HybridCast: A Hybrid Probabilistic/Deterministic Approach for Adjustable Broadcast Reliability in Mobile Wireless Ad Hoc Networks

Broadcast is a crucial yet expensive building block for many applications in bandwidth-scarce mobile wireless ad hoc networks. We propose a hybrid deterministic/probabilistic, decentralized broadcast protocol with adjustable broadcast reliability and overhead. The paper first proposes a purely probabilistic, topology-aware broadcast algorithm. The probabilistic broadcast adjusts each node's broadcast forwarding probability locally such that the average broadcast reliability requirement is met. An extension of the probabilistic broadcast to tolerate node mobility and packet loss is then presented. Furthermore, the paper augments the proposed probabilistic broadcast scheme with an existing deterministic broadcast protocol in order to reduce excessive broadcast overhead. The proposed hybrid protocol, called HybridCast, combines good characteristics of probabilistic broadcasts, such as adjustable reliability and resilience to mobility, with good characteristics of deterministic broadcasts, such as few retransmissions and low packet collisions. The simulation results show that the proposed protocol can achieve the system's reliability requirement with good tolerance to mobility and packet losses while incurring low broadcast overhead.