Conference Paper

Direct Space-Time GF(q) LDPC Modulation

Adv. Sensor Tech. Group, MIT Lincoln Lab., Lexington, MA
DOI: 10.1109/ACSSC.2006.354958 Conference: Signals, Systems and Computers, 2006. ACSSC '06. Fortieth Asilomar Conference on
Source: IEEE Xplore


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.

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    • "Some simplifications are possible, but in general the GF(q) decoding complexity per iteration grows as O(n S q log q). The reader is referred to [11] for details regarding GF(q) LDPC decoding and reducedcomplexity implementations, and to [7], [8], [12] for more details on the direct LDPC space-time modulation and coding. "
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    ABSTRACT: Wireless communication using multiple-input multiple-output (MIMO) systems improves throughput and enhances reliability for a given total transmit power. Achieving a higher data rate in MIMO systems requires utilizing an effective space-time coding and modulation scheme. The appropriate algorithm to use for a system will depend on parameters such as the number of transmit/receive antennas, target spectral efficiency, complexity limitations, channel environment, and other factors. In this paper, we examine the performance of various two-transmit and four-transmit space-time coding schemes under different channel types and target data rates. We compare the performance of state of the art space-time coding schemes including direct non-binary LDPC GF(q) modulation, bit interleaved coded modulation using iterative detection, and space-time trellis coded modulation. We obtain a tradeoff between performance and complexity of these various schemes.
    Signals, Systems and Computers, 2009 Conference Record of the Forty-Third Asilomar Conference on; 12/2009
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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; 10/2008
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    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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