Precoded turbo equalization for MEEPR4 channel

A transmitter-based turbo equalization is presented which reduces the trellis complexity. It is designed for separable channels, where part of a channel is taken care of on the transmitter side, resulting in a new trellis with expanded alphabet. The new structure is used for a high-density magnetic recording channel, the MEEPR4 channel, together with serially-concatenated turbo code, and loses about 0.3 dB compared with the full trellis structure. Additional loss is due to the constellation expansion.