Resource allocation and interference management for opportunistic relaying in integrated mmWave/sub-6 GHz 5G networks

Future fifth generation (5G) networks are envisioned to use millimeter wave (mmWave) bands to provide Gbps throughput. To extend the coverage of extreme data rates provided by mmWave technologies, we consider two-hop relaying based on device-to-device (D2D) communication in an integrated mmWave/sub-6GHz 5G network. Compared to single-hop multi-cell networks, two-hop D2D relaying in this network will complicate the network management. Relay selection and beam selection should be considered together as relaying in mmWave bands is based on directional transmissions. MmWave/sub-6GHz multi-connectivity has to be managed, and resources have to be allocated across frequencies with disparate propagation conditions. In this article, a hierarchical network control framework is considered to address the relay and beam selection, resource allocation and interference coordination problems. The sub-6GHz band is responsible for network control and for providing reliable communications, while the mmWave band provides high throughput enhancement. Opportunistic relay selection and mmWave analog beamforming are used to limit the signaling overhead. We evaluate mmWave/sub-6GHz multi-connectivity with and without two-hop relaying in urban outdoor scenarios for different site deployment densities. MmWave/sub-6GHz multi-connectivity with relaying shows considerable promise for reaching consistent user experience with high end-to-end throughput in a cost-effective network deployment.