UAV-Assisted C-RAN with Rate Splitting Under Base Station Breakdown Scenarios

The flexibility and mobility of unmanned aerial vehicles (UAVs) make them a viable candidate in improving connectivity and coverage of cloud-radio access networks (CRANs). To investigate this aspect and facilitate efficient interference mitigation, this paper studies a C-RAN in the downlink, where base stations (BSs) are assisted by UAVs in scenarios where a subset of BSs break down. BSs and UAVs apply the concept of rate-splitting (RS) which divides messages into a common and a private part. Under this strategy, we formulate a weighted sum-rate maximization problem subject to fronthaul capacity and peak transmit power constraints. This non-convex optimization problem is then solved via a low complexity convex-concave procedure (CCP) algorithm. Simulation results suggest that our proposed RS method in an UAV-embedded C-RAN system yields significant improvement in achievable sum-rate over schemes which adopt treating interference as noise as a receiving strategy. Further, the scenario where UAVs are assigned for common messages and BSs for private message is the preferred RS allocation choice.