An efficient uplink multi-connectivity scheme for 5G millimeter-wave control plane applications

The millimeter-wave (mm-wave) frequencies offer the potential of orders of magnitude that increases in capacity for next-generation cellular systems. However, links in mm-wave networks are susceptible to blockage and may suffer from rapid variations in quality. Connectivity to multiple cells at mm-wave and/or traditional frequencies is considered essential for robust communication. One of the challenges in supporting multi-connectivity in mm-waves is the requirement for the network to track the direction of each link in addition to its power and timing. To address this challenge, we implement a novel uplink measurement system that, with the joint help of a local coordinator operating in the legacy band, guarantees continuous monitoring of the channel propagation conditions and allows for the design of efficient control plane applications, including handover, beam tracking, and initial access. We show that an uplink-based multi-connectivity approach enables less consuming, better performing, faster and more stable cell selection, and scheduling decisions with respect to a traditional downlink-based standalone scheme. Moreover, we argue that the presented framework guarantees: 1) efficient tracking of the user in the presence of the channel dynamics expected at mm-waves and 2) fast reaction to situations in which the primary propagation path is blocked or not available.