E-SPAN: enhanced-SPAN with directional antenna

A mobile ad-hoc network (MANET), also referred as independent basic service set (IBSS), has nodes which not only send/receive packets associated with them but also co-operate in forwarding data and control packets for the network. Efficient use of energy by the mobile nodes is very important to increase the lifetime of a MANET. Since nodes seldom have packets to receive, they remain in idle mode for long periods of time, which causes a lot of energy drain. Coordination algorithms reduce the time a node is in the idle mode by keeping it in sleep mode as much as possible while coordinators buffer packets for these sleeping nodes. For a given transmit energy, a directional antenna has larger transmit range as compared to an omni-directional antenna. This feature of directional antennas can be used in protocols which assume a sparse network. We have chosen SPAN (Benjie, C. et al., ACM Wireless Networks Journal, vol.8, no.5, 2002) to validate our claim. SPAN is a protocol which elects a sparse network (i.e. backbone) of coordinators to buffer packets for sleeping nodes. Enhanced SPAN (E-SPAN) is SPAN modified to use a directional antenna. Simulations prove the effectiveness of the directional antenna and show that E-SPAN reduces the average power consumed by the nodes in the network by about 20%.