Adaptive Modulation Systems for Predicted Wireless Channels.

Sorour Falahati, Uppsala University,
Arne Svensson, Chalmers U. of Technology,
Torbjörn Ekman, Uppsala University and
Mikael Sternad, Uppsala University

7th Wireless World Research Forum Workshop , Eindhoven, the Netherlands, Dec 2002.

Outline:

The Wireless IP project within the PCC program studies problems that are crucial in the evolution of UMTS towards high data rates, as well as in future 4G technologies aimed at rapidly mobile terminals. The goal is to attain higher througputs for packet data in particular in downlinks, without bandwidth expansion and while providing acceptable quality of service for various classes of traffic.

Abstract:

When adaptive modulation is used to counter short-term fading in mobile radio channels, signaling delays create problems with outdated channel state information. The use of channel power prediction will improve the performance of the link adaptation. It is then of interest to take the quality of these predictions into account explicitly when designing an adaptive modulation scheme.

We study the optimum design of an adaptive modulation scheme based on M-QAM modulation assisted by channel prediction for the flat Rayleigh fading channel. The data rate and in some variants transmit power are adaptedto maximize the spectral efficiency, subject to average power and bit error rate constraints.

The key issues studied here are how a known prediction error variance will affect the optimized transmission properties such as the SNR boundaries that determine when to apply different modulation rules, and to what extent it affects the spectral efficiency. This investigation is performed by analytical optimization of the link adaptation, using the statistical properties of a particular but efficient channel power predictor.

Optimum solutions for the rate and transmit power are derived based on the predicted SNR and the prediction error variance. The analytical result are evaluated and presented.

Related publications:

Journal paper, (IEEE TCOM 2004).

Proc. of the IEEE (Dec. 2007) invited paper on adaptive transmission in beyond-3G wireless systems.

PhD Thesis on channel prediction by Torbjörn Ekman, Oct. 2002.

Licenciate Thesis by Sorour Falahati, Feb. 2000.

VTC02-fall paper on channel prediction over 0.1-0.8 wavelengths.

A system proposal in which predictive adaptive modulation is used (RVK02).

An overview of the Wireless IP Project, RVK02.

Source:

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