Investigation of a joint channel estimation technique for PAPR reduction in OFDM systems

The orthogonal frequency division multiplexing (OFDM) has attracted many researchers in the last decade due to the many advantages of this system. The intersymbol interference (ISI) free transmission and the high bit rate are two of the OFDM´s advantages. Although, OFDM systems as the other communication systems, they need to estimate the channel state information to reduce the Bit Error Rate (BER), therefore, many estimation techniques have been developed such as the least squares error (LSE). However, these estimation methods involve insertion of pilot tones in the original OFDM signal, where this OFDM signal suffers from the effect of high peak powers when compared to the average power, which known as the peak to average power ratio (PAPR). Hence, a PAPR reduction technique should be employed to overcome the problem without affecting the pilot tones. In this paper, the joint performance of some PAPR-based reduction techniques and the comb-type-based channel estimation method has been proposed and evaluated. The simulation results show that the selected mapping (SLM), amplitude clipping, and the unitary matrix transformation (UMT) based PAPR reduction methods have different effects on the estimated channel, where the SLM did not affected by the pilot tones while the UMT will destroy the pilot tones as like the amplitude clipping, because the SLM did not change the pilot power while the UMT do that, so that, the UMT and clipping methods are not recommended without preprocessing if the OFDM designer needs good estimated channel state information.