Abstract:
A point-to-point emulation apparatus and method in a broadband wireless communication system are provided. In a communication method in an RAS in a broadband wireless communication system, an ID of a source terminal and an ID of a destination terminal are registered in a database by mapping the ID of the source terminal to the ID of the destination terminal, for communications between terminals registered to the RAS. Upon receipt of traffic data from the source terminal, a header of the traffic data is converted using the database, for transmission to the destination terminal on a downlink.

Description:
PRIORITY  
       [0001]     This application claims priority under 35 U.S.C. § 119 to an application entitled “Apparatus and Method for Point-to-Point Emulation in a Broadband Wireless Communication System” filed in the Korean Intellectual Property Office on Jul. 14, 2005 and assigned Serial No. 2005-63608, the contents of which are herein incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to a point-to-point emulation apparatus and method in a broadband wireless communication system, and in particular, to an apparatus and method for enabling users belonging to the same Radio Access Station (RAS) to communicate with each other without intervention from a higher-layer system.  
         [0004]     2. Description of the Related Art  
         [0005]     Along with the introduction of a cellular mobile communication system in the U.S. in the late 1970s, Korea began to implement a voice communication service by deploying a first Generation (1G) mobile communication system, Advanced Mobile Phone Service (AMPS). In the mid 1990s, a 2 nd  Generation (2G) mobile communication system, Code Division Multiple Access (CDMA), came into use to provide voice and low-speed data service.  
         [0006]     International Mobile Telecommunication-2000 (IMT-2000), which was introduced in the late 1990s to realize advanced wireless multimedia services, worldwide roaming, and high-speed data service, has been partially deployed at present.  
         [0007]     Today, mobile communication technology is evolving from 3 rd  Generation (3G) mobile communication systems to 4 th  Generation (4G) mobile communication systems. Beyond the traditional, simple wireless communication services provided by the previous-generation mobile communication systems, the 4G systems are under standardization for the purpose of efficient interworking and integration between wireless and wired communication networks. The following description is made in the context of an International Electrical and Electronics Engineers (IEEE) 802.16 based system (e.g. Wireless Broadband (WiBro)).  
         [0008]      FIG. 1  illustrates a hierarchical protocol architecture of a Radio Access Station (RAS) in a conventional broadband wireless communication system. The protocol stack is comprised of a PHYsical (PHY) layer  100 , a Medium Access Control (MAC) layer  110 , and a convergence sublayer  120 .  
         [0009]     Referring to  FIG. 1 , the convergence sublayer  120  converts data associated with digital audio/video multicast, digital telephony, and Internet connection in compliance with an 802.16 MAC protocol. The convergence sublayer  120  converts an Internet Protocol (IP) packet to a MAC Packet Data Unit (PDU) with a corresponding Connection Identifier (CID) and provides the MAC PDU to the MAC layer  110 . The coverage sublayer  120  also converts a MAC PDU received from the MAC layer  110  to an IP packet and sends the IP packet to a higher-layer router of the RAS.  
         [0010]     The MAC layer  110  controls access to a common wireless medium and controls flows of data and control signals according to the MAC protocol that specifies the time when the RAS or a Mobile Station (MS) starts transmission. In addition, the MAC layer  110  creates a frame with MAC PDUs received from the convergence sublayer  120  and provides the frame to the PHY layer  100 . The MAC layer  110  also extracts MAC PDUs from data received from the PHY layer  100  and provides the MAC PDUs to the convergence sublayer  120 .  
         [0011]     The PHY layer  100  processes the frame data received form the MAC layer  110  by coding, modulation, Inverse Fast Fourier Transform (IFFT), and Radio Frequency (RF) modulation, for transmission on a radio link. For reception, the PHY layer  100  processes a signal received on the radio link by RF demodulation, Fast Fourier Transform (FFT), demodulation, and decoding and provides the processed signal to the MAC layer  110 .  
         [0012]     In general, an MS connected to an RAS is allocated downlink and uplink CIDs in a signaling procedure. The signal procedure results in creation of a mapping table illustrated below in Table 1.  
                       TABLE 1                       IP address   Downlink CID   Uplink CID                   102.124.25.1   234   110:       .   .   .       .   .   .       .   .   .                  
