Abstract:
Disclosed is a ISDN subscriber accommodating and accessing system having: subscriber side controlling means for accommodating plurality of ISDN subscribers, which is provided with a frame relay function which is defined by a link access protocol (LAP) and a partial terminating function; access network (AN) side controlling means having a frame relay function which is defined by the LAP and a function for terminating an interface line; and local exchange device (LE) side terminal means having a function to terminate a frame of the LAP via the interface line; wherein the ISDN subscriber accommodating and accessing system limits the number of frame relays for confirming a link to be intercommunicated between the respective means.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an ISDN subscriber accommodating and accessing system. More specifically, the present invention relates to an ISDN subscriber accommodating and accessing system for decreasing traffic in an accommodating and accessing system apparatus.  
         BACKGROUND OF THE INVENTION  
         [0002]    [0002]FIG. 1 is an intercommunication sequence view of an example of a conventional ISDN subscriber accommodating and accessing system. According to this conventional example, in step  61 , in an access network AN (Access Network), information I (Information) frame I (0, 0) including a transmission order number N (s)=0 and a reception order number N(r)= 0  of ISDN subscriber is only relayed to a local exchange apparatus (LE) side terminating device but it is not terminated.  
           [0003]    The LE side terminating device starts from N(s)=2, N(r)=0, receives the I (0, 0) frame from the subscriber in step  62  and transmits a RR (Receive, Ready) frame RR (1) showing that the LE side terminating device is capable of receiving as transmittal confirmation thereof. Subsequently, in step  63 , the LE side terminating device transmits an I frame I (2, 1) including N(s)=2, N(r)=1 to the subscriber.  
           [0004]    In step  64 , the subscriber receives a frame I (2, 1) and transmits a frame RR ( 3 ) to the LE side terminating device. In step  65 , a frame RR ( 1 ) is transmitted and received between the subscriber and the LE side terminating device. In step  66 , a frame RR (3) is transmitted and received between the subscriber and the LE side terminating device.  
           [0005]    Thus, in the case that no frame is flowed between the subscriber and the LE side terminating device during T203 timer, the RR frame RR (1) to be transmitted in step  65 , is only relayed through AN (step  66 ).  
           [0006]    According to the above-described conventional ISDN subscriber accommodating and accessing system, the access network (AN) has to relay all frames from ISDN subscribers to the local exchange device (LE) under the ISDN protocol.  
           [0007]    On this account, in the case that there are few communication channels in a constitution such that radio transmission is used between a subscriber accommodating apparatus for accommodating the ISDN subscriber and the local exchange device (LE), this constitution has a line concentration function of n:m (n&gt;m). When the line concentration ratio is high and there are many ISDN subscribers, there occurs a problem such that a heavy load is given to a line section, which is line-concentrated.  
           [0008]    Because, the RR frames are periodically transmitted and received between the ISDN subscriber and the local exchange device (LE) even when there are few numbers of transmission of I frame per subscriber (low traffic).  
           [0009]    Also, there may exist a subscriber terminal such that the ISDN subscriber is continuously connected such as a PVC (Permanent Virtual Circuit). This subscriber terminal transmits the RR frame even when it is not used actually and it does not transmit the I frame. Therefore, in this case, the traffic of the I frame increases. Further, since each ISDN subscriber terminal can use multiple terminal identifying TEIs (Terminal Equipment Identifiers), there occurs a problem such that traffic increases by the number of TEIs.  
           [0010]    Also, in order to make the frame of all ISDN subscribers frame-relayed, the access network (AN) is required to have resources in large quantities. Therefore, this involves a problem such that the access network becomes expensive.  
           [0011]    Furthermore, since the transmission of RR frame caused by the T203 timer does not include user data of the ISDN subscriber, this involves a problem such that the throughput in frame relay of I frame deteriorates.  
         SUMMARY OF THE INVENTION  
         [0012]    An ISDN subscriber accommodating and accessing system according to the present invention is characterized by comprising subscriber side controlling means for accommodating plurality of ISDN subscribers which is provided with a frame relay function which is defined by a link access protocol (LAP) and a partial terminating function, access network (AN) side controlling means having a frame relay function which is defined by the above-described LAP and a function for terminating an interface line, and local exchange device (LE) side terminal means having a function to terminate a frame of the above-described LAP via the above-described interface line. The above-described ISDN subscriber accommodating and accessing system limits the number of frame relays for confirming a link to be intercommunicated between the above-described respective means.  
