Patent Publication Number: US-2007121646-A1

Title: Method and apparatus for multiplexing dial-up internet sessions

Description:
TECHNICAL FIELD  
      The present invention relates to a method and apparatus for multiplexing dial-up internet sessions. In particular, it relates to a method and apparatus for multiplexing dial-up internet sessions by combining the dial-up internet sessions in a timeslot.  
     BACKGROUND OF THE INVENTION  
      In data communication, such as Internet access, dial-up connections are made to a local exchange, where the data (internet protocol packets) is terminated in a modem bank. The data is then multiplexed onto an E1 (2.048Mb/s rate, multiplexed line) or multiple E1s for transmission to an Internet Service Provider (ISP). The links between the local exchange and the exchange serving the ISP are composed of E1 trunks, operated at 2Mbits/s or larger STM 1 , digital optical transmission lines, operating at 155Mbits/s. Over these lines, a circuit-switched connection is established per user. Each of these connections occupies 64kbits/s timeslots.  
      Normally, a dial-up Internet connection uses standard 64kbits/s connections across the PSTN to the local exchange. However, the dial-up Internet connection will never actually require a 64kbits/s upstream. This is because currently available digital and analogue modem pairs for use in connecting to the PSTN have data rates of up to 56kbits/s downstream and 33.6kbits/s upstream. Although the maximum downstream data transmission rate is 56kbits/s, a more realistic speed is 40-44kbits/second (the achieved data transmission rate). The achieved data transmission rate is dependent on a number of factors, one of which is the line quality. The data rate is also dependent on the network congestion between the user&#39;s PC or terminal and the remote server or proxy-cache server. This can further reduce the maximum achievable data rate. The data rate can also be affected by the long periods of inactivity when the user is preparing a request or reading a response, for example, which would naturally occur during normal Internet use.  
      There has been a rapid increase in the use of the Internet in recent years and the volumes of data transmitted during Internet access has increased which require increasing resources of the PSTN Network. If the user is achieving a data rate of less than 64kbits/s. then the usage of the channel is not optimum. Since most dial-up connections can expect only circa 40kbits/s, then the usage of the PSTN and/or the circuit-switched connection is never at optimum levels.  
      One solution is to increase the speed of the modems to make these more closely match the rates of the PSTN, E1 or STM1 links. However, there are physical constraints on the speed modems can operate at over normal PSTN connections. The next generation modems will focus on shorter set up times and the ability to place a data connection on hold, so as to take a voice call.  
      Another solution is proposed by U.S. Pat No. 5,809,070 in which the Internet packets are separated between multiple modems. However this system would still transmit the Internet packet over the PSTN at the same rate as mentioned above and usage of the PSTN is not at its optimum.  
     SUMMARY OF THE INVENTION  
      The aim of the present invention is to provide a method and apparatus which enables more efficient use of the PSTN Transit Network. This may be achieved by multiplexing multiple dial-up Internet sessions onto 64kbits/s timeslots.  
      In the present invention, it is proposed to multiplex calls or dial-up connections by combining them in a timeslot(s).  
      According to an aspect of the present invention, there is provided a method of communicating a plurality of calls over a communication link in a plurality of timeslots. Calls identified as calls to an Internet Service Provider (ISP) are combined such that n calls are transmitted in a timeslot, wherein n is a positive integer or fraction.  
      The method may further comprise the step of: de-multiplexing the calls by separating the combined calls into their separate distinct calls.  
      According to a second aspect of the present invention, there is provided apparatus for multiplexing a plurality of calls to an Internet Service Provider (ISP) for transmission in a plurality of timeslots, the apparatus comprising a combining unit for combining n calls to an ISP in an assigned timeslot, wherein n is a positive integer or fraction.  
      According to a third aspect of the present invention, there is provided a communication system for communicating a plurality of calls over a communication link, the communication link transmitting calls in a plurality of timeslots. The system comprises means for identifying a call to an Internet Service Provider and means for multiplexing each call identified as a call to an ISP. The multiplexing means combines n calls identified as a specific type of call in a timeslot, wherein n is a positive integer or fraction.  
