M-T2F: A High-Efficient Contention Protocol for Wireless Networking in Cyber-Physical-Social Systems

Abstract

Cyber-physical-social systems (CPSS) as an emerging computing paradigm are revolutionizing the relationship between humans, devices and physical environments and will be expected to have a fundamental impact and influence in our daily lives. In a typical CPSS scenario, plenty of nodes (or devices) often adopt wireless distributed contention protocols to transmit sensed environment states for decision making. Therefore, designing a high-efficient and collision-less contention protocol is of great importance for wireless networking. As is known, in the classic time-to-frequency (T2F) protocol, each node signals on one randomly chosen subcarrier for contention. Though reducing the conventional time-domain contention time, T2F leads to many contention collisions (i.e., multiple nodes choose the same subcarrier) when the number of nodes is large. Aiming at this challenge, in this paper, we propose M-T2F (where each node signals on multiple randomly chosen subcarriers for contention) and analyze its consensus achievement. Specifically, M-T2F supports more nodes for transmission but introduces less collision, benefiting from lots of multicarrier choice combinations. Since the subset relationship between subcarrier choices poses a challenge to reach a consensus among nodes, M-T2F enables all nodes to reach a consensus by excluding the subset relationship and meanwhile reduces the contention time by utilizing wireless broadcast characteristics. As a result, our designs significantly outperform related designs in terms of the collision probability, throughput, delay, and fairness. For instance, for a network of 50 nodes adopting 8 subcarriers, in our designs, the collision probability is as low as 0.1 (i.e., a reduction of 70%) and the throughput efficiency is up to 0.9 (i.e., an improvement of 34%). Extensive simulations verify the effectiveness of our designs and validate the accuracy of our theoretical analysis. This study is very helpful to achieve satisfactory quality of experience and quality of services for wireless networking in CPSS.