           [0013]    Further, the ISDN subscriber accommodating and accessing system according to the present invention is characterized in that, in the case that an ISDN subscriber who is contained in the AN device portion which is connected to the above-described LE side terminal means by a VS interface (ETS300-324, 300-347) line is in a communication state, the intercommunication for confirming a link in a RR frame due to a T203 timer which is defined by an existing ISDN protocol is established between the above-described ISDN subscriber and the above-described subscriber side controlling means and between the above-described AN side controlling means and the above-described LE side terminal means.  
           [0014]    Alternatively, the ISDN subscriber accommodating and accessing system according to the present invention is characterized in that the above-described subscriber side controlling means has an analyzing portion for identifying varieties of LAPV5 frames which are received from the ISDN subscriber, a processing portion for editing the frame by analysis of the above-described RR frame, and a subscriber N(r) value conserving portion for conserving a N(r) value which is included in the RR frame which is received from the above-described ISDN subscriber. In the case that the above-described received N(r) value of the RR frame is identical with the above-described conserved N(r) value, the RR frame including the above-described conserved N(r) value is transmitted to the above-described ISDN subscriber in accordance with the T203 timer function which is defined by the ISDN protocol. Alternatively, in the case that the above-described received N(r) value is not identical with the above-described conserved N(r) value, the above-described received RR frame which is updated to the above-described conserved N (r) value is transmitted to the above-described AN side controlling means.  
           [0015]    Further, the ISDN subscriber accommodating and accessing system according to the present invention is characterized in that the above-described AN side controlling means has an analyzing portion for identifying varieties of LAPV5 frames which are received from the above-described LE side terminal means, a processing portion for editing the frame by analysis of the above-described RR frame, and a LE side reception N(r) value conserving device for conserving a N(r) value which is included in the RR frame. In the case that the above-described received N(r) value of the RR frame is identical with the above-described conserved N(r) value, the RR frame including the above-described conserved N(r) is transmitted to the above-described LE side terminal means in accordance with a T203 timer function which is defined by the ISDN protocol and in the case that the above-described received N(r) value is not identical with the above-described conserved N(r) value, the above-described received RR frame which is updated to the above-described conserved N (r) value is transmitted to the above-described subscriber side controlling means.  
           [0016]    Alternatively, the ISDN subscriber accommodating and accessing system according to the present invention is characterized by comprising a subscriber side radio device for accommodating a plurality of ISDN subscribers who are connected by a fixed line and having a frame relay function of a frame which is defined by a LAPV5-DL, a partial terminating function and a radio communication function, a radio base station for terminating a V5 interface line, having a frame relay function of a frame which is defined by the above-described LAPV5-DL and a partial terminating function and being connected to the above-described subscriber side radio device via a radio relay device, and the above-described LE side device for accommodating the frame from the above-described radio base station by the above-described V5 interface line of the above-described LAPV5-DL.  
           [0017]    Alternatively, the ISDN subscriber accommodating and accessing system according to the present invention is characterized in that the above-described radio relay device has an analyzing portion for identifying varieties of LAPV5 frames which are received from the ISDN subscribers who are connected by air, a processing portion for editing the frame by analysis of the above-described RR frame, and a subscriber N(r) value conserving portion for conserving the N(r) value which is included in the RR frame which is received from the above-described ISDN subscriber. In the case that the above-described received N(r) value of the RR frame is identical with the above-described conserved N(r) value, the RR frame including the above-described conserved N(r) is transmitted to the above-described ISDN subscriber in accordance with the T203 timer function which is defined by the ISDN protocol and in the case that the above-described received N(r) value is not identical with the above-described conserved N(r) value, the above-described received RR frame which is updated to the above-described conserved N (r) value is transmitted to the above-described radio base station.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is an intercommunication sequence view of an example of a conventional ISDN subscriber accommodating and accessing system;  
         [0019]    [0019]FIG. 2 is a block diagram of an embodiment according to the present invention;  
         [0020]    [0020]FIG. 3 is a block diagram of another embodiment according to the present invention;  
         [0021]    [0021]FIG. 4 is a detailed block diagram of the present embodiment;  
         [0022]    [0022]FIG. 5 is an intercommunication sequence view of a frame of the present embodiment; and  
         [0023]    [0023]FIG. 6 is a flow chart for explaining an operation of the present embodiment.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    Preferable embodiments of the present invention will be explained below with reference to the drawings. FIG. 2 is a block diagram of an embodiment according to the present invention. According to the present embodiment, a subscriber side device  6  contains a plurality of ISDN subscribers  8  and has a subscriber side controlling device  7  having a relay function of a frame which is defined by a LAP (Link Access Protocol) and a partial terminating function. The subscriber side device  6  is connected to a relay line  9 .  
