Modelling link failure in the presence of extended hidden terminals over multi‑hop wireless ad hoc networks

摘要

IEEE 802.11 uses RTS/CTS (request to send/clear to send) reservation mechanism in multi-hop ad hoc networks to prevent collision drops caused by the hidden terminals. Extended hidden nodes impose great challenges to RTS/CTS mechanism by creating additional interferences and route failures. We introduce a Markov model to compute the probability of collision due to hidden and extended hidden nodes present in multi-hop ad hoc network under saturated traffic loads. This model is derived from the well-known Bianchi Markov chain model of IEEE 802.11 Distributed coordination function by introducing additional states in every back-off stage. Our model differentiates the collisions that could happen to RTS/CTS and data packets. We also compute the probability of link failure that occurs when the maximum retry limit is exceeded. The model is tested for varying network sizes with number of nodes 10, 50, 100, 150 and 200. The model validates the throughput, collision probability and link failure probability against the Bianchi model and ns-2.35 simulation result.