An RSSI-Based Cross Layer Protocol for Directional Ad Hoc Networks and Its Implementation

Smart antenna (or directional antenna) technology has been developed recently, which can control its antenna beam pattern to a specified direction by software. Medium access control (MAC) protocols using smart antennas, called directional MAC protocols, have the following potentials: higher spatial reuse, larger extension of communication range, less interference and higher total throughput compared to that with omni-directional antennas. Despite the great potential, there is rare implementation of directional MAC protocols for ad hoc networks. In this paper, we propose and implement a RSSI (Receive Signal Strength Indicator)-based cross-layer protocol for directional ad hoc networks. In the proposed protocol, the RSSI is used for computing the direction and randomizing backoff time. Moreover, backoff time is weighted according to number of hops from a source node. Additionally, simple incorporated routing functions are implemented. We implement the proposed protocol on a testbed with the electronically steerable parasitic array radiator (ESPAR) antenna and IEEE 802.15.4. The results of fundamental evaluation show that the proposed protocol can achieve about 2.4 times higher data arrival ratio than the conventional random backoff method with directional antennas.