Multiplex communications – Pathfinding or routing – Through a circuit switch
Reexamination Certificate
1997-12-31
2002-01-08
Holloway, III, Edwin C. (Department: 2635)
Multiplex communications
Pathfinding or routing
Through a circuit switch
C340S002250
Reexamination Certificate
active
06337859
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention is directed to a crossconnect apparatus that is used at a switching station in communications networks. More particularly, the present invention relates to a non-blocking crossconnect apparatus used in communications networks.
2. Description of Related Art
Telecommunications companies have constructed communication networks throughout the world to satisfy the ever increasing demand for communications. Some of these communication networks are fabricated from copper wire while others are fabricated from fiber optic cables. For proper provisioning of the communications network, switching stations are used for routing purposes.
As the demand for communications increases, larger crossconnects are required at the switching stations to meet the demand. Rather than building larger and larger crossconnects to meet the demand for communications, commonly-used design techniques for building crossconnects that are fabricated from multiple smaller components yet provide the desired switching pattern are available.
One such crossconnect is a three-stage Benes crossconnect
2
as shown in FIG.
1
. The three-stage Benes crossconnect
2
is considered a fully-connected, rearrangeably, non-blocking architecture. The architecture is rearrangeably non-blocking because any connection can be added to the crossconnect but it may require rearranging one or more of the connections that are already established. The three-stage Benes crossconnect includes two N/2×N/2 crossconnects with N 2×2 crossconnects. In this example of a three-stage Benes crossconnect, N is equal to 8.
Respective ones of the outputs “&sgr;
1
” from four 2×2 crossconnects in stage
1
are inputted into respective ones of the two N/2×N/2 crossconnects in stage
2
. Respective ones of the outputs “&sgr;
2
” from the two N/2×N/2 crossconnects in stage
2
are inputted into respective ones of the remaining four 2×2 crossconnects in stage
3
.
Another type of crossconnect which is used to reduce the complexity of a switching matrix is a three-stage Clos crossconnect
4
as shown in FIG.
2
. The three-stage Clos crossconnect
4
is a fully-connected, strictly non-blocking architecture. A strictly non-blocking architecture means that any connection can be added without disturbing any of the other connections already established. The three-stage Clos crossconnect
4
includes four 2×3 crossconnects in stage
1
connected to three N/2×N/2 crossconnects in stage
2
which, in turn, are connected to four 3×2 crossconnects in stage
3
. For this example in
FIG. 2
, N is equal to 8. A respective one of the three outputs “&sgr;
4
” of the 2×3 crossconnects in stage
1
are connected to respective inputs of each of the three N/2×N/2 crossconnects in stage
2
. Respective ones of the outputs “&sgr;
5
” of the three N/ 2×N/2 crossconnects in stage
2
is connected to respective inputs of each 3×2 crossconnects in stage
3
.
Even though the Benes and Clos crossconnects are commonly used to reduce the complexity of the switch matrix, there continues to be a problem in that these popular crossconnects require an unnecessary number of crossconnect components.
SUMMARY OF THE INVENTION
The crossconnect apparatuses of the present invention employ the concept of the symmetry to further reduce the number of crossconnect components needed to construct a rearrangeably non-blocking crossconnect apparatus or a strictly non-blocking crossconnect apparatus. Communications networks are typically inherently symmetrical because when party A communicates with party B, party B, in turn, communicates with party A. Thus, symmetry is achieved when A goes to B and, in turn, B goes to A. Additionally, the non-blocking crossconnect apparatuses of the present invention include bi-directional signal ports and bi-directional signal leads that facilitate crossconnect apparatuses that yield the desired results of the Benes and Clos crossconnects but with less crossconnect components.
A first exemplary embodiment of a rearrangeably non-blocking crossconnect apparatus of the present invention includes a primary bi-directional crossconnect device and a plurality of secondary bi-directional crossconnect devices. The primary crossconnect device has N/2 pairs of bi-directional signal ports where N is an even integer greater than 1. A first one of each of the N/2 pairs of bi-directional signal ports is arranged in a first set and a corresponding second one of each of the N/2 pairs of the bi-directional signal ports is arranged in a second set. Each secondary crossconnect device is associated with a respective one of the N/2 pairs of bi-directional signal ports and has a pair of secondary bi-directional signal ports and a pair of bi-directional signal leads. A first one of each pair of bi-directional signal leads is operably connected to a respective one of the bi-directional signal ports in the first set of the primary crossconnect device and a second one of each pair of the bi-directional signal leads is operably connected to a respective one of the bi-directional signal ports in the second set of the primary crossconnect device.
A second embodiment of a non-blocking crossconnect apparatus of the present invention includes a first primary bi-directional crossconnect device, a second primary bi-directional crossconnect device and N/2 secondary bi-directional crossconnect devices. Each of the first and second bi-directional primary crossconnect devices has N/2 pairs of bi-directional ports where N is an even integer greater than 1. A first one of each of the N/2 pairs of bi-directional signal ports is arranged in a first set and a corresponding second one of each of the N/2 pairs of bi-directional signal ports is arranged in a second set. Each secondary crossconnect device has a pair of secondary bi-directional signal ports arranged in a first group and four bi-directional signal leads arranged in a second group. A first bi-directional signal lead and a second bi-directional signal lead of each of the N/2 secondary crossconnect devices are operably connected to respective ones of the bi-directional signal ports in the first and second sets respectively of the first primary crossconnect device. A third bi-directional signal lead and a fourth bi-directional signal lead of each of the N/2 secondary cross connect devices are operably connected to respective ones of the bi-directional signal ports in the first and second sets respectively of the second primary crossconnect device.
REFERENCES:
patent: 3760103 (1973-09-01), Condon
patent: 4635250 (1987-01-01), Georgiou
patent: 5010545 (1991-04-01), Jacob
patent: 5325089 (1994-06-01), Goeldner
patent: 5430722 (1995-07-01), Jacob
Hiroshi Toshiyoshi and Hiroyuki Fujita, “Electrostatic Micro Trosion Mirrors for an Optical Switch Matrix”, Journal of Microelectromechanical Systems, vol. 5, No. 4, Dec., 1996, pp. 231-237.
Goldstein Evan Lee
Lin Lih-Yuan
Saleh Adel Abdel Moneim
Simmons Jane Marie
AT&T CORP.
Holloway III Edwin C.
Oliff & Berridg,e PLC
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