 
         [0013]     As described above, the RAS accesses the mapping table such as Table 1, acquires a downlink CID corresponding to the destination (IP address) of an IP packet to be sent to the MS (or user), and generates a MAC PDU with the downlink CID. The MAC PDU is sent to the MS via a radio link. Reversely, the RAS creates an IP packet using a MAC PDU received via the radio link and sends the IP packet to the higher-layer router.  
         [0014]      FIG. 2  illustrates communication paths between users in the conventional broadband wireless communication system.  
         [0015]     Referring to  FIG. 2 , User # 1  and User # 2  have been registered to a first RAS  210 , while User # 3  has been registered to a second RAS  220 . User # 1  and User # 3  belonging to different RASs communicate with each other in Path # 1  running between them through the first RAS  210 , a router  200 , and the second RAS  220 . User # 1  and User # 2  belonging to the same RAS communicate with each other in Path # 2  running between them through the first RAS  210  and the router  200 . In this way, a data communication path is established between users via the router  200  (or access router).  
         [0016]     Path # 1  and Path # 2  are set up in the same signaling procedure. Regarding Path # 2 , User # 1  and User # 2  perform IEEE 802.16 network entry and then a Dynamic Service Add (DSA) procedure for data transmission. During the DSA procedure, User # 1  and User # 2  each are allocated different downlink and uplink CIDs from the first RAS  210 . It is assumed that User # 1  has an uplink CID of CID 100  and a downlink CID of CID 200 , while User # 2  has an uplink CID of CID 300  and a downlink CID of CID 400 .  
         [0017]     User # 1  first sends data to the first RAS  210  using CID  100 . The first RAS  210  converts the data to an IP packet and forwards the IP packet to the router  200 . The router  200  identifies the destination (User # 2 ) of the IP packet and sends the IP packet to the first RAS  210  to which User # 2  has been registered. The first RAS  210  checks the destination (User # 2 ) of the IP packet and sends the traffic to User # 2  using the downlink CID 400  of User # 2 .  
         [0018]     As described above, in the conventional system, when communications occur between users within the same RAS, there is no way for the RAS to find out that the communications occur within its coverage area. Thus, an inefficient communication path is established, which runs through the router above the RAS. As a consequence, unnecessary traffic is increased between the RAS and the router. The broadband wireless communication system supports up to 1 Gbps between the RAS and the MS. Hence, upon generation of unnecessary traffic, network resources are consumed as much and user-requested Service of Quality (QoS) cannot be ensured.  
         [0019]     Considering that the broadband wireless communication network may evolve into an ad-hoc or multi-hop network, data communications may take place frequently between users within the same RAS. If the router above the RAS routes traffic to a destination, QoS cannot ensured and time delay occurs particularly to real-time traffic such as voice communication, thereby impeding service provisioning.  
       SUMMARY OF THE INVENTION  
       [0020]     An aspect 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 aspect of the present invention is to provide a point-to-point emulation apparatus and method for an RAS in a broadband wireless communication system.  
         [0021]     Another aspect of the present invention is to provide an apparatus and method for enabling users within the same RAS to communicate with each other without intervention from a higher-layer system through point-to-point emulation in a broadband wireless communication system.  
         [0022]     A further aspect of the present invention is to provide an apparatus and method for, in case of communications between users within the same RAS, sending traffic data directly to a corresponding user without forwarding the traffic data to a higher-layer router in the RAS in a broadband wireless communication system.  
         [0023]     The above aspects are achieved by providing a point-to-point emulation apparatus and method in a broadband wireless communication system.  
         [0024]     According to one aspect of the present invention, in a communication apparatus in an RAS in a broadband wireless communication system, a MAC layer extracts a MAC PDU from uplink data received from a physical layer and transmits the MAC PDU to an emulation layer. The emulation layer identifies a destination of the MAC PDU received from the MAC layer, and if the MAC PDU is associated with communications between terminals registered to the same RAS, the emulation layer converts a header of the MAC PDU and transmits the MAC PDU with the converted header to the MAC layer, for transmission to the destination terminal.  
         [0025]     According to another aspect of the present invention, in a communication apparatus in an RAS in a broadband wireless communication system, a database manages an ID of a source terminal and an ID of a destination terminal for communications between terminals registered to the RAS by mapping the ID of the source terminal to the ID of the destination terminal. A header converter, upon receipt of traffic data from the source terminal, converts a header of the traffic data using the database to transmit the traffic data to the destination terminal on a downlink.  
