BS (if relay info               indicator is set to 0,               this field shall be               discarded.)                             For(j=0;j&lt;N_RS;j++) {                                     Length   8   Length of RS information                                 within the iteration of               N_RS in bytes.                                 PHY synchronization info   TBD   Information for physical                                 synchronization                                 RS info   TBD   Information of this RS           TLV encoded RS information   Vari-   TLV specific                             able                                 }                         }                  
 
      As shown in Table 4, the MOB_NBR-ADV message includes a relay info indicator that is added to each NEIGHBOR information in a conventional MOB_NBR-ADV message (defined in Table 1) to indicate whether there is an RS managed by a corresponding neighbor BS. When the relay info indicator is ‘0’, it indicates that the corresponding NEIGHBOR information does not include neighbor RS information. When the relay info indicator is ‘1’, it indicates that the corresponding NEIGHBOR information includes neighbor RS information. If the relay info indicator is ‘1’, the corresponding NEIGHBOR information includes not only information about a neighbor BS but also neighbor RS information managed by the neighbor BS. The neighbor RS information may include RS ID information, RS PHY synchronization information (e.g., physical channel profile information and RS frequency information), RS scheduling information supported by the RS, and an RS DCD message or an RS UCD message transmitted by the RS. In addition, a length field value (defined in Table 4) may indicate the amount of information about each NEIGHBOR, excluding the amount of neighbor RS information managed by the NEIGHBOR.  
      In step  713 , the node starts to process information about each NEIGHBOR of the MOB_NBR-ADV message including the relay info indicator. A plurality of NEIGHBORs included in the MOB_NBR-ADV message may be sequentially processed. The subsequent process for each type of node will now be described.  
      A case where the node receiving the MOB_NBR-ADV message is an RS supporting a multi-hop relay communication mode will be described first.  
      In step  717 , the node (RS) processes neighbor BS information included in corresponding NEIGHBOR information.  
      In step  719 , the node (RS) determines if the relay info indicator in the corresponding NEIGHBOR information is ‘1’. If so, the procedure proceeds to step  721 ; and if not, the procedure proceeds directly to step  723 . In step  721 , the node (RS) detects that the corresponding NEIGHBOR information includes neighbor RS information, and processes the neighbor RS information in the corresponding NEIGHBOR information.  
      In step  723 , the node (RS) determines if processing of information about all NEIGHBORS included in the MOB_NBR-ADV message is completed. If so, the procedure proceeds to step  725 ; and if not, the procedure returns to step  717  to process information about the next NEIGHBOR. In step  725 , the node (RS) reconstructs neighbor BS/RS information included in the MOB_NBR-ADV message to generate a neighbor node information message, and transmits the generated neighbor node information message to lower nodes managed by the node (RS).  
      A case where the node receiving the MOB_NBR-ADV message is an MS supporting a multi-hop relay communication mode will now be described.  
      In step  729 , the node (relay mode MS) processes neighbor BS information included in corresponding NEIGHBOR information.  
      In step  731 , the node (relay mode MS) determines if the relay info indicator in the corresponding NEIGHBOR information is ‘1’. If so, the procedure proceeds to step  733 ; and if not, the procedure proceeds directly to step  735 . In step  733 , the node (relay mode MS) detects that the corresponding NEIGHBOR information includes neighbor RS information, and processes neighbor RS information in the corresponding NEIGHBOR information.  
      In step  735 , the node (relay mode MS) determines if processing of information about all NEIGHBORS included in the MOB_NBR-ADV message is completed. If so, the procedure proceeds to step  737 ; and if not, the procedure returns to step  729  so as to process information about the next NEIGHBOR. In step  737 , the node (relay mode MS) completes processing of neighbor node information.  
      A case where the node receiving the MOB_NBR-ADV message is an MS supporting a conventional IEEE 802.16e communication mode will now be described.  
      In step  741 , the node (802.16e mode MS) processes neighbor BS information included in corresponding NEIGHBOR information.  
