System and method for encoding data such that after precoding the data

Abstract

A system comprises an encoder, a precoder, a PR channel, a detector, and a decoder. An input signal is received by the encoder. The encoder generates a code string by adding one or more bits and outputs the code string to the precoder. The encoder applies such encoding such that the code string after being modified by the precoder has a pre-selected parity structure. The encoder provides a systematic encoding scheme in which many of the encoded bits are the same as the input bits used to generate the encoded bits. This systematic approach of the present invention provides an encoder that is easy to implement because a majority of the bits are directly 'feed through' and non-trivial logic circuits are only needed to generate the control bits. The systematic encoding also dictates a decoder that is likewise easy to construct and can be implemented in a circuit that simply discards the control bit. The encoder preferably comprises a serial-to-parallel converter, a code generator and a parallel-to-serial converter. The code generator produces one of three trellis codes such as a rate 8/9, 8/10 or 9/11 code. The present invention also includes a method that is directed to encoding bit strings and comprises the steps of: 1) converting the input string to input bits, and 2) adding at least one bit to produce a pre-selected parity structure after precoding.