Block Coded Modulation Schemes Research Articles

Block‐Coded Modulation Using Reed‐Muller Component Codes and Multistage Decoding

AbstractUsing a 2‐step partitioning of the signal constellation and Reed‐Muller component codes, we construct block‐coded modulation (BCM) schemes that achieve an asymptotic coding gain close to 6 dB. The component code associated to the first partitioning step is a distance‐4 or a distance‐8 Reed‐Muller code, and the code associated to the second partitioning step is a simple parity‐check code. We investigate BCM schemes with square signal constellations and a fractional number of information bits per symbol as well as BCM schemes with circular signal constellations and an integer number of information bits per symbol. We use multistage decoding with a Viterbi algorithm for the first component code using the trellis description given by Forney. Our results indicate that with short block lengdis, these BCM schemes compare favorably with trellis coded modulation (TCM) of similar complexity. Due to the rapid increase of the error coefficient, however, they lose their advantage as the block length increases.

Block coded modulation and concatenated coding schemes for error control on fading channels

Block coded modulation (BCM) for digital communication over fading channels is considered. The performance of some known BCM codes designed for Gaussian channels is evaluated on slow Rayleigh fading channels. Design criteria for fading channels are used to construct new BCM codes with improved error rate. To achieve high coding gains with acceptable complexity, concatenated codes with BCM inner codes are investigated. The performance gains that are achieved by concatenated BCM schemes relative to uncoded reference systems are illustrated via some examples. Also, a comparison with corresponding schemes based on trellis coded modulation (TCM) is presented. Both analytical and simulation approaches are used to estimate the error rate performance.

Block codes on a dispersive channel

The paper considers the effect of a dispersive channel on block codes and block coded modulation schemes. It makes use of a generalised code model which is applicable to both binary codes and more general coded modulation schemes, and a generalised channel model which models the dispersive channel in terms of its complex impulse response. This is especially applicable to the multipath and Rayleigh fading channel, but applies in general. Two types of receiver are considered, one a straightforward correlation receiver without channel equalisation, and the other a true maximum-likelihood receiver, including channel equalisation. It is shown that the auto- and crosscorrelation functions of the code sequences are important, and the implications for code design are examined. It is also shown that with channel equalisation and sufficiently large block lengths, performance degradation due to even very heavily dispersive channels is slight. Finally, three types of system are proposed, based on the results in the paper, to signal at various rates on various types of dispersive channel, giving significant advantages over the systems used at present.

Design and performance of block-coded modulation for digital microwave radio systems

Two block-coded modulation (BCM) families particularly suited for high-capacity digital microwave radio systems are presented. The first family is based on one-step partitioning, and the second family is based on two-step partitioning of the signal constellation. The alphabet expansion is a decreasing function of the block length, and the constellation is constructed in such a way as to minimize both the average and peak signal powers. Using short block lengths, specific modulation schemes are described that transmit 4, 6, and 8 information bits per symbol. The asymptotic coding gain is only on the order of 2 dB in the first family, and of 3 dB in the second family, but their detection simplicity makes the presented BCM schemes particularly attractive for high-speed applications where trellis-coded modulation (TCM) decoders may be difficult to implement.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>