Optimal Power and Rate Control for Minimal Average Delay: The Single-User Case
IEEE Transactions on Information Theory
Delay Optimal Transmission Policy in a Wireless Multiaccess Channel
IEEE Transactions on Information Theory
Optimal Cross-Layer Scheduling of Transmissions Over a Fading Multiaccess Channel
IEEE Transactions on Information Theory
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In previous study on multi-user delay optimal problem, the exponentially increasing state space become one of the main obstacle. Moreover, packet drop due to finite buffer size is not taken into account. In this paper, we exploit the birth-death dynamics of the buffered SDMA systems and proposed a new approach, namely stochastic decomposition, to derive the delay optimal power adaptation scheme in a SDMA system. Unlike the conventional CSI-only power control solution, the delay-optimal power control has the multi-level water-filling structure in which the QSI determines the water-level and the CSI determines the power allocation across the SDMA users. This new approach overcomes the complexity issue mentioned above and allow us to obtain closed-form performance expressions so as to obtain the following first-order insights: 1) The water-filling levels {1/αk,qNk} under different QSIs q ∈ {1, 2, ...L} is an increasing geometric series. 2) The optimal average delay Uk* achieved by the multilevel water filling algorithm is τ/O(log Pk) + O(log log Pk)-λk while that achieved by traditional CSI-only scheme is (τ/O(log Pk)-λk ċ 3) Minimum average power required to satisfy a packet drop rate constraint ơd (due to finite buffer) is given by: log log (Pk,min) α -log ơd/L + log(λk) + log(Nk).