Radio Resource Allocation and Retransmission Schemes for URLLC Over 5G Networks

Low latency targets for ultra-reliable low latency communications (URLLC) may be conflicting with their stringent reliability requirements due to the need for re-transmissions. We explore, in this paper, the different resource allocation schemes for transmissions and re-transmissions depending on the requirements of the underlying service and on the traffic characteristics, focusing on the Industrial Internet of Things. We, namely, consider schemes with individual reservation versus a pool of contention-based reserved resources. We provide novel resource allocation schemes for initial transmissions and re-transmissions and derive corresponding analytical models for loss rates. We then show how to set the system parameters that allow meeting the URLLC requirements with low resource consumption.