Performance Comparison Between Turbo Code and Rate-Compatible LDPC Code for Evolved Utra Downlink OFDM Radio Access

Abstract

This paper compares the Release 6 turbo code and rate-compatible low-density parity-check (LDPC) codes based on the packet error rate (PER) performance and decoding complexity in order to clarify the most appropriate channel coding scheme in the OFDM based evolved UTRA (E-UTRA) downlink. Simulation results and manipulation of the decoding complexity show that although the rate-compatible/quasi-cyclic (RC/QC)-LDPC code employing a normalized layered belief propagation (BP) method can reduce the computational complexity by approximately 30% for the channel coding rate of R=3/4, the required average received signal energy per bit-to-noise power spectrum density ratio (E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) is degraded by approximately 0.2-0.3 dB both for R=1/3 and 3/4 compared to that for the turbo code. Moreover, the decoding complexity level of the RC/QC-LDPC code with the delta-min algorithm is almost the same or higher than that for the turbo code with a slight degradation in the required received E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Although the decoding complexity level of the ZigZag code is decreased compared to that of the turbo code, the code brings about a distinct loss in the required average received E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> of approximately 0.4 dB. Finally, the turbo single parity check (SPC) code improves the PER performance compared to the ZigZag code, i.e., achieves almost the same PER performance as that for the turbo code, at the cost of a two-fold increase in the decoding complexity. As a result, we conclude that the turbo code is more promising than the LDPC codes for prioritizing the achievable performance and as the channel coding scheme for the shared data channel in the E-UTRA