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SAIEE Africa Research Journal

On-line version ISSN 1991-1696
Print version ISSN 0038-2221


DLODLO, B.; XU, H.  and  PILLAY, N.. Bandwidth efficiency improvement for differential Alamouti space-time block codes using M-QAM. SAIEE ARJ [online]. 2018, vol.109, n.4, pp.217-223. ISSN 1991-1696.

We propose a technique that enhances the bandwidth efficiency of the two transmit antenna differential space-time block code (DSTBC) by use of space-time block code (STBC) expansion and trellis coding. STBC expansion is realized by expanding the conventional Alamouti STBC using unitary matrix transformation. This is followed by trellis code-aided mapping of additional bits to space-time codes of the expanded set. Trellis code-aided mapping of additional bits enhances the bandwidth efficiency of the proposed DSTBC scheme. The proposed scheme sends more information bits in each transmitted space-time code than the conventional differential detection-aided DSTBC (CDD-DSTBC) scheme, and yet retains the same error performance. For each additional bit sent with the transmitted space-time codeword, the proposed scheme using 16QAM achieves a 12.5% increase in bandwidth efficiency, while the scheme using 64QAM realises an 8.3% increase. Simulation results demonstrate that the error performance of the proposed scheme tightly matches that of CDD-DSTBC with improvement in bandwidth efficiency. The bandwidth efficiency is enhanced at the expense of a moderate increase of the computational complexity at the receiver.

Keywords : Bandwidth efficiency; coherent detection; differential Alamouti space-time block codes; differential detection; noncoherent detection; trellis code.

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