Wireless Sensor and Actuator Networks: Algorithms and Protocols for Scalable Coordination and Data Communication

4.6 BEACONLESS GEOROUTING

The greedy forwarding algorithms normally need to periodically exchange “hello” messages (beaconing) with maximum signal strength by each node in order to broadcast current position information to all one-hop neighbors. The beaconing process of greedy routing costs additional energy consumption, which occurs independently of current data traffic.

Heissenbuttel and Braun proposed the beaconless routing (BLR) algorithm in Heissenbuttel and Braun (2004). Beaconless routing was further integrated with the IEEE 802.11 medium access control (MAC) layer in the contention-based forwarding (CBF) by Füßler et al. (2003) and implicit geographic forwarding (IGF) by Blum et al. (2003). In BLR, node S currently holding the packet destined for node D will include its own and location of D in the packet, and retransmit either only the request for forwarding or the full message content. Upon receiving the packet, the neighboring node, a candidate for forwarding with a progress, calculates a waiting time-out depending on the relative location coordinates of itself, S, and D. The node located at the “best” location introduces the shortest delays and forwards the packet first (or responds first with the offer to retransmit). The (most) remaining nodes then cancel the scheduled transmission of the same packet.

Beaconless routing is illustrated in Figure 4.12. To ensure that all potential forwarding nodes detect transmission of S, selection of candidate nodes for the next forwarding ...