Abstract:
When channel allocation is scheduled in a dynamic TDMA frame for communications with a plurality of terminals and then the scheduling results are reflected in a frame table, a shift register is used as the frame table. The shift register comprises a plurality of register units coupled in tandem. Each of the register units is allocable to a channel for one of the plurality of terminals. A shift controller is coupled to the shift register, and controls the shift register such as to write a new channel defining data at a given register unit and collectively shift a plurality of channel defining data respectively stored in a plurality of register units so as to make space for said new channel defining data at said given shift register.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the invention  
           [0002]    The present invention relates generally to a data communications system using TDMA (Time Division Multiple Access) frames, and more specifically to techniques of scheduling channel allocation in the dynamic TDMA frame.  
           [0003]    2. Description of Related Art  
           [0004]    As is well known in the art. TDMA allows each user to access the full spectrum allocation for a fraction of the time. TDMA is a technique in which the available spectrum resource is occupied by one modulated carrier, and each of the whole “n” channels gains access to that carrier for 1/n of the time in an ordered sequence. However, such a fixed channel TDMA technique has proven unable to meet the situation where the data rate required varies every moment and the user demands a high date rate in the broadband communications. In order to solve the problems with the fixed channel TDMA technique, dynamic TDMA has been proposed which dynamically assigns the channels in the TDMA frame. With the dynamic TDMA, it is possible to obviate the difficulties inherent in the fixed channel TDMA. By way of example, the dynamic TDMA technique is adopted in HIPERLAN/2 (High PERformance LAN type 2) that is an European standard specified by ETSI (European Telecommunications Standards Institute) protect BRAN (Broadband Radio Access Networks) in 5 GHz frequency band.  
           [0005]    Before turning to the present invention, it is advantageous to briefly describe, with reference to FIGS.  1 - 5 , the background of the present invention,  
           [0006]    [0006]FIG. 1 is a sketch which schematically shows one example of a short-range high-speed radio access system provided in indoor or outdoor environments. An access point AP serves as a base station and a bridge between a wireless network and a larger Ethernet network, the Internet, etc. A plurality of mobile terminals (denoted by MT 1  to MTx), which are located in a service area  10  of the access point AT, are able to establish bidirectional radio links (uplink and downlink) with the access point AP and/or with each other via the access point AP.  
           [0007]    [0007]FIG. 2 schematically shows one TDMA frame wherein a plurality of channels are dynamically allocated so as to realize an effective use of the limited capacity in the TDMA frame. Although many kinds of channels are defined in the HIPERLAN/2, only three channels are referred to in the instant disclosure for the sake of simplifying the description. That is to say, as shown in FIG. 2, the TDMA frame generally comprises a broadcast channel BCH, downlink channels, and uplink channels. A guard space is typically provided between the downlink and uplink channels. When generating each TDMA frame, if no further channel generation becomes unnecessary, the remaining time space in the frame is blanked. Each channel consists of a plurality of time slots that are numbered as shown in FIG. 2, and thus, each channel can be defined by specifying the time slots at start and end positions of the channel.  
           [0008]    The broadcast channel BCH, which may be called a frame header, is used to advise the mobile terminals MTs of the TDMA frame structure in order to enable the communications between the access point AP and the mobile terminals MTs. More specifically, the broadcast channel BCH indicates the frame&#39;s front position so as to establish frame synchronization at each of the mobile terminals MTs. Further, the BCH is used to advise each mobile terminal MT of the length of the data (downlink and/or uplink), and further to inform each MT where the data is located in the frame using the time slot numbers at the start and end of the data. To this end, the broadcast channel BCH includes the following pieces of information with respect to each packet: the MT number (viz., MT identification (ID)), the kind of channel to be used (viz,, user channel or control channel), the distinction between the downlink and the uplink via which the packet is conveyed, the start position (viz., starting time slot number) of the packet in the frame, and the packet data length. Thus, the broadcast channel BCH serves to define the frame structure in order that the access point AT is able to communicate with the mobile terminals MTs using the dynamically allocated channels.  