         [0026]     According to a further aspect of the present invention, in a communication method in an RAS in a broadband wireless communication system, an ID of a source terminal and an ID of a destination terminal are registered in a database by mapping the ID of the source terminal to the ID of the destination terminal, for communications between terminals registered to the RAS. Upon receipt of traffic data from the source terminal, a header of the traffic data is converted using the database, for transmission to the destination terminal on a downlink.  
         [0027]     According still another aspect of the present invention, in a communication method in an RAS having a database for managing an ID of a source terminal and an ID of a destination terminal for communications between terminals registered to the same RAS by mapping the ID of the source terminal to the ID of the destination terminal, upon receipt of traffic data from a terminal, an ID is acquired from the traffic data. It is determined whether the ID is registered in the database. If the ID is registered in the database, an ID of a destination terminal to communicate with the terminal is acquired from the database. The ID of the destination terminal is written in the traffic data and the traffic data is transmitted to the destination terminal on a downlink. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]     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:  
         [0029]      FIG. 1  illustrates a hierarchical protocol architecture of an RAS in a conventional broadband wireless communication system;  
         [0030]      FIG. 2  illustrates communication paths between users in the conventional broadband wireless communication system;  
         [0031]      FIG. 3  illustrates a hierarchical protocol architecture of an RAS in a broadband wireless communication system according to the present invention;  
         [0032]      FIG. 4  illustrates the structure of a MAC PDU in an IEEE 802.16 system;  
         [0033]      FIG. 5  illustrates the structure of a MAC header in the IEEE 802.16 system;  
         [0034]      FIG. 6  is a detailed block diagram of a Point-To-Point Emulation (PTPE) layer according to the present invention;  
         [0035]      FIG. 7  is a flowchart illustrating a procedure for processing a signaling message in the PTPE layer according to the present invention;  
         [0036]      FIG. 8  is a flowchart illustrating a procedure for processing traffic in the PTPE layer according to the present invention; and  
         [0037]      FIG. 9  illustrates communication paths between users in the broadband wireless communication system according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]     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.  
         [0039]     The present invention provides a technique for, during communications between users registered to the same RAS or Base Station (BS), sending traffic data to a corresponding user without forwarding the traffic data to a higher-layer router by the RAS.  
         [0040]      FIG. 3  illustrates a hierarchical protocol architecture of an RAS in a broadband wireless communication system according to the present invention.  
         [0041]     Referring to  FIG. 3 , the protocol stack of the RAS includes a PHY layer  300 , a MAC layer  310 , a PTPE (Point-to-Point Emulation) layer  320 , and a convergence sublayer  330 .  
         [0042]     The convergence sublayer  330  converts data associated with digital audio/video multicast, digital telephony, and Internet connection in compliance with an 802.16 MAC protocol. The convergence sublayer  330  converts an IP packet to a MAC PDU with a corresponding CID and provides the MAC PDU to the PTPE layer  320 . It also converts a MAC PDU received from the PTPE layer  320  to an IP packet and sends the IP packet to a higher-layer router above the RAS.  
         [0043]     The PTPE layer  320  preserves a mapping table (hereinafter, a PTPE table) for managing source CIDs and destination CIDs for communications between users within the same RAS. The PTPE layer  320  analyzes the header of a MAC PDU received from its lower MAC layer  310 . If determining that the header is associated with communications between users within the same RAS, the PTPE layer  320  converts the MAC PDU header referring to the PTPE table and provides the MAC PDU header to the MAC layer  310 . Otherwise, the PTPE layer  320  transfers the received MAC PDU to its higher layer, i.e. the convergence sublayer  330 . On the other hand, the PTPE layer  320  provides a MAC PDU received form the convergence sublayer  330  to the MAC layer  310 .  
         [0044]     The MAC layer  310  controls access to a common wireless medium and controls flows of data and control signals according to the MAC protocol that specifies the time when the RAS or an MS starts transmission. In addition, the MAC layer  310  creates a frame with MAC PDUs received from the PTPE layer  320  and provides the frame to the PHY layer  300 . The MAC layer  310  also extracts MAC PDUs from data received from the PHY layer  300  and provides the MAC PDUs to the PTPE layer  320 .  
