Towards overhead mitigation in state-free geographic forwarding protocols for wireless sensor networks

Routing has been the most consumptive of all processes engaged in the Wireless Sensor Network communications, thus improving this consumptive process by minimizing the number of overhead bits transmitted is vital. This paper investigates the State-free Geographic Forwarding (SGF) protocols, which employ the cross-layering concept that combines the tasks of the routing and Medium Access Control (MAC) layer to minimize energy consumption. Unfortunately, the numerous SGF protocols proposed in the past utilize a modified variant of the basic 802.11 Distributed Coordinated Function MAC protocol for their routing operations due to its ability to mitigate the hidden terminal problem using the four-way handshake mechanism. The mechanism, however, incurs a substantial amount of overhead, which subsequently affects the end-to-end delay and energy consumption of the network. In line with these, a Directional Compact Geographic Forwarding (DCGF) approach is proposed to mitigate the excessive overhead generated due to the repeated subjection of a multi-hop network to the four-way handshake mechanism. The proposed DCGF utilizes a smart antenna and Quality of Service (QoS) aware aggregation approach to mitigate the spread in a broadcast received and multiple unicast transmissions, respectively. The simulation results show that the proposed DCGF significantly outperforms its base protocol (Dynamic Window Secure Implicit Geographic Forwarding) in terms of message overhead, energy consumed and end-to-end delay.