           [0009]    In the dynamic TDMA, in the case where there exist two or more channels directed to the same mobile terminal MT in the downlink channels and/or the uplink channels, these channels are respectively neighbored in the downlink channels and/or the uplink channels so as to reduce overheads which otherwise are required for each channel. As one simple example, if the access point AP receives a large amount of data from the network, which is directed to a certain mobile terminal, the access point AP assigns all the channels of the frame to the same mobile terminal MT so as to transmit the data at a high rate to the mobile terminal. The dynamic channel (viz., time slot) allocation in the frame is referred to “scheduling” that is carried out at a scheduler, which will be described in more detail with reference to FIGS. 3 and 4.  
           [0010]    Referring to FIG. 3, the hardware arrangement of the access point AT is schematically shown in block diagram form. As shown, the access point AT generally comprises a transceiver (Rx/Tx)  18 , a framer  20 , a packet buffer unit  22 , a control data processor  24 , a scheduler  26 , an interface  28  provided between the access point AP and the network, and a frame table  30 , all of which are functionally coupled as illustrated. The present invention is particularly concerned with the scheduler  26  and the frame table  30 , and as such, the remaining blocks are briefly described.  
           [0011]    In order to simplify the description of the instant disclosure, it is assumed that the wireless communications have already been established between the access point AP and some of the mobile terminals MTs located in the service area  10  (FIG. 1). When the access point AP receives the user data (packet(s)) from the network via the interface  28 , the user data are successively stored in a buffer B 1  of the packet buffer unit  22  in the order of arrival under the control of a controller  23  provided in the unit  22 . The controller  23  is used to control the data read/write operations with respect to the buffers provided in the packet buffer unit  22 .  
           [0012]    In the instant specification, the data to be transmitted from the access point AP to the mobile terminals MTs may be referred to as downlink data, while the data received at AP from the mobile terminals MTs may be referred to as uplink data.  
           [0013]    The information required for scheduling with respect to each user data (packet) stored in the buffer B 1  is applied to the scheduler  26  via a line L 2 . The information applied to the scheduler  26  includes the address pointer indicating the first address of the packet stored in the buffer B 1 , the mobile terminal ID to which the packet is to be transmitted, a kind of channel (user data channel in this case) to be generated for the packet, the number of time slots (viz., data length) to be allocated to the packet in the frame.  
           [0014]    On the other hand, the control data, which are transmitted from the mobile terminals MTs to the access point AP, are successively applied to a buffer B 2  of the packet buffer unit  22  via lines L 4  and L 6 . The control data stored in the buffer B 2  are successively applied, via a line L 8 , to the control data processor  24  to be analyzed thereat. That is to say, the control data processor  24  determines the data rate (viz., the number of time slots used in the frame) which the mobile terminal MT requires, the number of control data which the mobile terminal further wishes to transmit to the access point AP, etc. The control data to be transmitted to the mobile terminal MT are applied, via a line L 10 , to a buffer B 3  of the packet buffer unit  22  and then stored therein.  
           [0015]    Further, the control data processor  24  supplies, via a line L 12 , the scheduler  26  with the information needed for scheduling with respect to the control data and/or user data channels. That is to say, in the case of the control data, the control data processor  24  supplies the scheduler  26  with the address pointer indicating the first address of the control data stored in the buffer B 3 , the mobile terminal ID to which the control data is transmitted, a kind of channel (control data channel in this case) to be generated, the number of time slots (data length) to be allocated to the control channel in the frame for the mobile terminal specified above. On the other hand, in the case of user data to be transmitted to the access point AP, the control data processor  24  supplies the scheduler  28  with the mobile terminal ID from which the user data is to be transmitted, the address pointer of a buffer  4  into which the transmitted user data is stored, a kind of channel (user data channel in this case) to be generated, the number of time slots (data length) to be allocated to the user data channel in the frame for the mobile terminal specified above.  
           [0016]    In addition, the scheduler  26  receives the information needed to transmit data over the broadcast channel BCH, which broadcasting data is stored in a buffer B 5  of the packet buffer unit  22 . The data to be transmitted using the broadcast channel BGH have been described above.  
