Abstract
Bit-interleaved coded modulation with iterative decoding (BICM-ID) is investigated for bandwidth efficient transmissions, where the error performance can be improved by employing a suitable symbol mapping. In this paper, we introduce a low-complexity irregular mapping optimization for BICM-ID with irregular doping and 8-ary phase-shift keying (8PSK) modulation over both additive white Gaussian noise (AWGN) and Rayleigh fading channels, for the purpose of achieving near-capacity performances. The Euclidean distance spectrum and the extrinsic information transfer (EXIT) chart analysis are aided for the proposed optimization to provide design guidelines of mappings. The bit error rate (BER) results demonstrate that the BICM-ID system with the proposed optimal irregular mapping and doping outperforms the other typical symbol mappings, and yields a gain of about 0.1 and 0.5 dB for AWGN and Rayleigh fading channels, respectively. Moreover, it is only about 0.5 and 0.73 dB away from the discrete-input continuous-output memoryless channel (DCMC) capacity limits of AWGN and Rayleigh fading channels, respectively, at the BER of 10−4 and for the spectral efficiency of 2 bits/channel use.
Highlights
Bit-interleaved coded modulation (BICM) [1,2] is the serial concatenation of a channel encoder, a bitwise interleaver, and a symbol mapper
According to the above backgrounds and discussions, as a goal of this paper, we propose a lower complexity irregular mapping optimization for Bit-interleaved coded modulation with iterative decoding (BICM-iterative decoding (ID)) with 8-ary phase shift keying (8PSK) modulation compared with the existing algorithms
We only focus on a small number of unique mappings out of the total mappings of the constellation, according to the classification with the Euclidean distance spectrum
Summary
Bit-interleaved coded modulation (BICM) [1,2] is the serial concatenation of a channel encoder, a bitwise interleaver, and a symbol mapper. The dependent bits have a significant influence on the mutual information exchanges and bring about an arbitrary low error rate with an infinite interleaver length It has been demonstrated in [6] that the error floor can be reduced or even removed by doping techniques in iterative schemes based on BICM. Instead of using the exhaustive search for all mappings of 8PSK constellation, 86 unique mappings and 86 unique EXIT curves are under consideration for the design of our optimization algorithm Taking advantage of this classification, the computational complexity of the search for suitable mappings is significantly reduced.
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