Improved performance of LDPC-coded MIMO systems with EP-based soft-decisions

Abstract

Abstract-Modern communications systems use efficient encoding schemes, multiple-input multiple-output (MIMO) and high-order QAM constellations for maximizing spectral efficiency. However, as the dimensions of the system grow, the design of efficient and low-complexity MIMO receivers possesses technical challenges. Symbol detection can no longer rely on conventional approaches for posterior probability computation due to complexity. Marginalization of this posterior to obtain per-antenna soft-bit probabilities to be fed to a channel decoder is computationally challenging when realistic signaling is used. In this work, we propose to use Expectation Propagation (EP) algorithm to provide an accurate low-complexity Gaussian approximation to the posterior, easily solving the posterior marginalization problem. EP soft-bit probabilities are used in an LDPC-coded MIMO system, achieving outstanding performance improvement compared to similar approaches in the literature for low-complexity LDPC MIMO decoding.

Probabilistic MIMO Symbol Detection With Expectation Consistency Approximate Inference

“…To avoid cluttering, we do not include in our experiments the GMPID algorithm [30], since it performs close to CHEMP. For similar reasons, we do not include the EP method proposed in [33], since it performs similarly to GTA when used for probabilistic detection [36].…”

Performance Enhancement in LDPC coded high-dimension MIMO-OFDM systems

“…We used m = r = 32 scenarios with a 16-QAM modulation in MIMO-OFDM system. We have applied LDPC code of length n = 5120 bits with equivalent to [9]. In our simulation, we have applied multipath Rayleigh fading channel matrix.…”

“…The Expectation Propagation (EP) algorithm in the soft-output detector is proposed in [9]. Applying EP can able to achieve better performance improvements than MMSE soft-output detectors in terms one order of magnitude for rate-1/2 LDPC codes in the MIMO system.…”

“…It is positively not the top selection, as we are interested in matching the posterior distribution. Therefore, the [9] proposes a technique, where the prior distribution is enhanced to warrant that the approximating Gaussian posterior equals the initial two moments of the posterior distribution.…”

“…Therefore, we concentrate on receiver part, we used Expectation Propagation (EP)-based soft-decisions MIMO detector algorithm [9] for receiver part of LDPC-coded MIMO systems. The EP solves marginalization problem of the symbol vector posterior p(s|r) probability generalizes belief propagation (BP) in two ways.…”