Viterbi receivers in the presence of severe intersymbolinterference

摘要

A method of reducing the number of states in the Viterbi receiver,called PDFE (parallel decision feedback estimation), is described. Fourdifferent ISI (intersymbol interference) removal systems and twodifferent TCM (trellis-coded modulation) systems using PDFE arepresented and simulated. The simulated channel is a telephone cableoperating at high bit rates and causing severe ISI. Gains of between 0.6and 2.3 dB have been achieved in this severe ISI environment usingViterbi receivers with various proportions of four or 16 states devotedto either ISI mitigation or TCM decoding. With no ISI, the gain offour-state TCM is 3.1 dB and the gain of 16-state TCM is 4.0 dB. Thegains of TCM received using PDFE with the severe ISI HDSL (high-ratedigital subscriber line) channel are about one half of the gains with noISI