Resource allocation for power-efficient TDMA under individual rate constraints

We deal with energy-efficiency issues and resource allocation policies for time division multi-access (TDMA) over fading channels under average individual rate constraints. Supposing that the channels are frequency-flat block-fading and transmitters have full channel state information (CSI), we minimize power under average individual rate constraints and show that the optimal rate and time allocation policies can be obtained by a gready water-filling strategy. Our approach not only provides fundamental power limits when each user can support an infinite number of capacity-achieving codebooks, but also yields guidelines for practical designs where users can only support a finite number of adaptive modulation and coding (AMC) modes with prescribed symbol error probabilities.