Channel estimation in OFDM systems operating under high mobility using Wiener filter combined basis expansion model

Ke Zhong,Xia Lei,Binhong Dong,Shaoqian Li

doi:10.1186/1687-1499-2012-186

Abstract

In this article, we first thoroughly analyze Wiener filter combined least squares based channel estimation (WF-LS) and then illustrate its limitation in high-speed mobile environments. Based on the analysis, we propose to combine WF with basis expansion model (BEM) based channel estimation to deal with channel estimation in various mobile environments, especially in high-speed cases. The expression for Wiener filter combined BEM based channel estimation (WF-BEM) is derived and the result explicitly considers the effect of intercarrier interference (ICI) that occurs in orthogonal frequency division multiplexing (OFDM) systems when operating under high mobility. The simulation results demonstrate that our proposed WF-BEM is better than WF-LS in time-varying channels, and the performance improvement is significant especially in fast time-varying channels.

Highlights

Due to its high data rate transmission capability and its robustness to multipath delay spread, orthogonal frequency division multiplexing (OFDM) has been adopted in most parts of modern wireless communication sytstems, such as wireless local area networks (WLAN) [1], digital audio and video broadcasting [2], and so as OFDM being standardized for the future wireless communication systems, such as wireless metropolitan area networks (WiMAX) [3] and 3GPP long term evolution (LTE) [4]
Blind channel estimation methods can save bandwidth by avoiding the trans-mission of any pilot or training symbols, they must exploit the statistic of the received signals, either explicitly or implicitly, which requires the wireless channel is time invariant during several OFDM symbols (e.g., cyclic prefix (CP) [5] or virtual carriers [6] based blind channel estimation method, etc.)
Because the channel estimation at pilot symbols is fixed to least squares (LS) based channel estimation, if we want to improve the performance of Wiener filter (WF)-LS, one has to resort to WF-LS with higher orders (i.e., choosing M >2 in (2)) and hopefully that by adopting WF-LS with higher orders we can improve the estimation accuracy through using more pilot symbols, i.e., the MSE of channel estimation may be decreased by collecting more pilot symbols [17]

Summary

Introduction

Due to its high data rate transmission capability and its robustness to multipath delay spread, orthogonal frequency division multiplexing (OFDM) has been adopted in most parts of modern wireless communication sytstems, such as wireless local area networks (WLAN) [1], digital audio and video broadcasting [2], and so as OFDM being standardized for the future wireless communication systems, such as wireless metropolitan area networks (WiMAX) [3] and 3GPP long term evolution (LTE) [4]. Time estimation methods adopted to obtain the channel estimate of pilot symbols assume that the wireless channel is static during an OFDM symbol period, which means that the channel frequency response matrix is a diagonal matrix [7] This assumption holds when the users are in indoor environments or is approximately valid in slow speed moving environments. This convergence will change with fDT , as can be observed from Figure 3 In this case, WF-LS with orders 3 will “degrade” into WF-LS with orders 2, which means that even more pilot symbols are adopted to estimate H Wd F−LS(k) , there will be no performance gains at all.

The position of p

Findings

10-1 BLER 10-2