System for providing simultaneous voice and data transmission

Details System for providing simultaneous voice and data transmission System for providing simultaneous voice and data transmission

1998-03-13

2001-06-05

Hsu, Alpus H. (Department: 2662)

Multiplex communications

Pathfinding or routing

Combined circuit switching and packet switching

C370S466000, C370S493000, C370S522000

Reexamination Certificate

active

06243377

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to voice and data communication systems, and in particular but not solely to systems which enable simultaneous voice and data transmission over a single telephone line. More particularly the invention relates to improved methods which enable residential subscribers to telephone and Internet services to access both services simultaneously over a single two wire copper line.
BACKGROUND TO THE INVENTION
The traditional method of Internet access from a subscribers home is by way of a dialled up connection to a modem pool at a server operated by an Internet Service Provider. A connection of this kind is set up in the PSTN (Public Switched Telephone Network) and information is transferred in the form of TCP/IP (Transmission Control Protocol/Internet Protocol) packets. The subscriber typically uses a PC (Personal Computer) connected through their telephone line by way of a modem at speeds of around 33 kb/s or possibly up to 56 kb/s in some cases. However, once the connection is set up the telephone line is generally unable to be used for other incoming or outgoing calls. Further, the connection does not make efficient use of PSTN resources in that Internet sessions are relatively long and bursty in nature.
A wide range of systems have been proposed to enable use of a single telephone line for multiple simultaneous data and/or voice related calls. Subscribers to ISDN (Integrated Services Digital Network) can access the Internet using DSL (Digital Subscriber Line) techniques which provide one, two or more B channels. ISDN basic access provides a 2B+D transmission format in which the B and D channels form a TDM (Time Division Multiplexed) signal and operate at speeds of 64 kb/s and 16 kb/s respectively. If one B channel is in use for Internet access another can carry incoming or outgoing telephone calls simultaneously, and both B channels may be used for Internet data when no telephone call is underway. However, ISDN requires an entirely new network solution, and for Internet access generally makes the same relatively inefficient use of PSTN resources as the traditional modem connection.
There is rapid development of other DSL access technology, such as ADSL (Asymmetric Digital Subscriber Line) which provides up to about 9 Mb/s downstream to subscribers and up to about 640 kb/s upstream depending on length of the copper pair. VDSL (Very high rate DSL) provides up to about 20 Mb/s in both directions. These are more expensive and complex than ISDN in that frequency bands above that of the PSTN are generally used, and are less able to operate effectively over long lines. Still other developments for simultaneous use of a single telephone line include Pairgain systems, DSVD (Digital Simultaneous Voice and Data) modems, and IP modems by which data and voice signals are combined in an IP data stream at the subscribers home. Most of these except the IP modem, also make inefficient use of PSTN circuit switching resources.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide for telephone line communication systems which are improved over existing simultaneous voice and data systems in terms of cost, complexity, availability or efficiency of connection, or which at least provide a useful alternative to existing systems.
Accordingly in one aspect, the invention broadly consists in a method of transmitting voice and data signals simultaneously over a single telephone line between subscriber premises and a communication service provider, wherein the signals occupy two or more channels of a TDM format. The signals are multiplexed or demultiplexed at the service provider premises so that an incoming or outgoing data signals for the subscriber passes through a packet network rather than the PSTN. Although an incoming or outgoing voice signal passes through the PSTN generally in the usual way, the data signal is received directly from or sent directly into the packet network and so avoids the relative inefficiency of the PSTN for such signals. Preferably the TDM format makes use of ISDN basic access channels although the ISDN network solution itself is not used. Preferably the TDM signal is encoded using a compressed transmission format such as 2B1Q.
In another aspect the invention consists in apparatus for the subscriber and service provider premises which enable transmission of TDM signals over the subscriber telephone line, and multiplexing or demultiplexing of outgoing or incoming signals respectively at each premises. At the exchange premises connections are made such that voice signals pass through the circuit switched public telephone network in the usual way while data signals pass through a packet switched network and avoid the telephone network. Remote terminal equipment is provided for installation at the subscriber premises while corresponding central terminal equipment is installed at the service provider or exchange premises.


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“Enhanced Network Performance . . . FAST”—Ericsson PGS2 Digital Pair Gain System publication, Ericsson Communications Limited (folded 2-page brochure).
“Improving Access” Hawke's Bay Herald Tribune, May 30, 1997 (1-page news article).
Dave King, “Napier Team Engineers High-Speed Technology”, NZ Infotech Weekly, May 26, 1997 (1-page news article).
“Internet Access Made Faster, Better”, Company Profile Ericsson New Zealand, NZ Infotech Weekly, Monday, Dec. 15, 1997 (2-page news article).

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