Multi-dimensional combined equalizer and decoder

Abstract

A multi-dimensional equalizer/decoder is disclosed for equalizing a channel transmitting electrical pulses corresponding to a plurality of interdependent symbols formed according to the rules of a multi-dimensional code (e.g. block lattice coded modulation). The symbols are received by the equalizer/decoder over multiple symbol (baud) periods because it takes more than one symbol period to receive a minimum decodable number of symbols on the given number of physical channels. The equalizer/decoder employs a preliminary and a final decision device which cooperate with the components of an 'equalization layer.' A plurality of equalization layers may be used if the symbols are received over a plurality of physical channels. Each equalization layer has first, second, and third, adaptive, feed forward filters, along with appropriately located buffers for collecting decodable groups of the transmitted symbols for group-by-group provision to the decision devices. The equalizer/decoder beneficially permits equalization of a channel used to transmit a multi-dimensional code block, for example, without requiring that a decodable number of symbols arrive in a single symbol interval. Accordingly, a communication system incorporating the equalizer/decoder may implement a high order, multidimensional code that provides enhanced coding gain even where the number of symbols in the code is so large that, given the physical channels available, it must be transmitted over multiple symbol periods. Where the code permits, the equalizer/decoder may make preliminary decisions regarding a reduced number of symbols while continuing to make final decisions using the maximum number of symbols to achieve maximum code gain.