Abstract:
An apparatus for allocating one or more connection identifiers in a base station of a wireless communication system is used in a base station. The base station has a function of allocating one or more connection identifiers used for specific call communication between the base station and a mobile station. The apparatus includes a unit for defining one or more connection identifiers used for the specific call communication and one or more burst profiles that are attributes related to wireless communication using the one or more connection identifiers. Also included is a unit for broadcasting the one or more connection identifiers used for the specific call communication and the one or more burst profiles to the mobile station.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present invention claims priority to Japanese Patent Application No. JP 2007-284545, filed Oct. 31, 2007, which is incorporated in its entirety by reference herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The embodiments discussed herein are directed to a method and apparatus for allocating a connection identifier (CID) in a wireless communication system, such as a WiMAX system, and particularly to a technique for allocating a CID for reducing time until the establishment of call connection. 
         [0004]    2. Description of the Related Art 
         [0005]    WiMAX (Worldwide Interoperability for Microwave Access) is a communication connection standard. WiMAX is used for the so-called last one mile and the like in an area where the laying of a broadband line is difficult. WiMAX is also a standard of a wireless communication technology that is expected to be used as a communication connection standard for high speed mobile communication. WiMAX is intended for wireless communication covering a medium and long distance area in a range of several km to several tens of km. WiMAX is technology that forms a MAN (Metropolitan Area Network) exceeding a LAN (local area network). 
         [0006]    The standardization of WiMAX is promoted by the IEEE 802.16 Working Group and WiMAX Forum, an industry organization, to ensure interconnectivity between different equipment. 
         [0007]    In the WiMAX standard, BS connection management part  1401 - 2  in BS  1401  and MS connection management part  1402 - 2  in MS  1402  execute a communication connection establishment control operation, as shown in  FIG. 14 , while the BS transmission and reception part  1401 - 1  in the base station (hereinafter referred to as “BS”)  1401  and the MS transmission and reception part  1402 - 1  in the mobile station (hereinafter referred to as “MS”)  1402 , which is a portable terminal, perform wireless communication. 
         [0008]    At this time, BS  1401  and MS  1402  exchange and determine an identifier called a connection identifier (hereinafter referred to as “CID”) with each other. BS  1401  and MS  1402  also perform user data communication using this determined CID. 
         [0009]      FIG. 15  is an operation sequence diagram showing procedures until a CID is allocated and user data flows between BS  1401  and MS  1402  shown in  FIG. 14  in the WiMAX standard. 
         [0010]    First, the channel scan procedure of operation S 1501  is carried out. In this procedure, the operations of downstream channel complement and synchronization establishment are executed. MS connection management part  1402 - 2  searches for WiMAX wireless signals from BS  1401  and receives messages of DCD (Downlink Channel Descriptor), UCD (Uplink Channel Descriptor), DL-MAP (Downlink Map), and UL-MAP (Uplink Map), in which information on the channel is written, according to this procedure. 
         [0011]    Next, the initial ranging procedure of operation S 1502  is carried out. In this procedure, first, MS  1402  sends a ranging code message to BS  1401 . In response to this, timing adjustment information, output adjustment information, frequency adjustment information, and the like are transmitted from BS  1401  to MS  1402  in order that BS  1401  continuously receives a signal from MS  1402 . Next, MS  1402  sends a RNG-REQ message to BS  1401 . In response to this, BS connection management part  1401 - 2  allocates to MS  1402  a basic connection ID (hereinafter referred to as “basic CID”) and a primary connection ID (hereinafter referred to as “primary CID”). The basic connection ID and the primary connection ID are used for the subsequent message exchange, using a RNG-RSP message. The BS connection management part  1401 - 2  simultaneously records these CIDs in a connection identifier database (hereinafter referred to as “CID-DB”)  1401 - 3  ( FIG. 14 ). After this, message exchange between BS  1401  and MS  1402  is carried out using a fixed CID in each procedure until the transport connection establishment procedure of operation S 1505 . The fixed CID is the above-described basic CID or primary CID. 
