Abstract:
A multiplexing apparatus multiplexes two or more data streams and output to an arbitrarily selected circuit, and includes a time division switch for multiplexing inputted data and outputting the multiplexed data to a selected circuit, and a memory unit which stores real control data for controlling actual connection operations of the time division switch and virtual control data for controlling virtual connection operations.

Description:
This application is a continuation of international application number PCTJP99/05682, filed Oct. 14, 1999. 

   BACKGROUND OF THE INVENTION, 
   1. Field of the Invention 
   The present invention relates to a multiplexing method, a multiplexing apparatus and a network including the multiplexing apparatus, and especially relates to the multiplexing method and the apparatus that multiplex a plurality of data streams and output to an arbitrarily selected circuit and the network including the multiplexing apparatus. 
   2. Description of the Related Art 
   A time division switch (called TSW hereinafter) not only multiplexes two or more data streams but also often performs cross-connect processing that outputs the multiplexed data to an arbitrarily selected circuit. 
     FIG. 1  shows a block diagram of an example of a multiplexing apparatus  10 . A conventional multiplexing apparatus  10  includes a low-speed multiplexing unit  20  which multiplexes low-speed data supplied from terminal units and outputs to a transmission path  28 , and a cross-connect unit  30  which performs a cross-connect process of the data supplied from the transmission path  28 . 
   The low-speed multiplexing unit  20  and the cross-connect unit  30  assign addresses to the terminal unit, the circuit, and the transmission, path  28 , and have access control memory units  25  and  33  (henceforth ACM), respectively, that store information about relations between the addresses. The TSW  24  and  32  perform the multiplexing and the cross-connect process using the ACM  25  and ACM  33 . 
   Technical progress in recent years has realized an economical high-speed and large-capacity TSW. Accordingly, one TSW unit can now replace the TSW  24  and  32  of  FIG. 1 . 
     FIG. 2  shows a block diagram of another example of a multiplexing apparatus  12 . The multiplexing apparatus  12  of  FIG. 2  replaces the TSW  24  and TSW  32  with one unit of TSW  40 , thereby the low-speed multiplexing unit  20  and the cross-connect unit  30  are combined into one unit. In addition, ACM 42  assigns addresses to terminal units and circuits, and stores information about relations between the addresses. 
   However, since the multiplexing apparatus  10  of  FIG. 1  includes the two TSWs, namely TSW  24  and TSW  32 , there is a problem that delay increases. Moreover, since the two ACMs, namely ACM  25  and ACM  33  are required, synchronization of the ACMs is necessary to attain correct operations. 
   On the other hand, the multiplexing apparatus  12  of  FIG. 2  is structured with one each of TSW (the TSW 40 ) and ACM (the ACM 42 ), avoiding the problems of the delay and the synchronization as in the case with the multiplexing apparatus  10  of  FIG. 1 . However, there emerges another problem in that user convenience in circuit operations is facilitated if the multiplexing process and the cross-connect process are separated. That is, when a user operates a circuit, it is easier to manage the two processes separately, one for multiplexing and the other for cross-connect using two TSWs. 
   SUMMARY OF THE INVENTION 
   In view of the above-mentioned point, the present invention aims at offering a multiplexing method, a multiplexing apparatus, and a network therewith, wherein data for controlling a time division switch is virtually configured in two parts to facilitate management of the time division switch. 
   In order to achieve the above-mentioned objective, the multiplexing apparatus of the present invention includes a time division switch that multiplexes data inputted, and outputs the multiplexed data to a selected circuit, and a memory unit that stores real control data that controls actual connections of the time division switch and virtual control data that controls virtual connections. 
   By providing the two sets of data, namely the real control data and the virtual control data in the memory unit, one time division switch can be configured as if there were two time division switches. Accordingly, while maintaining ease in the management of the time division switch, an economical multiplexing apparatus can be realized. 
   Alternatively, the multiplexing apparatus of the present invention can include a memory unit that contains a first control data that controls connections of the time division switch when multiplexing inputted data, a second control data that controls connections of the time division switch when-outputting the multiplexed data, and virtual control data that virtually connects the first control data and the second control data. 
   In this manner, by separating the real control data to be stored in the memory unit into the first control data and the second control data, it becomes possible to control the multiplexing apparatus as if there were a first time division switch for multiplexing and a second time division switch for outputting the multiplexed data. 
   Moreover, the above-mentioned memory unit of the multiplexing apparatus of the present, invention may be structured such that an address is assigned to each terminal unit that provides data, and each circuit to which the multiplexed data is outputted, and a virtual address is set up to virtually connect the address of the terminal unit and the address of the circuit. 
