Multiplex communications – Fault recovery – Bypass an inoperative channel
Reexamination Certificate
1999-06-02
2004-11-30
Nguyen, Hanh (Department: 2662)
Multiplex communications
Fault recovery
Bypass an inoperative channel
C370S241000, C370S245000, C379S221040
Reexamination Certificate
active
06826146
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to the field of telecommunications trunk rerouting and, in particular, to the rerouting of intra-office digital signals, for example, for maintenance or circuit rearrangement purposes or in the event of an imminent or actual intra-office cable failure.
2. Description of the Relevant Art
It is known to reroute inter-office telecommunications trunks in the event of a failure or imminent failure or for maintenance purposes. For example, a restoration system known as FASTAR, which is described and claimed in U. S. Pat. No. 5,182,744, assigned to AT&T, is being utilized within the United States toll network to assist in the automatic rerouting of inter-office facilities. Inter-office telecommunications trunks connect central offices together via various means including satellite, microwave, wireless, coaxial cable, twisted pair cable and other means. Redundancy is often provided in inter-office trunking facilities that may be path diverse (for example, satellite, microwave, optical fiber, repeatered land line, submarine cable or other inter-office facility), equipment diverse or otherwise redundant.
Intra-office signal communication, that is, transport of a signal simply across a telephone central office, however, has developed over the years with a significantly less degree of equipment, facility or other redundancy. Inside a telephone central office, there exist frames of equipment that may be spread over multiple floors of a central office building with overhead cable racks in which intra-office cables have been lying for years. Satellite and microwave dishes which receive signals from all over the world may be mounted on top of the multi-story central office building. Cable vaults underneath the building provide access to land lines below ground level. Insulation can rot on and within cables layered in cable racks or run between building floors. Individual cable pairs of wires can short together, the copper wires break open, connectors can deteriorate or come loose and the like. Cables and cable connectors can succumb to aging, environmental changes, moisture and stress causing them to deteriorate. The placement of new cable layers upon layers of existing cable, bending cables around the central office and the weight of cables stressed due to floor-to-floor drops causes cable and cable connector deterioration over time. The failure of an intra-office trunk can mean not only the instantaneous disconnect of one or more calls but, with the loss of one intra-office transport means, the efficiency of the entire telecommunications network can become at risk. Intermittent problems due to the deterioration of a cable or cable connector can cause chronic problems for a customer's service.
Referring to
FIG. 1
, a typical telecommunications network is shown and many terms such as intra-office, inter-office, subscriber line, central office (including local, tandem and toll offices) and the like will be defined. The North American numbering plan will be used by way of example and should not be deemed to be limiting on the scope of the present invention. Starting with a typical subscriber
101
, subscriber
101
is connected to a local telephone central office by a subscriber loop or line
105
. Line
105
may typically comprise a twisted wire cable pair (which may provide an asynchronous digital subscriber line connection). Line
105
may also comprise a wireless connection, for example, to a serving cellular service switch. In a cable telephony/television environment, line
105
may comprise a shared bandwidth portion of bandwidth provided via a hybrid fiber coaxial cable distribution system. Local central office
111
may be a wire center such as a #1 or #5 Electronic Switching System manufactured by Lucent Technologies serving several telephone exchanges.
Subscriber
101
may be in the 654 exchange of the 301 area code having the directory number 654-2321. Local central office
111
may be a wire center having several exchanges and will have intra-office trunks, for example, intra-office trunk
109
which can carry calls across the central office from one exchange to another exchange within the same central office to another subscriber, for example, subscriber
103
who may be in the 652 exchange of the 301 area code. Intra-office trunk
109
carries a signal across a central office in this example from one exchange to another. The interexchange, intra-office trunk is but one example of an intra-office trunk. Other examples will now be further described.
Subscriber
101
may wish to communicate with subscriber
153
in the 630 area code. As can be seen from
FIG. 1
, there are many alternative paths between local central office
111
serving subscriber
101
and local central office
149
serving subscriber
153
who is connected to office
149
by subscriber loop or line
151
. Inter-office trunks are transport means for connecting central offices together. Examples of interoffice trunks include trunks
113
,
115
,
117
,
123
,
125
,
133
,
135
,
137
,
139
,
141
,
143
and
147
. Subscriber
101
may be connected to subscriber
153
, for example, via interoffice trunks
117
and
147
. Another route might be via interoffice trunks
115
,
143
,
147
. Another route might be via trunks
113
,
123
and
141
. Other routes are seen from the figure.
These alternative inter-office routes involve central offices that may not be within boundaries of a regional telephone operating company and, consequently, must involve an interexchange carrier (IXC) such as AT&T. The IXC operates and maintains tandem central offices and toll central offices one of whose functions is to provide switching or cross-connection between inter-office trunks. Tandem central office
127
connects toll offices
121
and
131
together or can connect a toll office to a tandem office, such as tandem office
145
. The local exchange carrier (LEC) may also operate toll and tandem central offices, such as tandem office
145
that connects local central offices
119
and
149
together.
Telephone central offices have switching and cross-connect equipment. Many paths through an office are switched; many are not switched at all but merely cross-connected. An intra-office trunk within a toll or tandem office is defined as a telecommunications channel between two pieces of equipment within the same toll or tandem office that may or may not be switched. With reference to toll central office
121
, for example, there may be an intra-office trunk or trunk group of channels that connect ports toward local central office
111
to ports toward tandem office
127
. Looking at the combinations, there may be A-B, A-C, and A-D intra-office trunks, also, B-C, B-D and C-D intra-office trunks shown in
FIG. 1
by dotted lines. In practice, some IXC toll offices may provide many more intra-office trunk groups than the six groups identified for toll office
121
. These intra-office trunks may typically comprise pairs of wires carrying many digitally multiplexed channels. Wires go open, wires break and whole intra-office trunk groups of channels can fail when a single wire breaks or a connector fails. There is an opportunity to repair, replace or perform preventative maintenance on connectors and the like on a routine basis. Thus, there is a need in the art for a system and method for rerouting intra-office trunks. Moreover, with digital systems such as T1 digital carrier systems where a single pair of wires may represent 24 DSO channels or T3 systems where a single pair of wires may represent 28 T1 channels, the problem becomes more complicated as all 24 DS0 or 28 T1 channels must be rerouted together and simultaneously in order to minimize service disruption. Moreover, it would be desirable if rerouting is effectuated as rapidly as possible after a determination of a necessity to reroute is made. Finally, it would be desirable if a rerouting of signals occur through the central office via alternative paths upon the detection and reporting, for
Blenis James
Channell Leigh B.
Lystad Gerald D.
AT&T Corp.
Nguyen Hanh
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