      The present invention uses the same concept to dial-up connections over PSTN, between the local exchange serving the end user terminal (for example a modem in a PC), and the local exchange serving the ISP.  
      In effect, multiplexing/demultiplexing apparatus is provided, used for dial-up data connections. On recognising that a call is to an ISP, for example, either by virtue of the B-number, or other method, the call is routed (as a 64kbits/s channel) to the multiplexing apparatus of the present invention, where it is combined with other similar calls before sending it onto the ISP.  
      At the exchange serving the ISP, the calls are again routed through demultiplexing apparatus, and reconstituted as distinct 64kbits/s channels before being passed to the ISP.  
      Therefore, the amount of bandwidth needed to support dial-up Internet traffic is reduced. In this way less of the telephone network is given over to generating Internet traffic. Therefore, service providers can lease less capacity from the network provider to support the Internet traffic and the Network is utilised more efficiently. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  is a block schematic diagram of a communication system incorporating the apparatus in accordance with the present invention;  
       FIG. 2  is a block schematic diagram of the apparatus in accordance with a first embodiment of the present invention;  
       FIG. 3   a  illustrates separate connections of the end user of the communication system of  FIG. 1 ;  
       FIG. 3   b  illustrates the call mapping in accordance with the first embodiment of the present invention;  
       FIG. 4  illustrates the call mapping in accordance with a second embodiment of the present invention;  
       FIG. 5  is a block schematic diagram of the apparatus in accordance with a second and third embodiment of the present invention; and  
       FIG. 6  illustrates the call mapping in accordance with a third embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      With reference to  FIGS. 1, 2 ,  3   a  and  3   b , the first embodiment of the present invention will be described. The communication system comprises a plurality of end users l 00   a  to  100   f , for example user terminals, PCs and modems etc are connected to the PSTN Transit Network via separate connections  105   a  to  105   f  and an access. controller or node  110  as standard in the art. Data transmitted from each end-user  100   a  to  100   f  is routed onto the communication link  130  in separate bandwidths  135   a - 135   f  as shown in  FIG. 3   a . The communication link  130  transfers the data to a local exchange or central office  120  where the data is terminated into a modem bank and multiplexed onto a circuit-switched communication link  140  such as an E1 link, multiple E1s (or T1, STM1, etc). A circuit-switched connection is established over the E1 type link  140  having timeslots of 64kbits/s. Multiplexing apparatus  150 , as shown in  FIG. 2 , according to a first embodiment of the present invention, is incorporated in the central office or local exchange  120 .  
      The multiplexing apparatus  150  comprises an identifier  152  for identifying the type of call transmitted in the separate bandwidths  135   a  to  135   f . The input of the identifier  152  is connected to the communication link  130 . The outputs of the identifier  152  are connected to a combining unit  154  and an output multiplexer  156 . The output multiplexer  156  comprises a plurality of output channels connected to the circuit-switched communication link  140 .  
      An incoming call is routed to the identifier  152  in which the type of call is determined. In the preferred embodiment, the call contains an identifying code such as the B-number. If a call is identified as a conventional call, the call is routed directly to the output multiplexer  156  to be transferred onto the link  140  in accordance with the conventional method mentioned above. If a call is identified as a call to an Internet Service Provider, the call is routed to the combining unit  154 . Here, the call is combined into an assigned timeslot(s) of the circuit-switched communication link  140 .  
      In accordance with the first embodiment, the calls are combined based on a static mapping illustrated in  FIG. 3   b , in which each call is assumed to require the same bandwidth, and the output multiplexer  156  always allows for this bandwidth. Once a connection is made, the timeslot is assigned, regardless of whether it is currently in use or not. The second connection is similar to the first except if the timeslot is not currently in use; it is allocated to the next connection requiring bandwidth.  
