Pulse or digital communications – Transceivers
Reexamination Certificate
1998-03-18
2001-08-21
Tse, Young T. (Department: 2634)
Pulse or digital communications
Transceivers
C375S377000
Reexamination Certificate
active
06278728
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates in general to digital subscriber line (XDSL) communication systems, and more particularly to a remote XDSL transceiver unit and method of operation.
BACKGROUND OF THE INVENTION
Conventional XDSL transceiver units (xTU's) are located remotely as customer premises equipment (CPE) as well as being located at the loop termination point (e.g., central office, remote terminal). Conventional XDSL transceiver units typically turn on the XDSL transceiver and train the XDSL physical layer connection at power up of the unit. This conventional operation is appropriate for conventional XDSL communication schemes in which each subscriber has a dedicated XDSL transceiver unit at the loop termination point.
SUMMARY OF THE INVENTION
In accordance with the present invention, a remote XDSL transceiver unit having digital off-hook control and a method of operation are disclosed that provide advantages over conventional remote XDSL transceiver units.
According to one aspect of the present invention, the remote XDSL transceiver unit includes an XDSL transceiver and a control block. The XDSL transceiver is operable to establish and communicate across an XDSL physical layer. The control block is coupled to the XDSL transceiver and operates to initiate a request for service to a loop termination point. The control block also operates to control power-up and training of the XDSL transceiver such that the XDSL physical layer can be dynamically brought up and down. In one embodiment, the control block operates to store profile information for an established XDSL physical layer to use for future re-establishment of the XDSL physical layer.
According to another aspect of the present invention, a method is provided for operating a remote XDSL transceiver unit. A first state is provided corresponding to a digital on-hook condition. A second state is provided corresponding to a pending request for service to a loop termination point, and a third state is provided corresponding to a digital off-hook condition. The method includes responding to a busy signal, when in the second state, by moving to the first state. Further, the method includes responding to a grant signal, when in the second state, by moving to the third state. The method also includes training and establishing an XDSL physical layer after moving to the third state. As mentioned above, in one embodiment profile information from the XDSL physical layer can be stored for later use.
A technical advantage of the present invention is the provision of a remote XDSL transceiver unit that has the ability to control transmission and training of the XDSL physical layer. The XDSL physical layer can be dynamically brought up and down based upon data traffic or other conditions.
Another technical advantage of the present invention is the storing of profile information defining the XDSL physical layer after training so that the XDSL physical layer can be quickly brought back up after having been dropped. The XDSL transceiver unit can include an XDSL chipset and a number of registers associated with the XDSL chipset. A control block coupled to the XDSL chipset and the registers can receive profile information and store the profile information in preparation for XDSL communication. The profile information may specify filter coefficients, equalizer tap values, sub-band weighting, data rates, margins, and other information that reflects electrical and/or physical parameters of the twisted pair lines. In a particular embodiment, the XDSL transceiver unit performs a training session at a variety of bands and rates to generate profile information. The profile information can be stored in an appropriate non-volatile memory. The XDSL transceiver unit retrieves the stored profile information to engage in XDSL communication without a protracted training period. The XDSL transceiver unit may also perform a full or partial retraining of the line as needed. The profile information may include, for example, digital filter coefficients used in carrier-less amplitude phase (CAP) modulation, discrete multi-tone (DMT) modulation, or other suitable modulation.
An additional technical advantage of the present invention is the ability to communicate and exchange information between the loop termination point and the customer premises equipment regarding the intent to take down the physical layer to insure that the physical layer is dropped only with the consent of both end points. This can be important for the ability to allow a data link to remain open while the physical link is dropped and restored.
Other technical advantages of the present invention should be apparent from the drawings, description and claims.
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Cantrell Craig
Harrod Jonathan
Locklear, Jr. Robert H.
McClanahan Kip
McHale John F.
Baker & Botts L.L.P.
Cisco Technology Inc.
Tse Young T.
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