Texas Instruments Corporation

3com Corporation

British Telecommunications Public Limited Company

Richard G Williams

Michael Golanbari

Iain Craig Robertson

Srikanth Gummadi

Tim Murphy

Martin Staszak

Scott A Lery

A Joseph Mueller

John R Rosenlof

Andy L Norrell

The present disclosure provides methods and apparatus for adapting a relatively high data rate second order SERDES receiver to receive relatively low data rate serial data, the receiver having a jog realignment by and having means for receiving the serial data as a plurality of repeated bits at the high data rate; framing the data as frames of repeated bits of the same value; examining the bits of the frame for the presence of bits which are not of the same value; upon detecting such a presence that is indicative of a framing error jogging the SERDES receiver for frame realignment; and supplying to an output of the SERDES receiver one of the bits of said same value from each frame at the low data rate.

Data transfer clock recovery for legacy systems

The present invention provides method and apparatus for adapting a relatively high data rate second order serdes receiver to receive relatively low data rate serial data, the receiver having jog realignment by and having means for receiving the serial data as a plurality of repeated bits at the high data rate; framing the data as frames of repeated bits of the same value; examining the bits of the frame for the presence of bits which are not of the same value; upon detecting such a presence that is indicative of a framing error jogging the serdes receiver for frame realignment; and supplying to an output of the serdes receiver one of the bits of said same value from each frame at the low data rate.

A method and apparatus is presented for detecting the presence of a packet being transmitted on a communications medium using self-correlation of samples taken from the communications medium. The method saves on power consumption by sampling the communications medium at a sampling rate that is lower than the sampling rate used for sampling the data in the packet. An unexpected result is achieved when packet detection performs better at the lower sampling rate than at the higher sampling rate.

Low-power packet detection using decimated correlation

A method for detecting a boundary between two sequences in a wireless local area network is presented that permits rapid detection of the boundary. The method includes provisions for proper operation when significant interference and multi-path can degrade the received transmission significantly. Additionally, when a modification is made to the signaling format to signal a special enhanced mode with performance and features above those that are specified in a single technical standard, the method detects the boundary between sequences regardless of whether they have the standard format or the modified format.

Short and long sequence boundary detection algorithm for wireless LAN modems

A multi-carrier communications system with a programmable interleaver and de-interleaver that can change the interleaving rate for data transmitted and received in the communications system is presented. The programmable interleaver and de-interleaver permits a level of flexibility in determining the immunity of the communications system to errors and sources of interference. The multi-carrier communications system is able to vary the interleaving rate based on input from a user or from data that it maintains from actual network performance. The multi-carrier communications system can change the interleaving rate during the initial installation of the multi-carrier communications system or whenever the system is reset or restarted or on any individual transmission unit.

Interleaving to avoid wideband interference in a multi-carrier communications system

Detecting a boundary between training sequences in a transmission is an important operation. In many communications systems, there are no special boundaries or markers to denote the end of one sequence and the beginning of another. Correlation has been a commonly used technique to detect sequences and a fall in the correlation can be used to indicate such boundaries, but classical correlation can be slow and a significant portion of the new sequence is received prior to the boundary being detected. A method and apparatus is presented that allows rapid detection of the boundary and only a small amount of the new sequence needs to be received prior to the detection of the boundary. Additionally, the method and apparatus can be used to detect the presence of a transmission on the communications medium.

Boundary detection using multiple correlations

A method for recovering from an excessive power cutback in a splitterless asymmetric digital subscriber line modem. The modem may apply a power cutback to enable simultaneous use of the modem and a telephone. The modem determines if the modem's power after the cutback is sufficient to support data communication with the central office. If the power is insufficient, the modem gradually reduces the power cutback, checks the sufficiency of the power again, and repeats this cycle. The modem repeats the cycle until the modem attains an acceptable transmit power where the power requirements for data transfer and noise reduction are balanced.

