Abstract:
Disclosed a method of increasing the whole switch capacity by utilizing the presently used switch network as it is. The present invention, the method of increasing a switch capacity in a switch network system in which three or more switch stages including a plurality of switching elements are connected in serial by using a predetermined logical circuit, the method comprising the steps of: adding switch stage including a plurality of switching elements to correspond to the each switch stage; grouping switching elements of a first switch stage and last switch stage in the switch stage and the added switch stage by a predetermined unit, respectively; and connecting the grouped switching elements of the first stage with corresponding switching elements of an intermediate switch stage which is placed between the first stage and last stage, respectively, and connecting the grouped switching elements of the last switch stage with the corresponding switching elements of the intermediate switch stage, respectively.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to a cross connect system. In particular, the present invention relates to a switch capacity increasing method which can increase the switch capacity by utilizing the existing switch network as it is. 
   2. Background of the Related Art 
   Generally, a 3-stage Clos switch network as shown in  FIG. 1  has been widely used in a cross connect system. Referring to  FIG. 1 , the 3-stage Clos switch network comprises a first stage  10  having a plurality of switching elements  10   a – 10   n , a second stage  20  having a plurality of switching elements  20   a – 20   n  connected to the switching elements  10   a – 10   n  of the first stage  10  in a many-to-many relationship, and a third stage  30  having a plurality of switching elements  30   a – 30   n  connected to the switching elements  20   a – 20   n  of the second stage  20  in a many-to-many relationship. 
   Here, the whole switch capacity N of the switch network is predetermined when the switch network is designed. If the number of input/output of a switching element is defined by n, the ratio of the input number to the output number of each switching element in the first stage  10  becomes n×2n, and the ratio of the input number to the output number of each switching element in the third stage  30  becomes 2n×n. 
   Also, the ratio of the input number to the output number of each switching element in the second stage  20  becomes N/n×N/n. Accordingly, the first stage  10  and the third stage  30  have a symmetrical arrangement based on the second stage  20 . 
   Such a switch network as described above has the reduced number of cross points and high accessibility of crossbars, and a non-blocking is effected when two terminal points are connected to each other since at least one path is provided through the network to connect the two terminal points together. Because of the above reason, there is a tendency to apply the switch network as shown in  FIG. 1 , for instance, to the product name DACS IV (digital access communication system IV) manufactured by Lucent in the United States and to the product name 1631SX manufactured by Alcatel in the United States. 
   In the above-described switch network, the switching elements in the respective stages  10 – 30  are inserted into a shelf of the cross connect system in the form of a module or unit. On the rear surface of the shelf is provided a mother board in which a plurality of patterns for connecting input/output terminals of the respective modules as designed. Accordingly, the designer of the cross connect system should design or produce the switch network after determining the whole switch capacity of the switch network required at the present time and in the future. 
   In the conventional cross connect system as shown in  FIG. 1 , the method of increasing the whole capacity of the switch network may be classified into two. 
   One method is to produce the switch network having the switch capacity of 2N if the designer judges that the whole switch capacity required at the present time is N, but the switch capacity of 2N will be required thereafter. Another method is to produce and use the switch network having the switch capacity of N, and if required thereafter, to produce a new switch network having the switch capacity of 2N without using the previous switch network having the switch capacity of N any more. 
   However, the former method has problems that unnecessary expenses are spared on producing the switch network having the switch capacity of 2N though the switch capacity of N is only required at the present time. The latter method also has problems that excessive expenses are spared on producing a new switch network having the switch capacity of 2N since the previous switch network having the switch capacity of N is not used any more. 
   Such problems are caused by the fixed structure of the produced switch network. Specifically, the fixedly patterned structure of the shelf and the mother board of the cross connect system, which is just like a printed circuit board (PCB), causes the problems in case of increasing the switch capacity of the present switch network. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is directed to a switch capacity increasing method that substantially obviate one or more of the problems due to limitations and disadvantages of the related art. 
   An object of the present invention is to provide a method of increasing switch capacity which can increase the whole switch capacity by utilizing the presently used switch network as it is. 
   Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings. 
   To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a method of increasing a switch capacity in a switch network system in which three or more switch stages including a plurality of switching elements are connected in serial by using a predetermined logical circuit, the method comprising the steps of: adding switch stage including a plurality of switching elements to correspond to the each switch stage; grouping switching elements of a first switch stage and last switch stage in the switch stage and the added switch stage by a predetermined unit, respectively; and connecting the grouped switching elements of the first stage with corresponding switching elements of an intermediate switch stage which is placed between the first stage and last stage, respectively, and connecting the grouped switching elements of the last switch stage with the corresponding switching elements of the intermediate switch stage, respectively. 
   In another aspect, a method of increasing a switch capacity in a switch network system in which three or more switch stages including a plurality of switching elements are connected in serial by using a predetermined logical circuit, the method comprising the steps of: adding switching elements to an intermediate switch stage which is placed between the first stage and last stage, respectively; and connecting extra input/output terminals of switching elements in first and last switch stages with the added switching elements, respectively. 