   In this manner, one time division switch can be handled as if there were two time division switches. 
   Moreover, the above-mentioned memory unit of the multiplexing apparatus of the present invention may be structured such that an n address of a virtual transmission path for virtually connecting the terminal unit and the circuit is set up when setting up connections at the time division switch. 
   In this manner, by assigning an address to each of the terminal units and each of the circuits for outputting multiplexed data and by setting up an address to the virtual transmission path for virtually connecting a terminal unit and a circuit, one time division switch can be handled as if there were two time division switches. 
   Moreover, the memory unit of the multiplexing apparatus of the present invention may be structured such that it detects real control data that is virtually connected by using the virtual control data when controlling connection operations of the time division switch. 
   In this manner, the detected real control data is used to control the connection operations of the time division switch, thereby one time division switch can be handled as if there were two time division switches. 
   Moreover, the multiplexing apparatus of the present invention may further include means for setting up the real control data and virtual control data. 
   This setting up means facilitates setting up of the real control data and virtual control data. 
   Moreover, the multiplexing method of the present invention includes a step of setting up the real control data for controlling actual connection operations of the time division switch that multiplexes inputted data, and outputs the multiplexed data to a selected circuit, a step of setting up the virtual control data for controlling virtual connection operations of the time division switch, a step of virtually connecting the real control data and the virtual control data, and a step of detecting the real control data connected by deleting the virtual control data. 
   In this manner, by providing the two sets of data, namely the real control data and the virtual control data, one time division switch can be handled as if there were two time division switches. Accordingly, while maintaining ease of a time division switch management, an economical multiplexing apparatus can be obtained. 
   Moreover, the multiplexing method of the present invention includes a step of assigning addresses for each terminal unit which supplies data and every circuit through which multiplexed data is outputted, a step of setting up a virtual address that virtually connects the address of the terminal unit and the address of the circuit, a step of virtually connecting the address of the terminal unit and the address of the circuit using the virtual address, and a step for detecting the addresses of the terminal and the circuit that are connected by deleting the virtual addresses. 
   Thus, by assigning addresses and virtual addresses, one time division switch can be handled as if there were two time division switches. 
   A network of the present invention is structured by a multiplexing apparatus that includes a time division switch for multiplexing inputted data and outputting the multiplexed data to a selected circuit, and a memory unit that stores real control data for controlling actual connection operations of the time division switch and virtual control data for controlling virtual connection operations. 
   Thus, by providing the two sets of data, namely the real control data and the virtual control data, in the memory unit, an economical multiplexing apparatus can be realized and as a result, an economical network can be realized. 
   Moreover, in the network of the present invention, the memory unit may be structured with first control data for controlling the connection operations of the time division switch when multiplexing inputted data, second control data for controlling the connection operations of the time division switch when outputting the multiplexed data, and virtual control data for virtually connecting the first control data and the second control data. 
   By separating the first control data from the second control data, it appears to a user that there are a first time division switch for multiplexing and a second time division switch for outputting the multiplexed data, facilitating management of the multiplexing apparatus and realizing an economical multiplexing apparatus. Accordingly, an economical network can be realized. 
   Moreover, the memory unit of the network of the present invention may include the multiplexing apparatus that assigns addresses to each terminal unit that supplies data and every circuit that outputs the multiplexed data, and sets up an address of the virtual transmission path that virtually connects the address of the terminal unit and the address of the circuit. 
   By providing the address of the virtual transmission path that virtually connects the address of the terminal unit and the address of the circuit, a multiplexing apparatus that is able to configure one time division switch as if there were two time division switches can be realized, thereby an economical network is realized. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Features and advantages of the present invention will become clearer by reading the following detailed explanation, referring to an attached drawing. 
       FIG. 1  is a block diagram of an example of a multiplexing apparatus. 
       FIG. 2  is a block diagram of another example of the multiplexing apparatus. 
       FIG. 3  is a figure for explaining operations of an example of a TSW. 
       FIG. 4  is a block diagram of an embodiment of a multiplexing apparatus of the present invention. 
       FIG. 5  is a block diagram of an embodiment of a TSW. 
       FIG. 6  is a block diagram of addresses stored in an ACM. 
       FIG. 7  is a flowchart explaining an embodiment of processing of the multiplexing apparatus of the present invention. 
       FIG. 8  is a block diagram of an example of a network including the multiplexing apparatus of the present invention. 
       FIG. 9  is a detailed block diagram of an embodiment of the multiplexing apparatus of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the following, embodiments of the present invention are described with reference to the accompanying drawings. 