      In step  743 , the node (802.16e mode MS) determines if the relay info indicator in the corresponding NEIGHBOR information is ‘1’. If so, the procedure proceeds to step  745 ; and if not, the procedure proceeds directly to step  747 . In step  745 , the node (802.16e mode MS) disregards (or discards) neighbor RS information following the relay info indicator.  
      In step  747 , the node (802.16e mode MS) determines if processing of information about all NEIGHBORS included in the MOB_NBR-ADV message is completed. If so, the procedure proceeds to step  749 ; and if not, the procedure returns to step  741  so as to process information about the next NEIGHBOR. In step  749 , the node (802.16e mode MS) completes processing of neighbor node information.  
      According to this example, using a relay info indicator added to a conventional MOB_NBR-ADV message, an 802.16e mode MS can determine whether the corresponding NEIGHBOR information includes the neighbor RS information.  
      Unlike a conventional MOB_NBR_ADV message defined in Table 1, an MOB_NBR-ADV message according to the present invention includes neighbor RS information for a multi-hop relay communication mode, as well as neighbor BS information for a conventional IEEE 802.16e communication mode. In this case, a length field is used to indicate whether the NEIGHBOR information includes neighbor RS information. This will be described below.  
       FIG. 8  shows another example of a procedure for receiving and processing a neighbor advertisement message in a multi-hop relay BWA system according to the present invention. A node receiving the neighbor advertisement message may be an RS, a relay mode MS, or an 802.16e mode MS.  
      Referring to  FIG. 8 , a node receives a neighbor advertisement (MOB_NBR-ADV) message broadcast by a BS, in step  811 . The MOB_NBR-ADV message may include neighbor RS information for supporting the multi-hop relay communication mode, as well as the neighbor BS information defined in Table 1.  
      Table 5 below shows another example of a format of an MOB_NBR-ADV message including neighbor RS information according to the present invention. The neighbor BS information in the MOB_NBR-ADV message is the same as that defined in Table 1, and information about one NEIGHBOR is shows in Table 5.  
                       TABLE 5                          ...   . . .   . . .       N_NEIGHBORS   8   Number of neighbor BSs       For(i=0; i&lt;N_NEIGHBORS;       i++) {                                 Length   8   Length of BS information                                 within the iteration of               N_NEIGHBORS in bytes,               except RS information.                                 PHY synchronization info   TBD   Information for physical                                 synchronization                                 Neighbor station info   TBD   Information of this                                 neighbor station                                 TLV encoded neighbor   Vari-   TLV specific                         information   able                                     N_RS   8   Number of neighbor RSs                                 in this BS                             For(j=0;j&lt;N_RS;j++) {                                     Length   8   Length of RS information                                 within the iteration of               N_RS in bytes.                                 PHY synchronization   TBD   Information for physical           info       synchronization           RS info   TBD   Information of this RS           TLV encoded RS   Vari-   TLV specific           information   able                                 }                         }                  
 
      As shown in Table 5, the MOB_NBR-ADV message includes not only information about a corresponding neighbor BS but also neighbor RS information managed by the corresponding neighbor BS. Pure neighbor BS information, excluding the neighbor RS information, is recorded in a length field indicating the amount of information about each NEIGHBOR. Accordingly, the node having receiving the MOB_NRB-ADV message can recognize information corresponding to a length field value as the pure neighbor BS information and can recognize information exceeding the length field value as the neighbor RS information managed by the neighbor BS. The neighbor RS information may include RS ID information, RS PHY synchronization information (e.g., physical channel profile information and RS frequency information), RS scheduling information supported by the RS, and an RS DCD message or an RS UCD message transmitted by the RS.  
      In step  813 , the node starts to process information about each NEIGHBOR of the received MOB_NBR-ADV message. A plurality of NEIGHBORs included in the MOB_NBR-ADV message may be sequentially processed. The subsequent process for each type of node will now be described in detail.  
      A case where the node receiving the MOB_NBR-ADV message is an RS supporting a multi-hop relay communication mode will be described first.  
      In step  817 , the node (RS) processes neighbor BS information included in corresponding NEIGHBOR information.  
