Telephonic communications – Telephone line or system combined with diverse electrical... – Having transmission of a digital message signal over a...
Reexamination Certificate
1998-05-22
2001-08-28
Woo, Stella (Department: 2743)
Telephonic communications
Telephone line or system combined with diverse electrical...
Having transmission of a digital message signal over a...
C379S093010, C379S093080
Reexamination Certificate
active
06282273
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates in general to data communication, and more particularly to a communication server apparatus using frequency multiplexing and method.
BACKGROUND OF THE INVENTION
A communication server provides access to communication facilities. For example, a communication server having a bank of modems may provide subscriber access to the modems for data communication. A communication server may be associated with its own dedicated communication network, or with an existing communication network, such as the public switched telephone network (PSTN).
As communication networks provide greater connectivity and access to information, there is an increasing demand for data communication at higher rates. One solution to provide increased data rates replaces existing twisted pair wiring with high bandwidth media, such as coaxial cables or fiber optic links. Other solutions adopt improved communication techniques using the existing hardware infrastructure. For example, digital subscriber line (XDSL) technology provides higher bandwidth data service over existing twisted pair wiring.
To deliver data service to the subscriber, a communication server may provide a dedicated or permanent connection to its communication facilities. For example, an existing communication server at a central office provides enough communication facilities to simultaneously service all PSTN subscribers. However, all telephone subscribers may not desire data service. Furthermore, the subscribers that desire data service may not simultaneously access the communication server.
SUMMARY OF THE INVENTION
In accordance with the present invention, the disadvantages and problems associated with communication servers have been substantially reduced or eliminated. In particular, a communication server apparatus using frequency multiplexing and method are disclosed that provide data service to a number of subscribers using a reduced number of XDSL communication facilities.
In accordance with one aspect of the present invention, a communication server includes a plurality of pairs of receiver/buffers and transmit/buffers coupled to associated twisted pair data lines. The communication server also includes a plurality of pairs of frequency agile modulators and demodulators. Each frequency agile modulator and demodulator pair is coupled to an associated receiver/buffer and transmit/buffer pair and is set to operate at a unique frequency. The communication server further includes a plurality of pairs of demodulators and modulators. Each demodulator and modulator pair has a designatable operation frequency. A plurality of XDSL modems are each coupled to an associated demodulator and modulator pair. A mixer is coupled to the pairs of frequency agile modulators and demodulators and coupled to the pairs of demodulators and modulators. The mixer operates to combine signals from the frequency agile modulators and provide the combined signal to the demodulators. The mixer further operates to combine signals from the modulators and provide the combined signal to the frequency agile demodulators. The communication server includes a detector that operates to detect a need for data service on a selected twisted pair data line. A controller is coupled to the detector and to the pairs of demodulators and modulators. The controller operates to select one of the XDSL modems in response to detecting the need for data service. The controller further operates to couple the selected twisted pair data line to the selected XDSL modem by designating the demodulator and modulator pair associated with the selected XDSL modem to operate at the unique frequency of the frequency agile modulator and demodulator associated with the selected twisted pair data line.
According to another aspect of the present invention, a method is provided for coupling a selected subset of a plurality of twisted pair subscriber lines to a plurality of XDSL modems. Each twisted pair subscriber line is split into a twisted pair data line and a twisted pair phone line. For each twisted pair data line, signals received on the twisted pair data line are modulated at a unique frequency associated with the twisted pair data line. The modulated received signals are mixed to produce a combined incoming signal. For each XDSL modem, the combined incoming signal is demodulated at a designated frequency associated with the XDSL modem and outgoing signals are modulated at the designated frequency. The modulated outgoing signals are mixed to produce a combined outgoing signal. For each twisted pair data line, the combined outgoing signal is demodulated at the unique frequency associated with the twisted pair data line to recover signals for transmission on the twisted pair data line. A need for data service is detected on a selected twisted pair data line, and one of the XDSL modems is selected in response to detecting the need for data service. The selected XDSL modem is then coupled to the selected twisted pair data line by setting the designated frequency associated with the XDSL modem to the unique frequency associated with the selected twisted pair data line.
An important technical advantage of the present invention is that frequency multiplexing can be beneficial to a communication server located at a cable operator.
Another important technical advantage of the present invention is the distribution of the switching function to allow scalability of the number of supported data lines and over-subscription of XDSL modems.
Important technical advantages of the present invention include a communication server that provides data service to a number of subscribers using a reduced number of XDSL communication facilities. Over-subscription of data service is accomplished by selectively coupling a number of twisted pair data lines to a reduced number of XDSL modems. A controller polls the data lines in succession to determine which subscribers of the communication system need data service. Upon detecting a need for data service on a selected data line, the controller directs a switch to couple the selected data line to an available modem. The communication server may then provide data service suitable for high bandwidth applications, such as video-on-demand, multimedia, or Internet access.
Another important technical advantage of the present invention includes a communication server that provides over-subscribed XDSL data service using the existing infrastructure of the public switched telephone network (PSTN). Asymmetric digital subscriber line (ADSL), symmetric digital subscriber line (SDSL), high-speed digital subscriber line (HDSL), very high-speed digital subscriber line (VDSL), or other suitable XDSL technology can provide higher bandwidth data service over existing twisted pair wiring. These technologies may support data service simultaneously with traditional telephone service using a separation technique, such as frequency division multiplexing. In one embodiment, a splitter divides each incoming twisted pair subscriber line into a twisted pair phone line and a twisted pair data line. The phone line is coupled to a telephone switch to provide telephone service and the data line is coupled to the communication server to provide over-subscribed XDSL data service. The communication server and splitter may be located at a central office of the PSTN.
Another important technical advantage of the present invention includes the management and monitoring of XDSL data service provided to subscribers. To accomplish this, the communication server maintains an activity table to determine status information on twisted pair data lines and XDSL modems. In addition, the communication server can track subscriber usage, monitor subscriber information and generate billing and demographic information. In a particular embodiment, an activity detector disconnects a subscriber after a predetermined period of inactivity to release a modem for use by another subscriber.
An additional important technical advantage of the present invention includes switching the conne
Hall Clifford L.
Ham Ronald E.
Locklear, Jr. Robert H.
McCullough Jason
McHale John F.
Baker & Botts L.L.P.
Cisco Technology Inc.
Woo Stella
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