No abstract

In opportunistic networks, a congestion phenomenon may occur if the remaining buffer of a node cannot accept any arrival message. Energy is consumed by dropping the messages stored in the buffer to provide space for new messages. In order to reduce and balance the energy consumption of nodes during congestion in opportunistic networks, a novel congestion control scheme is proposed. Nodes dynamically update their residual energy level and query the residual energy level of their neighbors in current local environment and adjust their threshold ratio using the learning automata principle while moving around. Nodes will only receive messages whose remaining TTL (time to live) proportion of initial TTL is larger than the threshold ratio when congestion occurs. Simulation results show that the Epidemic routing protocol with the proposed congestion control scheme can efficiently reduce and balance energy consumption among nodes. Also, the routing performances such as delivery ratio, overhead ratio, and deliver latency are improved. Furthermore, the network lifetime is obviously improved since much more energy is left.

No abstract

Disaster Area Wireless Networks (DAWNs) are widely deployed in natural or man-made disaster scenes, since the communication infrastructure may be completely destroyed by the disaster. This paper proposes a hybrid network architecture for DAWNs due to the mobility of first responders and refugees. Based on the link characterization of DAWNs, we choose four essential criteria and propose a multi-criteria decision-making method for emergency communication protocol (MCDM-ECP), which utilizes the analytic hierarchy process (AHP) method and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method to find the optimal next-hop node in DAWNs. Routing discovery and routing maintenance processes are included in the novel protocol. The simulation results show that MCDM-ECP performs better than other classical protocols both in energy consumption and packet received rate (PRR) for long-term emergency communications.