Improving routing protocol performance in delay tolerant networks using extended information

Delay tolerant networks (DTNs) are wireless mobile networks that do not guarantee the existence of a path between a source and a destination at any time. When two nodes move within each other’s transmission range during a period of time, they can contact each other. The contact of nodes can be periodical, predictable and nonpredictable. In this paper, we assume the contact of nodes is nonpredictable so that it can reflect the most flexible way of nodes movement. Due to the uncertainty and time-varying nature of DTNs, routing poses special challenges. Some existing schemes use utility functions to steer the routing in the right direction. We find that these schemes do not capture enough information of the network. Thus, we develop an extended information model that can capture more mobility information and use regression functions for data processing. Experimental results from both our own simulator and real wireless trace data show that our routing algorithms based on the extended information model can increase the delivery ratio and reduce the delivery latency of routing compared with existing ones.     

节点能量敏感的容迟/容断网络概率路由算法

针对容迟/容断网络(DTN)中节点能量受限的问题,提出一种节点能量敏感的概率路由算法。该算法将网络中的节点划分能量状态,针对不同能量状态的节点采取有区别的消息转发机制和节能的缓存管理策略,实现消息交付率与网络能耗之间的平衡。仿真结果表明,与其他几种算法相比,该算法能够在低能耗的基础上提高消息交付率并降低网络开销,具有较长的网络寿命。     

A dynamic multicast tree based routing scheme without replication in delay tolerant networks

Delay tolerant networks (DTNs) are a special type of wireless mobile networks which may lack continuous network connectivity. Multicast is an important routing function that supports the distribution of data to a group of users: a service needed for many potential DTN applications. While multicasting in the Internet and in mobile ad hoc networks has been studied extensively, efficient multicasting in DTNs is a considerably different and challenging problem due to the probabilistic nature of contact among nodes. This paper aims to provide a non-replication multicasting scheme in DTNs while keeping the number of forwardings low. The address of each destination is not replicated, but is assigned to a particular node based on its contact rate level and active level. Our scheme is based on a dynamic multicast tree where each leaf node corresponds to a destination. Each tree branch is generated at a contact based on the compare–split rule proposed in this paper. The compare part determines when a new search branch is needed, and the split part decides how the destination set should be partitioned. When only one destination is left in the destination set, we use either wait (no further relay) or focus (with further relay) to reach the final destination. The effectiveness of our approach is verified through extensive simulations. Ratio-based-split performs best in the compare–split step, both in synthetic and real traces. Using the wait scheme can reduce the number of forwardings, while using the focus scheme can reduce the latency.     

延迟容忍移动无线传感器网络路由策略综述*

近年来,关于间断连通的延迟容忍移动无线传感器网络（DTMSN）有很多研究,其中最关键的问题之一是路由,因此针对DTMSN提出了不同的路由协议。对DTMSN路由协议进行分类,着重介绍几种当前具有代表性的路由协议,并对协议的能量效率、服务质量和扩展性等方面进行了分析和比较。最后对DTMSN路由协议的进一步研究进行了展望。     

基于卡尔曼滤波理论的容迟与容断网络自适应感知路由算法

针对容迟与容断网络中的单播通信问题,提出了一种自适应感知路由协议(adaptive context aware routing protocol,ACRP);并引入卡尔曼滤波理论,给出最优的消息轮渡节点选取策略.仿真实验表明,与常见的单副本拷贝或多副本拷贝协议相比,提出的面向情境感知的自适应路由协议拥有更好的传输性能和稳定性.     

An architecture of an intelligent system for routing user requests in a network of heterogeneous databases

We present a general purpose model for routing user requests, e.g. queries, in a network of autonomous heterogeneous databases. The database schemas and other information on the database nodes are used to construct a multi-level knowledge-base (MKB) that resides in various nodes. Access to the databases is not done by creating direct connections between the user and the nodes where the data are presumably located. Rather, the user approaches the network by contents via an intelligent system that utilizes the MKB in order to identify the nodes and databases where the most relevant information resides, and establishes access routes to those nodes.     

Development and Verification of Simulation Model Based on Real MANET Experiments for Transport Layer Protocols （UDP and TCP）

There is a lack of appropriate guidelines for realistic user traces, mobility models, routing protocols, considerations of real-life challenges, etc. for general-purpose mobile ad hoc networks (MANET). In this paper, four laptops are used in an open field environment in four scenarios to evaluate the performances of Internet control message protocol (ICMP) based ping and transmission control protocol (TCP) based streaming video applications using optimised link state routing (OLSR) implementation in an IEEE 802.11g wireless network. Corresponding simulations are developed in Network Simulator ns-2 by setting simulation parameters according to the real experiments. Difficulties faced to regenerate real-life scenarios have been discussed and the gaps between reality and simulation are identified. A setup guideline to produce realistic simulation results has been established.