Performance of trellis-coded modulation for equalized ISI channels

MLSE and soft-output equalization for trellis-coded continuous phase modulation

“…Two types of discrete-time multipath channels are simulated. The first is the two-ray model, which has been widely employed in IS-136 systems [6], has the channel impulse response p(7) = A o 6 (~) + A i S ( r -TI) (18) where 7-1 is the relative delay between the first and the second path; the second is the 6-ray typical urban (TU) GSM channel profile, displayed in Table I with the original r-spaced model and the adjusted T/4-spaced model. The tap gains are assumed known a t the equalizer so that the performance of different schemes can be compared fairly.…”

“…In a fading IS1 channel, however, the insertion of interleaving will prohibit joint decoding and equalizat,ion, except for some specially designed interleaver-deinterleaver pairs [6]. Therefore, equalization has to be performed prior tJo the decoding.…”

Systematic Trellis-coded Modulation on Multipath Fading ISI Channels

“…Separation of the equalizer and decoder usually degrades the performance, except at high signal-to-noise *This research was supported by the National Science Foundation under Grant NCR-9304185. 0-7803-1 81 4-5/94 $4.00 0 1994 IEEE ratios (SNRs) [6]. Even more disturbing is the fact that many good trellis codes for AWGN channels, and interleaved flat fading channels, actually fail on multipath fading ISI channels with joint maximum likelihood sequence estimation (MLSE) equalization and decoding, meaning that they perform worse than the equivalent uncoded system [6].…”

“…0-7803-1 81 4-5/94 $4.00 0 1994 IEEE ratios (SNRs) [6]. Even more disturbing is the fact that many good trellis codes for AWGN channels, and interleaved flat fading channels, actually fail on multipath fading ISI channels with joint maximum likelihood sequence estimation (MLSE) equalization and decoding, meaning that they perform worse than the equivalent uncoded system [6]. One approach to the code design problem for these channels is to develop code design criteria that account for the error mechanism during a fade [8].…”