Performance analysis for contention adaptation of M2M devices with directional antennas

In the directional carrier sense multiple access-collision avoidance (directional-CSMA-CA) mechanism, the efficient channel access mechanism with a collision-controlled concept is one of the most challenging topics. Especially, in capillary machine-to-machine (M2M) where wireless personal area network (WPAN) is a key technology for its wireless connectivity, a contention-based medium access control (MAC) protocol is crucial to enable numerous M2M devices to concurrently access the channel. This paper presents an analytical model for the slotted directional-CSMA-CA mechanism of 802.15.3c networks under saturated environment. By presenting a multi-class approach of directional-CSMA-CA mechanism to reduce collision occurrences, we support an adaptive back-off exponent of M2M device on the required frame payload size. For the mathematical analysis, the discrete-time Markov chain model is applied with the features of PHY/MAC of millimeter Wave (mm-Wave) network and the effects of directional antennas. In addition, extensive simulations are performed to verify the analytical model. The obtained results of the analytic and simulation show that the collision probability of M2M device is reduced by differentially adapting the contention rate to each M2M device, and the fairness property can be improved because there are remarkable increases of opportunities to transmit short-frame payloads.