      In step  819 , the node (RS) determines if the amount of the processed information exceeds the information amount corresponding to the length field value of the NEIGHBOR. If so, the procedure proceeds to step  821 ; and if not, the procedure proceeds directly to step  823 . As described above, because the amount of information recorded in the length field value of the NEIGHBOR is the amount of the pure neighbor BS information, the node (RS) recognizes information corresponding to the length field value as the neighbor BS information. That is, if the amount of the processed information does not exceed the information amount corresponding to the length field value of the NEIGHBOR, the node (RS) detects that the corresponding NEIGHBOR information does not include the neighbor RS information.  
      In step  821 , the node (RS) detects that the corresponding NEIGHBOR information includes neighbor RS information, and processes the neighbor RS information in the corresponding NEIGHBOR information.  
      In step  823 , the node (RS) determines if processing of information about all NEIGHBORS included in the received MOB_NBR-ADV message is completed. If so, the procedure proceeds to step  825 ; and if not, the procedure returns to step  817  so as to process information about the next NEIGHBOR. In step  825 , the node (RS) reconstructs neighbor BS/RS information included in the MOB_NBR-ADV message to generate a neighbor node information message, and transmits the generated neighbor node information message to lower nodes managed by the node (RS).  
      A case where the node receiving the MOB_NBR-ADV message is an MS supporting a multi-hop relay communication mode will now be described.  
      In step  829 , the node (relay mode MS) processes neighbor BS information included in corresponding NEIGHBOR information.  
      In step  831 , the node (relay mode MS) determines if the amount of the processed information exceeds the information amount corresponding to the length field value of the NEIGHBOR. If so, the procedure proceeds to step  833 ; and if not, the procedure proceeds directly to step  835 . As described above, because the amount of information recorded in the length field value of the NEIGHBOR is the amount of the pure neighbor BS information, the node (RS) recognizes information corresponding to the length field value as the neighbor BS information. That is, if the amount of the processed information does not exceed the information amount corresponding to the length field value of the NEIGHBOR, the node (RS) detects that the corresponding NEIGHBOR information does not include the neighbor RS information.  
      In step  833 , the node (relay mode MS) detects that the corresponding NEIGHBOR information includes neighbor RS information, and processes the neighbor RS information in the corresponding NEIGHBOR information.  
      In step  835 , the node (relay mode MS) determines if processing of information about all NEIGHBORS included in the MOB_NBR-ADV message is completed. If so, the procedure proceeds to step  837 ; and if not, the procedure returns to step  829  so as to process information about the next NEIGHBOR. In step  837 , the node (relay mode MS) completes processing of neighbor node information.  
      A case where the node receiving the MOB_NBR-ADV message is an MS supporting a conventional IEEE 802.16e communication mode will now be described.  
      In step  841 , the node (802.16e mode MS) processes neighbor BS information included in corresponding NEIGHBOR information.  
      In step  843 , the node (802.16e mode MS) determines if the amount of the processed information exceeds the information amount corresponding to the length field value of the NEIGHBOR. If so, the procedure proceeds to step  845 ; and if not, the procedure proceeds directly to step  847 . As described above, because the information amount recorded in the length field value of the NEIGHBOR is the pure neighbor BS information amount, the node (802.16e mode MS recognizes the information corresponding to the length field value as the neighbor BS information. In this case, an N_RS field (defined in Table 5) indicating the number of neighbor RSs managed by the neighbor BS is meaningless to the node (802.16e mode MS). Accordingly, the node (806.16e mode MS) recognizes the remaining information corresponding to the length field value minus 8 bits of the N_RS field as an actual length value of the neighbor BS information.  
      In step  845 , the node (802.16e mode MS) disregards (or discards) neighbor RS information following the information corresponding to the length field value.  
      In step  847 , the node (802.16e mode MS) determines if processing of information about all NEIGHBORS included in the MOB_NBR-ADV message is completed. If so, the procedure proceeds to step  849 ; and if not, the procedure returns to step  841  so as to process information about the next NEIGHBOR. In step  849 , the node (802.16e mode MS) completes processing of neighbor node information.  
