PAPR Reduction in MIMO-OFDM Systems using Modified PTS and SLM without Side Information

Limiting the peak to average power ratio (PAPR) to an acceptable level is of great importance to MIMO-OFDM systems. Otherwise, a series of undesirable interventions due to the large PAPR is encountered, such as inter-modulation distortion and out-of-band radiation. In this paper, we have proposed a modified partial transmit sequence (PTS) scheme and implemented a new selected mapping (SLM) technique without side information to reduce the peak to average power ratio (PAPR) in multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) systems. In our proposed PTS scheme, an input symbol sequence is partially transformed using the first I stages of inverse fast Fourier transform (IFFT) into an intermediate signal sequence and is then separated into a number of intermediate signal subsequences. The remaining n — I stages of IFFT are applied to each of the intermediate signal subsequences and the results are summed after being multiplied by each member of a set of W rotating vectors to yield W distinct OFDM signal sequences. The one with the lowest peak PAPR among these OFDM signal sequences is selected for transmission. By considering the example of a MIMO OFDM system using quadrature phase shift keying (QPSK) modulation, it is shown that our proposed PTS method performs very well in comparison to the conventional PTS scheme and the existing SLM schemes in terms of PAPR reduction, bit error rate (BER), probability of error, power spectral efficiency and computational complexity. A detailed analysis of our proposed schemes has also been furnished in our paper.