Link disruption has a considerable impact on routing in multilayered satellite networks, which includes predictable disruption from the periodic satellite motion and unpredictable disruption from communication faults....Link disruption has a considerable impact on routing in multilayered satellite networks, which includes predictable disruption from the periodic satellite motion and unpredictable disruption from communication faults. Based on the analysis on the predictability of satellite links, a link disruption routing strategy is proposed for multilayered satellite networks, where, a topology period is divided into non-uniform slots, and a routing table in each slot is calculated by the topology predictability of satellite networks, and a congestion control mechanism is proposed to ensure the reliable transmission of packets, and a flooding mechanism is given to deal with the routes selection in the case of unpredictable link disruption. This routing strategy is implemented on the satellite network simulation platform, the simulation results show that the strategy has less delay and higher link utilization, and can meet the routing requirements of multilayered satellite networks.展开更多
In this paper, we address the problem of routing in delay tolerant networks (DTN). In such networks there is no guarantee of finding a complete communication path connecting the source and destination at any time, esp...In this paper, we address the problem of routing in delay tolerant networks (DTN). In such networks there is no guarantee of finding a complete communication path connecting the source and destination at any time, especially when the destination is not in the same region as the source, which makes traditional routing protocols inefficient in that transmission of the messages between nodes. We propose to combine the routing protocol MaxProp and the model of “transfer by delegation” (custody transfer) to improve the routing in DTN networks and to exploit nodes as common carriers of messages between the network partitioned. To implement this approach and assess those improvements and changes we developed a DTN simulator. Simulation examples are illustrated in the article.展开更多
Satellite networks have many inherent advantages over terrestrial networks and have become an important part of the global network infrastructure.Routing aimed at satellite networks has become a hot and challenging re...Satellite networks have many inherent advantages over terrestrial networks and have become an important part of the global network infrastructure.Routing aimed at satellite networks has become a hot and challenging research topic.Satellite networks,which are special kind of Delay Tolerant Networks(DTN),can also adopt the routing solutions of DTN.Among the many routing proposals,Contact Graph Routing(CGR) is an excellent candidate,since it is designed particularly for use in highly deterministic space networks.The applicability of CGR in satellite networks is evaluated by utilizing the space oriented DTN gateway model based on OPNET(Optimized Network Engineering Tool).Link failures are solved with neighbor discovery mechanism and route recomputation.Earth observation scenario is used in the simulations to investigate CGR's performance.The results show that the CGR performances are better in terms of effectively utilizing satellite networks resources to calculate continuous route path and alternative route can be successfully calculated under link failures by utilizing fault tolerance scheme.展开更多
This paper addresses the problem of routing in delay tolerant networks (DTNs). Delay tolerant networks are wireless networks where disconnections occur frequently due to mobility of nodes, failures of energy, the low ...This paper addresses the problem of routing in delay tolerant networks (DTNs). Delay tolerant networks are wireless networks where disconnections occur frequently due to mobility of nodes, failures of energy, the low density of nodes, or when the network extends over long distances. In these cases, traditional routing protocols that have been developed for mobile ad hoc networks prove to be ineffective to the extent of transmitting messages between nodes. To resolve this problem and improve the performance of routing in delay tolerant networks we propose a new routing protocol called Spray and Dynamic;this approach represents an improvement of the spray and wait protocol by combining it with the two protocols: MaxProp and the model of “transfer by delegation” (Custody Transfer). To implement our approach Spray and Dynamic, we have developed a DTN simulator according to DTN network architecture.展开更多
This paper presents a new graph-based single-copy routmg method m delay tolerant networks （DTN）. With time goes on in the networks, a DTN connectivity graph is constituted with mobility of nodes and communication, a...This paper presents a new graph-based single-copy routmg method m delay tolerant networks （DTN）. With time goes on in the networks, a DTN connectivity graph is constituted with mobility of nodes and communication, and a corresponding greedy tree is obtained using a greedy algorithm in DTN connectivity graph. While there are some bad nodes such as disabled nodes or selfish nodes in delay tolerant networks, the nodes can choose the next p^oper intermediate node to transmit the mes- sage by comparing the location of neighboring nodes in the greedy tree. The single-copy routing method is very appropriate for energy-constrained, storage-constrained and bandwidth-constrained applications such as mobile wireless DTN networks. We show that delivery ratio is increased significantly by using the graph-based single-copy routing when bad nodes exist.展开更多
