Uppsala universitet

Simplified Kalman Estimation of Fading Mobile Radio Channels:
High Performance at LMS Computational Loads

Lars Lindbom

IEEE International Conference on Acoustics, Speech and Signal Processing,
Minneapolis, MN, vol III, pp 352-355, April 27-30, 1993. © 1993 IEEE.

Paper In Pdf.


Outline:
Parameters of time-varying systems are often estimated by adaptive algorithms with sliding time-windows, which discount old data. We may then face a dilemma: the use of a short data window (or, equivalently, a large adaptation gain) results in noisy estimates. With a long data window (small gain), time varying parameters are tracked with a considerable delay. To improve the accuracy, the present paper suggests a low-complexity algorithm which takes a priori information about the properties of the time-variations into account, in the form of stochastic models.

Abstract:
Low complexity algorithms for channel estimation in Rayleigh fading environments are presented. The channel estimators are presumed to operate in conjunction with a Viterbi detector, or an equalizer. The algorithms are based on simplified internal modelling of time-variant channel coefficients and approximation of a Kalman estimator.

A novel averaging approach is used to replace the on-line update of the Riccati equation with a constant matrix. The associated Kalman gain is expressed in an analytical form. Compared to RLS tracking, both a significantly lower bit error rate and a much lower computational complexity is attained.

Related publications:
Sinusoid modelling of time-varying channel coefficients in IS-136 systems.

A series of four papers outlining the later development of a complete design methodology, based on stochastic models of time-varying parameters:

Design of general constant-gain adaptation algorithms.
Part II: Analysis of stability and performance, for slow and fast variations.
The Wiener LMS adaptation algorithm, a special case with low complexity.
A Case Study on IS-136 1900MHz channels.
PhD Thesis by L. Lindbom 1995, presenting the general design methodology.

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