Multiplex communications – Pathfinding or routing – Through a circuit switch
Reexamination Certificate
1998-10-02
2002-06-25
Marcelo, Melvin (Department: 2663)
Multiplex communications
Pathfinding or routing
Through a circuit switch
C370S902000
Reexamination Certificate
active
06411619
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a switching or connecting network, and in particular to a remotely reconfigurable switching network for a telephone system.
Remotely controllable “real” cross-connect switching networks such as the Remote Cable Pair Switching System (RECAPSS) or the Remote Pair Cross Connect System (REPACCS) manufactured by Remote Switch Systems, Inc. or the Smart-MDF product manufactured by OKI are well known and widely used as an interface to establish connections between input terminals and output terminals in a predetermined manner from a remote location. An example of a conventional “real” cross-point switching network is shown in
FIGS. 1
a
and
1
b
. The network includes two cross-point switches
100
,
150
each having N input lines running horizontally through the switch and N output lines running vertically through the switch. Switching elements
110
,
160
represented by the small circles at the intersections of the input and output lines are placed at the nodes, that is the intersections or cross-points of the horizontal and vertical lines. Normally, the switching elements are in an open state with no connection between the input and output lines. A desired connection between an input and an output line may be formed by remotely controlling the switching element at the node where the two lines intersect. In this manner, any prescribed connection between input and output lines may be realized by remotely accessing the respective switching element.
“Real” cross-connect switching networks are commonly employed in the telecommunications industry wherein telephone subscribers are allowed to switch between local exchange carriers. Switching local carriers may require a physical rewiring or cross-connection between the subscriber's loop owned by the incumbent local exchange carrier (ILEC) and the network facilities of the competitive local exchange carriers (CLECs). In one specific application the switching network may be used to provide a particular type of service, for example, Asymmetric Digital Subscriber Loop (ADSL) service, to an existing plain old telephone service (POTS) subscriber loop served out of a central office. To provide additional services to the subscriber loop adjunct equipment
115
such as ADSL modems, line cards, diplexers and filters may be installed between the two switches
100
,
150
.
By way of example, in
FIG. 1
the adjunct equipment
115
is installed only at output line #
1
. It should be noted, however, that additional adjunct equipment may be added to other output lines as the demand for such services among subscribers increases. The first switch
110
is used to connect a given input terminal of a subscriber requesting the particular service provided by the adjunct device
115
to output line #
1
. The signal from output line #
1
is then split off and passes through the adjunct equipment
115
which provides the additional service, for example, ADSL service. In addition, the signal from output line #
1
also passes through the second switch
150
that returns the signal lines to their original arrangement. This “real” cross-connect switching network is disadvantageous in that each switch requires a relatively large number of switching nodes which are expensive. In particular, an N×N switch has N
2
switching nodes, for example, in a 2×2 switch there are 4 switching nodes, in a 4×4 switch there are 16 switching nodes, and in an 8×8 switch there are 64 switching nodes.
V. E. Benes developed a switch described in “Optimal Rearrangeable Multistage Connecting Networks”, The Bell System Technical Journal, pp. 1641-1656 (July 1964), incorporated herein by reference, that requires fewer switching nodes than a “real” cross-connect switch. The basic component of a Benes switch is a beta network, as shown in
FIGS. 2
a
and
2
b
, including two relays, such as two double pole double throw (DPDT) latching relays. Beta network
200
has two input lines, “a”, “b”, and two output lines “c”, “d”, wherein the input and output lines are switchable between two states. In the first state shown in
FIG. 2
a
input lines “a”, “b” are directly connected to output lines “c”, “d”, respectively. In the second state shown in
FIG. 2
b
, the lines are crossed, that is, input lines “a”, “b” are connected to output lines “d”, “c”, respectively. It is clear that since two states can be achieved using a single beta network (Benes node) the number of nodes in the switch is reduced.
A plurality of beta networks may be arranged to form a Benes switch. By way of example, an 8×8 Benes switch
200
is shown in
FIG. 2
c
. The 8×8 Benes switch includes 20 beta networks, as compared to 64 crosspoints in the prior art cross-connect switch. The 2×2 beta network is grown into a 4×4 Benes switch with three-stages of beta networks by duplicating the original switch and positioning the duplicated switch below the original switch. Specifically, the original 2×2 switch
210
U is duplicated to form a lower switch
210
L positioned below the upper switch. Then the appropriate number of additional input and output beta networks
215
a-
215
d
are connected to the inputs and outputs of the upper and lower switches. Each additional beta network has one output connected to the upper switch
210
U and the other output connected to the lower switch
210
L to create the 4×4 Benes switching network
230
with three stages of beta networks.
Similarly, an 8×8 Benes switching network may be created following the same procedure described above with respect to building the 4×4 Benes switch, except that the original or upper switch is now the 4×4 switch
230
, instead of the 2×2 switch
210
U. Specifically, the 4×4 Benes switch
230
is duplicated to form a lower switch
250
positioned directly below the upper switch. Then the appropriate number of additional input and output beta networks
205
a-
205
h
are connected to the inputs and outputs of the upper and lower switches. Each additional beta network
205
a-
205
h
has one output connected to the upper switch
230
and the other output connected to the lower switch
250
to form an 8×8 Benes switching network with five stages of beta networks. By following these basic steps the Benes network may be expanded as desired.
Benes switches may also be used to interconnect input and output terminals in order to provide additional services to predetermined subscribers. In a configuration similar to that described above with respect to cross-point switches, one or more adjunct devices may be disposed between two Benes switches. Specifically, the switching network includes a first Benes switch for selecting a particular subscriber to receive the additional service, an adjunct device connected to at least one output line of the first Benes switch to provide the necessary additional service capabilities depending on subscriber demand, and a second Benes switch connected to the output lines of the first Benes switch to return the signal lines to their original arrangement. This switching network is disadvantageous in that it still requires two Benes switches, each including a relatively large number of Benes nodes, and thus is relatively expensive to manufacture.
It is therefore desirable to develop a remotely accessible switching network that may be reconfigured to provide adjunct equipment specifically tailored to satisfy subscriber demand for a particular service while minimizing the number of switching nodes.
SUMMARY OF THE INVENTION
The present invention is directed to a remotely reconfigurable switching network. In a preferred embodiment the remotely reconfigurable N×N switching network includes an N×N Benes switch having a plurality of stages of beta networks. The Benes switch is separated into a left half section and a right half section, with one of the sections having one less stage of beta networks than the other section. An additional stage of beta networks is connected to
Savicki Joseph Peter
Schwartz Andrew
Abelson Ronald
Avaya Technology Corp.
Dinicola Brian
Marcelo Melvin
LandOfFree
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