Iterative Multistage Decoding Research Articles

Low-Complexity Soft-Decision Detection of Coded OFDM With Index Modulation

In this paper, the low-complexity soft-decision detectors of the orthogonal frequency division multiplexing with index modulation (OFDM-IM) in both single- and two-level coded modulation systems are studied. In the single-level coded OFDM-IM, the bitwise Markov chain Monte Carlo (b-MCMC) detector can overcome the drawback of the conventional symbolwise MCMC detector that the signal vectors obtained by Gibbs sampling are trapped in the activation pattern (AP) of the initial vector. By integrating with the randomized step further to alleviate the stalling problem, the randomized b-MCMC detector is proposed. In the two-level coded OFDM-IM, the framework of iterative multistage decoding (IMSD) with two component detectors for AP and symbol information, respectively, is employed. To reduce the complexity of IMSD, the efficient processing of the multiplicative interference in the component detectors is proposed. Finally, the effectiveness of the proposed detectors is verified by computer simulations.

A Class of Nonbinary LDPC Codes with Fast Encoding and Decoding Algorithms

This letter is concerned with a class of nonbinary low-density parity-check (LDPC) codes, referred to as column-scaled LDPC (CS-LDPC) codes, whose parity-check matrices have a property that each column is a scaled binary vector. The CS-LDPC codes, which include algebraically constructed nonbinary LDPC codes as subclasses, admit fast encoding and decoding algorithms. Specifically, for a code over the finite field F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2p</sub> , the encoder can be implemented with p parallel binary LDPC encoders followed by a series of bijective mappers, while the decoder can be implemented with an iterative decoder in which no message permutations are required during the iterations. In addition, there exist low-complexity iterative multistage decoders that can be utilized to trade off the performance against the complexity. Simulation results show that the performance degradation caused by the iterative multistage decoding algorithms is relevant to the code structure.

Novel decoding of square QAM modulated mimo systems based on turbo multiuser detection

By introducing the bit-level multi-stream coded Layered Space-Time (LST) transmitter along with a novel iterative MultiStage Decoding (MSD) at the receiver, the paper shows how to achieve the near-capacity performance of the Multiple-Input Multiple-Output (MIMO) systems with square Quadrature Amplitude Modulation (QAM). In the proposed iterative MSD scheme, the detection at each stage is equivalent to multiuser detection of synchronous Code Division Multiple Access (CDMA) multiuser systems with the aid of the binary representation of the transmitted symbols. Therefore, the optimal Soft-Input Soft-Output (SISO) multiuser detection and low-complexity SISO multiuser detection can be utilized herein. And the proposed scheme with low-complexity SISO multiuser detection has polynomial complexity in the number of transmit antennas M, the number of receive antennas N, and the number of bits per constellation point M c . Simulation results demonstrate that the proposed scheme has similar Bit Error Rate (BER) performance to that of the known Iterative Tree Search (ITS) detection.

On multilevel codes and iterative multistage decoding

This paper develops an approach to iterative multistage decoding of multilevel codes. This involves passing reliability information to previous and subsequent decoders instead of only hard decisions to subsequent decoders. The paper also develops an adaptive version of the suboptimal soft output decoding algorithm of Picart and Pyndiah (1996). This adaptive algorithm provides a gain of approximately 0.24 dB at a bit error rate (BER) of 10/sup -5/ after four iterations and approximately 0.43 dB after ten iterations over the algorithm of Picart et al. If the adaptive algorithm is used in conjunction with iterative multistage decoding then a gain of approximately 0.62 dB is obtained at a BER of 10/sup -5/ after four iterations and approximately 0.9 dB after ten iterations over the algorithm of Picart et al.