           [0017]    The scheduler  26  is supplied with the above-mentioned information for frame scheduling, and determines each structure of the TDMA frames that are repeatedly transmitted to the mobile terminals MTs at predetermined time intervals. In brief, the scheduler  26  determines, with respect to each mobile terminal related to the frame, the kind of channel (control data or user data channel), the number of channels, the channel location in the frame, etc. The frame structure determined by the scheduler  26  is reflected on the frame table  30  which takes the form of an random access memory (RAM) functionally divided into a plurality of memory blocks MB 1 -MBy. The memory block MB 1  is dedicated to the broadband channel, and the remaining blocks MB 2 -MBy are assigned to the channels for the control data and/or the user data.  
           [0018]    The scheduling is carried out considering preference of data to be transmitted and received. Although the data are in practice classified into more than two different preference groups, it is assumed for the sake of simplicity that the control data is given a higher priority relative to the user data. Therefore, the scheduler  26  assigns the control data in preference of the user data in the frame, and if the frame table  30  affords to accept the user data, then the scheduler  26  writes the user channel defining data into the available memory blocks. It is not seldom that all the memory blocks MB 2 -MBy are assigned to the control channel defining data except for the memory block MB 1  dedicated to the broadband channel BCH.  
           [0019]    The scheduler  26  initially selects the leading memory block MB 1  and writes thereinto the following channel defining data: the channel information indicating that the channel assigned to MB 1  is the BCH; the number of time slots (which is typically fixed) allocated to the BCH, the address pointer specifying the location of the BCH data stored in the buffer  5  of the packet buffer unit  22 , etc. Following this, the scheduler  26  successively selects the subsequent memory blocks MB 2 , MB 3 , . . . , and write thereinto the control channel defining data for use in generating the downlink control channels at the framer  20 . Further, the scheduler  26  selects a memory block which is preceded by the last memory block for the control channel, and assigns the same as the guard space. Thereafter, the scheduler  26  implements the similar operations as mentioned above with respect to the memory blocks to be assigned to the uplink control channels, in the case where one or more memory blocks are left after all the control channel defining data are written into the memory blocks, the scheduler  26  writes the user channel defining data into the memory blocks left over. Contrarily, if the scheduler  26  is unable to store all the control channel defining data currently handled into all the memory blocks MB 1 -MBy, the scheduler  26  waits until the memory blocks become available, and thereafter begins writing the remaining control channel defining data into the memory blocks from MB 2  after writing the BCH channel defining data into MB 1 .  
           [0020]    Referring to FIG. 4, the frame table  30  will be described in more detail in connection with the operations of the scheduler  26  and the framer  20 . As mentioned above, the contents of the frame table  30  reflect the result of the scheduling. The outline of the frame table  30  has already been described, and the descriptions given in the above may be omitted or simplified for brevity. The memory blocks MB 1 -MBy are accessed by the scheduler  26  and the framer  20  as well. The channel defining data stored in the memory block MB 1  assigned to the BCH has been described. Each of the memory blocks MB 2  to MBs in this particular case stores the channel information indicating the mobile terminal ID, a distinction between the control data and the user data, the number of time slots assigned to the mobile terminal, and the address pointer indicative of the first address of the buffer B 1  or B 3  or B 4  in order that the framer  20  is able to retrieve the data related to the mobile terminal defined above.  
           [0021]    The framer  20 , in the first place, accesses the memory block MB 1 , and retrieves the address pointer therefrom which is applied to the packet buffer unit  22  via a line L 14  and reads out the BCH data stored in the buffer  5  of the packet buffer unit  22  using the number of timing slots stored in the MB 1 . The data read out of the buffer  5  is applied to the framer  20  via a line L 16  (FIG. 3). The detail of the data retrieval from the buffer  5  using the number of time slots is not given because the present invention is not concerned therewith. The framer  20  applies the data thus read out of the buffer  5  to the transceiver  18  via a line L 18  (FIG. 3). It is assumed that only the memory blocks MB 2 -MBs are used and the remaining memory blocks are blanked. In a manner similar to the above, the framer  20  successively accesses MB 2 -MBs, and retrieves respectively the address pointers stored therein and reads out the data stored in the corresponding buffer in the packet buffer unit  22 , after which the framer  20  applies the retrieved data to the transceiver  18 .  
