Research On Routing And Scheduling In Constrained Delay Tolerant Network

Delay Tolerant Networks(DTNs) are hot topics in wireless network in recent years. Due to high node mobility, short radio range, energy management, sleeping scheduling and environmental factor, it is hard to maintain a stable end-to-end path at the same duration in DTNs, which even keeps partitions most of time. DTNs can be extensively applied in many applications except Internet, such as mobile ad hoc networks, satellite network, wildlife monitoring network, networks in the war, networks in remote areas and social networks, etc.Due to node mobility, sleeping scheduling, energy constraint and environmental factor, DTNs always keep high and changeful delay, transmission interruption, high bit-error-rates and huge difference on related transmission speed. Delay Tolerant Net-works are thus proposed to provide high quality network services in such environment, which suffers from high delay, high errors, packets losses and neighborless for commu-nication, etc. The key problem of routing and scheduling in DTNs is how to achieve high transfer performance(namely, high delivery ratio and short delivery delay, etc) and maintain mitigatory overhead (such as bandwidth and buffer) at the same time. How-ever, due to the heterogeneous and diversity of network architecture, there are many different challenges in routing and scheduling, especially when they are applied into real DTNs. Namely, the problem becomes more and more complicated on condition that the bandwidth and buffer size are limited. Therefore, DTNs are regarded as the key technology to implement "Ubiquitous Network", and they are worth of study.This paper investigates routing and scheduling problem in resource-constrained DTNs, supported by National Grand Fundamental Research973Program of China and National Natural Science Foundation of China, etc. The main contributions of this paper can be concluded as follows:1. Propose data transfer model in DTNs based on dynamic flow network. The model can represent bandwidth and buffer-constrained DTNs, and help design routing and scheduling scheme based on the existed classic minimum cost maximum flow algorithm. The simulation result show that the protocol can achieve high perfor-mance on delivery ratio, delay and hop. 2. Propose semi-distributed online scheme of routing and scheduling in DTNs based on static flow network algorithm. The scheme can be applied in many DTN ap-plications. In the progress of delivery, each node builds its local model of flow network first, and then routes and schedules messages referring to the result of minimum cost maximum flow. The simulation results show that the delivery delay of the scheme is at least49%shorter than that of existing works. At the meantime, the delivery ratio is also the highest.3. Propose ant colony-based distributed routing scheme in DTNs. The scheme us-es ant colony optimization to improve the adaption to dynamic topology, and the advantages of the scheme can be concluded as distribution and self-adapting optimization. The simulation result show the delivery delay of forwarding-based scheme is at least25.8%shorter than related protocols and replication-based scheme can achieve at least22.5%on delivery delay.4. Design and implement the simulation platform for routing and scheduling in DTNs. The platform can simulate the scenario of resource-constrained DTNs and the progress of routing and scheduling. The platform can also investigate and an-alyze the simulation result. It can evaluate the performance of algorithm with lower cost(e.g.,time and funds). The results also have high value on reference.