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Summary: An EM Based Frequency Domain Channel Estimation Algorithm
for Multi-Access OFDM Systems
T. Y. Al-Naffouria,
, M. S. Sohailb
a
Electrical Engineering Department, University of Southern California, CA 90089
b
Electrical Engineering Department, King Fahd University of Petroleum &
Minerals, Dhahran 31261, Saudi Arabia
Abstract
Channel estimation is an important prerequisite for receiver design. In this paper we
present a semi-blind low complexity frequency domain based channel estimation algorithm
for multi-access OFDM systems. Our algorithm is based on eigenvalues interpolation and
makes a collective use of data and channel constraints. We exploit these constraints to
derive a frequency domain maximum a posteriori (MAP) channel estimator. Furthermore,
we develop a data aided (expectation maximization based) estimator incorporating frequency
correlation information. The estimator is further enhanced by utilizing the time correlation
information through a Forward Backward (FB) Kalman filter. We also explore various
implementation for the FB Kalman filter. The simulation results are provided validating the
applicability of the proposed algorithm.
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