Cross-Layer Design with Adaptive Modulation: Delay, Rate, and Energy Tradeoffs

We present a cross-layer framework for optimizing the performance of wireless networks as measured by applications or upper layer protocols. The approach combines adaptive modulation with network utility maximization. We extend the approach to find optimal source rates and transmitter power and rate policies without explicit knowledge of the distribution of channel states. These optimal power and rate policies balance delay (backlog), transmission rate and energy to maximize network performance under constraints on average transmitter power and link buffer arrival and departure rates. Explicit policies are found for single links, and algorithmic methods presented to find optimal policies for complex interfering networks.