In this paper, we analyze the effects of using directional antennas for broadcasting in DTNs (Delay Tolerant Networks) in realistic mobility scenarios. Directional antennas (DA) can create longer range contacts than omnidirectional antennas with the same transmission power, and hence have the potential to cover a larger area faster if deployed suitably. In many DTN applications, reducing the latency and the amount of network resources used for broadcasting a message is important for properly utilizing the message and prolonging the life time of the mobile devices used in DTNs. We investigate the use of DA in DTNs to reduce the latency and the diameter (i.e., largest number of hops needed for an agent to receive a message) in broadcasting. In particular, we analyze the performance of classical SIRS epidemic dynamics for broadcasting in DTNs, using a combination of omnidirectional and directional antennas, assuming various realistic mobility models. Compared to using only omnidirectional antennas, we show that the use of agents with DA can significantly reduce the broadcast latency, but the diameter for broadcasting is not always reduced. We also study the effects of different antenna and mobility parameters on the performance of the system.
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