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In this paper, the problem of optimal power control for delay-constrained communication over fading channels is studied. The objective is to find a power control law that optimizes the link layer performance, specifically, minimizes delay bound violation probability (or equivalently, the packet drop probability), subject to constraints on average power, arrival rate and delay bound. The transmission buffer size is assumed to be finite; hence, when the buffer is full, there will be packet drop. The fading channel under study has a continuous state, e.g., Rayleigh fading. Since directly solving the power control problem (which optimizes the link layer performance) is particularly challenging, the problem is decomposed into three subproblems and the three subproblems are solved iteratively; the resulting scheme is called joint queue length aware (JQLA) power control, which produces a local optimal solution to the three subproblems. It is proved that the solution that simultaneously solves the three subproblems is also an optimal solution to the optimal power control problem. Simulation results show that the JQLA scheme achieves superior performance over the time domain water filling and the truncated channel inversion power control.
Date of Publication: June 2011