      According to this example, using the length field of the corresponding NEIGHBOR, the 802.16e mode MS can acquire the pure neighbor BS information except neighbor RS information.  
      Configurations of the 802.16e mode MS, the relay mode MS, the RS, and the BS will be described in detail. The 802.16e mode MS, the relay mode MS, the RS, and the BS using the same interface module (communication module) have the same block configuration. Thus, the configurations of the 802.16e mode MS, the relay mode MS, the RS, and the BS will be described.  
       FIG. 9  shows an example of an 802.16e mode MS (a relay mode MS, an RS, or a BS) in a multi-hop relay BWA system according to the present invention. The following description will be made assuming that the MS (the relay mode MS, the RS, or the BS) uses a Time Division Duplex (TDD)/OFDMA scheme.  
      Referring to  FIG. 9 , the 802.16e mode MS (the relay mode MS, the RS, or the BS) includes an antenna, an RX radio frequency (RF) processor  901 , an analog-to-digital converter (ADC)  903 , an OFDM demodulator  905 , a decoder  907 , a message processor  909 , a controller  911 , a neighbor node information processor  913 , a message generator  915 , an encoder  917 , an OFDM modulator  919 , a digital-to-analog converter (DAC)  921 , a TX RF processor  923 , a switch  925 , and a time controller  927 .  
      The time controller  927  controls a switching operation of the switch  925  based on frame synchronization. For example, when being in an RX section of a frame, the time controller  927  controls the switch  925  so that the antenna is connected to the RX RF processor  901 . When being in a TX section of the frame, the time controller  927  controls the switch  925  so that the antenna is connected to the TX RF processor  923 .  
      In the RX section of the frame, the RX RF processor  901  converts an RF signal received through the antenna into a baseband analog signal. The ADC  903  converts the analog signal into sample data (digital data). The OFDM demodulator  905  Fast Fourier Transform (FFT)-processes the sample data to output frequency-domain data.  
      The decoder  907  selects data of desired subcarriers from the frequency-domain data, and decodes the selected data in accordance with a modulation &amp; coding scheme (MCS) level.  
      The message processor  909  processes a control message received from the decoder  907  and provides the resulting information to the controller  911 . According to the present invention, the message processor  909  extracts a variety of control information from the received control message and provides the extracted control information to the controller  911 .  
      The controller  911  performs an operation corresponding to the information received from the message processor  909  and provides the results to the message generator  915 . The neighbor node information processor  913  manages neighbor node information under the control of the controller  911 .  
      The message generator  915  generates a message using a variety of information received from the controller  911  and provides the message to the encoder  917 .  
      The encoder  917  encodes data received from the message generator  915  in accordance with an MCS level. The OFDM modulator  919  Inverse Fast Fourier Transform (IFFT)-processes data received from the encoder  917 , thereby generating sample data (OFDM symbols). The DAC  921  converts the sample data into an analog signal. The TX RF processor  923  converts the analog signal received from the DAC  921  into an RF signal and transmits the RF signal through the antenna.  
      In the above-described configuration, the controller  911  is a protocol controller that controls the message processor  909 , the message generator  915 , and the neighbor node information processor  913 . That is, the controller  911  can perform the functions of the message processor  909 , the message generator  915 , and the neighbor node information processor  913 . Although separate units are provided for respective functions of the controller  911 , the controller  911  can perform all or some of the functions instead of such separate units.  
      Operations of the 802.16e mode MS, the relay mode MS, the RS, and the BS will now be described with reference to the configuration shown in  FIG. 9 , focusing on a control message processing in a MAC layer.  
      The operation of the 802.16e mode MS will be first described.  
      The message processor  909  processes a control message received from a BS and provides the results to the controller  911 . When the 802.163 mode MS receives a neighbor advertisement (MOB_NBR-ADV) message including neighbor BS information and neighbor RS information (defined in Table 2, Table 3, Table 4, or Table 5), the message processor  909  extracts a variety of information from the MOB_NBR-ADV message and provides the extracted information to the controller  911 .  