      The mapping of calls to timeslots is static and based on a mathematical formula based on the average bandwidth required for dial-up connections, for example: 
 
3(calls)×40bits/ s≦ 2(timeslots)64kbits/ s  
 
      This is a simple mapping allocating 1.5 calls to each timeslot. Although 1.5 calls are combined in this embodiment, it can be appreciated that any number or fraction of calls may be combined, depending on the bandwidth required for the call and the capacity of the link. In formulating the number of calls to be combined, it would also be necessary to consider, for example, the overhead to allow for differentiation of the different calls within the timeslot.  
      As shown in  FIG. 3   a , the multiplexing apparatus  150  receives the separate calls  135   a - 135   f  made by the users  100   a - 100   f.  The multiplexing apparatus  150 , according the present invention, multiplexes the call into assigned timeslots on the inter-exchange link  140 , so that one timeslot contains call  135   a  and a percentage of the call  135   b , the next timeslot contains the remainder of the call  135   b  and the call  135   c , etc. In this way a fixed mapping occurs to allocate each call either to one timeslot in its entirety, or sharing a timeslot with another call. The output channels of the output multiplexer  156  then route the combined calls as normal to the circuit-switched communication link  140 . It would therefore be possible to fit up to 45 calls to an ISP onto 30 channels, a bandwidth saving of 33%.  
      Although not illustrated here, it is appreciated that functionality would be required at the other end of the connection to break-up and re-assemble the affected calls. Thus, at the terminating end, it would be necessary to de-multiplex the  45  calls back into 45 distinct separate connections.  
      The second embodiment according to the present invention comprises a system and method for mapping calls to timeslots dynamically, ie. the way calls are mapped onto the timeslots is based on whether the connections are currently active or not. The mapping ratio is fixed.  
      The apparatus according the second embodiment of the present invention, as shown in  FIG. 5 , is similar to that of the first embodiment. The apparatus of the second embodiment further comprises a scheduler  158  connected to the combining unit  154  and the output multiplexer  156 . The apparatus  150  further comprises a control unit  160  connected to the scheduler  158 , combining unit  154  and the circuit-switched communication link  140 .  
      Internet connections, even while active, are not always transmitting/receiving data at a steady rate. Consequently 6 , not all the connections will have a fixed connection at all times. The scheduler  158  ensures that all connections get access to the bandwidth to the ISP, even though they may not have fixed connections at all times.  
      As illustrated in  FIG. 4 , three connections CALL 1 , CALL 2  and CALL 3  are made. The identifier  152 , as described with reference to the first embodiment above, identifies the type of each call.  
      In this case, it is assumed that connections CALL 1 , CALL 2  and CALL 3  contain calls which have been identified as calls to an Internet Service Provider. These calls are routed to the combining unit  154 . Here the calls are combined by the combining unit  154 . The scheduler  158  and the control unit  160  control the combination of-the calls. The scheduler  158  determines if the call requires bandwidth at the present time, and allocates it to the next free timeslot(s) as required. Each timeslot T 1 , T 2 , T 3  etc is allocated calls on a first come, first served basis. The controller  160  determines when a call no longer needs bandwidth, and informs the scheduler  158  to remove that call from the connection and replace it with another, as required.  
      As illustrated in  FIG. 4 , CALL 1  comprises a plurality of data transmission packets  200   a ,  200   b ,  200   c , CALL 2  comprises a plurality of data transmission packets  210   a ,  210   b ,  210   c  and CALL 3  comprises a plurality of data transmission packets  220   a ,  220   b , and  220   c . In the example illustrated in  FIG. 4 , 1.5 data transmission packets are allocated to each timeslot. Therefore, on receipt of data packets  220   a  and  210   a , these are combined such- that data packet  220   a  is allocated to T 2  and is combined with a percentage (50% in this case) of data packet  210   a , the remainder of data packet  210   a  being allocated to timeslot T 3 . Data packet  200   a  is allocated timeslot T 3  and combined with the remainder of data packet  210   a . Upon termination of the data packet  200   a , the controller  160  determines that the connection CALL 1  no longer requires bandwidth and informs the scheduler  158  to remove CALL 1  from the connection and, upon receipt of the data packet  220   b , allocates this data packet to timeslot T 3 . This is combined with a percentage (50% in this case) of data packet  210   b  and the remainder of data packet  210   b  is allocated to timeslot T 2  and so on.  
