Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-09-21
2003-11-11
Ton, Dang (Department: 2664)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S542000, C370S519000, C370S216000
Reexamination Certificate
active
06647028
ABSTRACT:
TECHNICAL FIELD
The present invention relates to high speed synchronous communication networks and more particularly to a system and method for detecting a failure on one or more among N physically separate telecommunication lines and then for automatically re-adjusting the available user bandwidth to efficiently utilize the remaining operational telecommunication lines.
BACKGROUND ART
The present communication carrier networks have evolved over time from data transmission using mostly analog techniques into entirely digital networks. New industry standards for the transmission and the reception of data have emerged including among other things, methods for channelization, data multiplexing and demultiplexing, switching and cross-connection routing of data from one user to another . . . . The CCITT standards specify data signal voltage levels and template characteristics, framing formats, clocking and signal jitter characteristics. They allow the different manufacturers to connect their equipment to the carrier networks and to inter-operate with each other. In the United States, said standards have been, in particular, the object of a large number of patents relative to clock recovery, alignment and synchronization within a single channel:
U.S. Pat. No. 4,394,758, “Timing circuits for PCM reception”—Donne et al.
U.S. Pat. No. 4,394,759, “Digital information transmission system”—Donne et al.
U.S. Pat. No. 4,417,348, “Digital channel protection switching for radio communications”—Abbruscato et al.
U.S. Pat. No. 4,458,356, “Carrier wave restoration circuit for receiver”—Toy et al.
U.S. Pat. No. 4,630,286, “Multiple telephone circuit synchroniser for high speed data”—Betts et al.
U.S. Pat. No. 4,675,886, “Frame synchronising unit with word-locking decoder”—Surie et al.
U.S. Pat. No. 4,734,920, “High speed modem for multiple communication”—Betts et al.
U.S. Pat. No. 4,744,095, “Diversity channel switch with automatic data rephasing”—Cornet et al.
U.S. Pat. No. 4,775,987, “Transmitter for high bit rate data over telephone system”—Miller et al.
U.S. Pat. No. 4,818,995, “Parallel transmission system using step as line coding type”—Takasaki et al.
Standardization, while useful, is sometimes not cost effective because the granularity of bandwidth to the user does not always meet his needs. The user must reserve bandwidth in the increments tariffed by the individual countries. If a higher bandwidth is required than provided by a given type of channel, the user is forced to buy the next higher increment of bandwidth even though the tariffed bandwidth far exceeds his requirement. For example, in Europe, a user requiring more than the E1 bandwidth of 2 Mbps is forced to buy E3 bandwidth of 34 Mbps. A user in the US requiring more than T1 bandwidth of 1.544 Mbps is forced to buy T3 bandwidth of 44.736 Mbps.
Other patents in the field of interest deal with combining a number of low speed transmission lines to provide a higher bandwidth to the user without the need to “jump” to the next tariffed level of bandwidth service.
U.S. Pat. No. 5,251,210 entitled “Method and Apparatus for Transforming Low Bandwidth Telecommunications Channels into a High Bandwidth Telecommunications Channel”—Mann et al discloses a method and system for combining lower bandwidth channels to produce a higher bandwidth channel.
European patent application 96480090.8 (U.S. patent application Ser. No. 807496) entitled “System and Method for creating N-times E1/J1 bandwidth from N separate physical E1/T1 lines”—Poiraud et al—describes a system and method for aggregating data on multiple physically separate lower-speed E1/J1 channels to generate a higher bandwidth. The high speed data stream is first divided into lower bandwidth channels and then transmitted through the network. The previously divided data stream arrives with varying delays depending on the physical characteristics of the network. Low bandwidth channels are aggregated together into a high bandwidth channel by determining the different geographical delay parameters among the lower speed channels, adjusting the transmission delays by alignment circuitry, and then combining the lower speed signals into one high bandwidth channel for the user. The method for the delay adjustment consists in adding a pseudo-random noise pattern to each of the lower bandwidth channels, measuring the time difference among all the channels, and then adjusting the time differences in the received data stream so that the combination of the signals produces a coherent higher bandwidth data stream. This application is an improvement of U.S. Pat. No. 5,521,210 adapted to the European telecommunication environment.
However, the field of these patents is limited in scope because they do not disclose any error recovery or bandwidth adjustment mechanism in case one of the lower bandwidth channels becomes inoperative.
It is therefore the object of the present invention to provide a method and system for detecting a failure on one or more among N physically separate telecommunication lines and then for automatically re-adjusting the available user bandwidth to efficiently utilize the remaining operational telecommunication lines. It is also the purpose of this invention to allow the user to buy a service using N+1 physical lines and to use N physical lines for normal data transmission with the possibility to replace a failing line with the spare line if one line becomes unusable.
When a high bandwidth data stream, multiple of lower bandwidth channels, is separated into N separate physical data streams according to the method claimed in the aforementioned U.S. Pat. No. 5,251,210 and European Patent application 96480090.8 (U.S. patent application Ser. No. 807496) data are transmitted over different physical paths and are received with different delays among the N physical lines. The aforementioned inventions take into account the different delay characteristics of the different physical lines. The object of the present invention is to continuously detect line status and adjust the bandwidth so as to provide the maximum bandwidth available if one of the physical lines becomes unusable and also to detect and adjust the bandwidth if the previously unusable line becomes usable once again.
The alignment of lower bandwidth data into a higher bandwidth operates by using some of the bandwidth of each lower bandwidth channel as a common timing signal. Each lower bandwidth signal is transmitted to the network with identical timing information. At the destination, the timing information is recovered for each signal independently and is used to recombine the low bandwidth signals into a single high bandwidth signal. The term for this process is to cohere the output from the network into a high bandwidth signal. This process is briefly described below since knowledge of this technique is necessary for understanding how to detect and adjust bandwidth when one of the physical lines becomes unusable.
The timing information is a “superframe” signal added into one bit position of each lower bandwidth channel frame. The effective bit rate of each constituent link is thus reduced, but not significantly. For example, the bit rate of N cohered E1 links is N×1976 kbps versus the available bandwidth of 1984 kbps. The T1 or J1 bit rate is reduced to 1536 kbps from 1544 kbps. The “superframe” signal is a pseudo-random noise sequence from a shift register generator. The auto-correlation properties of pseudo-random noise sequences make them ideal for such timing purposes.
At the source, the same bit of the pseudo-random noise sequence is inserted on each line. These pseudo-random noise sequences inserted on each transmission line are used at the destination to align the data received from the network. At the destination, pseudo-random noise sequence receivers independently acquire the phase of the timing information in each physically separate signal. However, since separate physical paths are used for the transmission of the data, the data at the receiving end is not in the same data-bit sequence as the data t
Gustave Poiraud Clement Yvon
Lancon Emmanuel
Suffern Edward Stanley
Teleoglou Spiros Joseph
Cesari and McKenna LLP
Cisco Technology Inc.
Ton Dang
Tran Phuc
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