An EM Algorithm-Based Disintegrated Channel Estimator for OFDM AF Cooperative Relaying

Jeng-Shin SHEU  Wern-Ho SHEEN  

IEICE TRANSACTIONS on Communications   Vol.E96-B   No.1   pp.254-262
Publication Date: 2013/01/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E96.B.254
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
channel estimation,  orthogonal frequency-division multiplexing,  amplify-and-forward relaying,  expectation-maximization algorithm,  

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The cooperative orthogonal frequency-division multiplexing (OFDM) relaying system is widely regarded as a key design for future broadband mobile cellular systems. This paper focuses on channel estimation in such a system that uses amplify-and-forward (AF) as the relaying strategy. In the cooperative AF relaying, the destination requires the individual (disintegrated) channel state information (CSI) of the source-relay (S-R) and relay-destination (R-D) links for optimum combination of the signals received from source and relay. Traditionally, the disintegrated CSIs are obtained with two channel estimators: one at the relay and the other at the destination. That is, the CSI of the S-R link is estimated at relay and passed to destination, and the CSI of the R-D link is estimated at destination with the help of pilot symbols transmitted by relay. In this paper, a new disintegrated channel estimator is proposed; based on an expectation-maximization (EM) algorithm, the disintegrated CSIs can be estimated solely by the estimator at destination. Therefore, the new method requires neither signaling overhead for passing the CSI of the S-R link to destination nor pilot symbols for the estimation of the R-D link. Computer simulations show that the proposed estimator works well under the signal-to-noise ratios of interest.