   According to the aspects of the present invention as described above, the whole switch capacity can be increased by adding a new switch network to the presently used switch network and manually changing the connection of the respective switching elements. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention: 
     In the drawings: 
       FIG. 1  is a block diagram illustrating the construction of a conventional switch network. 
       FIG. 2  is a block diagram illustrating the construction of the switch network whose switch capacity is increased by the integral number of times according to a first embodiment of the present invention. 
       FIG. 3  is a block diagram illustrating the equivalent construction of the switch network of  FIG. 2 . 
       FIG. 4   a  is a block diagram illustrating the construction of the switch network having the whole switch capacity of 2. 
       FIG. 4   b  is a block diagram illustrating the construction of the switch network whose switch capacity is increased from 2 to 4. 
       FIG. 4   c  is a block diagram illustrating the construction of the switch network having the whole switch capacity of 4. 
       FIG. 5   a  is a block diagram illustrating the construction of the switch network having the switch capacity of 4×4. 
       FIG. 5   b  is a block diagram illustrating the construction of the switch network whose switch capacity is increased from 4×4 to 6×6 according to a second embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     FIG. 2  is a block diagram illustrating the construction of the switch network whose switch capacity is increased by the integral number of times according to a first embodiment of the present invention. 
   Referring to  FIG. 2 , the switch network according to the first embodiment of the present invention includes first stages  40  and  70  having a plurality of switching elements  40   a – 40   n  and  70   a – 70   n , second stages  50  and  80  having a plurality of switching elements  50   a – 50   n  and  80   a – 80   n  respectively connected to the switching elements  40   a – 40   n  and  70   a – 70   n  of the first stages  40  and  70  in a many-to-many relationship, and third stages  60  and  90  having a plurality of switching elements  60   a – 60   n  and  90   a – 90   n  respectively connected to the switching elements  50   a – 50   n  and  80   a – 80   n  of the second stages  50  and  80  in a many-to-many relationship. 
   Here, if the input number of the switching element is defined by n and the whole switch capacity of the switch network is defined by N, the ratios of the input number to the output number of the switching elements provided in the first, second, and third stages are n×2n, N/n×N/n, and 2n×n, respectively. 
   Accordingly, the switch network according to the first embodiment of the present invention has a symmetrical arrangement based on the second stages  50  and  80 . Also, the switching elements provided in the first stages  40  and  70  and the second stages  50  and  80  and the switching elements provided in the second stages  50  and  80  and the third stages  60  and  90  are respectively connected through communication lines (for instance, cables) which can change the input/output connection ports of the switching elements. Accordingly, in case of increasing the switch network, the shelf or mother board of the existing cross connect system are used as they are, and only the input/output connection ports thereof are changed according to the first embodiment of the present invention. 
   Hereinafter, the switch capacity increasing method for a cross connect system according to the first embodiment of the present invention will be explained in detail. 
   First, a new switch network is added to the existing switch network. Thereafter, the switching elements  40   a – 40   n ,  70   a – 70   n ,  60   a – 60   n , and  90   a – 90   n  respectively provided in the first stages  40  and  70  and the third stages  60  and  90  of the existing switch network and the new switch network are classified into pairs.  FIG. 2  shows 2 pairs of the switching elements  45   a ,  45   b ,  75   a ,  75   b ,  65   a ,  65   b ,  95   a , and  95   b  in each stage. Then, the first switching elements  40   a ,  40   n - 1 ,  70   a , and  70   n - 1  of the pairs  45   a ,  45   b ,  75   a , and  75   b  of the switching elements in the first stages  40 ,  70 ,  60 , and  90  of the existing switch network and the new switch network are connected to the switching elements  50   a – 50   n  provided in the second stage  50  of the existing switch network in a many-to-many relationship, and the second switching elements  40   b ,  40   n ,  70   b , and  70   n  of the pairs  45   a ,  45   b ,  75   a , and  75   b  of the switching elements are connected to the switching elements  80   a – 80   n  provided in the second stage  80  of the new switch network in a many-to-many relationship. Thereafter, the first switching elements  60   a ,  60   n - 1 ,  90   a , and  90   n - 1  of the pairs  65   a ,  65   n ,  95   a , and  95   n  of the switching elements in the third stages  60  and  90  of the existing switch network and the new switch network are connected to the switching elements  50   a – 50   n  provided in the second stage of the existing switch network in a many-to-many relationship, and the second switching elements  60   b ,  60   n ,  90   b , and  90   n  of the pairs  65   a ,  65   n ,  95   a , and  95   n  of the switching elements are connected to the switching elements  80   a – 80   n  provided in the second stage  80  of the new switch network in a many-to-many relationship. 
   As described above, the switch network is increased by classifying the switching elements provided in the first stages  40  and  70  and the third stages  60  and  90  into pairs and then connecting the input/output terminals of the switching elements in a manner as described above.  FIG. 3  illustrates the equivalent circuit of the increased switch network of  FIG. 2 . 
