Paradyne Corporation

At+t Corp.

Summit Technology Systems, LP

Edward Arthur Thoenes

P Michael Henderson

Joseph Q Chapman

William Lewis Betts

Gordon F Bremer

Anthony A Tzouris

J Scott Alexander

The preferred embodiments of the present invention generally provide improved communications over a subscriber loop that is loaded with at least one and potentially a plurality of load coils. The preferred embodiments of the present invention will work over loaded subscriber loops that also support a native POTS interface as well as over loaded subscriber loops that are not providing a native POTS interface. Furthermore, although the preferred embodiments of the present invention are intended to address the technical and business problems of service providers delivering digital subscriber line service over loaded loops, the preferred embodiments will also work over unloaded loops. Various duplexing strategies such as, but not limited to, time-division duplexing (TDD), adaptive time-division duplexing (ATDD), four-wire duplexing, and/or extended performance echo cancelled duplexing (EP ECD) provide improved performance on loaded loops that generally offer significant signal attenuation at frequencies above 4 KHz. In addition, such duplexing strategies can start and stop quickly enough to pass various POTS interface signaling generally without creating a significant adverse effect on DSL data communications.

Digital subscriber line service over loaded loops

Disclosed is a circuit and method that eliminates the problem of voice echo created by the use of simultaneous voice and data (SVD) modems in a remote office application. In the instant invention, a voice signal originates in a remote office telephone and is modulated with a data signal and sent from a first SVD modem to a second SVD modem, where it is demodulated and then routed from the second SVD modem back into the switching network to a second telephone where a voice echo signal may be created by existing hybrid transformers. This echo signal will follow the return path of the voice signal to the second SVD modem where it is modulated with a data signal, sent back to the first SVD modem, demodulated, and then routed back to the remote telephone. The echo and voice signal is thus delayed by the modulation and demodulation of the voice and data signals in both SVD modems by a time period of greater than thirty-five milliseconds. The result is an intolerable and disruptive echo signal that is perceived by the person speaking in the remote which is eliminated by the introduction of voice echo cancellation in the circuit.

Voice echo cancellation for SVD modems

The present invention provides a method and apparatus for multi-protocol, point-to-point communications which allocates processing tasks between a processor of an end point device and a processor of a communication device. The processor of the end point device performs all higher level protocol processing and the processor of the communication device performs lower level protocol processing. Internet service providers usually have several modems connected to each host computer for providing simultaneous point-to-point communication with a plurality of end users. The modems normally are located on cards which reside inside of the host computer, which may be a personal computer. To prevent the host processor from having to perform all of the protocol processing tasks for each session, the present invention provides for off-loading at least a portion of the Point-to-Point Protocol processing onto the modem processors. The host and the communication device or devices are interfaced via a shared memory device. This increases throughput and leaves the host processor free to perform other tasks. Preferably, the modem processors perform the portion of Point-to-Point Protocol processing which includes framing and unframing, Frame Check Sequence generation and checking and shielding and unshielding.

Method for processing asynchronous low-level protocols in a

In a multidrop data communication system operating at a first bit rate using the High-Level Data Link Control (HDLC) protocol, dial restoral of communications with a particular tributary at a second, lower bit rate is accomplished without requiring the system as a whole to back down to that lower bit rate. Specifically, the outgoing data is buffered in the dial restoral modem, which discards the data stored in the buffer upon receipt of the HDLC frame which follows any frame in which the so-called 'poll' bit is set.

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St. Petersburg, FL, United States of America

Edward Arthur Thoenes