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Open Access Research Article

Adaptive Modulation with Smoothed Flow Utility

Ekine Akuiyibo* and Stephen Boyd

Author Affiliations

Information Systems Laboratory, Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA

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EURASIP Journal on Wireless Communications and Networking 2010, 2010:815213  doi:10.1155/2010/815213

Published: 21 September 2010

Abstract

We consider the problem of choosing the data flow rate on a wireless link with randomly varying channel gain, to optimally trade off average transmit power and the average utility of the smoothed data flow rate. The smoothing allows us to model the demands of an application that can tolerate variations in flow over a certain time interval; we will see that this smoothing leads to a substantially different optimal data flow rate policy than without smoothing. We pose the problem as a convex stochastic control problem. For the case of a single flow, the optimal data flow rate policy can be numerically computed using stochastic dynamic programming. For the case of multiple flows on a single link, we propose an approximate dynamic programming approach to obtain suboptimal data flow rate policies. We illustrate, through numerical examples, that these approximate policies can perform very well.