Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1997-10-10
2002-07-02
Kizou, Hassan (Department: 2662)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S401000, C375S222000
Reexamination Certificate
active
06414952
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to computer network gateways and more particularly to computer network gateways that connect a local area network to one or more distinct networks sharing the same electrically contiguous communication channel.
2. Description of the Related Art
The expansion of the Internet and the world wide web, the prevalence of telecommuting, and the anticipation of video on demand has generated a demand for the delivery of digital information to customer premises at bandwidths higher than can be delivered using traditional voice-grade modem technology.
Various solutions to the high bandwidth delivery problem are under development. Unfortunately, many of these solutions require the installation of a new wiring or cabling infrastructure to deliver information to a customer premises. One class of technology that does not have this drawback is digital subscriber line (xDSL) technology. Digital subscriber line technology has the advantage that it uses the existing subscriber line (local loop) infrastructure to deliver a higher bandwidth signal to a customer premises. This means that it uses the existing unshielded twisted pair (UTP) copper wiring that connects to a customer premises (subscriber premises).
The preferred xDSL technology, Asymmetric Digital Subscriber Line (ADSL), achieves the delivery of higher bandwidth by installing ADSL modems at both ends of the subscriber loop (e.g., at the telephone central office and at the customer premises). ADSL signals are then transmitted between the ADSL modem at the central office (ATU-C), and premises ADSL modem (ATU-R) over the existing UTP subscriber loop wiring.
FIG. 1
illustrates the spectral allocation
100
on an asymmetrical digital subscriber line (ADSL). The baseband portion of the spectrum is allocated for POTS connections
101
and the portion from 25 KHz to 1.1 Mhz is allocated for ADSL signals
102
. ADSL signals
102
provide access to wide area computer networks and the POTS connections provide access to the public switched telephone network (PSTN).
Many customer premises provide xDSL access to more than one computer at a premises. Conventionally, this multiple access is provided using a 10baseT LAN to connect multiple computers to an xDSL modem/hub. The xDSL modem/hub performs xDSL modem functions and additionally may perform gateway (networking bridging) functions to facilitate communication between the premises LAN and the WAN made accessible via xDSL technology.
FIG. 2
illustrates a conventional xDSL system that provides multiple computers
201
with access to a wide area network (WAN)
202
via xDSL. The exemplary xDSL system uses asymmetrical digital subscriber loop (ADSL) technology. The system includes a conventional ADSL modem/hub
203
that operates as a network hub (e.g., a 10/100baseT Ethernet hub) for local area network
205
. LAN
205
, also known as the Premises Distribution Network is a point to point LAN having a star configuration centered around the hub portion of ADSL modem/hub
203
. Installing LAN
105
involves the installation of a wiring network that supports 10/100baseT Ethernet. This means that new wiring or cabling must be “pulled” for each computer
201
to be included in LAN
205
ADSL modem/hub
203
is coupled to a telephone central office
207
via a subscriber loop. ADSL modem/hub
203
includes a POTS splitter
213
that may couple plain old telephone service signals to the exiting (installed) plain old telephone service (POTS) UTP wiring (POTS wiring)
206
at the customer premises
204
.
In operation, a conventional ADSL modem
208
(ATU-C) located at central office
207
receives digital signals from a wide area network
202
, modulates the received signals and then places them on the UTP subscriber loop using a POTS splitter at the central office. This POTS splitter combines ADSL signals and POTS signals for transmission to the premises and conversely splits POTS and ADSL signals upon reception from the premises.
Preferably, ADSL modem/hub
203
is located at the telephone Network Interface (TNI)
210
at the demarcation point between the subscriber loop and the customer premises so that the output of the POTS splitter
213
is coupled to the premises UTP wiring before any branching occurs and before the installation of any RJ-11 jacks. The subscriber loop is thus terminated at the ADSL modem/hub, which is an active device requiring AC power. Locating POTS splitter
213
elsewhere at a customer premises requires knowledge of the customer premises wiring topology and the willingness to electrically “break” the wiring at the splitter insertion point in order to insert the active device (e.g., the ADSL modem/hub
203
). Without a clear understanding of the customer premises wiring topology, it is difficult to know which part of the premises wiring will carry both ADSL and POTS signals as opposed to only POTS signals. Most typically, the POTS splitter is integral with the ADSL modem/hub (as shown in
FIG. 1
) therefor, it is preferred to install the ADSL modem/hub
203
at or near the TNI
210
. Placing on ADSL modem/hub
203
at the TNI
210
, however, has certain drawbacks such as the need for an AC power source/outlet near the TNI and the risk of exposure to harsh environmental elements (e.g., temperature extremes, rain, etc.). Further, when the hub and the modem are combined, new wiring must be “pulled” to the TNI from computers
201
to complete network connections.
The above described system known in the art provides for communication between multiple device networks: a WAN, a LAN at a customer premises and the PSTN. This communication is enabled using an active device (e.g., an ADSL modem/hub) that breaks the electrical continuity between the subscriber loop and the premises LAN (Premises Distribution Network) with the installation of an active device, typically a hub, in order to provide hub/gateway functionality between the LAN and the WAN.
The above described system has several drawbacks. The system requires the installation of a new active device (the hub
203
) that adds considerable cost and installation complexity. Further, installing new wiring for a LAN at the customer premises is complex and costly, and the LAN and the subscriber loop do not share the same electrically contiguous communications medium. The LAN wiring does not support DC current flow from the subscriber loop, which means POTS, and more particularly, POTS lifeline service, is not supported on the LAN wiring.
Thus, there is a need for an improved system and method for interconnecting distinct premises LAN and subscriber loop WAN device networks without the need for insertion of an active hub/gateway device between the premises POTS wiring and the subscriber loop, without the pulling of new cable to implement the premises LAN, and without breaking the electrical continuity (DC current capability) of the wiring—which would preclude POTS lifeline service.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a system and method for providing bi-directional communication between a first device network and a second device network using a shared electrically contiguous communication channel such as an existing (already installed) customer premises plain old telephone (POTS) wiring. Each device network is coupled to the shared electrically contiguous communication channel and each are further allocated separate spectral bands for use on the shared communication channel. Thus, two distinct device networks coexist on a single shared communication channel using frequency division multiplexing. Communication between the distinct device networks is perfected by converting signals from the spectral band associated with the source network to the spectral band(s) associated with the destination network.
The gateway server of the present invention is advantageously operatively coupled to the shared communication channel without breaking the electrical continuity of the shared communication channel. Because electrica
Broadcom Homenetworking, Inc.
Christie Parker & Hale LLP
Kizou Hassan
Pezzlo John
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