   According to the first embodiment of the present invention, the whole switch capacity of the increased switch network becomes 2 N  times as large as that of the previous switch network by adding the second switch network  70 ,  80 , and  90  which is identical to the existing first stage  40 , second state  50 , and third stage  60 . For example, the whole switch capacity of the switch network can be increased from 2 to one of 4, 8, 16, 32, . . . . 
   In case that the whole switch capacity of the existing switch network is N, and that of the new switch network is 2N, the number and the input/output number of the switching elements provided in the respective stages of the existing switch network and the new switch network are identical. 
     FIGS. 4   a  to  4   c  illustrate the first embodiment of the present invention exemplifying that the whole switch capacity of the switch network is increased from 2 to 4. 
     FIG. 4   a  is a block diagram illustrating the construction of the switch network having the whole switch capacity of 2.  FIG. 4   b  is a block diagram illustrating the construction of the switch network whose switch capacity is increased from 2 to 4 according to the switch capacity increasing method of the present invention.  FIG. 4   c  is a block diagram illustrating the construction of the switch network initially designed to have the whole switch capacity of 4. Upon comparing the switch networks in  FIGS. 4   b  and  4   c , it can be recognized that the same switching paths are provided. 
     FIGS. 5   a  and  5   b  show the switch network according to the second embodiment of the present invention wherein the switch capacity is increased fraction times. 
     FIG. 5   a  is a block diagram illustrating the construction of the switch network having the switch capacity of 4×4, and  FIG. 5   b  is a block diagram illustrating the construction of the switch network whose switch capacity is increased from 4×4 to 6×6 according to the second embodiment of the present invention. 
   Referring to  FIGS. 5   a  and  5   b , the switch network according to the second embodiment of the present invention includes a first stage  300   a  having a plurality of switching elements SE 41  and SE 42 , a second stage  400   b  having a plurality of switching elements SE 51 –SE 56  connected to the switching elements SE 41  and SE 42  of the first stage  300   a  in a many-to-many relationship, and a third stage  500   a  having a plurality of switching elements SE 61  and SE 62  connected to the switching elements SE 51 –SE 56  of the second stage  400   b  in a many-to-many relationship. 
   Here, if the input number of the switching element is defined by n and the whole switch capacity of the switch network is defined by N, the ratio of the input number to the output number of the first stage  300   a  becomes 1.5 times 2×4 (i.e., 3×6), the ratio of the input number to the output number of the second stages  400   a – 400   c  becomes 2×2, and the ratio of the input number to the output number of the third stage  500   a  becomes 1.5 times 4×2 (i.e., 6×3). 
   According to the second embodiment of the present invention, when the connection ports of the input/output terminals of the switching elements in the first stage  300   a  and the third stage  500   a  are initially connected, the input/output terminals indicated as dotted lines in  FIGS. 5   a  and  5   b  are not connected. Thereafter, if the increase of the switch capacity by 1.5 times is required due to the increase of subscribers, only the second stage  400   c  is added to the existing switch network as shown in  FIG. 5   a , and the input/output terminals which have not been used as indicated as the dotted lines in  FIG. 5   a  are connected in a many-to-many relationship to the switching elements SE 55  and SE 56  of the newly added second stage  400   c . Also, according to the second embodiment of the present invention, the switching elements provided in the first stage  300   a  and the second stage  400   a  and the switching elements provided in the second stage  400   a  and the third stage  500   a  are respectively connected through communication lines which can change the input/output connection ports of the switching elements. Accordingly, in case of increasing the switch network, the existing shelf or mother board of the existing cross connect system are used as they are, and only a portion of the input/output connection ports thereof is changed according to the second embodiment of the present invention. 
   Hereinafter, the switch capacity increasing method for a cross connect system according to the second embodiment of the present invention will be explained in detail. 
   First, the new second stage  400   c  is added to the existing switch network to increase the whole switch capacity. Thereafter, the input/output terminals, which have not been used (shown as the dotted lines in  FIGS. 5   a  and  5   b ), of the switching elements SE 41 , SE 42 , SE 61 , and SE 62  provided in the first stage  300   a  and the third stage  500   a  are respectively connected to the switching elements SE 55  and SE 56  of the newly added second stage  400   c  in a many-to-many relationship. In  FIGS. 5   a  and  5   b , each dotted block tying the switching elements indicates a module, and the increase of the switch capacity is performed in the unit of a module. 
   The switch capacity increasing method according to the second embodiment of the present invention wherein the whole switch capacity is increased by 1.5 times will be a more economical and effective method if the whole switch capacity of the switch network becomes larger. 
   As described above, according to the present invention, the switch capacity of the switch network can be increased by adding a new switch network to the existing switch network, and changing the connection of the communication lines as proposed by the present invention. At this time, the increase of the switch network by both 2 N  times of 2N and 1.5 times of 2 N  is possible. 
   Consequently, according to the present invention, a switch network having a proper switch capacity can be produced when designing or manufacturing a cross connect system, and in case of increasing the switch capacity of the switch network, the existing switch network can be used as it is, thereby preventing unnecessary or excessive expenses from being spared. 
   While the present invention has been described and illustrated herein with reference to the preferred embodiments thereof, it will be apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of the appended claims and their equivalents.