Direct Space-Time GF(q) LDPC Modulation
ABSTRACT Wireless communication using multiple-input multiple-output (MIMO) systems improves throughput and enhances reliability for a given total transmit power. In this paper, potential performance gains are investigated via a direct Galois field [GF(q)] low-density parity-check (LDPC) space-time coding and modulation scheme. The field order q is chosen such that the number of bits per GF(q) LDPC symbol matches the number of bits per space-time symbol. The result is an elegant coding and decoding scheme that leverages the powerful LDPC iterative decoding technique. Results for 2, 3, and 4 transmitter systems with relatively short block lengths of around 2000 bits are provided, demonstrating frame-error- rate performances as close as 0.5 dB to the probability of outage upper bound.
Conference Paper: Rate adaptive non-binary LDPC codes with low encoding complexity[Show abstract] [Hide abstract]
ABSTRACT: For error-correction codes, the optimal coding rate can vary and depend on factors including channel, time-varying fading, environmental interference, power, bandwidth allocation, communication content, and application. Rate adaptive coding schemes are thus important for robust communications. This writeup proposes and studies a rate adaptive low density parity check (LDPC) coding scheme using non-binary Galois fields (GF). The algorithm uses a single low complexity encoding structure, but maintains strong near-capacity performance at arbitrary rational rates. The rate adaptive encoder can be used in a space-time code for multiple-input multiple-output (MIMO) communication systems and is shown to achieve near capacity performance at various rates and different MIMO configurations.Signals, Systems and Computers (ASILOMAR), 2011 Conference Record of the Forty Fifth Asilomar Conference on; 01/2011
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ABSTRACT: Multiple-input multiple-output (MIMO) wireless communication systems enhance reliability and improve throughput for a given total transmit power. In actual systems, the channel and noise parameters must be estimated to capture the MIMO gains. In this paper, we couple a direct, q-ary Galois field [GF(q)], low-density parity-check (LDPC) space-time coding and modulation scheme with a receiver that iterates between decoding the transmitted symbols, estimating the convolutive MIMO channel with pilots and symbol decisions, and removing inter-symbol interference. The result is a powerful system that outperforms linear space-time equalization and performs within one decibel of a system with perfect channel knowledge and no inter-symbol interference.Signals, Systems and Computers, 2008 42nd Asilomar Conference on; 01/2008
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ABSTRACT: Non-binary low density parity check codes (LDPC) have been shown to outperform their binary counterparts and attain the best-known performance among error-correction codes. At the same time, it has also been established that wireless communication using multiple-input multiple-output (MIMO) schemes dramatically increases system capacity and reliability when information symbols are appropriately coded and modulated across transmit antennas. Recent works have studied techniques for applying non-binary LDPC codes to MIMO systems and demonstrated near-capacity performance. However, the constellation sizes in the proposed approaches are limited by the Galois field (GF) size of the non-binary LDPC code, thus limiting the maximum spectral efficiency of the proposed joint modulation-coding approaches. In practice, the GF size may be limited by computational complexity reasons but high spectral efficiencies are desired. Thus, we study iterative coded modulation based techniques for applying non-binary LDPC codes to higher order modulations. These methods have been well-studied for binary codes but not for non-binary codes. It is demonstrated that performance of the technique is dependent on the mapping of GF symbols to constellations, but applying the appropriate mapping attains near-capacity performance. To reduce the error floor region for smaller field sizes, while maintaining steep waterfall curves, we combine a nonbinary-based accumulator with a parallel concatenated coding scheme.Signals, Systems and Computers (ASILOMAR), 2012 Conference Record of the Forty Sixth Asilomar Conference on; 01/2012