Iterative Interference Suppression for Pseudo Random Postfix OFDM based Channel Estimation

Abstract

This contribution proposes an iterative channel impulse response (CIR) estimation scheme in the context of the pseudo-random-postfix OFDM (PRP-OFDM) modulation. While conventional techniques reduce noise and interference of OFDM data symbols on the CUR estimates by simple mean value calculation, the new proposal uses soft decoder outputs in order to perform iterative OFDM data symbol interference cancellation. In a typical example for 64QAM constellations, the mean-square-error (MSE) of the CIR estimates is improved by approx. 12 dB after three iterations. Based on PRP-OFDM postfixes only, it is thus possible to perform channel estimation for higher order constellations (64QAM and higher) with an initial CIR estimation over a small observation window (for 64QAM typically 30 to 40 OFDM symbols). Any loss in throughput due to additional redundancy for CIR estimation purposes, e.g. pilot tones, learning symbols, etc. is avoided at the cost of an increase in decoding complexity.