Downlink Transmission Strategies for Cloud Radio-access Networks

This thesis studies transmission strategies for the downlink of a cloud radio-access network, in which the base stations are connected to a centralized cloud-computing based processor with digital backhaul links. We provide a system-level performance comparison of two fundamentally different strategies, namely the data-sharing strategy and the compression strategy, that differ in the way the backhaul is utilized. It is observed that the performance of both strategies depends crucially on the available backhaul capacity. When the backhaul capacity is low, the data-sharing strategy performs better, while the compression strategy is superior under moderate-to-high backhaul capacity. Using insights from such a comparison, we propose a novel hybrid strategy, combining the data-sharing and compression strategies, that allows for better control over the backhaul capacity utilization. An optimization framework for the hybrid strategy is proposed. Numerical evidence demonstrates the performance gain of the hybrid strategy.M.A.S