Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1999-06-02
2001-05-29
Patel, Ajit (Department: 2662)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S524000, C370S254000
Reexamination Certificate
active
06240107
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to communication systems, and is especially directed to a new and improved customer premises equipment-associated communication device, that is operative to automatically configure itself to interface a selected one of a plurality of different types of digital communication signals that may be transported over a telecommunication channel, such as, but not limited to a basic range integrated services digital network (ISDN) channel and an extended range ISDN channel. For the case of differential range ISDN channels, the communication device of the invention is operative to determine whether the line to which it is coupled transports a basic rate ISDN channel (typically having a repeaterless two-wire transport range on the order of 15-18 Kft), or whether extended range ISDN service having an extended repeaterless two-wire transport range (e.g., a distance on the order of 25 Kft or greater) is employed. Once this determination is made, the equipment automatically configures itself to interface the identified communication channel type.
BACKGROUND OF THE INVENTION
In order to satisfy ANSI requirements for digital data communications, telephone subscriber copper wire lines have had to comply with specified industry standard performance criteria, that inherently limit the operational range of a two-wire loop. For example, in the case of ISDN basic rate digital subscriber lines (having a data rate of 160 kilobits per second, including bidirectional data payload and overhead maintenance channels), the ANSI standard T1.601 for two-binary/one, quaternary/four level (2B1Q) modulation, two-wire, full-duplex data transport with echo cancellation, requires that the two-wire loop loss of the ISDN channel not exceed 42 dB at 40 KHz, or 1300 ohms, resistive. This loss limitation necessarily constrains the operational range of a 2B1Q ISDN two-wire loop to a range on the order of 15-18 kft, using No. 26 (American Wire Gauge) wire, and commercially available ISDN transceiver interface equipment.
Extending ISDN communications to digital communication equipment at a customer premises that lies geographically beyond this range requires that the service provider either install repeaters, or use a different communication medium, such as a T1 carrier fiber optic link. Unfortunately, each of these proposed solutions to the extended range problem carries with it a substantial cost penalty that the customer is unwilling to bear. The repeater approach is especially costwise egregious, as it requires installation of both an office end repeater powering unit, plus a repeater mounting pole, or a subterranean, environmentally hardened housing (bell jar) for the repeater. Not only does this involve the use of additional equipment (including the cost of the repeater hardware and its installation), but it entails the expense and labor of maintaining the repeater enclosure.
Similarly, although T1 channel banks located in both the switch office and another downstream location (office or remote hut), that is geographically ‘close’ to the subscriber premises, can accept basic rate interface transmission extender (BRITE) cards for T1 carrier extension, the fact that T1 carrier systems have a capacity for ‘multiple’ extended basic rate service means that their use to deliver only a single basic rate extended service is prohibitively expensive and impractical.
Advantageously, these problems are solved by the invention described in U.S. Pat. No. 5,809,033 (hereinafter referred to as the '033 patent), issued Sep. 15, 1998 to M. Turner et al, entitled: “Use of Modified Line Encoding and Low Signal-to-Noise Ratio Based Signal Processing to Extend Range of Digital Data Transmission Over Repeaterless Two-Wire Telephone Line,” assigned to the assignee of the present application and the disclosure of which is incorporated herein. Pursuant to the invention described in the '033 patent, the range of digital data communication services, such as a basic rate ISDN channel, is ‘repeaterlessly’ extendable to well beyond the basic rate ISDN two-wire loop range, by a communication mechanism which changes the line code or modulation format, and employs enhanced signal processing techniques, which may be of the type employed in high bit rate digital subscriber line systems, to accommodate a diminished signal-to-noise ratio resulting from the added insertion loss inherent in the extended transport distance of the two-wire pair.
Now although the digital telecommunication range extension scheme described in the '033 patent enables the telecommunication service provider (TELCO) to deliver two different types of digital communication signals (basic range and extended range digital signals) to its customers, from a hardware inventory and delivery standpoint, the TELCO prefers to stock and install only one type of digital communication equipment, and desires that what is installed be the correct equipment for the line of interest. This is particularly true, for example, in the case of ISDN service where the customer premises equipment is located at the outer edge of the basic rate (ISDN) service range.
SUMMARY OF THE INVENTION
In accordance with the present invention, this issue is successfully addressed by a ‘universal’ digital communication device that supports multiple types of communication signals, such as basic rate ISDN signalling capability and extended range ISDN signalling capability, as non-limiting examples. As will be described, the invention incorporates a line type resolution mechanism that is operative to automatically determine the type of service—e.g., basic rate ISDN channel, or extended range ISDN service. The device then configures itself to interface the identified service type.
For this purpose, the digital communication device of the present invention comprises a plurality of different types of signaling units; for the case of ISDN channels,—a basic rate (2B1Q) ISDN signalling unit, and an extended range (3B1O) ISDN signalling unit, such as that described in the above-referenced '033 patent. This extended range signaling unit contains an encoding and translation operator that achieves a reduction in symbol rate equivalent to transmitting three information or payload bits per symbol (a construct for which may be expressed as or represented by a (three binary, one octal/eight level) line code), instead of the two bits per symbol that are transmitted using 2B1Q line code modulation.
For a 160 kilobits per second ISDN basic rate interface, an initial symbol rate reduction of transmitting three information or payload bits per symbol instead of two bits per symbol means that the same number of information bits can be transmitted at two-thirds the standard symbol rate, or at a symbol rate of 53,333 symbols per second, which has the inherent property of increasing the transmission distance over the two-wire link that will comply with the above-referenced ANSI loss standards.
The basic rate (2B1Q) ISDN signalling unit and the extended range (3B1O) ISDN signalling unit are selectively coupled through a processor-controlled digital terminal equipment (DTE) associated multiplexer unit to digital terminal equipment (DTE) of a customer premises served and to the network. On the network side, the DTE multiplexer unit is coupled to a TELCO interface of the telephone network. On the DTE side of the device, the multiplexer unit is coupled by way of a digital link such as an RS-232 link to customer premises equipment.
The basic rate ISDN signalling unit, which may comprise a commercially available “U”-chip, has a first bidirectional signalling port coupled to a control and data bus interface of the device's control processor. The control processor is operative to interface data in the appropriate format (e.g., RS-232) with the customer premises equipment, and to interface 2B1Q ISDN data with each of the basic rate signalling unit “U”-chip and the extended range ISDN signalling unit. The ISDN “U” chip has a second bidirectional signalling port coupled via an IDL in
Glass, III James M.
McElroy Paul Graves
Mitchell Bruce E.
Adtran Inc.
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Nguyen Hanh
Patel Ajit
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