A Grid Approach to Tracking of Mobile Radio
Channels in D-AMPS 1900
Report UPTEC 97 035E, 93 pages,
Adaptive equalization, with focus on estimation of mobile radio
channels, specified by the D-AMPS 1900 standard, is studied. The
considered channel estimators, referred to as WLMS
and incorporate a priori information about second order moment
characteristics of the mobile radio channels.
In this study,
autoregressive (AR) models are used to describe this priori knowledge.
The potential tracking performance gain by using a grid of WLMS
algorithms, instead of a single algorithm, is investigated. The specific
choice of estimator is determined by the experienced signal-to-noise
ratio and Doppler frequency, which both have to be estimated. The
utility of using WLMS estimators based on higher order
AR-models is of particular interest.
The overall goal with the grid approach is to
maximize the performance over a large operation area with
maintained low computational complexity.
Guidelines on how to match WLMS algorithms with
respect to SNR and
Doppler frequency, from a theoretical point of view, are given.
Different approaches to robustify WLMS algorithms are considered.
The bit error performance obtained by using a grid of multi-step
estimators together with Viterbi detectors, implemented as
interference rejection combiners (IRC), is investigated.
The initialization stage of each burst has proved to be crucial for the
performance, especially for algorithms based on higher order
AR-models, due to their poor transient behaviour.
If the effect of the initialization stage is eliminated, a grid of
algorithms based on higher order AR-models can improve
the performance substantially.
The gain can be up to 60 %, compared to an algorithm
based on a lower order AR-model tuned to the correct signal-to-noise
ratio and Doppler frequency.
- Mikael Sternad and Lars Lindbom
by L Lindbom 1995, presenting the general design methodology.
by Lindbom, Ahlen, Sternad and Falkenström on tracking of
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