         [0012]    Next, the basic capability procedure of operation S 1503  is carried out. In this procedure, MS connection management part  1402 - 2  transmits the basic function of MS  1402  to BS  1401 , using a SBC-REQ message. Then, BS connection management part  1401 - 2  transmits a function common to BS  1401  and MS  1402  to MS  1402 , using a SBC-RSP message. 
         [0013]    Subsequently, the authentication/encryption procedure of operation S 1504  is carried out. In this procedure, a control operation in which BS  1401  authenticates MS  1402  is carried out. Specifically, MS connection management part  1402 - 2  transmits an authentication request to BS  1401  using an AuthRequest message. In response to this, BS connection management part  1401 - 2  carries out the authentication of MS  1402 . If the authentication is successful, BS connection management part  1401 - 2  transmits an authentication key to MS  1402 , using an AuthReply message. 
         [0014]    Next, the registration procedure of operation S 1505  is carried out. In this procedure, network parameters are determined between BS  1401  and MS  1402  using a REG-REQ message that is transmitted from MS connection management part  1402 - 2  to BS  1401 , and a REG-RSP message that is transmitted, in response to this, from BS connection management part  1401 - 2  to MS  1402 . 
         [0015]    Subsequently, the transport connection procedure of operation S 1506  is carried out. In this procedure, MS connection management part  1402 - 2  or BS connection management part  1401 - 2  requests of MS  1402  or BS  1401  the setting of a service flow. The service flow setting is a pass for performing data communication using a DSA-REQ message. The BS connection management part  1401 - 2  or MS connection management part  1402 - 2  that receives the DSA-REQ message responds using a DSA-RSP message and establishes a service flow. At this time, BS connection management part  1401 - 2  selects an unused CID by performing an inquiry to CID-DB  1401 - 3 . The BS connection management part  1401 - 2  then transmits the CID as a transport connection ID (hereinafter referred to as “transport CID”) for user data transfer, with service flow parameters, to MS  1402 , using a DSA-RSP message. Also, BS connection management part  1401 - 2  records information on the allocation of the transport CID in CID-DB  1401 - 3 . 
         [0016]    When MS  1402  first starts data transmission using this transport CID, the bandwidth allocation procedure of operation S 1507  is carried out. In this procedure, a request for the allocation of a bandwidth for data transmission is performed by MS  1402  to BS  1401 . MS connection management part  1402 - 2  performs bandwidth ranging and requests of BS  1401  the allocation of a bandwidth for transmitting a bandwidth request message for notifying a necessary bandwidth. By reflecting the result of this request in a UL-MAP message, BS connection management part  1401 - 2  allocates to MS  1402  a bandwidth for transmitting a bandwidth request message. By transmitting a bandwidth request message using this allocated bandwidth, MS connection management part  1402 - 2  performs a request for a bandwidth necessary for the upstream line to BS  1401 . BS connection management part  1401 - 2  transmits the result of this request to MS  1402 , using an UL-MAP message. 
         [0017]    Subsequently, MS  1402  transmits and receives user data to and from BS  1401  using the transport CID. Upstream user data from MS  1402  to BS  1401  is transmitted using a bandwidth determined by the above-described UL-MAP message. 
         [0018]    In this manner, in the conventional WiMAX standard, user data communication is started with many procedures as described above. In urgent communication, on the other hand, such as an emergency call, there is a strong desire to omit sequences as much as possible to reduce time until connection and to start communication immediately. 
         [0019]    Also, the Ministry of Land, Infrastructure and Transport, and the National Police Agency promote ITS (Intelligent Transport Systems) in which road traffic problems, such as a traffic accident jam, are solved by networking people, roads, and vehicles with information using leading-edge information communication technology. When WiMAX wireless communication is applied to the communication technology for ITS, BS-MS communication should be performed within a limited service area and for a short time because the moving speed of a vehicle in which an MS is mounted is fast. Particularly, information on safety (the notification of the risk of an intersection accident, and the like) should be instantaneously transmitted. 
         [0020]    However, in the above-described conventional art, a CID is determined on the BS side and transmitted to the MS, so that time is required for the exchange. 
