WSN07-6: A Directional MAC Protocol for Practical Smart Antennas

Recently, several MAC protocols using directional antennas, typically referred to as directional MAC protocols, have been proposed for wireless ad hoc networks. However, the MAC protocols in the previous studies were evaluated using simulation with ideal antenna forms. When using practical antenna beam forms, side lobes and back lobes exist which may cause new problems. In this paper, we evaluate the performance of the directional MAC protocol in the previous studies with practical antenna beam forms. In addition, we propose a directional MAC protocol that assumes practical antenna beam forms. The proposed MAC protocol mitigates data collisions due to the effects of minor lobes by the following two schemes. First, the nodes rotate directional receiving antenna beams in an idle state. Second, nodes transmit NAV (Network Allocation Vector) request frames to avoid collisions from neighboring nodes. By controlling the transmitting power, our protocol allows nodes to communicate with nodes beyond the omni-directional transmission range. The simulation results show that the proposed directional MAC protocol improves throughput performance compared to existing directional MAC protocol when using practical antenna beam forms.