國立清華大學 數學系

Abstract:
As the ultra-reliability and low-latency are essential requirements for the applications of critical Internet of Things (IoT), in this talk we revisit collision channels without feedback. There are two main medium access control (MAC) approaches to a collision channel without feedback: random (slotted ALOHA) and deterministic (protocol sequence-based) schemes. Unlike the traditional slotted ALOHA, protocol sequence-based scheme is able to guarantee a positive individual throughput within an expectable period of time, even the time synchronous is hard to be achieved. In the first part of this talk, I will survey some results on protocol sequence-based schemes, including user-irrepressible (UI) sequences and conflict-avoiding codes (CACs), which have some interesting combinatorial structures. Then, for a fair comparison, deadline-constrained slotted ALOHA schemes will be introduced to maximize the probability that a packet can be successfully received within an pre-assigned deadline. Some recent progress including the uniqueness of the optimal transmission probability that maximizes the successful delivery probability under multiple-packet reception (MPR) technology is addressed as well.