           [0022]    In FIG. 4, one example of the TDMA frame outputted from the framer  20  is illustrated. The notation “USER” indicates the user data channel, while “CONT” the control data channel. The TDMA frame shown in FIG. 4 will be understood without difficulty from the descriptions so far given in the instant disclosure.  
           [0023]    When the access point AP receives the data transmitted from a given mobile terminal using the TDMA frame such as shown in FIG. 4, the framer  20  accesses the corresponding MB and retrieves therefrom the information of the memory location of the buffers in the unit  22  into which the received data are to be stored. Thereafter, the framer  20  stores the received data in the predetermined memory area in the unit  22 .  
           [0024]    Returning to the scheduling which is implemented at the scheduler  26 , when the scheduler  26  is going to write a certain new channel defining data into the frame table  30 , if one or more channel defining data directed to the same mobile terminal MT have been stored in the memory block in the same link channel, the new channel defining data is stored into the memory block adjacent to the memory block already used for the same MT. In such a case, after the scheduler  26  determines the memory block into which the new channel defining data is to be written, the scheduler  26  stores the new channel defining data into the memory block. One known technique of writing the new channel defining data into the memory block, which neighbors the memory block already used to store the channel defining data for the same mobile terminal, will be described with reference to FIGS.  5 (A) to  5 (C).  
           [0025]    As shown in FIGS. 5A and 5B, it is assumed that the memory blocks MB 1 -MBm are used to store the channel defining data (FIG. 5A), and further assumed that a new channel defining data for the mobile terminal MT 2  is to be written into the memory block MB 4  (FIG. 5B). In this case, it is necessary to make space for the new channel defining data at MB 4  by moving respectively the contents stored in MB 4  to MBm to MB 5  to MBn one by one. That is to say, the channel defining data shifting inevitably requires that the data stored in the last memory block MBm is first read out and then stored in the next one MBn, and then the data of the memory block MB(m−1) is read out and stored in MBm, and so on, and such operation is repeated until the data stored in MB 4  is moved to MB 5 . It is understood that such data read/write operations at the memory blocks MB 4 -MBn suffers from undesirable consumption of a relatively large amount of time. Further, such a conventional technique has encountered the problem that it may occur that the scheduling can not be completed within the time duration assigned to one TDMA frame.  
         SUMMARY OF THE INVENTION  
         [0026]    It is therefore an object of the present invention to provide a technique, via which the new channel defining data can be inserted into the frame table, and concurrently the channel defining data stored in a plurality of frame table&#39;s storage units can be moved collectively for making space for the new data.  
           [0027]    Another object of the present invention is to provide a technique via which the storage unit in the frame table, into which the new channel defining data is to be written, can be determined in a very short time duration.  
           [0028]    In brief, these objects are achieved by the techniques wherein when channel allocation is scheduled in a dynamic TDMA frame for communications with a plurality of terminals and then the scheduling results are reflected in a frame table, a shift register is used as the frame table. The shift register comprises a plurality of register units coupled in tandem. Each of the register units is allocable to a channel for one of the plurality of terminals. A shift controller is coupled to the shift register, and controls the shift register such as to write a new channel defining data at a given register unit and collectively shift a plurality of channel defining data respectively stored in a plurality of register units so as to make space for said new channel defining data at said given shift register.  
           [0029]    One aspect of the present invention resides in a hardware arrangement for scheduling channel allocation in a dynamic TDMA frame for communications with a plurality of terminals and reflecting the scheduling results in a frame table, comprising: a shift register being used as the frame table, the shift register comprising a plurality of register units coupled in tandem, each of the register units being allocable to a channel for one of the plurality of terminals; and a shift controller being coupled to the shift register, the shift controller controlling the shift register such as to write a new channel defining data into a given register unit and collectively shift a plurality of channel defining data respectively stored in a plurality of register units so as to make space for the new channel defining data at the given register unit.  