         [0045]     The PHY layer  300  processes the frame data received form the MAC layer  310  by coding, modulation, IFFT, and RF modulation, for transmission on a radio link. For reception, the PHY layer  300  processes a signal received on the radio link by RF demodulation, FFT, demodulation, and decoding and provides the processed signal to the MAC layer  310 .  
         [0046]     The PTPE table designed to manage communications between users within the same RAS has the following configuration shown in Table 2.  
                           TABLE 2                                   Source CID   Destination CID                           124   234           .   .           .   .           .   .                      
 
         [0047]     In Table 2, source CID indicates the uplink CID of a source MS that sends data, and destination CID indicates the downlink CID of a destination MS.  
         [0048]     Now a description will be made of the format of a MAC PDU according to the present invention.  
         [0049]      FIG. 4  illustrates the structure of a MAC PDU in an IEEE 802.16 system.  
         [0050]     Referring to  FIG. 4 , the MAC PDU transmitted via a radio link is so configured that a Generic MAC Header  401  precedes Payload  403  and a Cyclic Redundancy Check (CRC)  405  follows the Payload  403 .  
         [0051]     The Generic MAC Header  401  is formatted as illustrated in  FIG. 5 . Referring to  FIG. 5 , the Generic MAC Header includes a Header Type (HT) for writing header type information therein, an Encryption Control (EC) for providing encryption control information, a Type for identifying Payload, a CRC Indicator (CI) indicating the presence or absence of the CRC, an Encryption Key Sequence (EKS) for providing an encryption key sequence, a Length (LEN) indicating the length of the MAC PDU, and a Header Check Sequence (HCS) for writing a header check sequence code therein.  
         [0052]     The MAC PDU is identified as a signaling message (e.g. a DSA message) or traffic data according to the value of the Type field.  
         [0053]     In accordance with the present invention, when a signaling message (i.e. DSA) indicates communications between users within the same RAS, the PTPE layer  320  registers the source and destination CIDs of the users in the PTPE table. The PTPE layer  320  checks whether the CID of a MAC PDU received from the lower layer exists in the PTPE table. If the CID is found in the PTPE table, which implies communications between users within the same RAS, it writes a corresponding destination CID in the header of the MAC PDU and provides the MAC PDU to the MAC layer, instead of transferring the MAC PDU to the higher layer.  
         [0054]      FIG. 6  is a detailed block diagram of the PTPE layer  320  according to the present invention.  
         [0055]     Referring to  FIG. 6 , the PTPE layer  320  includes a receiver  601 , a controller  603 , a header converter  605 , a transmitter  607 , and a PTPE table  609 .  
         [0056]     In operation, the receiver  601  analyzes the header of a MAC PDU received from the MAC layer  310 . If the analysis indicates that the MAC PDU is a DSA message, the receiver  601  provides the MAC PDU to the controller  603 . If the analysis indicates that the MAC PDU is traffic, the receiver  601  determines whether the CID of the MAC PDU exists in the PTPE table  609 . In the presence of the CID in the PTPE table  609 , the receiver  601  provides the MAC PDU to the header converter  605  and otherwise, it provides the MAC PDU to the convergence sublayer  330 .  
         [0057]     The controller  603  analyzes the signaling message received from the receiver  601  and determines whether the destination of the MAC PDU is a user registered to the RAS, i.e. whether the MAC PDU is associated with communications between users within the same RAS. In case of communications between users within the same RAS, the controller  603  registers the source CID and destination CID of the MAC PDU in the PTPE table  609  by mapping them and then transfers the signaling message to the convergence sublayer  330 . If the MAC PDU is not associated with communications between users registered to different RASs, the controller  603  sends the signaling message directly to the convergence sublayer  330 . Thus, the controller  603  manages the PTPE table  609 .  
         [0058]     For example, a signaling message (DSA) defined by IEEE 802.16e includes Automatic Repeat reQuest (ARQ) and Convergence Sublayer (CS) parameters. The CS parameter indicates the IP address of a destination. Therefore, communications between users within the same RAS can be identified using the IP address of the destination of the DSA message.  
         [0059]     The header converter  605  acquires a destination CID referring to the PTPE table  609  using the CID of the MAC PDU received from the receiver  601 . The header converter  605  writes the destination CID in the header of the MAC PDU for downlink transmission and sends the MAC PDU to the transmitter  607 .  
