Maximum likelihood blind channel estimation in the presence of Doppler shifts

Author

Cirpan, Hakan A. ; Tsatsanis, Michail K.

Author_Institution

Dept. of Electr. & Comput. Eng., Stevens Inst. of Technol., Hoboken, NJ, USA

Volume

47

Issue

6

fYear

1999

fDate

6/1/1999 12:00:00 AM

Firstpage

1559

Lastpage

1569

Abstract

Transmitter/receiver motion in mobile radio channels may cause frequency shifts in each received path due to Doppler effects. Most blind equalization methods, however, assume time-invariant channels and may not be applicable to fading channels with severe Doppler spread. We address the problem of simultaneously estimating the Doppler shift and channel parameters in a blind setup. Both deterministic and stochastic maximum likelihood methods are developed and iterative solutions proposed. The stochastic maximum likelihood solution is based on the modified version of the Baum-Welch (1970) algorithm, which originated in the study of hidden Markov models. The proposed methods are well suited for short data records appearing in TDMA systems. Identifiability and performance analysis issues are discussed, and Cramer-Rao bounds are derived. In addition, some illustrative simulations are presented

Keywords

Doppler shift; adaptive antenna arrays; adaptive estimation; blind equalisers; fading channels; hidden Markov models; iterative methods; land mobile radio; maximum likelihood estimation; multipath channels; radio receivers; radio transmitters; stochastic processes; time division multiple access; Cramer-Rao bounds; Doppler shift estimation; Doppler spread; TDMA systems; adaptive equalizers; blind equalization methods; channel parameters; deterministic maximum likelihood method; fading channels; frequency shifts; hidden Markov models; identifiability; iterative solutions; maximum likelihood blind channel estimation; mobile radio channels; modified Baum-Welch algorithm; multipath; performance analysis; short data records; simulations; stochastic maximum likelihood method; time-invariant channels; transmitter/receiver motion; Blind equalizers; Doppler effect; Fading; Frequency; Hidden Markov models; Land mobile radio; Maximum likelihood estimation; Radio transmitters; Receivers; Stochastic processes;

fLanguage

English

Journal_Title

Signal Processing, IEEE Transactions on

Publisher

ieee

ISSN

1053-587X

Type

jour

DOI

10.1109/78.765125

Filename

765125