{HEAD ~ A symbol detector} converts {TAIL ~ initial symbol estimates} of received symbols to soft estimates for decoding 
converts
{ HEAD ~ A symbol detector } converts { TAIL ~ initial symbol estimates } of received symbols to soft estimates for decoding
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH