Power Minimization via Rate Splitting in Downlink Cloud-Radio Access Networks

Minimizing the power consumption in mobile communication networks while guaranteeing quality of service (QoS) requirements is essential in light of the unprecedented increase in the number of connected devices and the associated data traffic. Conventional cloud-radio access networks (C-RAN) assume treating interference as noise (TIN) while dealing with the provisioning of wireless interference. This paper considers a C-RAN system, where a central processor (CP) at the cloud is connected to several base-stations (BSs) via limited capacity fronthaul links. The paper then assumes a communication scheme where the CP applies rate splitting (RS) to the messages requested by the users, and enables common message decoding (CMD) at the receivers side. The paper addresses the problem of minimizing the weighted transmit power subject to minimum QoS and fronthaul capacity constraints, which is generally a non-convex and difficult problem to solve. We, therefore, propose an iterative approach based on inner-convex approximations (ICA) to obtain a stationary point of the optimization problem. The simulations show the power savings achieved by the proposed RS-CMD scheme as compared to the conventional TIN, especially at high QoS requirements.