Abstract: Apparatus and a technique for equalizing non-linear distortion in a received modulated data signal by (1) forming tentative decisions as to the values of data symbols represented by the signal preferably using a receiver including a conventional linear equalizer, (2) constructing a replica of the non-linear distortion in response to the tentative decisions, and (3) forming a final decision as to the data symbol values in response to signals including the replica. If desired, the final decisions can also be stored and fed back to the processor which forms the replica, so that the replica is a joint function of past final decisions and future tentative decisions regarding the data symbols represented by the signal samples. The present invention provides increased accuracy by using tentative decisions rather than input samples to form the non-linear distortion replica.

Abstract: In a transmitter for image signals, a variable-length coder whose code set has been optimized for the order statistics of a run-length-coded bilevel image is used to code a stream of differential-pulse-code-modulated (DPCM) errors representing a multi-level image. The DPCM errors are first rearranged on a line-by-line basis in such a way that the rearranged error stream contains many long runs. Individual words in the rearranged error stream are then changed in such a way that, for at least one value of n, the n most-frequently-occurring words in the resulting, processed signal substantially have the aforementioned order statistics. The resulting signal is then run-length-coded, applied to the variable-length coder, and then transmitted. The reverse processing is performed at the receiver.

Abstract: Weighted sums of samples of an interference-corrupted data signal are generated to form phase-compensated, symbol-spaced samples. The interference-corrupted signal is at the same time subjected to conventional adaptive equalization and is otherwise processed so as to form tentative decisions as to the transmitted data. Cancellation signals representing the interference components of the phase-compensated samples are generated by forming respective weighted sums of the tentative decisions and each cancellation signal is combined with a respective phase-compensated sample to provide cancelled samples from which final data decisions are made. The weighting coefficients used to form the phase-compensated samples and the cancellation signals are adaptively updated in response to error signals derived from the difference between each cancelled sample and the corresponding final decision.