DEVELOPMENT OF A MODIFIED ARTIFICIAL FISH SWARM ALGORITHM PARTIAL TRANSMIT SEQUENCE TECHNIQUE FOR PEAK TO AVERAGE POWER RATIO REDUCTION IN ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING

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Department of Engineering

ABSTRACT
Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier frequency multiplexing scheme used in broadband wireless communication systems and has advantages such as high spectral efficiency, simple channel equalization and flexibility.One of its major challenges is the high Peak-to-Average Power Ratio (PAPR) of the signal which can cause a nonlinear signal distortion and reduction in power efficiency. One of the techniques used to reduce PAPR is the Partial Transmit Sequence (PTS) technique which can be applied to the transmit data. However, selecting the right phase factor sequence that can give the least PAPR is the major challenge faced by the PTS technique due to its non-linear optimization problem of phase factor sequence selection. Also, it suffers from high complexity and memory use when there is a large number of non-overlapping sub-blocks in one symbol. In order to address this, an intelligent search optimization algorithm is required to aid selecting the right phase factor sequence that gives the least PAPR. Therefore, this research work developed a modified Artificial Fish Swarm Algorithm (AFSA) based PTS technique and generated an optimum phase factor sequence, which in turn aided in PAPR reduction. The proposed technique was implemented using MATLAB R2015a and simulations were carried out using Bit Error Rate (BER) and Complementary Cumulative Density Function (CCDF) as performance metrics to evaluate its performance. Simulation results showed that the modified AFSA based PTS technique outperformed the AFSA based PTS technique in PAPR reduction with a percentage improvement of (6.67%), (3.33%) and (3.13%), when the number of subcarriers were 32, 128 and 256 respectively. Subsequently, the obtained results were compared with those of Zhou et al., (2014) as a means of validation and it was found out that the modified AFSA based technique had an improved percentage performance of (1.69%) in PAPR reduction over MECAFSA-PTS technique. These results showed that the modified AFSA-PTS technique is effective in reducing the PAPR of an OFDM system.