         [0021]    A technique described in Japanese Laid-Open Patent Publication No. 2006-526308 is a technique in which a BS broadcasts uplink channel information (UL-MAP) including one or more CIDs to an MS. The MS selects a CID randomly for a connection request and transmits a connection request message to the BS. But, this technique is not a technique for selecting a transport CID for user data transmission. 
         [0022]    Also, a technique described in Japanese Laid-Open Patent Publication No. 2001-53675 is a technique in which a BS allocates and transmits an unused CID for user data transmission to an MS. But, in this technique, the BS performs allocation determination, so that time for notifying the allocated CID from the BS to the MS is required. 
       SUMMARY OF THE INVENTION 
       [0023]    According to an aspect of embodiments, an apparatus for allocating one or more connection identifiers in a base station of a wireless communication system, the apparatus being used in a base station that has a function of allocating one or more connection identifiers used for specific call communication between the base station and a mobile station, the apparatus includes a unit for defining one or more connection identifiers used for the specific call communication and one or more burst profiles that are attributes related to wireless communication using the one or more connection identifiers. Also included is a unit for broadcasting the one or more connection identifiers used for the specific call communication and the one or more burst profiles to the mobile station. 
         [0024]    The above-described embodiments of the present invention are intended as examples, and all embodiments of the present invention are not limited to including the features described above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a configuration diagram of first and second embodiments; 
           [0026]      FIG. 2  is an operation sequence diagram of the first embodiment; 
           [0027]      FIG. 3  is a diagram of the WiMAX frame structure of the first embodiment; 
           [0028]      FIG. 4  is a diagram of the UL-MAP message format of the first embodiment; 
           [0029]      FIGS. 5A and 5B  are diagrams explaining the effect of the first embodiment; 
           [0030]      FIG. 6  is an operation sequence diagram of the second embodiment; 
           [0031]      FIG. 7  is a diagram explaining the operation of the second embodiment; 
           [0032]      FIG. 8  is a diagram of the UL-MAP message format of the second embodiment; 
           [0033]      FIG. 9  is a configuration diagram of a third embodiment; 
           [0034]      FIG. 10  is a diagram explaining the operation of the fourth embodiment (1); 
           [0035]      FIG. 11  is a diagram explaining the operation of the fourth embodiment (2); 
           [0036]      FIG. 12  is a diagram explaining the operation of the fifth embodiment; 
           [0037]      FIG. 13  is a diagram of the UL-MAP message format of the fifth embodiment; 
           [0038]      FIG. 14  is a configuration diagram of the related art; and 
           [0039]      FIG. 15  is an operation sequence diagram of the related art. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0040]    Reference may now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
         [0041]    Embodiments will be described below in detail with reference to the drawings. 
       First Embodiment 
       [0042]      FIG. 1  is a configuration diagram of a first embodiment. 
         [0043]    Base station (hereinafter referred to as “BS”)  101  constitutes a base station of a WiMAX wireless communication system. BS  101  comprises a base station transmission and reception part (hereinafter referred to as “BS transmission and reception part”)  101 - 1 , a base station connection management part (hereinafter referred to as “BS connection management part”)  101 - 2 , a connection ID database (hereinafter referred to as “CID-DB”)  101 - 3 , and an emergency call burst profile creation part  101 - 4 . 
         [0044]    MS  102  constitutes a mobile station of the WiMAX wireless communication system. MS  102  comprises a mobile station transmission and reception part (hereinafter referred to as “MS transmission and reception part”)  102 - 1 , a mobile station connection management part (hereinafter referred to as “MS connection management part”)  102 - 2 , and a connection identifier determination part (hereinafter referred to as “CID determination part”)  102 - 3 . 
         [0045]    In the first embodiment, emergency call burst profile creation part  101 - 4  in BS  101  can determine burst profiles and emergency call CIDs. Burst profiles are areas where MS  102  can randomly determine and use a transport CID. The emergency call burst profile creation part  101 - 4  can transmit them to the MS  102  side via BS connection management part  101 - 2  and BS transmission and reception part  101 - 1 . 
         [0046]      FIG. 2  is an operation sequence diagram of the first embodiment, and  FIG. 3  is a diagram showing frame structures in accordance with the WiMAX standard in the first embodiment. 
