Sidelink-Assisted URLLC Built on Cooperative Retransmissions with Optimum Power Control

The fifth generation of wireless technology (5G) has advanced exceptionally in the past few years, giving rise to challenging quality of service (QoS) requirements and diverse deployment scenarios. Among the set of available services, ultra-reliable low-latency communication (URLLC) imposes stringent reliability and latency requirements. For improving the reliability under strict latency constraints in an error-prone downlink (DL), we have proposed a sidelink (SL)-assisted cooperative retransmission scheme, which takes advantage of multiple independently fading device-to-device (D2D) links. For the cooperative scheme, power control is useful for balanced user contributions and to control additional interference imposed to the system. Hence, this paper focuses on designing an optimal power control for the cooperative sidelink retransmission scheme, which gradually increments the power with every retransmission attempt. The objective is to utilize minimum power without compromising the desired latency and reliability performance. Results from system level evaluation reveal significant power savings in comparison to the reference power control scheme, which uses the maximum transmit power per device, limited by the DL path-loss power constraint only.