           [0030]    Another aspect of the present invention resides in a method of scheduling channel allocation in a dynamic TDMA frame for communications with a plurality of terminals and reflecting the scheduling results in a frame table, comprising the steps of: determining a given register unit among a plurality of register units which are coupled in tandem and are used as the frame table, each of the plurality of register units being allocable to a channel for one of the plurality of terminals; and writing a new channel defining data into the given register unit and collectively shifting a plurality of channel defining data respectively stored in a plurality of register units so as to make space for the new channel defining data at the given register unit. 
       
    
    
     HE DRAWINGS  
       [0031]    The features and advantages of the present invention will become more clearly appreciated from the following description taken in conjunction with the accompanying drawings in which like elements or portions are denoted by like reference numerals and in which:  
         [0032]    [0032]FIG. 1 is a sketch schematically showing a plurality of mobile terminals located in a service area of an access point AP, having referred to in the opening paragraphs;  
         [0033]    [0033]FIG. 2 is a diagram showing one TDMA frame structure, having been referred to in the opening paragraphs;  
         [0034]    [0034]FIG. 3 is a diagram schematically showing an arrangement of the conventional access point AP, having been referred to in the opening paragraphs;  
         [0035]    [0035]FIG. 4 is a diagram showing in detail a frame table shown in FIG. 3, one example of a TDMA frame to be transmitted to the mobile terminals such as shown in FIG. 1, and the blocks functionally coupled to the frame table, having referred to in the opening paragraphs;  
         [0036]    FIGS.  5 A- 5 C are each showing a TDMA frame for describing a conventional technique for shifting the data stored in memory blocks of the frame table one by one, having been referred to in the opening paragraphs;  
         [0037]    [0037]FIG. 6 is a diagram schematically showing an arrangement of an access point AP according to the first embodiment of the present invention;  
         [0038]    [0038]FIG. 7 is a diagram showing in detail a frame table shown in FIG. 6, one example of a TDMA frame to be transmitted to the mobile terminals such as shown in FIG. 1, and the blocks functionally coupled to the frame table;  
         [0039]    [0039]FIG. 8 is a block diagram showing in detail the frame table and a shift controller both shown in FIG. 6;  
         [0040]    FIGS.  9 A- 9 C are each showing a TDMA frame for further describing the first embodiment of the present invention; and  
         [0041]    [0041]FIG. 10 is a diagram schematically showing a second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0042]    A first embodiment of the present invention will be described with reference to FIGS.  6  to  9 C.  
         [0043]    [0043]FIG. 6 is a diagram schematically showing an arrangement of an access point AP, such as illustrated in FIG. 1, in accordance with the first embodiment. As shown in FIG. 6, a frame table unit  38  comprises a shift register  40  used as a frame table, and a shift controller  42 , while a scheduler  44  is arranged to issue a shift pulse. Other than this, the arrangement and operations of the access point AP of FIG. 6 is substantially identical with those of FIG. 3, and as such, the descriptions already made with reference to FIG. 3 will be omitted for the sake of simplifying the instant disclosure. The shift register  40  comprises a plurality of register units RU 1  to RUy whose data shift when inserting a new channel defining data is controlled by the shift controller  42  as will be described later.  
         [0044]    [0044]FIG. 7 is substantial Identical to FIG. 4 except that the memory blocks MB 1 -MBy of FIG. 4 is replaced by the register units RU 1 -RUy, and hence further descriptions of FIG. 7 is deemed redundant, and accordingly, will be omitted for simplifying the disclosure.  
