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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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Subject: 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.
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    Design optimization of anisotropic pressure vessels with manufacturing uncertainties accounted for
    (Elsevier, 2013-04) Tabakov, Pavel Y.; Walker, Mark
    Accurate optimal design solutions for most engineering structures present considerable difficulties due to the complexity and multi-modality of the functional design space. The situation is made even more complex when potential manufacturing tolerances must be accounted for in the optimizing process. The present study provides an original in-depth analysis of the problem and then a new technique for determining the optimal design of engineering structures, with manufacturing tolerances accounted for, is proposed and demonstrated. The numerical examples used to demonstrate the technique involve the design optimization of anisotropic fibre-reinforced laminated pressure vessels. It is assumed that the probability of any tolerance value occurring within the tolerance band, compared with any other, is equal, and thus it is a worst-case scenario approach. A genetic algorithm with fitness sharing, including a micro-genetic algorithm, has been found to be very suitable to use, and implemented in the technique.
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    Lay-up optimization of multilayered anisotropic cylinders based on a 3-D elasticity solution
    (Elsevier, 2006) Tabakov, Pavel Y.; Summers, E. B.
    Exact elasticity solutions are obtained using the stress function approach, where the radial, circumferential and shear stresses are determined, taking into account the closed ends of the cylindrical shell. The system of the governing algebraic equations is derived to accurately analyse a multilayered pressure vessel with an arbitrary number of layers and any thickness. The approach used is straight-forward compared to other three-dimensional solutions found in the literature. The design of multilayered composite pressure vessels is accomplished using the genetic algorithm and subject to the Tsai–Wu failure criterion. The genetic algorithm is optimized to serve this particular problem