Rate-Splitting Multiple Access for Cooperative Multi-Cell Networks
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As a promising downlink multiple access scheme, Rate-Splitting Multiple Access (RSMA) has been shown to achieve superior spectral and energy efficiencies compared with Space-Division Multiple Access (SDMA) and Non-Orthogonal Multiple Access (NOMA) in downlink single-cell systems. By relying on linearly precoded rate-splitting at the transmitter and successive interference cancellation at the receivers, RSMA has the capability of partially decoding the interference and partially treating the interference as noise, and therefore copes with a wide range of user deployments and network loads. In this work, we further investigate RSMA in cooperative multi-cell networks. Specifically, we study the optimal beamformer design to maximize the Weighted Sum-Rate (WSR) of all the users subject to individual Quality of Service (QoS) rate constraints and per base station power constraints. Numerical results show that, in a fully cooperative multi-cell network, RSMA achieves significant WSR improvement over SDMA and NOMA in a wide range of inter-user and inter-cell channel strength disparities. Specifically, SDMA (resp. NOMA) is more suited to deployments with little (resp. large) inter-user channel strength disparity and large (resp. little) inter-cell channel disparity, while RSMA is suited to any deployment. We conclude that RSMA provides rate, robustness and QoS enhancements over SDMA and NOMA in cooperative multi-cell networks.
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