High-Rate Full-Diversity STBC Design with Option to Provide Unequal Error Protection

摘要

A new rate-7/4 full-diversity Space Time Block Code for 2 TX has been designed by enlarging the signalling set of quaternions [14]. Power-scaling and constellation-rotation of information symbols have been incorporated in order to extend the signalling set. The proposed coding scheme achieves a 75% rate enhancement in comparison to the traditional Alamouti [3] code for QPSK modulation without requiring any additional system resources, e.g. power or bandwidth. The use of power-scaling and constellation-rotation also guarantee full-rank of codeword difference matrices in the extended set, while maximizing the coding gain and minimizing the transmitted signal peak-to-average power ratio. We propose a reduced-complexity efficient decoding algorithm, which does not result in any loss of useful information in comparison to the full-length ML decoding. The proposed high-rate code can also be utilized to provide unequal error protection to two different levels of source bits and hence, is useful in applications where the notion of unequal error protection supports varying degree of fidelity to source data, for example multimedia communications. Extensions to general M-PSK constellations and code design for more than 2 transmit antennas are straightforward.