Joint relay selection and beamforming for mmWave fronthauling network

Millimeter-wave (mmWave) fronthaul for Cloud-RAN has been considered as a promising 5G technique to meet the surging demand for high data rate. However, the Non-line-of-sight (NLOS) transmission problem seriously impacts the reliability of fronthauling network, and may leads to the breakdown of network. In this context, deploying high density relays could be an effective approach to improve reliability of mmWave fronthaul. In this paper, we focus on improving the network throughput of relay assisted mmWave fronthauling network utilizing relay selection and beamforming. To design the optimal beamformers structure, we propose a modified Zero-Forcing (ZF) precoding algorithm for the two-slot transmission. For the relay selection scheme designed for each radio remote unit (RRU), we adopt matching theory to obtain the best connection relationship between RRUs and relays. Specifically, the rate-specific preference list is formulated for each RRU, which make a significant impact on relay selection results. Finally, the simulation results show that the proposed method and algorithm can enable the NLOS transmission and significantly improve the network performance for mmWave based fronthauling network.