An Adaptive Routing Protocol with Congestion Avoidance for Opportunistic Networks 王冉茵

Abstract The importance of routing and forwarding of messages in opportunistic networks. The necessity of congestion avoidance. Congestion aware adaptive routing protocol.

Introduction The adaptive routing protocol. ‒ Based on the expected level of connectedness and predictability of nodes. ‒ Some popular nodes will become congested and devote more of their resources than others for the overall benefit.

Conventional congestion control approaches in MANETs. ‒ 1) In order to allocate buffer space for arriving nodes, which results in dropping of a significant number of nodes ‒ 2) The protocols are built based on the assumptions of an end-to-end feed-back loop are not applicable for such partitioned.

Other Three Protocols: Epidemic routing protocol: Prophet routing protocol: Hibop routing protocol:

Congestion effects and the adaptive routing protocol

Just Drop Policy

Incorporating congestion avoidance in the adaptive routing protocol When the buffer occupancy is below one half of buffer size, the node can accommodate an arriving message without much problems. When the buffer space fills up and the occupied buffer space goes above a set threshold, say one half of the total buffer size, our congestion avoidance algorithm takes control in deciding which message are to be kept in the buffer.

The algorithm considers the available buffer space under two cases: In the first case it checks if the occupancy of the buffer is above a “safety” threshold margin which is dependent on the traffic generated rate of the node and the current occupancy of the buffer. In the second case the node checks if the occupancy of the buffer is above one half of the buffer size but below the “safety” threshold margin.

Algorithm Algorithm 1 and Algorithm 2 describe how each node limits its willingness to accept new messages whenever its buffer is occupied more than one half of its capacity.

Algorithm 1:Message Acceptance Logic - Receiver Algorithm 1 describes how a receiving node limits its willingness to receive packets when it senses self congestion.

Algorithm 2:Message Sending Logic - Sender Algorithm 2 describes how a sending node prepares its list of messages to be forwarded to a potential neighbor whom it had just met.

Congestion Aware Adaptive Routing Protocol(CAARP) In CAARP nodes will also advertise their buffer space availability and their willingness to store carry and forward messages for other nodes.

Simulation setup Message Delivery Ratio(MDR): We define message delivery performance as the system’s ability to deliver messages of application data in the presence of intermittent connectivity. This is expressed as the ratio of the messages delivered to the totally generated messages of each type.

Results and discussion

Conclusion The CAARP shows a higher MDR than adaptive routing when the buffer sizes are relativity larger. When the consumed energy is also taken in to account, for any given buffer size and a message delivery ratio, we have found that the CAARP has an overall superior performance with lower energy utilization than adaptive routing protocol.