Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-07-10
2001-11-06
Chin, Wellington (Department: 2664)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S465000, C370S485000, C370S493000, C370S463000, C379S093010, C375S222000
Reexamination Certificate
active
06314102
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to providing high-speed communications services to ordinary residences and small businesses on digital subscriber lines.
2. Background of the Invention
The sudden emergence of the Internet has produced an urgent demand for high-speed communications services to ordinary residences and small businesses. The terms broadband and wideband are used interchangeably herein to refer to these high-speed communication services. These services are distinguished by bursty data patterns and asymmetrical data transfer—far more information sent toward the subscriber premises than received from it. A partial response to this need, at least on the physical signal level, has been found in new “xDSL” transmission technologies, such as ADSL (Asymmetric Digital Subscriber Line). These have recently become sophisticated enough to allow dynamic bit-rate adaptation on each subscriber line, so that a wide range of loop lengths can be accommodated. But all this variability (bursty data, dynamic bit rates, etc.) has made it nearly impossible to predict, control, manage, or guarantee the Quality of Service (QoS) provided to each subscriber, as required for a viable commercial service.
Several companies are working on ADSL products using DMT (Discrete Multi-Tone) and/or CAP (Carrier-less Amplitude Phase Modulation) technology—each with their own equipment configurations and target applications. These products simply multiplex the ADSL data streams together with little or no flexible bandwidth control and no QoS management features.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the management problems described above by combining the data management features of ATM (Asynchronous Transfer Mode) with the physical-layer transmission flexibility of xDSL.
Another object of the present invention is to provide an architecture for a telecommunications system in which plain old telephone service and a broadband digital service are simultaneously provided to individual subscribers on conventional transmission lines already deployed for telephony.
Still another object of the present invention is to provide such an architecture in such a way as to provide maintainability of the digital subscriber line hardware without interfering with lifeline telephony service to subscribers.
Yet another object of the present invention is to provide the practical hardware components capable of carrying out the above objects for such a system.
According to a first aspect of the present invention, a telecommunications system for providing both narrowband and broadband services to a plurality of subscriber premises comprises at least one shelf for connection to a public switched telephone network (PSTN) and for connection to an asynchronous transfer mode (ATM) network for connecting the PSTN and the ATM network to the plurality of subscriber premises via a corresponding plurality of twisted copper pairs, and a plurality of subscriber modems for connection to the corresponding plurality of twisted copper pairs, wherein each of the twisted copper pairs is for providing a digital subscriber line that accommodates both plain old telephone service (POTS) and digital channels in an ATM format. The digital subscriber line may be an asymmetric digital subscriber line (ADSL). Moreover, it may use a discrete multitone (DMT) technique, as known from American National Standards Institute (ANSI) Specification ANSI T1.413-1995. Or, it may use carrierless amplitude phase modulation (CAP).
ATM and xDSL have not previously been combined in this way to create a complete, viable, general-purpose access communications system for local loops. In fact, ADSL itself has only recently become feasible, since it was not clear how to use the bandwidth above the telephony spectrum (up to 3.4 kHz) over long distances on existing copper pairs. New LSI (large-scale integration) and DSP (digital signal processing) technologies have now made ADSL practical at multi-megabit per second rates, and the demand for high-speed data services (particularly Internet access) has made it necessary. Local telcos are also under tremendous pressure to relieve existing telephone switching systems from the overwhelming Internet/modem traffic they were never designed to handle. By using the system described in this disclosure, operating companies can simultaneously remove congestion from telephony switches, offer high-speed services to customers as a new revenue producer, and expand the types of services (i.e., QoS classes) offered to fit customers' individual needs.
The full bandwidth flexibility of ATM provides the framework to support a wide range of services required by different applications and achieves high-resource utilization. It is particularly advantageous in the present invention that ATM provides the possibility to reserve resources in the network to meet the quality of service requirements of the applications desired by the subscribers. This is particularly so in the present invention, because of the nature of, e.g., asymmetric digital subscriber lines wherein a very large bandwidth is dedicated downstream with a relatively small bandwidth reserved for upstream communications from subscribers. In that case, with an architecture having a large number of subscribers connected to an upstream network element, there can be, depending on the number of subscribers potentially connected to the network element, a severe bandwidth contention problem in the upstream direction. This can be balanced to some extent, according to the present invention, by offering differing qualities of service to the subscribers, which can be implemented by telcos using different rate structures.
According to a second aspect of the invention, a telecommunications system comprises subscriber equipment and provider equipment, with the subscriber equipment including a lowpass filter for use at a subscriber's premises responsive to a telephony signal occupying a baseband position in a frequency-division multiplexed signal, also having a wideband signal occupying a position above baseband, for only providing the telephony signal for use in voice communications between the subscriber's premises and a public switched telephone network, and a digital subscriber line modem for use at the subscriber's premises, responsive to the frequency-division multiplexed signal for providing the wideband service for use in digital communications between the subscriber's premises and a packet network, and wherein the provider equipment includes a shelf, responsive to the telephony signal and to the wideband signal, for providing the frequency-division multiplexed signal.
The second aspect of the present invention allows telephone subscribers to obtain efficient, high speed digital services to their homes and businesses over existing telephony copper pairs—while conventional analog “lifeline” telephony services are simultaneously provided with high integrity on the same pairs.
The key to these and other aspects of the present invention is a unique system architecture and a novel combination of xDSL and packet technology that work together to economically deliver services such as Internet access at speeds more than 100 times faster than conventional analog modems.
By providing the lowpass filter separately from the digital subscriber line modem, the modem can be maintained separately and without interfering with the lifeline telephony services, thereby providing the above-mentioned high integrity. A similar separation of the telephony services from the wideband services can be accomplished in the shelf as well, by providing a separate lowpass filter that is not part of the line termination of the wideband service in the shelf.
The preferred embodiment described below overlays adaptive-rate ADSL-coded, ATM-formatted data on existing copper pairs, but it should be realized that the system architecture described below can incorporate any kind of packet network and/or any of a variety of Di
Bailey Richard H.
Boeykens Eduard C. M.
Borowski Emmanuel F.
Czerwiec Richard M.
De Wulf Koen A. G.
Alcatel
Chin Wellington
Duong Frank
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