         [0045]    [0045]FIG. 8 is a block diagram showing the frame table unit  38  in detail. As shown, the shift register  40  comprises a plurality of register units RU 1  to RUy each of which comprises a selector SEL, a register REG, and a buffer with an enable terminal. The selector SEL, in response to a high logic level H (for example) applied thereto, selects the data appearing on a line L 80  extending from the scheduler  44 , and otherwise (viz., in the case of a low logic level L) operates such as to select the data stored in the register REG in the preceding register unit. The buffer in each of the register units RU 1  to RUy, in response to a high logic level H, allows the data stored in the corresponding register REG, to pass therethrough. The data thus derived is applied to the scheduler  44  by way of a data output line L 82 . The shift controller  42  comprises a decoder  46 , OR gates denoted by  50 ( 2 ) to  50 (y), and buffers denoted by  52 ( 1 ) to  52 (y), all of which are coupled as illustrated.  
         [0046]    As mentioned above, before the scheduler  44  determines whether a new channel defining data assigned to a given mobile terminal MT is to be inserted such as to neighbor the register unit RU already allocated to the same mobile terminal as the given mobile terminal, it is necessary to examine all the data stored in the register units RU 1  to RUy. To this end, the scheduler  44  successively applies register unit ID codes (each k-bit (for example)) to the decoder  46  so as to respectively ascertain the data in the register units RU 1  to RUy. More specifically, the scheduler  44  initially supplies the decoder  46  with a register unit ID code specifying the register unit RU 1 , in response to which the decoder  46  issues a high logic level H only at the output  1  thereof. The high level H is applied to the selector SEL of the register unit  1 . During the data examining operation currently implemented, no shift pulse is applied to the shift controller  42  and thus the register REG of the register unit RU 1  does not acquire the output of the selector SEL. This implies that the data stored in the register REG of the unit RU 1  remains unchanged and appears on the data output line L 82 , and then applied to the scheduler  44 . Subsequently, the data stored in the registers REGs of the units RU 2 -RUy are successively read out and applied to the scheduler  42 .  
         [0047]    The scheduler  42  checks to determine, using the data applied thereto from the shift register  40  by way of the output line L 82 , whether the mobile terminal related to the new channel defining data has been assigned in the frame table (viz., shift register)  40  with respect to the same link connection. In the case where the check result is affirmative, the new channel defining data is written into the shift register  40  such as to neighbor the register unit assigned to the same mobile terminal, the operation of which will be described with reference to FIGS. 8 and 9A- 9 C.  
         [0048]    [0048]FIG. 9A shows one example of the contents of the register units RU 2  to RUy of the frame table  40 . It is assumed that the register units RU 2  to RUy have respectively been assigned to the control data of a plurality of mobile terminals, and assumed that the new channel defining data to be inserted into the frame table  40  is allocated to the mobile terminal MT 2 . It is further assumed that the new channel defining data is related to the downlink data. Thus, the new channel defining data of the mobile terminal MT 2  is to be written into the register unit RU 4 . On the above assumptions, the scheduler  44  issues the new channel defining data of the mobile terminal MT 2  on the input line L 80 , and applies the register unit ID code to the decoder  46  which, in response to the ID code, issues a high logic level H at the output  4  thereof and low logic levels Ls at the remaining outputs. The high logic level H is applied to the OR gate  50 ( 4 ) whose output takes a high logic level H.  
         [0049]    It is understood that the high logic level H, which appears at the output of the OR gate  50 ( 4 ), allows each of the following OR gates  50 ( 5 ). 50 (y) to issue a high logic level H, and also understood that each of the outputs of the OR gates  50 ( 2 )- 50 ( 3 ) preceding the OR gate  50 ( 4 ) remain unchanged (viz., continue to generate low logic levels Ls). Accordingly, the buffers  52 ( 4 )- 52 (y) are respectively enabled by high logic levels Hs applied to the corresponding enable terminal, while the buffers  52 ( 1 )- 52 ( 3 ) remain unable due to low logic levels Ls applied to the enable terminals thereof.  
