Generalised differential golden code modulation: error performance analysis and bandwidth efficiency.

Abstract

The receiver of a conventional differential modulation scheme performs detection without knowledge of the channel state information (CSI). This results in a 3dB performance loss compared to coherent modulation. In order to enhance this error performance, generalised differential modulation is utilised. This thesis firstly presents a generalised differential modulation scheme for the Golden code (GDMGC) based on quadrature amplitude modulation (QAM). The average bit error probability (ABEP) for the GDM-GC scheme is derived and simulations on bit error rates (BER) are carried out in order to verify the derived theoretical framework, where it is shown that BER results lie well within the derived bounds. In addition, compared to coherent GC with maximum likelihood (ML) detection both 16QAM and 64QAM GDM-GC result in approximately 0.4 dB performance loss for a frame length of L = 400. However, the computational complexity of the GDM-GC scheme is reduced significantly in comparison to the coherent ML detector. Secondly, this thesis extends the generalised differential modulation scheme to multiple input symbol Golden code and proposes a multiple input symbol generalised differential Golden code (MIS-GD-GC) scheme. This scheme not only boosts error performance in comparison to conventional differential multiple input symbol Golden code (MIS-GC), but it lso produces multiple diversity order compared to the conventional Golden code. The simulations on BER for the MIS-GD-GC scheme not only compare very well to the derived theoretical bounds but also show that the BER draws closer to that of coherent MIS-GC when the frame length is increased. For instance, at a frame length of L = 400 , the error performance gap between MIS-GD-GC and its coherent counterpart is only 0.4 dB. Finally, driven by the need to develop a scheme that can allow for transmission of more data to help meet the demands of modern wireless communication systems, this thesis seeks to improve the bandwidth efficiency of the GDM-GC scheme. An enhanced bandwidth efficient generalised differential Golden code (EBE-GD-GC) scheme based on QAM is proposed and its ABEP derived. The simulated BER results for the EBE-GD-GC scheme are shown to lie well within the derived ABEP and achieve almost the same error performance as GDM-GC at high signal-to-noise ratio (SNR) regions but with extra bit(s) of information sent in each transmitted space-time block code (STBC) compared to the typical GDM-GC scheme. In addition, compared to the conventional generalised differential Golden code, both 16QAM and 64QAM EBE-GD-GC result in < 1dB performance loss from a BER of 1 × 10−5.