         [0047]    In the first embodiment, the parts (# 1  to # 5 ) of an uplink (UL) frame shown in  FIG. 3  are used for an emergency call. Other parts (# 6  to #n) are used for user data transmission and reception in accordance with a general WiMAX standard. In other words, the first embodiment can coexist with conventional WiMAX wireless communication. 
         [0048]    BS connection management part  101 - 2  in  FIG. 1  writes a burst profile in a UL-MAP message and transmits it to the MS  102  side via BS transmission and reception part  101 - 1 , as a channel scan procedure shown by operation S 201  in  FIG. 2 . The burst profile comprises parameters such as the uplink (UL) frame structure in  FIG. 3 , the modulation scheme of each burst, and a coding rate. Also, BS connection management part  101 - 2  writes a CID used at this time in CID-DB  101 - 3 . 
         [0049]    MS connection management part  102 - 2  in  FIG. 1 , with timing shown by operation S 202  in  FIG. 2 , allows CID determination part  102 - 3  in  FIG. 1  to randomly determine a transport CID used for user data transmission from among one or more CIDs transmitted by the UL-MAP message that is received via MS transmission and reception part  102 - 1 . The MS connection management part  102 - 2  starts transmission by the user using the determined CID. 
         [0050]      FIG. 4  is a diagram showing the data format of the UL-MAP message (UL_MAP_IE: uplink map information element) in the frame structure in  FIG. 3  in the first embodiment. 
         [0051]    CIDs that are already assigned in WiMAX wireless communication are written in the UL-MAP message, also in a normal WiMAX standard. In the first embodiment, emergency call UL burst CIDs are also similarly transmitted by the UL-MAP message. 
         [0052]    However, when emergency call UL burst CIDs coexist with CID notification in the normal WiMAX standard, emergency call CIDs are set to, for example, numbers 60,000 and greater so that MS  102  does not erroneously select a CID used in the normal WiMAX standard. CID determination part  102 - 3  in  FIG. 1  randomly selects from among CIDs of numbers 60,000 and greater among CIDs transmitted by the UL-MAP message. This arrangement can be optionally determined between BS  101  and MS  102 . 
         [0053]    In the first embodiment, the UL-MAP format shown in  FIG. 4  that is defined as the WiMAX standard is utilized as it is. In the standard, CIDs that are dynamically allocated in response to an allocation request are written in the UL-MAP, but in the first embodiment, emergency call CIDs that are determined by emergency call burst profile creation part  101 - 4  and BS connection management part  101 - 2  in  FIG. 1  are fixedly written. 
         [0054]    In the first embodiment, a plurality of MSs  102  each randomly select from one or more CIDs broadcast from BS  101 , so that CID contention may occur among the plurality of MSs  102 . 
         [0055]    For example, when contention occurs between two MSs  102 , two cases can occur. The two cases are case 1: the possibility that BS  101  receives the signal of either MS  102 , or case 2: the possibility that BS  101  receives the signals of both MSs  102  and cannot demodulate the data of either MS  102 . 
         [0056]    BS  101  passes the packet to a relay process in case 1 and discards the packets in case 2. The operation after discard depends on whether a retransmission procedure is supported or not. When a retransmission procedure, such as ARQ and HARQ, is supported, BS  101  and MSs  102  operate according to the procedure. When the retransmission procedure is not supported, BS  101  simply discards the received packets, and the control of retransmission is left to an end-to-end (host application) operation. 
         [0057]    In either case, MS  102  decides that contention occurs when it detects once or continuously a predetermined number of times that there is no response at the application level when the retransmission procedure is not supported or that there is no ACK response when the retransmission procedure is supported, and MS  102  performs CID selection again. 
         [0058]    In this manner, in the first embodiment, in BS  101 , one or more burst profiles and one or more CIDs that can be used for an emergency call are defined by emergency call burst profile creation part  101 - 4  without a bandwidth allocation request from MS  102 , and the one or more CIDs and the one or more burst profiles are broadcast in the UL-MAP message. Then, in MS  102 , an emergency call CID is randomly selected by MS connection management part  102 - 2  and CID determination part  102 - 3 . 