         [0050]    Under these conditions, the scheduler  44  applies the new channel defining data of the mobile terminal MT 2  to the shift register (frame table)  40  on the data input line L 80 , and also applies a single shift pulse to the buffers  52 ( 1 )- 52 (y). Therefore, the register REG of RU 4 , in response to the shift pulse, acquires the new channel defining data of the mobile terminal MT 2  by way of the selector SEL of RU 4  in that the decoder  46  issues a high logic level H at the output  4  thereof. In addition, a selector signal SL taking a high logic level H is applied to the selectors SELs of the register units RU 5 -RUy, and thus, each of the selectors SELs of the RU 5 -RUn selects the data stored in the preceding register unit RU. As a result, when a single shift pulse is applied to the shift controller  42 , the data of the mobile terminal MT 2  is written into RU 4 , and concurrently, the data stored in the succeeding RU 4 -RUm are shifted to RU 5 -RUn, respectively. These operations of data insertion and the collective data shift to the right by one are schematically shown in FIGS. 9B and 9C.  
         [0051]    In the case where the scheduler  44  determines that no data has been assigned to the mobile terminal MT to which the new channel defining data is going to be assigned in the frame table  40 , then the scheduler  44  inserts the new channel defining data into the register unit RU which follows the last RU already used to store data in the frame table  40 . Contrarily, in the case that the scheduler  44  finds, in the frame table  40 , two or more data each of which has been assigned to the mobile terminal MT to which the new channel defining data is assigned, the scheduler  44  inserts the new data into the register unit RU which follows the last RU already assigned to the same mobile terminal. In this instance, it is not difficult to operate the scheduler  44  so as to specify the last register unit RU already assigned to the same mobile terminal.  
         [0052]    A second embodiment of the present invention will be described with reference to FIG. 10. As shown, the second embodiment is provided with comparators  90 ( 1 )- 90 (y) and a priority encoder  92 , except for which the second embodiment is substantially identical to the first embodiment. According to the second embodiment, it is no longer required, before implementing the data insertion into the frame table  20 , for the scheduler  44  to successively check the data stored in all the register units RU 1 -RUy in order to ascertain the register unit(s) to which the mobile terminal related to the new channel defining data is also assigned.  
         [0053]    The comparators  90 ( 1 )- 90 (y) are respectively provided such as to receive first inputs from the register units RU 1 -RUy and a second input from the scheduler  44 . Each of the first and second inputs represents the information which indicates “the mobile terminal ID” and “whether the data stored in the register unit is the downlink or uplink data”.  
         [0054]    The priority encoder  92  receives the comparison results from the comparators  90 ( 1 )- 90 (y). In the case where one comparison result indicates the coincidence between the first and second inputs, the priority encoder  92  is able to know the corresponding register unit from the comparison result, and issues a coded data specifying the register unit number at an output line  94 . In this case, it is possible to modify the operation of the priority encoder  92  such as to issue a coded data after adding +1 to the register unit number which the priority encoder  92  has specified.  
         [0055]    On the other hand, in the case the comparison results indicate that two or more neighboring (viz., adjacent) register units are detected which are assigned to an identical mobile terminal, the priority encoder  92  selects one register unit whose position number is the oldest. Further, if all the comparison results indicate no-hit (non-coincidence), then the priority encoder  92  issues data to that effect at an output  96 . The priority encoder  92  applies the outputs thereof to the scheduler  44  which in turn carries out the inserting operations of the new channel defining data as mentioned above depending on the contents of the data received. However, the present invention is not limited to the above, and may be modified so that the priority encoder  92  generates a code representing the youngest register number among the neighboring register units. Further, it is possible to modify the operation of the priority encoder  92  such as to issue a coded data after adding +1 to the above-mentioned oldest register number.  
         [0056]    In the descriptions thus far given, the present invention is applied to a high data rate radio access system. However, the present invention is applicable to the scheduling in the data communication through wire. Further, although the dynamic TDMA is based on TDMA/TDD (Time Division Duplex), the present invention can be applied to the scheduling of the downlink or uplink data. Accordingly, the present invention is applicable to the scheduling of the downlink or uplink data in FDD (Frequency Division Duplex) system.  
         [0057]    The foregoing descriptions show two preferred embodiments and some modifications thereof. However, other various modifications are apparent to those skilled in the art without departing from the scope of the present invention which is only limited by the appended claims. Therefore, the embodiments and modification shown and described are only illustrated, not restrictive.