In Delay Tolerant Networks （DTNs）, the offiine users can, through the encountering nodes, use the specific peer-to-peer message routing approach to deliver messages to the destination. Thus, it solves the problem th...In Delay Tolerant Networks （DTNs）, the offiine users can, through the encountering nodes, use the specific peer-to-peer message routing approach to deliver messages to the destination. Thus, it solves the problem that users have the demands to deliver messages while they are temporarily not able to connect to the Internet. Therefore, by the characteristics of DTNs, people who are not online can still query some location based information, with the help of users using the same service in the nearby area. In this paper, we proposed a location-based content search approach. Based on the concept of three-tier area and hybrid node types, we presented four strategies to solve the query problem, namely, Data Replication, Query Replication, Data Reply, and Data Synchronization strategies. Especially we proposed a Message Queue Selection algorithm for message transferring. The priority concept is set associated with every message such that the most ＂important＂ one could be sent first. In this way, it can increase the query success ratio and reduce the query delay time. Finally, we evaluated our approach, and compared with other routing schemes. The simulation results showed that our proposed approach had better query efficiency and shorter delay.展开更多
The delay tolerant network(DTN) is an emerging concept, which is used to describe the network, where the communication link may disrupt frequently. To cope with this problem, the DTN uses the store-carry-forward(SCF) ...The delay tolerant network(DTN) is an emerging concept, which is used to describe the network, where the communication link may disrupt frequently. To cope with this problem, the DTN uses the store-carry-forward(SCF) transmission mode. With this policy, the messages in the DTN are transmitted based on the nodes' cooperation. However, the nodes may be selfish, so the source has to pay certain rewards for others to get their help. This paper studies the optimal incentive policy to maximize the source's final utility. First, it models the message spreading process as several ordinary differential equations(ODEs) based on the meanfield approximation. Then, it mathematically gets the optimal policy and explores the structure of the policy. Finally, it checks the accuracy of the ODEs model and shows the advantages of the optimal policy through simulation and theoretical results respectively.展开更多
Delay/disruption tolerant networking （DTN） is an approach to networking where intermittent connectivity exists： it is often afforded by a store and forward technique. Depending on the capability of intermediary nod...Delay/disruption tolerant networking （DTN） is an approach to networking where intermittent connectivity exists： it is often afforded by a store and forward technique. Depending on the capability of intermediary nodes to carry and forward messages, messages can be eventually delivered to their destination by mobile nodes with an appropriate routing protocol. To have achieved a successful delivery, most DTN routing protocols use message duplication methods. Although messages are rapidly transferred to the destination, the redundancy in the number of message copies increases rapidly. This paper presents a new routing scheme based on a stochastic process for epidemic routing. Message redundancy is efficiently reduced and the number of message copies is controlled reasonably. During the contact process of nodes in the network, the number of message copies changes, and according to the variability in the number of copies, we construct a special Markov chain, birth and death process, on the number of message copies then calculate and obtain a stationary distribution of the birth and death process. Comparing the theoretical model with the simulation we have performed we see similar results. Our method improves on time-to-live （TTL） and antipacket methods, in both redundancy and delivery success efficiency.展开更多
This paper investigates the maximum network through- put for resource-constrained space networks based on the delay and disruption-tolerant networking （DTN） architecture. Specifically, this paper proposes a methodol...This paper investigates the maximum network through- put for resource-constrained space networks based on the delay and disruption-tolerant networking （DTN） architecture. Specifically, this paper proposes a methodology for calculating the maximum network throughput of multiple transmission tasks under storage and delay constraints over a space network. A mixed-integer linear programming （MILP） is formulated to solve this problem. Simula- tions results show that the proposed methodology can successfully calculate the optimal throughput of a space network under storage and delay constraints, as well as a clear, monotonic relationship between end-to-end delay and the maximum network throughput under storage constraints. At the same time, the optimization re- sults shine light on the routing and transport protocol design in space communication, which can be used to obtain the optimal network throughput.展开更多
