Deterministic medium access mechanism for time-critical wireless sensor network applications

Several wireless sensor network (WSN) applications will in the future be deployed for process control purposes which typically require timely data delivery. The main drawback with current WSNs is that they cannot guarantee predictable delay which is required in many applications. In this paper, we propose WirArb which is a new medium access control (MAC) protocol suitable for time-critical applications that needs deterministic delay guarantees. Each user is pre-defined arbitration frequency which is used to distinguish in which order the users can access the channel. The arbitration frequency is determined by orthogonal sub-carriers in the physical layer. The proposed mechanism will always guarantee the user with highest priority will gain channel access and users with lower priority needs to wait for their turn. We evaluate and compare the proposed WirArb with IEEE 802.15.4 and IEEE 802.11 in terms of latency and throughput. The obtained results show that for a star network with several users the proposed WirArb is superior.