         [0059]    As described above, in the first embodiment, message exchange for call establishment using a basic CID is omitted between BS  101  and MS  102 , so that the basic CID allocation operation in BS  101  is unnecessary, and the initial ranging procedure can be omitted. 
         [0060]    Also, by omitting the basic capability procedure, BS  101  cannot obtain information on what function is supported by MS  102 , but in the first embodiment, there is no problem if BS-MS exchange is performed, fixedly using only functions that should be necessarily provided as the WiMAX standard. 
         [0061]    In the first embodiment, the authentication/encryption procedure can be omitted by not carrying out authentication and encryption for an emergency call. 
         [0062]    In the first embodiment, BS  101  does not perform the management of which MS  102  is connected to BS  101  for an emergency call, so that the management of MSs  102  by the registration procedure is also unnecessary. 
         [0063]    Also, in the first embodiment, a transport CID is randomly selected in MS  102 , so that the transport connection establishment procedure is also unnecessary. In this case, BS connection management part  101 - 2  fixedly has service flow parameters corresponding to each CID, and the service flow parameters are uniquely determined when the CID is determined. 
         [0064]    Further, emergency call bandwidth allocation is uniquely determined corresponding to each CID by BS connection management part  101 - 2 , so that the bandwidth allocation procedure can also be omitted. 
         [0065]    In the above manner, the initial ranging procedure, basic capability procedure, authentication/encryption procedure, registration procedure, transport connection establishment procedure, and bandwidth allocation procedure that are necessary in the WiMAX standard can be omitted. 
         [0066]      FIG. 5A  is a diagram showing a measured value of time for a conventional transport connection establishment procedure.  FIG. 5B  is a diagram showing a measured value of time for a conventional bandwidth allocation procedure. As seen from these diagrams, in the first embodiment, the time for emergency call establishment can be reduced by  105  ms by omitting the transport connection establishment procedure and the bandwidth allocation procedure. 105 ms is, for example, the time during which a car running at a speed of 90 km/h moves 2.6 m, and is effective as time reduction for conveying emergency information. 
         [0067]    Also, the measured values shown in  FIGS. 5A and 5B  are the shortest measured values when there is one MS  102 , so that when there are a plurality of MSs  102 , time for the transport connection establishment procedure and the bandwidth allocation procedure is several times longer, therefore, in such a case, the first embodiment can provide greater effect. 
         [0068]    Also, as a whole, a time reduction of 40 frames (200 ms) or more can be expected, when each procedure is converted to 10 frames, by omitting the initial ranging procedure, the basic capability procedure, the authentication/encryption procedure, and the registration procedure. 
       Second Embodiment 
       [0069]    The configuration of a second embodiment is similar to that of the first embodiment shown in  FIG. 1 . 
         [0070]      FIG. 6  is an operation sequence diagram of the second embodiment. Operation S 201  in  FIG. 6  is similar to that in  FIG. 2 . 
         [0071]    In the second embodiment, when emergency call burst profile creation part  101 - 4  and BS connection management part  101 - 2  in  FIG. 1  broadcast one or more emergency call CIDs and one or more burst profiles in a UL-MAP message, they simultaneously notify one or more currently unused CIDs by referring to CID-DB  101 - 3  (operation S 301  in  FIG. 6 ). 
         [0072]    BS connection management part  101 - 2  detects CIDs used from the received uplink (UL) frame and registers the CIDs used in CID-DB  101 - 3 .  FIG. 7  is a diagram showing an example of the registration of CID-DB  101 - 3 . BS connection management part  101 - 2  broadcasts one or more unused CIDs (0x07D4 and 0x07D5 in the example in  FIG. 7 ) to the MS  102  side by referring to this registration content. 
         [0073]    BS connection management part  101 - 2  determines used/unused CIDs, for example, by determining whether each CID is used or not in the immediately preceding one frame or continuous frames. 
         [0074]    MS connection management part  102 - 2  allows CID determination part  102 - 3  to randomly select a CID to be used from among one or more CIDs that are described in the UL-MAP message and unused (operation S 302  in  FIG. 6 ). 
