A Risk Minimization Framework for Channel Estimation in OFDM Systems

TL;DR

This paper introduces a novel risk minimization framework for channel estimation in OFDM systems that does not require prior channel statistics, using Stein's lemma to optimize estimates and improve SNR.

Contribution

It proposes a new SURE-based channel estimation method for OFDM systems that enhances performance without prior statistical knowledge.

Findings

SURE-based estimates improve SNR by approximately 2.25 dB.

The method outperforms maximum-likelihood estimates in practical scenarios.

No prior channel statistics are needed for effective estimation.

Abstract

We address the problem of channel estimation for cyclic-prefix (CP) Orthogonal Frequency Division Multiplexing (OFDM) systems. We model the channel as a vector of unknown deterministic constants and hence, do not require prior knowledge of the channel statistics. Since the mean-square error (MSE) is not computable in practice, in such a scenario, we propose a novel technique using Stein's lemma to obtain an unbiased estimate of the mean-square error, namely the Stein's unbiased risk estimate (SURE). We obtain an estimate of the channel from noisy observations using linear and nonlinear denoising functions, whose parameters are chosen to minimize SURE. Based on computer simulations, we show that using SURE-based channel estimate in equalization offers an improvement in signal-to-noise ratio of around 2.25 dB over the maximum-likelihood channel estimate, in practical channel scenarios, without assuming prior knowledge of channel statistics.