Multiplex communications – Fault recovery – Bypass an inoperative switch or inoperative element of a...
Reexamination Certificate
1999-01-19
2002-02-26
Nguyen, Chau (Department: 2663)
Multiplex communications
Fault recovery
Bypass an inoperative switch or inoperative element of a...
C370S537000
Reexamination Certificate
active
06351452
ABSTRACT:
The present invention relates to a telecommunication device for use in interfacing central telephone networks to on-site customer equipment and in particular, the present invention relates to such telecommunication devices that have a more efficient architecture, provide for more efficient switching between redundant components, and provide for on-demand insertion of signaling bits.
BACKGROUND OF THE INVENTION
The modern world of telecommunication includes new equipment, standards, and applications being introduced at a rapid rate. In particular, the required speed and efficiency of telecommunication networks is increasing. One important area of telecommunication networks relates to the interface between a telephone company's central office (CO) and on-site equipment located at the customer premises.
Historically, the CO and the customer equipment had been connected by dedicated lines carrying analog signals. More recently, channels carrying time division multiplexed (TDM) signals have been carried on T-1 lines. The data carried on these T-1 lines is referred to as DS1 data which includes 24 DS0 channels, where each DS0 channel may carry a single telephone conversation. A DS0 channel operates at 64 kilobytes per second, or 8,000 8 byte samples per second.
The equipment used at the CO may be a Class 5 switch, a type of digital CO switch typically used in “end office” applications, serving local voice traffic subscribers. The Class 5 switch may have many T-1 links to various equipment at various customer sites. As stated before, each of these T-1 links can carry up to 24 DS0 voice channels. Of course, it is a waste of resources for the Class 5 switch to have dedicated T-1 lines to the various customer equipment, since all of the customer equipment will likely not be fully utilized at any given time. Accordingly, it is known in the industry to concentrate telephone conversations from a plurality of analog lines (to a set of T-1 lines that have fewer DS0s than the number of analog lines) with a digital loop carrier (DLC) utilizing a standard for concentrating such as Bellcore™ GR-303-CORE, IDLC Generic Requirements, Objectives, and Interface: Requirements Supporting Interfacing to the Digital Network, the contents of which are incorporated herein by reference. Also, it is known in the industry to multiplex
24
analog telephone lines into a single T-1 line at a customer premise, and to concentrate sets of T-1 lines into fewer T-1 lines in accordance with GR-303-CORE, also known as a GR303 concentrator. Such a DLC operating as a 303 concentrator may be inserted into the network between the Class 5 switch and the customer equipment that multiplexes analog telephone lines into T-1 lines.
In addition, it is known to provide cross-connect switching at the same point as the 303 concentrator, downstream of the CO switch. 1/0 digital cross-connects switches (DCS) switch DS0 channels within the same or various T-1 communication links. Hardware switches performing 1/0 DCS are known, such as Mitel's MT90820. In addition, it is known to provide a frame relay aggregation switch in the same point as the
303
concentrator and DCS, downstream of a CO frame relay switch. A frame relay switch provides frame relay services, wherein frames are packets of data that can be anywhere between 0 and 4,096 octets long. Each frame is preceded by a flag and address field and is followed by a frame check sequence and flag. Frame relay services are a desirable way to pass digitized data along a telecommunications network, particularly data that comes in bursts.
In the prior art, it has only been known to provide a
303
concentrator, a 1/0 DCS, and a frame relay switch in three separate boxes or components. Unfortunately, such an approach has been expensive, taken up an undesirably large volume of space, caused undesirable transmission delays affecting the quality of the transmission, and caused management of the various network elements to be very difficult. In addition, it has been the approach of most prior art devices to provide for connection to many different interfaces, or in other words to solve many different problems fairly well rather than one specific problem very well.
Some of the other drawbacks of employing such antiquated and segmented approaches to voice and data services include: (1) the traditional network deployment was not designed to support the ever-growing demand for voice and data services; (2) with traditional system components, many diverse pieces of equipment are required to route information from the customer site to the carrier voice and data network resources; (3) with diverse equipment, setting up and maintaining quality voice and data service to customers requires a large number of skilled technicians; (4) traditional systems also often require bandwidth and switching resources which are dedicated to a particular customer, this results in a significant amount of unused infrastructure during the high percentage of inactive times; (5) with a number of different types of equipment in the path, transmission delays and quality of service can become problems in providing voice and data services; and (6) new protocols are evolving to better utilize transport and switching bandwidths, but legacy, or currently-installed, equipment architectures do not effectively support these new capabilities.
Also, the reliability of telephone network equipment is an important issue. Because of the importance of reliability, it is known to supply redundancy (the use of spare or redundant components) in various types of telecommunication equipment. Spare circuits or cards can be automatically switched into replace active circuits or cards, in the case of certain types of faults which may be detected. It is important for the transition between active circuits and standby circuits to be as seamless as possible, particularly where the circuit may have been in the middle of a critical operation. Unfortunately, when redundant equipment is switched in to replace an active piece of equipment, data about the status and history of other components may be lost.
Many redundant systems have a complex switch-over mechanism. In order to finish a critical operation that was started by a failed primary or active circuit, a backup circuit must be well informed of the status when the backup circuit takes over. For instance, the backup circuit must be informed that the active circuit has started a particular critical operation. Also, if the critical operation requires a sequence of actions, the backup circuit must know which actions were completed before the fault occurred, and which actions were not yet completed. Only in this manner, can the backup equipment finish the not yet completed actions.
Another issue that is particular to digital cross-connect switches is the loss of signaling bits. Signaling bits are associated with frames of T-1 data to provide various types of signaling including ringing, dial tone, hang-up, and so forth. On T-1 communication links, voice circuits include signaling bits imbedded into each frame of data, typically the least significant bit every six frames of data. These frame bits can be recognized by the equipment at each end of a T-1 communication link. Unfortunately, a 1/0 DCS loses the signaling bits as part of its cross-connect switching. In this case, such DCS circuits require the signaling bits to be reinserted into the sixth, twelfth, eighteenth, and twenty-fourth frames of data on T-1 communication links. In the past, this has been done with signaling bit cross-connect hardware. Further, there is not believed to be any approach that provides for signaling bit translation to convert between different protocols and interfaces.
It is against this background, and the desire to solve the problems of and improve on the prior art, that the above invention has been developed.
SUMMARY OF THE INVENTION
The present invention is directed to a telecommunication device for interconnecting multiplexed high speed voice and data channels, each multiplexed DS1 high speed voice and data ch
Alaimo S. Christopher
Dodani Shri B.
Edwards Raviraj
Groth Timothy
Koenig Roger L.
Boakye Alexander O.
Carrier Access Corporation
Holland & Hart
Nguyen Chau
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