   First, processing of a TSW is explained briefly.  FIG. 3  shows a figure of an example explaining the operation of a TSW  50 . In  FIG. 3(A) , data having four time slots per cycle is supplied to the TSW  50  from an input highway. The data is supplied to the TSW  50  in the sequence of “A, B, C, D, A, B, C, D, and so on”. 
   As shown in  FIG. 3(B) , the data supplied to the TSW  50  is switched according to an address counter  54 , and is written in a data memory unit  52  for every time slot. Then, the data written in the data memory unit  52  is read from the data memory unit  52  to an output highway according to data set beforehand in an access control memory unit (henceforth ACM)  56 . 
   Specifically, the data supplied to the TSW  50  is written in the sequence of “A,B,C,D” in the data memory unit  52 , and read in the sequence of “D-A-B-C” according to the data set in the ACM  56 . By reading the data stored in the data memory unit  52  according to the data set beforehand in the ACM  56 , rearrangement of time slots is realized. 
   Next, a structure of a multiplexing apparatus of the present invention is explained with reference to  FIG. 4 .  FIG. 4  shows a block diagram of an embodiment of a multiplexing apparatus  100  of the present invention. 
   The multiplexing apparatus  100  of  FIG. 4  includes channel boards  101 – 103 , a TSW  110 , an ACM  120 , and multiplex IF boards  131  and  132 . The channel boards  101 – 103  are connected, for example, with a telephone, a terminal unit and the like, and low-speed signals, such as voice and data, are supplied. The multiplex IF boards  131  and  132  are connected to other multiplexing apparatuses and the like through a circuit. 
   After multiplexing low-speed signals supplied from the channel boards  101 – 103 , the TSW  110  performs a cross-connect process, and outputs to the multiplex IF boards  131  and  132 . The processing of the TSW  110  is performed according to addresses and the like stored in the ACM  120 . 
   The ACM  120  includes a real address area that stores addresses actually assigned to terminal units and circuits, and a dummy address area that stores dummy addresses. Further, each of the real address area and the dummy address area includes a low-speed multiplex setting area and a cross-connect setting area. The real address area of the low-speed multiplex setting area and the real address area of the cross-connect setting area are set up through the dummy address area. 
   By preparing the dummy area, the address area of the ACM can be considered as having a virtual two-step structure, appearing as if two TSWs were connected in series, although actually there is only one TSW. Specifically, it is possible to consider that the TSW  110  of  FIG. 4  is divided into two parts, and there is a dummy transmission path between them. 
   Accordingly, an actual circuit setup can be obtained by combining a setup of the low-speed multiplex setting area for a section from a terminal unit to a dummy transmission path and a setup of the cross-connect setting area for a section from the dummy transmission path to a circuit. 
   It is also possible to setup a direct connection of the real address areas without using the dummy address area. Further, a setup between a terminal unit and another terminal unit, and a setup between a circuit and another circuit are also possible. 
   Next, the structure of the TSW is further explained in detail with reference to  FIG. 5 .  FIG. 5  shows a block diagram of an embodiment of the TSW  110 . The TSW  110  includes buffer memory units  111  and  113 , and a high-speed memory unit  112 . 
   The channel boards  101 – 103  and TSW  110  are often connected by a high-speed bus B, and the buffer memory unit  111  is formed for providing synchronization between the bus B and the high-speed memory unit  112 . Further, the multiplex IF boards  131  and  132  and the TSW  110  are often connected by a high-speed bus B, and the buffer memory unit  113  is formed for providing synchronization between the bus B and the high-speed memory unit  112 . 
   Writing addresses and reading addresses stored in the ACM  120  control writing and reading processing of the high-speed memory unit  112 . The writing addresses and the reading addresses stored in the ACM  120  are set up by using an external console  124  connected via an I/O unit  122 . The external console  124  may be an independent unit, or may be structured by adding a keyboard and a display to the multiplexing apparatus  100 . 
   Next, an operation of the multiplexing apparatus  100  is explained with reference to  FIGS. 6 and 7 .  FIG. 6  shows a block diagram of an example of the addresses stored in the ACM  120 .  FIG. 7  shows a flowchart explaining a process of the embodiment of the multiplexing apparatus  100  of the present invention. 
   As shown in  FIG. 6 , the ACM  120  includes a low-speed multiplex area  140 , a virtual patch area  142 , and a cross-connect area  144 . Contents set to the low-speed multiplex area  140  and the cross-connect area  144  are transposed to real setup  150 , according to which actual connections are established through the process shown in the flowchart of  FIG. 7 . 
