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Research Publications (Engineering and Built Environment)

Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/215

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Author: search.filters.author.Xu, HongjunSubject: search.filters.subject.Genetic algorithms

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    A genetic algorithm for designing encoded space-time labelling diversity mappers
    (IEEE, 2018-10) Patel, Sulaiman Saleem; Quazi, Tahmid; Xu, Hongjun
    The extent to which Uncoded Space-Time Labelling Diversity is able to improve the error performance of spacetime block coded (STBC) systems is dependent on the binary mappers used to encode information. Existing design techniques are limited; as they either rely on symmetry-based heuristics, or constrain the size of the constellation due to high computational costs. This paper proposes a new genetic algorithm for labelling diversity (LD) mapper design which is applicable to constellations of any shape or size. The proposed algorithm is tested using 16QAM, 64QAM, 32PSK and three 16APSK constellations that do not display diagonal symmetry. The proposed LD mappers match the best heuristic designs for 16QAM and 64QAM. The 32PSK LD mapper produced achieves a diversity gain of ≈ 8dB when compared to the available heuristic-based LD mapper. In addition, the 16APSK mappers achieve a diversity gain of approximately 3 to 8dB compared to Alamouti-coded STBC systems for the three non-symmetric constellations considered.
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    Performance analysis of M-APSK generalised spatial modulation with constellation reassignment
    (Wiley, 2020-09-25) Khalid, Ahmad; Quazi, Tahmid; Xu, Hongjun; Patel, Sulaiman Saleem
    Generalised spatial modulation (GSM) is a recently developed multiple-input multiple-output (MIMO) technique aimed at improving data rates over conventional spatial modulation (SM) systems. However, for identical antenna array size and configurations (AASC), the bit error rate (BER) of GSM systems in comparison with SM systems is degraded. Recently, a GSM system with constellation reassignment (GSM-CR) was proposed in order to improve the BER of traditional GSM systems. However, this study focused on M-ary quadrature amplitude modulation (M-QAM) schemes. The focus of this paper is the application of a circular constellations scheme, in particular, amplitude phase shift keying (APSK) modulation, to GSM and GSM-CR systems. An analytical bound for the average BER of the proposed M-APSK GSM and M-APSK GSMCR systems over fading channels is derived. The accuracy of this bound is verified using Monte Carlo simulation results. A 4 × 4 16-APSK GSM-CR system achieves a gain of 2.5 dB at BER of 10−5 over the traditional 16-APSK GSM system with similar AASC. Similarly, a 6 × 4 32-APSK GSM-CR system achieves a gain of 2 dB at BER of 10−5 over equivalent 32-APSK GSM system.