Abstract
Abstract In this study, we consider the ways for concatenating the intersymbol interference (ISI) detector with a q-ary low-density parity-check (LDPC) decoder for transmissions over partial response (PR) channels. LDPC codes allow achieving performance close to the channel capacity in additive white Gaussian noise channels, while designing receivers employing these codes for transmissions over channels affected by ISI is still an open issue. Turbo equalization schemes are considered with a novel joint message-passing-based receiver, which is derived from a recently proposed joint algorithm for binary LDPC codes. Simulation results provide performance evaluation of these systems over three different PR channels, together with an analysis of the trade-off between error-rate performance and complexity.
Highlights
High data rate modern communication systems are affected by intersymbol interference (ISI) effects, due to frequency selective fading for microwave wireless transmissions or to increased bit density for magnetic recording systems
The joint MP algorithm for ISI channels has been extended to q-ary low-density parity-check (LDPC) codes and has been compared to turbo equalization (TE) architectures over some partial response (PR) channels
Simulation results for 16-ary LDPC code over three different PR channels showed that the best performance can be achieved by using a turbo equalizer whose detection is symbol-based
Summary
High data rate modern communication systems are affected by intersymbol interference (ISI) effects, due to frequency selective fading for microwave wireless transmissions or to increased bit density for magnetic recording systems. Bahl–Cocke–Jelinek–Raviv (BCJR) algorithm [3] can replace a Viterbi processor if the soft output information is employed in a concatenated scheme, feeding an outer channel decoder [4]. Regular LDPC codes have a parity check matrix in which all rows (and columns) have. Considering an LDPC-coded system, the most popular scheme to improve error-correction performance over channels affected by ISI has been to serially concatenate a soft-output detection algorithm and the binary LDPC decoder. We extend the joint detection-anddecoding scheme to q-ary LDPC codes. Each receiver architecture that has been taken into account employs a q-ary LDPC decoder and a BCJR detector that can either be bit-based (BB) or symbolbased (SB). The symbol-wise APPs are passed to the q-ary LDPC decoder to initialize the a priori probabilities
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