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HYBRID ALGORITHM FOR OPTIMIZING PEAK TO AVERAGE POWER RATIO PERFORMANCE IN MIMO-OFDM SYSTEM
*Agwah B. C., Nwabueze C. A. and Akaneme S. A.
This paper has examined the optimization of PAPR in Multiple-Input Multiple-Output (MIMO) -Orthogonal Frequency Division Multiplexing (OFDM) LTE network using hybrid technique. With many different PAPR reduction techniques available and each seems to outperform one another, a hybrid technique that uses precoded OFDM signal with repeated clipping and frequency domain filtering (RCF) and Mu-law companding was proposed for reducing PAPR of OFDM signal and with less computational cost in LTE network. The concept of PAPR in OFDM was initially examined and a conventional model of OFDM system introduced. This was followed by precoded OFDM signal model. Subsequently, different OFDM system models using RCF and Mu-law algorithms were presented. A hybrid algorithm for PAPR reduction was eventually developed combining RCF and Mu-law companding using precoded OFDM signal. Simulations were carried out for LTE network considering 256 data points with QPSK modulation scheme. Also, for optimal performance, RCF algorithm was studied by selecting a clipping ratio (CR) of 3 with four iteration process (clipping and filtering, CF1, CF2, CF3, CF4), oversampling factor of 4, and the Mu value of the Mu-law companding set at 100. Simulation was initially conducted for the conventional OFDM system model when there was no algorithm included to reduce the effect of PAPR and the value of PAPR obtained was 10.51 dB. With the PAPR of the conventional OFDM signal taken as reference value to be reduced, simulations were then carried out considering when RCF was incorporated with the conventional OFDM signal and precoded OFDM signal respectively. Results showed that with RCF and conventional OFDM, the overall reduction of PAPR was 5.739 dB representing 45.39% improvement whereas with precoded OFDM signal, the PAPR was reduced to 5.58 dB that is an improvement of 46.91%. Also, simulation was conducted with Mu-law companding and conventional OFDM signal. The result revealed that PAPR was reduced to 3.267 dB which represents 68.92% improvement in PAPR value. Finally, simulation test was carried out for the proposed hybrid system and the result obtained shows that the OFDM was significantly reduced to 1.757 dB which was 83.28% improvement in PAPR value. Thus, the proposed hybrid technique have shown capacity to largely and optimally reduce the PAPR of OFDM signal and as such is a promising scheme for addressing PAPR problem in MIMO-OFDM systems.[Full Text Article]