Towards Reliable Application Data Broadcast in Wireless Ad Hoc Networks

Application data broadcast in ad hoc networks is an important primitive that has received little systematic research - the main focus of prior research being on control data broadcast. In this paper, we show why control data broadcast and even multicast techniques are insufficient for reliable application data broadcast; in fact their reliability degrades sharply with increasing application data size. We discover the root cause of this to be IP fragmenting the application data but not providing good reliability control on the fragments. We hence propose READ (reliable and efficient application-data dissemination), a protocol based on higher-layer fragmentation with fragment-level reliability control. READ splits a data packet into fragments, and disseminates them separately at dynamically adaptive intervals. Receivers piggyback implicit NACKs when propagating the fragments, and retrieve missing fragments from neighbors. Through experiments, we show that READ consistently achieves high delivery ratio and short latency, outperforming all other examined protocols.