Table of Contents
ISRN Signal Processing
Volume 2011, Article ID 758918, 13 pages
http://dx.doi.org/10.5402/2011/758918
Research Article

Fisher-Information-Matrix Based Analysis of Semiblind MIMO Frequency Selective Channel Estimation

1Department of Electrical Engineering, I.I.T Kanpur, Kanpur 208016, India
2Department of Electrical and Computer Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0407, USA

Received 8 May 2011; Accepted 21 June 2011

Academic Editors: Y. H. Ha, C.-C- Hu, A. Ito, A. Maier, A. Wong, and B. Yuan

Copyright © 2011 Aditya K. Jagannatham and Bhaskar D. Rao. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We present a study of semiblind (SB) estimation for a frequency-selective (FS) multiple-input multiple-output (MIMO) wireless channel using a novel Fisher-information matrix (FIM) based approach. The frequency selective MIMO system is modeled as a matrix finite impulse response (FIR) channel, and the transmitted data symbols comprise of a sequence of pilot symbols followed by the unknown blind symbols. It is demonstrated that the FIM for this system can be expressed as the sum of the blind FIM Jb and pilot FIM Jp. We present a key result relating the rank of the FIM to the number of blindly identifiable parameters. We then present a novel maximum-likelihood (ML) scheme for the semiblind estimation of the MIMO FIR channel. We derive the Cramer-Rao Bound (CRB) for the semiblind scheme. It is observed that the semi-blind MSE of estimation of the MIMO FIR channel is potentially much lower compared to an exclusively pilot-based scheme. Finally, we derive a lower bound for the minimum number of pilot symbols necessary for the estimation of an FIR MIMO channel for any general semi-blind scheme. Simulation results are presented to augment the above analysis.