Abstract—Co-operative localisation in wireless sensor networks (WSNs) is a method in which wireless sensor nodes interact with each other as peers to determine their physical position. In such networks it is crucial for communication between nodes to be contention free to meet the strict timing requirements. Medium Access Control (MAC) protocols provide the strongest influence over contention control in WSNs. The focus of this work is the design and analysis of a WSN MAC protocol suitable for supporting co-operative localisation. This paper presents a design overview of the MAC protocol and details its control structure. Preliminary simulation results are also presented to evaluate network formation aspects of the protocol.