Millimeter-Wave Backhaul Traffic Alleviation via a Caching-Routing Strategy in 5G Cellular Networks

Coordinated Multipoint Joint Transmission (CoMP-JT) is a key technique for enhancing signal-to-noise ratio in the fifth generation ($\mathbf{5 G}$) networks with millimeter-wave (mmWave) mesh backhaul. Dense small base stations can exchange data over mmWave backhaul. However, in the CoMPJT, as identical content must be delivered to multiple base stations to serve a user, the mmWave backhaul suffers substantial pressure. However, we observe that different users may request the same popular files, which may be transmitted from far-source nodes, resulting in redundant transmissions and inefficient use of backhaul resources. To address this problem, we propose using a dedicated cache at each base station to buffer the ever-requested files to avoid transmitting files from far-source nodes. Then, we propose a JT cluster and caching-routing algorithm to reduce the mmWave backhaul traffic. Simulation results demonstrate that the proposed approach can efficiently reduce the backhaul burden compared with an existing algorithm. Our algorithm achieves better performance under higher file popularity conditions.