Iterative decision‐directed estimation and compensation of nonlinear distortion effects for OFDM systems

Abstract

Orthogonal frequency division multiplexing (OFDM) has been adopted for several wireless network standards due to its robustness against multipath fading. Main drawback of OFDM is its high peak-to-average power ratio (PAPR) that causes a signal degradation in a peak-limiting (e.g., clipping) channel leading to a higher bit error rate (BER). At the receiver end, the effect of peak limitation can be removed to some extent to improve the system performance. In this paper, a joint iterative channel estimation/equalization and clipping noise reduction technique based on minimum mean square error (MMSE) criterion is presented. The equalization weight that minimizes the mean square error (MSE) between the signal after channel equalization and feedback signal after clipping noise reduction is derived assuming imperfect channel state information (CSI). The MSE performance of the proposed technique is theoretically evaluated. It is shown that the BER performance of OFDM with proposed technique can be significantly improved in a peak-limited and doubly-selective (i.e., time-and frequency-selective) fading channel.

SINR analysis of FFH/OFDM over frequency selective Rayleigh fading channel

“…In this work, two different equalizers are considered: ZF equalizer and MMSE equalizer. The considered equalization techniques, MMSE and ZF, in this work have been applied to OFDM systems in many previous work such as and also has been practically implemented in some works such as . Besides, a MMSE equalization for OFDM is adapted to LTE and LTE‐Advanced systems in 3G partnership project .…”

Equation-Method with Enhanced Strategies For Reducing the Bit-errors Caused by Clipping Distortion in OFDM Signals

“…Iterative receivers such as Bussgang noise cancellation (BNC) and decision aided reconstruction (DAR) can reduce clipping noise effects at the receiver and ultimately reduce bit-errors [8]- [10], but these methods use an extra pair of IFFT/FFT transforms which increase the computational complexity. ISSN: 1473-804x online, 1473-8031 print [11] proposed a joint iterative channel estimation and clipping noise reduction technique which is based on the minimum mean square error (MMSE) criterion. Another research has focused on taking the clipping as rare event and hence evaluating and analyzing conditional probability of the bit-errors in such an event [12].…”