      The controller  911  performs an operation corresponding to the information received from the message processor  909 . At this point, the controller  911  processes only the neighbor BS information among the neighbor BS information and the neighbor RS information included in the MOB_NBR-ADV message.  
      The neighbor node information processor  913  manages the neighbor BS information extracted from the MOB_NBR-ADV message. Under the control of the controller  911 , the neighbor node information processor  913  reads information necessary for communication with a corresponding node (BS or RS) BS and provides the read information to the controller  911 .  
      The operation of the relay mode MS will now be described.  
      The message processor  909  processes a control message received from an RS or a BS and provides the results to the controller  911 . When the relay mode MS receives a neighbor advertisement (MOB_NBR-ADV) message including neighbor BS information and neighbor RS information (defined in Table 2, Table 3, Table 4, or Table 5), the message processor  909  extracts a variety of information from the MOB_NBR-ADV message and provides the extracted information to the controller  911 .  
      The controller  911  performs an operation corresponding to the information received from the message processor  909 . At this point, the controller  911  discriminatively processes both of the neighbor BS information and the neighbor RS information included in the MOB_NBR-ADV message.  
      The neighbor node information processor  913  manages the neighbor BS information and the neighbor RS information extracted from the MOB_NBR-ADV message. Under the control of the controller  911 , the neighbor node information processor  913  reads information necessary for communication with a corresponding node (BS or RS) and provides the read information to the controller  911 .  
      The operation of the RS will now be described.  
      The message processor  909  processes a control message received from an MS or a BS and provides the results to the controller  911 . When the RS receives a neighbor advertisement (MOB_NBR-ADV) message including neighbor BS information and neighbor RS information (defined in Table 2, Table 3, Table 4, or Table 5), the message processor  909  extracts a variety of information from the MOB_NBR-ADV message and provides the extracted information to the controller  911 .  
      The controller  911  performs an operation corresponding to the information received from the message processor  909 . At this point, the controller  911  discriminatively processes both of the neighbor BS information and the neighbor RS information included in the MOB_NBR-ADV message.  
      The neighbor node information processor  913  manages the neighbor BS information and the neighbor RS information extracted from the MOB_NBR-ADV message. Under the control of the controller  911 , the neighbor node information processor  913  reads information necessary for communication with a corresponding node (BS or RS) and provides the read information to the controller  911 .  
      Under the control of the controller  911 , the message generator  915  generates a message destined for a BS, a relay mode MS, or a lower node (RS) and provides the generated message to the encoder  917  of a physical layer. According to the present invention, using the neighbor BS information and the neighbor RS information managed by the neighbor node information processor  913 , the message generator  915  generates a neighbor node information message destined for a lower node of the physical layer. The generated neighbor node information message is processed at the physical layer and is transmitted through the antenna.  
      The operation of the BS will now be described.  
      The message processor  909  processes a control message received from an MS or an RS and provides the results to the controller  911 .  
      The controller  911  performs an operation corresponding to control information received from the message processor  909 . The neighbor node information processor  913  manages neighbor BS information and neighbor RS information, and provides a neighbor node list to the controller  911  under the control of the controller  911 .  
      Under the control of the controller  911 , the message generator  915  generates a message destined for an MS or an RS and provides the generated message to the encoder  917  of a physical layer. According to the present invention, the message generator  915  generates a neighbor advertisement (MOB_NBR-ADV) message including neighbor BS information and neighbor RS information (defined in Table 2, Table 3, Table 4, or Table 5), and provides the MOB_NBR-ADV message to the physical layer. Thereafter, the MOB_NBR-ADV message is processed suitable for communication and is transmitted through the antenna.  
      As described above, the neighbor advertisement message including the neighbor BS information and the neighbor RS information is broadcast in the BWA system where the 802.16e mode MS, the relay mode MS, the BS, and the RS coexist. In this case, each node can extract and process necessary neighbor node information efficiently. In addition, the present invention can provide a scheme for enabling the 802.16e mode MS to disregard the neighbor RS information contained in the neighbor advertisement message. Accordingly, it is possible to prevent unnecessary information processing.  
      While the invention has been shown and described with reference to certain preferred 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.