A new MIMO-OFDM transmit preprocessing using pilot symbol assisted rateless codes to mitigate fading and wavelet based OFDM for PAPR reduction

Orthogonal frequency division multiplexing (OFDM) is an attractive technique for wireless communication applications. The principal design problem encountered in wireless communications is how to overcome the distortion of received signals by a time-varying and frequency-selective propagation path due to the phenomenon called fading. Also, a well known problem of OFDM that is the casual occurrence of high peak-to-average power ratio (PAPR) in the time domain signal reduces the efficiency of transmit high power amplifier and limits the use of OFDM in low cost applications. In this paper, we propose a closed loop multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) transmit preprocessing system, where the channel coding method referred as pilot symbol assisted rateless coding (PSAR) is used mitigate the effects of fading and wavelet based OFDM (WOFDM) is used to reduce PAPR. In the proposed scheme wavelet is used in the place of FFT. Our rateless coding approach for mitigation of fading and reduction of peak-to-average power ratio combines the error correction capability of the channel encoder and achieves peak-to-average power ratio reduction in the OFDM system. The performance of proposed system is measured with the help of three parameters, bit error rate (BER), latency and complementary cumulative distribution function (CCDF) for PAPR. The proposed system achieves about 3 dB improvement in PAPR over the traditional OFDM. The need for CP is eliminated in the system design due to the good orthogonality and time frequency localization proprieties of the wavelet. Compared with conventional FFT based OFDM, the proposed PSAR codes with WOFDM is beneficial in terms of significantly reducing PAPR and the fading effects.