   In the flowchart of  FIG. 7 , a setting address is inputted, for example, from the external console  124  at step S 10 . Subsequently, the process moves on to step S 20  where a check is made as to whether the inputted address is for the low-speed multiplex area  140 . 
   If it is determined that the inputted address is for the low-speed multiplex area  140  (YES at S 20 ), the process moves on to step S 30 . Otherwise (NO at S 20 ), the process moves on to step S 40 . 
   At step S 30 , a check is made as to whether the inputted setting address is for terminal to terminal. If it is determined that the address is for terminal to terminal (YES at S 30 ), the process moves on to step S 60 . Otherwise (NO at S 30 ), the process moves on to step S 50 . 
   At step S 40 , a check is made as to whether the inputted setting address is for circuit to circuit. If it is determined that the address is for circuit to circuit (YES at S 40 ), the process moves on to step S 80 . Otherwise (NO at S 40 ), the progress moves on to step S 50 . 
   When it is determined that the setting address inputted is not for terminal to terminal at step S 30 , or when it is determined that the setting address inputted is not for circuit to circuit at step S 40 , the process moves on to step S 50 . Then, real addresses of a terminal and a circuit are inputted into the low-speed multiplex area  140  and the cross-connect area  144 , respectively, of the ACM  120 . For example, in  FIG. 6 , an address “aaa” is inputted for a terminal DTE 1  and an address “bbb” is inputted for a circuit EEE. 
   Following step S 50 , the process moves on to step S 70  where virtual patch area information for assigning a virtual address to a virtual transmission path is inputted. Subsequently at step S 90 , addresses set to the low-speed multiplex area  140 , the virtual patch area  142 , and the cross-connect area  144  are read. 
   Then, at step S 100 , contents of the virtual address are removed from the addresses read at S 90 . Further, at step S 120 , real addresses of a terminal and a circuit are set up. 
   In addition, at step S 30 , if it is determined that the setting address is for terminal to terminal (YES at S 30 ), the process moves on to step S 60  where real addresses of the terminals are inputted, without assigning virtual addresses. The process then progresses to step S 110  where the real addresses for terminal-to-terminal are set up. 
   If, at step S 40 , it is determined that the setting address is for circuit to circuit (YES at S 40 ), the process progresses to step S 80  where real addresses of the circuits are inputted, without assigning virtual addresses. Subsequently at step S 130 , the real addresses for circuit-to-circuit are set up. 
   After any one of step S 110 , step  120  and step  130 , the process progresses to step S 140  where the real addresses are stored in the ACM  120 , and then, a circuit is established at step S 150 . 
   Next, a description follows of a network that includes the multiplexing apparatus  100  of the present invention with reference to  FIG. 8 .  FIG. 8  shows a block diagram of an example of the network that includes the multiplexing apparatus  100  of the present invention. 
   Circuit management is easier to perform if a low-speed multiplexing apparatus that multiplexes low-speed signals supplied from voice or data terminals, and a cross-connect apparatus that is a component of-a digital path are separated. Especially in a mesh network as shown in  FIG. 8 , a role of the cross-connect apparatus in circuit setting becomes important, and it is necessary to separate the circuit setup of the cross-connect apparatus from circuit setup of the low-speed multiplexing processing. 
   In addition, in a control center of a network, when installing a network management system NMS that stores circuit setup data of the whole network and performs an alternate routing when a fault and the like occurs, it is possible to separate setting data of each ACM similarly as above. 
   Next, a structure of the multiplexing apparatus of the present invention is further explained in detail.  FIG. 9  shows a detailed block diagram of an embodiment of a multiplexing apparatus  200  of the present invention. 
   The multiplexing apparatus  200  of  FIG. 9  updates data stored in an ACM  222  by a device control unit that includes RAM  211 , CPU  212 , and ROM  213 . The CPU  212  generates real setting data  221  by calculating data stored in the ACM  222 , and performs circuit switching of TSW  215  using the real setting data. 
   An NMS  240  connected through an I/O-IF unit  230  includes a large-capacity disk  241  for storing the setting data of the whole network, and if needed, the setting data is distributed to a node in the network, and the NMS  240  performs alternate routing change processing when an obstacle and a fault occurs. 
   As mentioned above, in the present invention, two tasks of a multiplexing apparatus can be virtually achieved by one multiplexing apparatus, and circuit management can be facilitated. Further, because the number of TSWs decreases, an economical network is attained, and also a reduction in delay, an improvement in a voice quality, an improvement in data response, an increase in throughput, etc., can be realized.