      The output channels from the output multiplexer  156  are routed, as normal, to an E1 (or T1, STM1, etc) link  140 .  
      In accordance with the method and system of the second embodiment of the present invention it is possible to fit up to “n” calls to an ISP onto 30 channels, where “n” may typically be in the region of 60-150, resulting in a bandwidth saving of, say, 50-80%.  
      Although not illustrated here, it can be appreciated that functionality would be required at the other end of the connection to break-up and reassemble the affected calls, thus de-multiplexing the calls back onto the distinct separate connections.  
      The third embodiment comprises a system and method for mapping calls to timeslots dynamically, ie. the way the calls are mapped onto timeslots is based on whether the connection is currently active or not and on the bandwidth required for the connection. So, for example, this would utilise a scheduling mechanism to ensure that all connections get access to the bandwidth to the ISP, even though they do not have a fixed connection at all times. This would be a complex mapping, perhaps allocating “n” calls to each timeslot, and relying on the fact that Internet connections even while active are not always transmitting/receiving data at a steady rate.  
      The apparatus according the third embodiment of the present invention is similar to that described above with reference to the second embodiment.  
      As illustrated in  FIG. 6 , three connections CALL 1 , CALL 2  and CALL 3  are made. The identifier  152  as described with reference to the first and second embodiments identifies the type of each call.  
      Assuming that the connections CALL 1 , CALL 2  and CALL 3  as shown in  FIG. 6  have calls identified as calls to an Internet Service Provider, these calls are combined by the combining unit  154 , scheduler  158  and the controller  160 . The scheduler  158  determines if the call requires bandwidth just now, and allocates it the next free timeslot(s) as required. Each timeslot T 1 , T 2 , T 3  etc is allocated calls on a first come, first served basis and the bandwidth needed is based on the measured amount of bandwidth required by the call. The controller  160  determines when the call allocated bandwidth no longer needs bandwidth, and informs the scheduler  158  to remove that call from the connection and replace it with another, as required.  
      As illustrated in  FIG. 6 , the connection of CALL 1  comprises a plurality of data transmission packets  300   a ,  300   b ,  300   c , CALL 2  comprises a plurality of data transmission packets  310   a ,  310   b ,  310   c  and CALL 3  comprises a plurality of data transmission packets  320   a ,  320   b  and  320   c . In the example illustrated in  FIG. 6  data packets  300   a ,  300   b ,  310   a  and  320   c  require a low bandwidth and the remaining data packets require a high bandwidth. On receipt of data packets  320   a  and  310   a , these are allocated to timeslots T 2  and T 3 , respectively. Upon receipt of data packet  300   a , this can be combined with data packet  310   a  in timeslot T 3  as it only requires a low bandwidth. Upon termination of the data packet  320   a , the controller  160  determines that connection CALL 3  no longer requires bandwidth and informs the scheduling means  158  to remove CALL 3  from the connection and upon receipt of the data packet  320   b  allocates this data packet to timeslots T 1  and T 2 . A portion of data packet  310   b  is combined with data packet  320   b  in timeslot T 2  and the remainder of data packet  310   b  is allocated timeslot T 3  as connection CALL 1  no longer requires bandwidth. Data packet  300   b  is then allocated time slot T 3  and combined with the remainder portion of data packet  310   b  and so on.  
      The output channels of the output multiplexer  156  are routed, as normal, to the circuit-switched communication link  140 . In accordance with the method and system of the third embodiment of the present invention it is possible to fit up to “n” calls to an ISP onto 30 channels, where “n” may typically be in the region of 60-150, resulting in a bandwidth saving of, say, 50-80%.  
      Although not illustrated here, it can be appreciated that, at the terminating end, it would be necessary to de-multiplex the calls back onto distinct separate connections.  
      Although preferred embodiments of the method and apparatus of the present invention has been illustrated in the accompanying drawings and described in the forgoing detailed description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous verifications, modifications without departing from the scope of the invention as set out in the following claims.