 Multiple clock synthesizer |
| In a preferred embodiment of the invention, there is provided a multiple clock synthesizer having ... |
|
| Phase and frequency adjustable digital phase lock logic system |
| According to the present invention, a phase lock logic system is provided for determining (i) the ... |
|
| Digital phase alignment and integrated multichannel transceiver employing same |
| We claim: 1. A synchronizer for phase aligning an input signal, having a data transition, with a ... |
|
| Spread spectrum communication apparatus |
| It is an object of the invention to rapidly and properly set a transmission power. Another object ... |
|
| Advanced technology anti-G suit |
| Referring now to FIG. 1 of the drawings, there is shown a simplified perspective view of an anti-G ... |
|
| Multiple satellite repeater capacity loading with multiple spread spectrum gateway antennas |
| This invention is directed to a communication system, and to a method executed by same, for ... |
|
| Partial-response-channel precoding |
| In the HDTV system shown in FIG. 1, binary input data in the form of an HDTV signal is generated ... |
|
| Method of digital transmission of messages using dynamic-range-limited precoding |
| An object of the invention is to reduce the dynamic range of the received signal in a digital ... |
|
| Adaptive pre-equalizer for use in data communications equipment |
| In accordance with the invention, the foregoing error propagation problem is solved by using the ... |
|
|
Fast retrain based on communication profiles for a digital modem
| Details |
Inventors: Hamdi, Rabah S.;
Assignee: Compaq Computer Corporation (Houston, TX)
Primary Examiner: Chin; Stephen
Assistant Examiner: Jiang; Lenny
Attorney, Agent or Firm: Akin, Gump, Strauss, Hauer & Feld, LLP
A digital modem for operating in a splitterless environment that supports fast retrain based on communication profiles. The modem includes a memory that stores a plurality of communication profiles, ADSL communication logic that sends and receives information via a phone line and that operates according to any one of the plurality of communication profiles, and signal quality monitor logic that continuously monitors communication on the phone line. The monitor logic provides a signal change indication if the signal quality changes by at least a predetermined amount. The modem further includes fast retrain logic that selects another one of the profiles stored in the memory in response to the signal change indication, that retrains the communication logic to operate according to the selected profile and that cooperates with the communication logic to transmit a fast retrain indication via the phone line to the central office ADSL modem. The digital modem may also include training or measurement logic that determines the communication characteristics of the phone line, that generates a corresponding profile and that sends the new profile to the other modem via the phone lines. |
|
DETAILED DESCRIPTION A digital modem that supports fast retrain based on communication profiles according to the present invention includes a memory that stores a plurality of communication profiles.
The modem also includes communication logic that sends and receives information via a transmission medium and that operates according to any one of the plurality of communication profiles, and monitor logic that continuously monitors communication by the communication logic on the transmission medium according to any one of the plurality of communication profiles and that provides a signal change indication if the communication characteristics change by at least a predetermined amount.
The modem further includes fast retrain logic that selects another one of the communication profiles stored in the memory in response to the signal change indication, that retrains the communication logic to operate according to the selected communication profile and that cooperates with the communication logic to transmit a fast retrain indication via the transmission medium.
In the embodiments illustrated, the digital modem is an ADSL modem that operates according to the Discrete MultiTone (DMT) modulation method using a plurality of upstream and downstream tones, where each tone is within one of a plurality of sub-channels or sub-frequencies of the transmission medium bandwidth.
The ADSL modem may operate at a home location without requiring a POTS splitter.
The ADSL modem, otherwise referred to as the Remote ADSL Termination Unit (ATU-R), communicates with a Central Office ADSL Termination Unit (ATU-C) located at the central office of the telephone company.
Because a POTS splitter is not present, the digital modem operates on the same phone lines or transmission medium as one or more standard telephones operating according to POTS.
In this manner, POTS signaling and on/off hook transitions of the telephones change the communication characteristics of the phone lines and affect ADSL communications.
The signal quality is compromised so that the same data rate may not be maintained
|
|
Multiplexer-related 
