Modeling and performance analysis of RI-MAC under a star topology

RI-MAC is the most representative receiver-initiated (RI) duty-cycled MAC, designed to improve the throughput and minimize the power consumption of wireless sensor networks (WSNs). With RI-MAC, the receiver always initiates each transmission opportunity for all intended senders, while the senders compete for channel access based on the same backoff windows (BWs) controlled by the receiver. Such a WSN may encounter a throughput bottleneck under the star topology around a sink node in practice, and hence investigating the performance of RI-MAC under such a condition is of great importance. As opposite to the conventional sender-initiated MACs such as 802.11 and 802.15.4, in RI-MAC, data transmissions of all senders delivered to the same receiver are coupled closely due to the RI nature. Consequently, the well-known Bianchi model and its extensions for sender-initiated MACs are inapplicable for RI-MAC. In this paper, we develop a brand-new model from the perspective of a receiver. We study the system saturation throughput and the power consumption of RI-MAC with the model under a star topology. To the best of our knowledge, it is the first model for any kind of receiver-initiated duty-cycled MACs. Our model captures the most essential characteristics of receiver-initiated duty-cycled MACs and therefore has a wide application scope. With this model, we deeply reveal the relationship between the parameter settings and the RI-MAC performance, and further optimize the RI-MAC design. Extensive simulations verify that our model is very accurate. For instance, the average errors between the theoretical and simulation results are less than 6% for both the system saturation throughput and power consumption.