An efficient algorithm for joint carrier frequency offset and channel estimation in IEEE 802.16 OFDM systems

Abstract

This paper develops a novel and simple algorithm to perform joint carrier frequency offset and channel estimation in Orthogonal Frequency Division Multiplexing (OFDM) systems. Carrier frequency offset of upto several frequency subcarrier spacings has to be estimated and compensated in order to enhance the OFDM system performance. The time domain synchronization algorithms using the preamble structure provided for fixed broadband wireless OFDM uplink access (IEEE 802.16 LAN/MAN standards) can only measure a frequency offset with an ambiguity equal to an even number of subcarrier spacings, in case of the actual offset being more than a subcarrier spacing. Our proposed algorithm uses the received preamble to jointly estimate this remaining integer part of the frequency offset and the initial channel impulse response using a least squares criterion in an iterative manner. Computer simulations show that the proposed estimator is very robust at low signal to noise ratios (SNRs) and operate near the Cramer-Rao bound for the variance of the frequency offset estimate.

Turbo joint channel estimation, synchronization, and decoding for coded OFDM systems

“…Instead of estimating and updating all parameters simultaneously (i.e., solving a non-linear optimization problem), in [13,14], iterative procedures are repeated several times between different parameters in order to approach the joint optimum values while, in [15][16][17], the estimated parameters are changed in a certain step over the whole possible range until the correct values are found in a trial-anderror manner. This exhaustive search method can only be used for coarse estimation; otherwise, an impractically large amount of computation could be expected.…”

Frequency offset estimation with ambiguity of symbol timing offset for IEEE 802.16D OFDM system

“…In [9], a data-aided method is proposed for the IFO estimation with ambiguity of symbol timing, but it is based on pilots, not suitable for IEEE 802.16d preamble structure. The method in [10] works well in IEEE 802.16d frame structure, however it requires perfect symbol timing before the frequency offset estimation.…”

Estimation of FWA MIMO Channels

“…Some sequences with good autocorrelation and cross correlation properties were found by exhaustive search and tabulated in this paper. Although channel estimation in other systems has been studied extensively in both SISO and MIMO cases, this topic has been left relatively unaddressed for the FWA systems except in [11] where a joint frequency offset and channel impulse response estimation algorithm is proposed. It is designed under the least square criterion in an iterative manner and uses the preamble structure provided for an OFDM based FWA uplink.…”