Revising the Problem of Access Protocols in Ultra-Reliable Wireless Communications
Petar Popovski (Aalborg University)
Ultra-reliable low latency communication (URLLC) is an important new feature brought by 5G, with a potential to support a vast set of applications that rely on mission-critical links. Establishing and transmitting a short data packet is associated with multiple steps of the access protocols that involve auxiliary procedures (e.g. channel estimation) and exchange of metadata. The requirement for very high reliability is propagated and further augmented to each of those steps. This talk elaborates on the models used for access protocols and, specifically, provides a critical look on the assumptions used in random access protocols. The talk presents models for grant-free access and contrasts them to the traditional resource reservation procedures used in cellular systems. Specifically, the talk highlights the design alternatives for the authentication procedures, usually treated as an “afterthought” in the theoretical treatment of access protocols. Finally, a discussion is provided on techniques based on coded random access and successive interference cancellation with latency/reliability constraints.