Quality-aware millimeter-wave device-to-device multi-hop routing for 5G cellular networks

Millimeter-wave (mm-wave) transmission is a promising method for increasing capacity in next-generation cellular systems. However, since mm-wave signals are too weak to (i) do long-distance communication and (ii) survive in non-line-of-sight situations, multi-hop relaying is required. We thus study in this paper a multi-hop routing protocol at mm-wave (38 GHz and 28GHz) frequencies. Due to the great and steadily increasing importance of video streaming in cellular applications, we pay special attention to the maximization of video transmission quality, which makes the optimization problem different from the usual sum-rate maximization. Specifically, we develop a protocol that optimizes the 'sum quality' of the transmission of different video streams, subject to constraints (minimum quality) of separate streams. We take the unique properties of mm-waves (sparse angular power spectrum, leading to low interference) into account in our method. Extensive simulation results show the superiority of our approach compared to max-min flow routing which is widely used in QoS-sensitive applications.