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Optimal Routing, Link Scheduling and Power Control in Multi-hop Wireless Networks

We are generally interested in the problem of optimizing the timing and duration of sleep states on mobile devices, with the objective of minimizing power with respect to a QoS constraint. In our current model, there are two power consumption modes, sleep and active. There is associated rate of power consumption at the mobile terminal in each state, as well as a fixed energy consumed in transitioning between the two states. The QoS parameter we are focused on is
average delay.

To help gain a better understanding of the general problem, we considered a simple model where there is a single transmitter and receiver. The receiver is the mobile node whose mode we wish to
control. The transmitter can give commands to the receiver regarding its sleep state, and forwards incoming streaming data to the receiver appropriately. We formulated this as a Markov decision process, and solved it numerically using dynamic programming. The solutions from the numerical calculations strongly suggest that the optimal policy (that which minimizes average power consumption subject to an average delay constraint) is such that the transmitter should only command the receiver to sleep when there is no data queued at the transmitter. The system thus behaves as a single server queue with vacations. We were able to derive closed form expressions for the optimal sleep duration, as well as the associated minimal rate of power consumption. Future work will be focused on more elaborate models involving multiple users.


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