EXIT-chart-based LDPC code design for spatial modulation

Abstract

The low-density parity-check (LDPC) code optimization for spatial modulation (SM) is studied using the extrinsic information transfer (EXIT) chart technique. First, for the maximum a posteriori probability (MAP) detector of the SM, its EXIT chart is characterized through Monte Carlo simulations. Then, the optimized degree distribution is acquired by matching the check node decoder curve to the combined detector and variable node decoder curve. Simulation results show that these optimized codes have performance gains from 0.3 to 1.3dB, compared with the regular code and the optimized code for the additive Gaussian white noise channel, in 4×4 and 16×16 multiple-antenna systems.

LDPC Code Design for Two-Layer Spatial Modulation

“…In [11], LDPC codes are optimized in a SM-MIMO system under the one-layer approach by employing the extrinsic information transfer (EXIT) chart technique. In [13], the nonbinary LDPC coding with Gallager mapping was used also under the one-layer approach to eliminate the restriction of the number of active transmit antennas being a power of 2.…”

“…As this mutual information is a theoretical limit, we apply a slight rate reduction of 3.56%, from 1.856 to 1.79 bits/s/Hz. Correspondingly, using (10) and (11), in the proposed two-layer scheme the individual code rate values R s and R a are proportionally reduced from 0.9165 to 0.884 bits/s/Hz and from 0.9395 to 0.906 bits/s/Hz, respectively. In this scenario, for all schemes, we set the block length to 22400 bits and the SPA decoder performs 18 iterations.…”

“…In the so-called one-layer type, the most common approach, the two information streams (i.e., the ones associated with the conventional and spatial modulations) are jointly encoded. Under this approach, trellis coded modulation [8], [9], turbo codes [10], and LDPC (low-density paritycheck) codes [11], [12], [13] have been designed.…”

Low-complexity soft-decision aided detectors for coded spatial modulation MIMO systems

“…Recently, to reduce the impact of channel fading and noise on bit error ratio (BER) performance, SM-MIMO systems with powerful channel coding, such as turbo codes and low-density parity-check (LDPC) codes, have gained rekindled interests [10][11][12][13]. A novel trellis coded spatial modulation (TCSM) scheme was proposed in [10], where the concept of trellis coded modulation was applied to the spatial constellation of SM systems.…”

“…In [12], the authors designed a spectral efficiency transmission scheme, labeled as bit-interleaved coded spatial modulation (BICSM) with iterative demodulating/decoding, which provides substantial performance gains in all channel conditions. In [13], LDPC codes were optimized to match SM-MIMO systems based on the extrinsic information transfer chart technique. Although these prior works have significantly improved the understanding of error performance of coded SM-MIMO systems, the key limitation is that all of them employ the optimum maximum a posteriori probability (MAP) soft-output detector, the complexity of which is intractable when the number of transmit antennas is large or the modulation order is high.…”