General Instrument Corporation of Delaware

Gi, LLC

Zheng Huang

Chris Heegard

A convolutional interleaver and addressing scheme where up to B consecutive symbols containing errors can be interleaved such that they are separated from each other by at least N intervening symbols. Memory, such as RAM, is configured with (B-1) cells of increasing size for storing symbols from a data stream. A first one of the cells has M storage locations which store M symbols. Each successive one of the cells has M more storage locations than the immediately preceding cell for storing M more symbols than the immediately preceding cell, where M=N/B. The cells are successively addressed to write a next symbol from the stream into a next write symbol location in a currently addressed cell and to read a symbol from the location of the currently addressed cell immediately following the next write symbol location. The locations are accessed in a first revolving manner such that the last location in a cell is followed by the first location in that cell. The cells are addressed in a second revolving manner such that the (B-1)th cell is followed by the first cell, or vice versa. An intervening transfer stage between the (B-1)the cell and the first cell to directly transfers the next symbol to the interleaver output. Each consecutive symbol from the stream is written into a next consecutive one of the cells. A deinterleaver has the same structure.

Convolutional interleaver with reduced memory requirements and address

A method and apparatus are provided for recovering and tracking the carrier in a QAM communication system, even under heavy interference conditions. A subset of fixed points is defined on an ideal constellation pattern for comparison to the data points in a received signal. The subset includes all of the points intersected by n radii (e.g., the four diagonals) of the constellation pattern. Additional points along the perimeter of the constellation pattern can also be provided in the subset. Data points received via a carrier are correlated with the fixed points of the subset in order to generate an error signal indicative of a phase difference between the fixed points of the subset and the received data points correlated therewith.

Method and apparatus for recovering a qam carrier

An outer symbol error correcting code is concatenated with a punctured multidimensional trellis code to provide an optimal scheme for communicating digital television signals in a standard (e.g., approximately six MHz) bandwidth channel via a cable television network or the like. An input signal is encoded using an outer symbol error correcting code to produce successive blocks. Each block comprises N seven-bit coded symbols of which M represent information to be communicated and the remaining N-M coded symbols comprise error correcting information. M/N is either 120/126, 121/127 or 122/128. The blocks are interleaved, and may be supplemented with control symbols that include a synchronization pattern for M/N=121/127 or M/N=122/128. The interleaved blocks are convolutionally encoded using an inner trellis code having a punctured rate 4/5 (sixty-four QAM) or 3/4 (sixteen QAM). The output symbols are multilevel modulated for transmission over a communication path using, for example, sixteen or sixty-four QAM. The transmitted symbols are decoded using a trellis decoder, deinterleaved, and further decoded in an outer symbol error decoder concatenated with the inner trellis decoder.

Quadrature amplitude modulated data for standard bandwidth television

Block coded digital data is communicated with associated overhead data in a data stream having a succession of coded blocks. Each block contains N symbols wherein M of the symbols comprise information to be transmitted and the remaining N-M of the symbols comprise error correcting data. The ratio M/N comprises a first information rate. The coded blocks in the data stream are divided into a succession of frames, each comprising F of the coded blocks. A frame overhead symbol is added for each of the frames, to provide the data necessary for a receiver function such as synchronization. The addition of the frame overhead symbols effectively lowers the first information rate to a second desired information rate. A plurality of X of the frames are formed into a superframe containing FX coded blocks and associated frame overhead symbols. X is chosen to provide enough n-bit frame overhead symbols to implement the desired receiver function.

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Willow Grove, PA, United States of America

Zheng Huang