Method for asymmetric digital subscriber line modem recovery from insufficient transmit power

A method for rapid noise reduction from a splitterless ADSL modem. The modem stores a value for the power level of its transmitter in a table along with transmission characteristics of the telephone loop. The stored value for its power level is the power level that was previously successful with the transmission characteristics in achieving the Showtime data transfer mode. When the modem measures similar transmission characteristics of the telephone loop, such as a slope of the frequency response of the loop, a power level that would suppress downstream noise, or the dc voltage of the loop, the modem searches the table for matching transmission characteristics. If the table contains a table entry that matches these measured transmission to characteristics, the modem restores the stored transmitter power of the modem. In this manner, the modem may rapidly achieve Showtime because it is restoring a transmitter power level that was previously successful under the same condition of the telephone loop.

Method for rapid noise reduction from an asymmetric digital subscriber line modem

A frame mapping technique that uses aspects of Minimum Modulus Conversion (MMC) and Shell Mapping (SM) to map data bits to a sequence of data symbols, or points. The apparatus includes a modulus converter acting as a Mixed Base Ring Selector (MBRS) to generate ring indices from K data bits. The MBRS is combined with a signal point selector to generate a sequence of transmitted symbols. The signal point selector may operate on modulus conversion principles, trellis coding principles, or uncoded bit mapping techniques. The apparatus and method permit the use of constellations having any integer number of points per ring, and a varying number of rings from symbol time to symbol time.

Signaling method having mixed-base shell map indices

A system and method for generating and repetitively transmitting a single modulated symbol during idle periods in user data in a digital subscriber line (DSL) communication system. The modulated symbol to be transmitted is selected such that its spectral properties match those of user data modulated symbols. For an asynchronous DSL system, and variants thereof, a preferred idle symbol is the 'superframe' synchronization symbol. A separate modulated symbol would indicate the end of the idle state. In the preferred embodiment, the end-of-idle symbol is the idle symbol shifted by a 180.degree. phase shift. In a preferred embodiment, the transmitter in a DSL modem would calculate the idle state modulated symbol once at the start of the idle period and then simply repeat this symbol until the end of the idle period, in which case the transmitter would invert the final idle symbol. At the receiver, an idle state modulated symbol detector and phase detector are implemented. Symbol detection can be performed in the time-domain for faster and easier detection, requiring little processing power. Upon detection of a 180.degree. phase shift of the idle symbol, the receiver would exit the idle mode. The invention includes method, apparatus, and computer program implementations.

Idle mode for digital subscriber line

A method and apparatus for shell mapping that is independent of the number of bits to be mapped. Although the number of bits need to be known, the number does not affect the operation of the inventive algorithm and so filling with significant zeros may be used to obtain a large number of bits. This means that any tables used to efficiently implement the algorithm do not need to change when the data rate changes. In particular, the invention orders a set of shell combinations (the N-tuple [m.sub.1, m.sub.2, . . . m.sub.N ] defining a set of shell indices or selectors) such that any group of binary input bits having the same numerical value always selects a same shell combination.

Nested shell mapping

A combined frame mapping technique that uses aspects of Minimum Modulus Conversion (MMC) and Shell Mapping (SM) to map data bits to a sequence of data symbols, or points. The apparatus includes a shell mapper to generate ring indices from K data bits and a modulus converter to select the signal points from within the ring based on B data bits. The apparatus and method permits the use of constellations having any integer number of points per ring. Variations in the constellations from time-slot to time-slot within a frame are also accommodated. The number of rings in each constellation remains constant, but the moduli vary. MMSM produces d.sub.min equal to the best of MMC and SM, and in some cases d.sub.min, may be better than that for either MMC or SM.

Signaling method using multiple modulus shell mapping

Character codes input from a keyboard are transmitted to a remote computer which transmits the codes back by way of acknowledgement. A local display does not await the acknowledgement before displaying the characters but, rather, displays them right away and erases them if the acknowledgement is not received within a set period.

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San Diego, CA, United States of America

Richard G Williams