A Multi-Copy Delegation Forwarding Based on Short-Term and Long-Term Speed in DTNs

Delay Tolerant Networks (DTNs) are featured by unpredictable mobility patterns and easily-interrupted connections. Forwarding strategy has always been the research focus, in order to improve the delivery ratio. An enormous amount of researches pay attention to solving the following two problems: whether to forward, and how to forward. Therefore, forwarding metrics and forwarding strategies both play important roles in DTNs. In this paper, we consider a generalized random-waypoint model with heterogeneous nodes, the node's speed is regarded as the forwarding metric, which includes the short-term and long-term speed. Subsequently, we propose a multi-copy Delegation Forwarding based on Short-term and Long-term speed in DTNs (DFSL), which first determines a comprehensive mapping from short-term speed and long-term speed to the actual forwarding metric. Then, according to the forwarding metric and delegation forwarding strategy, DFSL utilizes some efficient nodes with higher forwarding metrics to assist in delivering messages, in order to improve the delivery ratio, while reducing the forwarding cost. Finally, we conduct simulations based on the synthetic mobility pattern and real trace. The results show that, compared with other multi-copy forwarding strategies, DFSL achieves the highest forwarding efficiency, which is defined as the result of delivery ratio divided by forwarding cost.