Abstract
This article proposes a novel design framework, EXIT-constrained binary switching algorithm (EBSA), for achieving near Shannon limit performance with single parity check and irregular repetition coded bit interleaved coded modulation and iterative detection with extended mapping (SI-BICM-ID-EM). EBSA is composed of node degree allocation optimization using linear programming (LP) and labeling optimization based on adaptive binary switching algorithm jointly. This technique achieves exact matching between the Demapper (Dem) and decoder's extrinsic information transfer (EXIT) curves while the convergence tunnel opens until the desired mutual information (MI) point. Moreover, this article proposes a combined use of SI-BICM-ID-EM with Doped-ACCumulator (D-ACC) and modulation doping (MD) to further improve the performance. In fact, the use of D-ACC and SI-BICM-ID (noted as DSI-BICM-ID-EM) enables the right-most point of the EXIT curve of the combined demapper and D-ACC decoder (Ddacc), denoted as DemDdacc, to reach a point very close to the (1.0, 1.0) MI point. Furthermore, MD provides us with additional degree-of-freedom in "bending" the shape of the demapper EXIT curve by choosing the mixing ratio of modulation formats, and hence the left most point of the demapper EXIT curve can flexibly be lifted up/pushed down with MD aided DSI-BICM-ID-EM (referred to as MDSI-BICM-ID-EM). Results of the simulations show that near-Shannon limit performance can be achieved with the proposed technique; with a parameter set obtained by EBSA for MDSI-BICM-ID-EM, the threshold signal-to-noise power ratio (SNR) is only roughly 0.5 dB away from the Shannon limit, for which the required computational complexity per iteration is at the same order as a Turbo code with only memory-2 convolutional constituent codes.
Highlights
The discovery of Turbo code [1] in 1993 is a landmark event in the history of coding theory, since the code can achieve near-Shannon limit performance
The results of simulations show that near-Shannon limit performance can be achieved with the proposed techniques; bit error rate (BER) simulation results show that 4-quadrature amplitude modulation (4-QAM) extended mapping (EM) with lmap = 5, the threshold Signal-tonoise power ratio (SNR) is only roughly 0.5 dB away from the Shannon limit with MDSI-BICMID-EM, for which required computational complexity for DemDdacc is almost the same as a Turbo code with only memory-2 convolutional constituency codes, per iteration
With the EXtrinsic Information Transfer (EXIT)-constrained binary switching algorithm (EBSA) framework, the labeling pattern used in the linear programming (LP)-based degree allocation optimization for DSIBICM-ID-EM are obtained by lowering the cost of Z map−1 as much as possible, while still keeping the vertical gap smaller than the predefined value δw
Summary
The discovery of Turbo code [1] in 1993 is a landmark event in the history of coding theory, since the code can achieve near-Shannon limit performance. Schreckenbach et al [6] propose another approach towards achieving good matching between the two curves by introducing different mapping rules, such as non-Gray mapping, which allows the use of even simpler codes to achieve BER pinch-off (corresponding to the threshold SNR) at an SNR value relatively close to the Shannon limit Another technique that can provide us with the design flexibility is extended mapping (EM) presented in [7,8] where with 2m-QAM, lmap bits (lmap >m), are allocated to one signal point in the constellation. The results of simulations show that near-Shannon limit performance can be achieved with the proposed techniques; BER simulation results show that 4-QAM EM with lmap = 5, the threshold SNR is only roughly 0.5 dB away from the Shannon limit with MDSI-BICMID-EM, for which required computational complexity for DemDdacc is almost the same as a Turbo code with only memory-2 convolutional constituency codes, per iteration.
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