         [0075]      FIG. 8  is a diagram showing the data format of the UL-MAP message (UL_MAP_IE) in the second embodiment. 
         [0076]    Also in the second embodiment, the UL-MAP format that is defined as the WiMAX standard is utilized as it is, as in the first embodiment ( FIG. 4 ). In this case, an undefined part in the UL-MAP that is prepared for extension is used. In the second embodiment, the UIUC of emergency call CID is set to  11  in  FIG. 8 . When this UIUC is  11 , the status of use of CID (CID status) is written in an UL_Extended-2 IE( ) area that is prepared for extension. When the CID is unused, the value of CID status is set to 0x00. When the CID is in use, the value of CID status is set to 0x01. 
         [0077]    By the configuration of the second embodiment as described above, MS  102  can randomly select a CID from among one or more currently unused CIDs, so that CID collision by a plurality of MSs  102  can be avoided. 
       Third Embodiment 
       [0078]      FIG. 9  is a configuration diagram of a third embodiment. Parts denoted by the same numerals as in the configuration diagram of the first embodiment shown in  FIG. 1  have the same function as in the first embodiment. 
         [0079]    In the third embodiment, in MS  102 , an emergency call CID it uses is previously fixedly held in mobile station CID hold part (hereinafter referred to as “MS-CID hold part”)  901 . MS connection management part  102 - 2  sees a UL-MAP message that is broadcast as in the first embodiment, and transmits an uplink burst at a burst position corresponding to its CID. 
         [0080]    By the configuration of the third embodiment as described above, the possibility of CID contention when a plurality of MSs  102  exist can be avoided, and also, it is possible to omit the function of randomly selecting a CID to simplify the apparatus. 
       Fourth Embodiment 
       [0081]    This embodiment shows an example of operation when an MS is mounted in a vehicle and the vehicle passes through a plurality of adjacent service areas, based on any of the above-described first to third embodiments. 
         [0082]      FIG. 10  is a diagram explaining the operation of the fourth embodiment (1). 
         [0083]    In this example, when vehicle  1001  in service area  1  moves and enters service area  2 , vehicle  1001  performs channel scan again and obtains a CID because in service area  2 , a UL-MAP message corresponding to the burst profiles of the area is broadcast. 
         [0084]      FIG. 11  is a diagram explaining the operation of the fourth embodiment (2). 
         [0085]    In this example, an emergency call burst position and CID are common to each cell, and this example is configured so that they can be continuously used when there is no user in a cell into which vehicle  1101  moves. 
       Fifth Embodiment 
       [0086]    In this embodiment, emergency call bursts are allocated once per two frames, as shown in  FIG. 12 , to increase the number of emergency calls, based on any of the above-described first to third embodiments. 
         [0087]    In this case, an MS can transmit per  10  ms ( 5  ms for allocation once per frame) so that the transmission is slow, but there is a merit that the number of MSs can be increased. 
         [0088]    In order to notify to the MS side whether emergency call bursts are sent once per a plurality of frames or sent per frame, for example, in a UL-MAP message format shown in  FIG. 13  as in  FIG. 8 , period information (“period” and the like) should be added to UL_Extended-2_IE( ). 
         [0089]    By the above-described embodiments, procedures for establishing a call, such as an initial ranging procedure, basic capability procedure, authentication/encryption procedure, registration procedure, transport connection establishment procedure, and bandwidth allocation procedure, which are necessary in the WiMAX standard, can be omitted, so that time necessary for the establishment of a specific call, such as an emergency call, can be reduced. 
         [0090]    Also, a mobile station can randomly select a connection identifier from among one or more currently unused connection identifiers, so that connection identifier collision by a plurality of mobile stations can be avoided. 
         [0091]    Also, by the above-described embodiments, the possibility of connection identifier contention when a plurality of mobile stations exist can be avoided, and also, it is possible to omit the function of randomly selecting a connection identifier to simplify the apparatus. 
         [0092]    Also, by enabling to randomly allocate a transport CID within an MS, sequence message exchange can be omitted, and the MS can transmit and receive user data immediately after channel search 
         [0093]    Although a few preferred embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.