         [0025]    An AN (Access Network) side device  4  is provided with an AN side controlling device  5  having a relay function of a frame which is defined by a LAP and a function to terminate the frame from an interface line  3  and is connected to the subscriber side device  6  via the relay line  9 .  
         [0026]    A LE (Local Exchange) device  1  is provided with a LE side terminating device  2  having a function to terminate a frame which is defined by the LAP via the interface line  3  from the AN side device  4 .  
         [0027]    [0027]FIG. 3 is a block diagram of another embodiment according to the present invention. In the present embodiment, a LE side terminating device  12  of a local exchange (LE) device  11  to be connected by V5 interfaces (ETS: European Telecommunication Standard) ETS300-324 and  327  terminates a link access protocol (LAP) V5 data link sublayer (DL) via a V5 interface line  3 .  
         [0028]    An access network (AN) device portion  1 A is configured by a radio base station  14 , a radio relay device  19  and a subscriber side radio device  16 .  
         [0029]    The subscriber side radio device  16  connects a radio transmission and reception function and a plurality of ISDN (Integrated Services Digital Network) subscribers  18  with a fixed-line to accommodate them. A subscriber side controlling device  17  has a frame relay function of a frame which is defined by a LAPV5-DL and a partial terminating function.  
         [0030]    The radio base station  14  terminates the V5 interface line  13  to be connected to the LE side device  11  and is provided with an AN side controlling device  15  having a relay function of a frame which is defined by the LAPV5-DL. Further, the radio base station  14  is connected to a subscriber side radio device  16  by a radio transmission and reception function via the radio relay device  19 .  
         [0031]    [0031]FIG. 4 is a detailed block diagram of the AN side controlling device  15  and the subscriber side controlling device  17 . A link access protocol (LAP) controlling device  20  is provided with a frame transmission and reception device  21  of a LAPV5 which transmits and receives a frame, a frame analysis device  22  of a LAPV5 which identifies varieties of frames, a RR frame processing device  23  for analyzing and editing a RR (Receive Ready) frame which includes a reception order number N(r) and shows that it is capable of receiving, an ISDN subscriber side N(r) value conserving device  24  for conserving a N(r) which is included in the RR frame which is received from the ISDN subscriber  18 , a LE side reception N(r) value conserving device  25  for conserving the N(r) which is included in the RR frame which is received from the LE side device  11 , and a T203 functional portion  26  having a T203 timer function which is defined by an existing ISDN protocol and an operational function when the T203 timer is time out.  
         [0032]    Next, the operation of the present embodiment will be explained with reference to FIGS. 3, 4,  5  and  6 . In the intercommunication sequence view of a frame in FIG. 5, an information I (Information) frame I (0, 0) including N(s)=0 and a reception order number N(r)=0 of the ISDN subscriber  18  is only relayed to the LE side terminating device  12  of the local exchange (LE) device  11  via the subscriber side controlling device  17  of the subscriber radio device  16 , the radio relay device  19  and the AN side controlling device  15  of the radio base station  14  in step  51  but it is not terminated.  
         [0033]    The LE side terminating device  12  starts from N(s)=2, N(r)=0. The LE side terminating device  12  receives I (0, 0) from the ISDN subscriber  18  in step  52  and transmits the RR (Receive Ready) frame RR (1) showing that it is capable of receiving as transmittal confirmation thereof. Consequently, the LE side terminating device  12  transmits the I frame I (2, 1) including N(s)=2, N(r)=1 to the ISDN subscriber  18  in step  53 .  
