Pilot-Assisted Time-Varying Channel Estimation for OFDM Systems

Abstract

Abstract-In this paper, we deal with channel estimation for orthogonal frequency-division multiplexing (OFDM) systems. The channels are assumed to be time-varying (TV) and approximated by a basis expansion model (BEM). Due to the time-variation, the resulting channel matrix in the frequency domain is no longer diagonal, but approximately banded. Based on this observation, we propose novel channel estimators to combat both the noise and the out-of-band interference. In addition, the effect of a receiver window on channel estimation is also studied. Our claims are supported by simulation results, which are obtained considering Jakes' channels with fairly high Doppler spreads.Index Terms-Basis expansion model (BEM), orthogonal frequency-division multiplexing (OFDM), pilot-assisted modulation, time-varying (TV) channels.

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

“…LTE uplink system [15,22] is considered in the simulation. The simulation parameters are listed in Table 1 and the generalized complex exponential BEM (GCE-BEM) [14] is adopted.…”

“…This assumption will generally not hold true in time-varying channels, especially in fast time-varying cases. In light of the above analysis and considering that BEM based channel estimation method [13,14] can accurately estimate the time-varying channel coefficients of an OFDM symbol, we propose to combine BEM based channel estimation with WF to deal with channel estimation in time-varying channels. …”

“…Basis expansion model based channel impulse response of the p i -th pilot symbol can be expressed as [13,14] …”

“…For the pilot subcarriers in the p i -th pilot symbol, an equation consisting of h q,l (p i ) can be expressed as [14] …”

“…Basis expansion model (BEM) based channel estimation method can accurately estimate both slow and fast time-varying coefficients of the wireless channel in an OFDM symbol period using the coefficients of BEM that are far less than the length of wireless channel [13,14]. Combining BEM based channel estimation with WF, in this article we derive the expression for Wiener filter combined BEM based channel estimation (hereafter called WF-BEM), which explicitly considers the effect of ICI.…”