Texas Instruments Corporation

Alantro Communications, Inc.

Other

Chris Heegard

John Timothy Coffey

Matthew Brendan Shoemake

Stanley K Ling

Richard G C Williams

Peter Murphy

Eric J Rossin

Scott Petler

The present invention provides methods for generating self-inverting turbo code interleavers having high separation and high dispersion characteristics. Methods are provided for deterministically generating self-inverting turbo code interleavers from a specification for an existing non-self-inverting interleaver. Methods are also provided for randomly generating self-inverting turbo code interleavers. The present invention also provides methods and apparatus for encoding digital data and communicating the digital data using self-inverting turbo code interleavers/de-interleavers.

Methods and apparatus for self-inverting turbo code interleaving with high separation and dispersion

A separated synchronizing scrambler/descrambler pair that removes the possibility of catastrophic error due to improper transmission of initial condition information without disrupting the OFDM modulation scheme of a system that includes error-correction coding circuitry and replay variation. A transmitting device within the pair includes a first and a second data scrambler wherein the first data scrambler couples to receive the incoming data stream and filters the incoming data stream to provide a first filtered signal using a key signal. The second data scrambler, having an initial condition, couples to receive the first filtered signal and converts it into a scrambled signal using a scrambling seed. The second data scrambler comprises a random series generator for generating the scrambling seed to convert the first filtered signal into a scrambled signal. The scrambled signal is transmitted to the receiving device. A receiving device within the pair includes a first and a second data descrambler coupled together. The first data descrambler, having an initial condition equivalent to that of the second data scrambler, couples to receive the transmitted scrambled input data stream to convert it into a descrambled signal using a descrambling seed equivalent to the scrambling seed. The first data descrambler includes a random series generator for generating the descrambling seed. The second data descrambler couples to receive the descrambled signal and filters it to provide a filtered descrambled signal using a feedforward filter and a key signal. The feedforward filter is structured similar to the feedback filter.

Separate self-synchronizing packet-based scrambler having replay variation

A method of increasing the data rate in a wireless Ethernet employs clock switching between the preamble and the encoded data portion of a packet structure. A shift block includes a tail sequence and a head sequence that is inserted between the preamble and the encoded data portion. The clock switching occurs within the shift block between the tail and the head sequences. The tail sequence and the head sequence are each constrained to be a fixed sequence.

Method of increasing data rate in a wireless data communication network via clock switching

The present invention provides a method and apparatus for selectively updating an adaptive element in a communications receiver based on a determination that the received data is accurate. When inaccurate data is received, the system determines that using that data to update the adaptive element will not be beneficial and excludes the data from being sent to the adaptive element. One mechanism for determining that data has been incorrectly received is the calculation of syndromes as part of a Forward Error Control (FEC) system. Detection of errors through use of the syndrome calculation can be supplemented through windowing to make a determination as to whether a number of received bits should be used or disregarded by the adaptive element. The adaptive element can comprise any number of decision-directed loops including adaptive processors and carrier and timing recovery loops.

Reliable decision directed adaptation in a communication system employing forward error control

A method and apparatus for accurately estimating the carrier frequency offset and the carrier phase offset of a digitally modulated signal using a signal processing algorithm to initialize the state variables of a Phase-Locked Loop (PLL) is disclosed. A sequence of phase values is estimated from a received sequence of symbols and the angular effect due to the modulation format is removed from the sequence of phase values. A curve-fit algorithm based in one embodiment on the RLS algorithm is then applied to a sequence of unwrapped phase values to estimate the carrier frequency offset and the carrier phase offset.

Phase-locked loop initialization via curve-fitting

A method and apparatus for joint equalization and decoding using a search-based decoding algorithm on a channel exhibiting intersymbol interference distortion is described. A sequence of information bits is encoded and modulated wherein a finite state machine described with a tree structure is implemented. The information bits are transmitted over a transmission channel having a finite impulse response. At the receiving end, a sequential decoding algorithm is used to retrieve the sequence of information bits. In one example embodiment, a Fano sequential decoder emulates the cascade of finite state machines formed by the trellis code and the channel finite response characterization to determine encoded symbols as prescribed by the path through the various branches of the tree in response to computed metrics. The distance metrics determine the path through the tree that best matches the received symbols.

Joint equalization and decoding using a search-based decoding algorithm

A 64-state binary convolutional code is disclosed for a high-speed physical layer (PHY) of a communication network. The proposed code provides improved performance in terms of signal to noise ratio (SNR) and multi-path rejection than previously known codes. The proposed system, which includes binary convolutional codes with scrambling in a packet-based system, is referred to herein as &ldquo;packet binary convolutional coding&rdquo; (PBCC). The substantial increase in performance that may be achieved by PBCC makes it an ideal solution for high performance forward error correction (FEC) in a high-speed PHY.

Packet binary convolutional codes

A method and apparatus for decision-directed adaptation for coded modulation is presented in which a modulation decoder and data re-encoder are used to create an estimated version of a received signal based on the use of a reliable modulation code. An adaptive equalizer is used to process the received signal, and the differences between the received signal passed through the adaptive equalizer and the estimated version are used by the adaptive equalizer to set the equalizer coefficients. A variety of adaptation algorithms can be used including Least Mean Squares (LMS) and Recursive Least Squares (RLS).

Decision-directed adaptation for coded modulation

A method and apparatus for performing a fast search in a search-based decoding algorithm. In one embodiment, the Fano sequential decoding algorithm is used in combination with a fast search-based decoding scheme to reduce the latency inherent in the decoding algorithm. The fast search-based decoding scheme provides a method for estimating metrics ahead of time for edges at distance d at least equal to 2. This allows a decision module such as a Fano state machine to readily make a decision as to which direction and edge to proceed on without further metrics calculation.

Fast search-based decoding scheme

A method and apparatus for producing a variable rate precoded signal are presented in which a variable rate encoder receives a rate control signal and a data signal and generates a constellation size signal and data symbols. The data symbols and constellation size signal can be used by a precoder to produce a variable rate precoded signal. The precoder can be a Tomlinson/Harashima-Miyakawa precoder which uses the constellation size signal as part of the quantization process. The system can also be used to generate a variable rate modulation encoded signal. The invention provides the ability to create a variable rate signal which can be precoded and to which error correcting codes can be readily applied.

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Santa Rosa, CA, United States of America

Chris Heegard