         [0060]     The transmitter  607  transfers MAC PDUs received from the convergence sublayer  330  and MAC PDUs emulated in the PTPE layer  320  to the MAC layer  310 , for downlink transmission.  
         [0061]      FIG. 7  is a flowchart illustrating a procedure for processing a signaling message in the PTPE layer  320  according to the present invention.  
         [0062]     Referring to  FIG. 7 , the PTPE layer  320  monitors reception of a signaling message (e.g. DSA) from a lower layer (e.g. the MAC layer) in step  701 . Upon receipt of the signaling message, the PTPE layer  320  acquires the IP address of a destination from the signaling message in step  703 .  
         [0063]     In step  705 , the PTPE layer  320  checks whether the user of the destination is registered to the RAS, i.e. whether the signaling message is associated with communications between users within the same RAS.  
         [0064]     In case of communications between users within the same RAS, the PTPE layer  320  maps the uplink CID of a source MS that has transmitted the signaling message to the downlink CID of the destination MS in the PTPE table  609  in step  707  and goes to step  709 .  
         [0065]     If the source MS and the destination MS are not registered to the same RAS, the PTPE layer  320  sends the signaling message to a higher layer (e.g. the convergence sublayer) in step  709  and ends the algorithm.  
         [0066]      FIG. 8  is a flowchart illustrating a procedure for processing traffic in the PTPE layer  320  according to the present invention.  
         [0067]     Referring to  FIG. 8 , the PTPE layer  320  monitors reception of a MAC PDU from a lower layer (e.g. the MAC layer) in step  801 . Upon receipt of the MAC PDU, the PTPE layer  320  acquires a CID from the header of the MAC PDU in step  803 .  
         [0068]     In step  805 , the PTPE layer  320  checks whether the CID is registered in the PTPE table  609 , i.e. whether the MAC PDU is destined for another user registered to the same RAS.  
         [0069]     In the absence of the CID in the PTPE table  609 , the PTPE layer  320  just transfers the MAC PDU to a higher layer (e.g. the convergence sublayer) in step  807 .  
         [0070]     If the MAC PDU is traffic destined for another user registered to the same RAS, the PTPE layer  320  reads a destination CID corresponding to the CID from the PTPE table  609 , writes the destination CID in the header of the MAC PDU, and provides the MAC PDU to the lower layer in step  809 .  
         [0071]      FIG. 9  illustrates communication paths between users in the broadband wireless communication system according to the present invention.  
         [0072]     Referring to  FIG. 9 , User # 1  and User # 2  have been registered to a first RAS  910 , while User # 3  has been registered to a second RAS  920 . User # 1  and User # 3  belonging to different RASs communicate with each other in Path # 1  running between them through the first RAS  910 , a router  900 , and the second RAS  920 . User # 1  and User # 2  belonging to the same RAS communicate with each other in Path # 2  running between them through the first RAS  910 . In this way, users registered to the same RAS conduct communications via the RAS alone without intervention from a higher-layer router.  
         [0073]     Regarding setup of Path # 2 , User # 1  and User # 2  perform IEEE 802.16 network entry and then a DSA procedure for data transmission. When User # 1  request DSA, User # 1  notifies the first RAS  910  of the IP address of User # 2  as a destination. The first RAS  910  determines whether User # 2  is registered to the first RAS  910  by searching its PTPE table. Because User # 2  is registered to the first RAS  910 , the first RAS  910  maps the uplink CID of User # 1  (a source ID) to the downlink CID of User # 2  (a destination CID) in the PTPE table (Table 2). Then upon receipt of traffic data destined for User # 2  from User # 1 , the first RAS  910  converts the header of the traffic data using the PTPE table and sends the traffic data to the User # 2  on the downlink, instead of forwarding the traffic data to a higher-layer router.  
         [0074]     In accordance with the present invention as described above, in the case of communications between users registered to the same RAS, a communication path is efficiently established between them by sending traffic data directly to a destination through point-to-point emulation in the RAS, without forwarding the traffic data to a higher-layer router (access router). The resulting prevention of an unnecessary traffic increase between the RAS and the router leads to a guarantee of the QoS of real-time traffic such as voice.  
         [0075]     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.