Complexity reduction in multicast beamforming for D2D assisted coded caching

A novel D2D aided beamforming scheme is proposed, where the local cache content exchange among nearby users is exploited. The transmission phase is split into two sub-phases: local D2D content exchange and downlink transmission. In the D2D sub-phase, users can autonomously share content with the adjacent users. In the downlink sub-phase, the Base station (BS) simultaneously serves some number of users to fulfill their remaining content requests by utilizing multicast beamforming. We first explain the main procedure via two simple examples and show the complexity involved in beamformer design. Then, we present the general formulation and detailed complexity analysis. We show analytically that, by exploiting the D2D exchange, the complexity of downlink multicast beamformer design can be greatly decreased. This provides significantly enhanced overall content delivery performance in terms of computational complexity and total delivery time.