         [0034]    In step  54 , the ISDN subscriber  18  receives the frame I (2, 1) and transmits the frame RR (3) to the LE side terminating device  2 .  
         [0035]    In step  55 , the subscriber side controlling device  17  receives the RR frame RR (3) due to the T203 timer from the ISDN subscriber  18  to identify whether the received RR frame RR (3) is subject to frame relay or not. When it is not subject to the frame relay, the frame is not relayed to the LE side terminating device  12  and the subscriber side controlling device  17  transmits the RR frame RR (1) to the ISDN subscriber  18  (step  56 ). Alternatively, the AN side controlling device  15  receives the frame RR (1) from the LE side terminating device  12  in step  55  to identify whether the received frame RR (1) is subject to the frame relay or not. When it is not subject to the frame relay, the AN side controlling device  15  transmits the frame RR (3) to the LE side terminating device  12  (step  56 ).  
         [0036]    Next, the operation of the present embodiment will be explained with reference to a flow chart in FIG. 6. In step  31 , a LAPV5 frame which is transmitted from the ISDN subscriber  18  by the ISDN protocol is received by the frame transmission and reception device  21  of the link access protocol (LAP) controlling device  20  in the AN side controlling device  15  or the subscriber side controlling device  17 . Then, the received LAPV5 frame is transmitted to the frame analysis device  22  and the frame analysis device  22  determines varieties of the received LAPV5 frame. If the received LAPV5 frame is a RR frame which is required to response, the frame is transmitted to the RR frame processing device  23 .  
         [0037]    In step  32 , the RR frame processing device  23  identifies whether the received LAPV5 frame is the LAPV5 frame which is received from the ISDN subscriber  18  or the LAPV5 frame which is received from the LE side device  11 .  
         [0038]    In step  33 , if it is the LAPV5 frame which is received from the ISDN subscriber  18 , the N(r) value which is conserved in the ISDN subscriber side reception N(r) value conserving device  24  is taken out therefrom to be compared with the N(r) value in the received RR frame.  
         [0039]    Alternatively, in step  33 , if the N(r) value in the received RR frame is different from the conserved N(r) value, the N(r) value which is conserved in the ISDN subscriber side reception N(r) value conserving device  24  is updated to the N(r) value in the received RR frame (step  35 ) and the received RR frame is transferred to the AN side controlling device  15  (step  40 ).  
         [0040]    Additionally, in step  34 , if the N(r) value in the received RR frame is different from the N(r) value which is conserved in the LE side reception N(r) value conserving device  25 , the conserved the N(r) value is updated to the N(r) value in the received RR frame (step  36 ) and the received RR frame is transferred to the subscriber side controlling device  17  (step  40 ).  
         [0041]    In the case that the T203 timer of the ISDN subscriber  18  or the LE side terminating device  12  detects time out by using the T203 timer function which is defined by the ISDN protocol, the T203 functional portion  26  performs the operation which is defined by the existing ISDN protocol. In this case, communication is established between the ISDN subscriber  18  and the LE side terminating device  12 , so that no-communication state between the ISDN subscriber  18  and the subscriber side controlling device  17  and no-communication state between the LE side terminating device  12  and the AN side controlling device  15  are identical.  
         [0042]    In the present embodiment, the constitution of the LAP controlling device  20  has the T203 function of the existing ISDN protocol. However, the LAP controlling device  20  may not have the T203 functional portion  26 . In this case, when no-response state of the ISDN subscriber  18  or the LE side terminating device  12  is generated, it is detected by the fact that when another (of the ISDN subscriber and the LE side terminating device  12 ) I frame (accommodating user data) is transmitted, the RR frame is not returned, so that the AN device portion  1 A does not detect it.  
         [0043]    The radio relay device  19  does not contain the subscriber. However, it may contain the ISDN subscriber by air by being provided with the function of the LAP controlling device  20 .  
         [0044]    As described above, according to the present invention, limiting the number of the frames for confirming a link, which is intercommunicated between subscriber side controlling means for accommodating the ISDN subscriber and access network side controlling means to be connected to the local exchange side device by the interface line, the traffic of the circuit between the subscriber side controlling means and the access network side controlling means is capable of being decreased.