为了应对容迟网络中拓扑结构剧烈变化、节点间连接频繁中断等问题,报文通常采用"存储—携带—转发"的方式进行传输:节点将报文存储在缓存中,携带报文直到遇到合适的机会才将报文转发给其他节点.因为缓存有限,这样的传输方式...为了应对容迟网络中拓扑结构剧烈变化、节点间连接频繁中断等问题,报文通常采用"存储—携带—转发"的方式进行传输:节点将报文存储在缓存中,携带报文直到遇到合适的机会才将报文转发给其他节点.因为缓存有限,这样的传输方式会使节点缓存溢出,导致拥塞的发生.在容迟网络环境下提出一种基于生命游戏的拥塞控制策略(game of life based congestion control strategy in delay tolerant networks,GLCCS),并将其应用于Epidemic路由方式.GLCCS借鉴生命游戏的演化思想,依据邻居节点中持有特定报文的节点比例来决定节点本地缓存中相应报文的操作.同时还提出了基于全网信息的报文排队机制和丢弃策略,依据传递或者丢弃一个报文对整个网络投递成功率的影响,计算出报文的效用值,按照效用值对缓存中报文进行排队和丢弃.在机会网络模拟器ONE中对仿真移动模型和真实运动轨迹进行模拟,实验结果表明,GLCCS与其他拥塞控制策略相比提高了投递成功率,减小了网络时延、丢包率以及负载比率.展开更多
文摘Link disruption has a considerable impact on routing in multilayered satellite networks, which includes predictable disruption from the periodic satellite motion and unpredictable disruption from communication faults. Based on the analysis on the predictability of satellite links, a link disruption routing strategy is proposed for multilayered satellite networks, where, a topology period is divided into non-uniform slots, and a routing table in each slot is calculated by the topology predictability of satellite networks, and a congestion control mechanism is proposed to ensure the reliable transmission of packets, and a flooding mechanism is given to deal with the routes selection in the case of unpredictable link disruption. This routing strategy is implemented on the satellite network simulation platform, the simulation results show that the strategy has less delay and higher link utilization, and can meet the routing requirements of multilayered satellite networks.
文摘In this paper, we address the problem of routing in delay tolerant networks (DTN). In such networks there is no guarantee of finding a complete communication path connecting the source and destination at any time, especially when the destination is not in the same region as the source, which makes traditional routing protocols inefficient in that transmission of the messages between nodes. We propose to combine the routing protocol MaxProp and the model of “transfer by delegation” (custody transfer) to improve the routing in DTN networks and to exploit nodes as common carriers of messages between the network partitioned. To implement this approach and assess those improvements and changes we developed a DTN simulator. Simulation examples are illustrated in the article.
基金Supported by the open project of Communication network transmission and distribution technologies Key Laboratory(ITD-12005/K1260011)the National Natural Science Foundation of China(61371126) and the National Natural Science Foundation of China(60903195)
文摘Satellite networks have many inherent advantages over terrestrial networks and have become an important part of the global network infrastructure.Routing aimed at satellite networks has become a hot and challenging research topic.Satellite networks,which are special kind of Delay Tolerant Networks(DTN),can also adopt the routing solutions of DTN.Among the many routing proposals,Contact Graph Routing(CGR) is an excellent candidate,since it is designed particularly for use in highly deterministic space networks.The applicability of CGR in satellite networks is evaluated by utilizing the space oriented DTN gateway model based on OPNET(Optimized Network Engineering Tool).Link failures are solved with neighbor discovery mechanism and route recomputation.Earth observation scenario is used in the simulations to investigate CGR's performance.The results show that the CGR performances are better in terms of effectively utilizing satellite networks resources to calculate continuous route path and alternative route can be successfully calculated under link failures by utilizing fault tolerance scheme.
文摘This paper addresses the problem of routing in delay tolerant networks (DTNs). Delay tolerant networks are wireless networks where disconnections occur frequently due to mobility of nodes, failures of energy, the low density of nodes, or when the network extends over long distances. In these cases, traditional routing protocols that have been developed for mobile ad hoc networks prove to be ineffective to the extent of transmitting messages between nodes. To resolve this problem and improve the performance of routing in delay tolerant networks we propose a new routing protocol called Spray and Dynamic;this approach represents an improvement of the spray and wait protocol by combining it with the two protocols: MaxProp and the model of “transfer by delegation” (Custody Transfer). To implement our approach Spray and Dynamic, we have developed a DTN simulator according to DTN network architecture.
基金Supported by the National High Technology Research and Development Programme of China （No. 2007AA01Z429, 2007AA01Z405 ） and the National Natural Science Foundation of China （No. 60633020, 60702059, 60872041 ）.
文摘This paper presents a new graph-based single-copy routmg method m delay tolerant networks （DTN）. With time goes on in the networks, a DTN connectivity graph is constituted with mobility of nodes and communication, and a corresponding greedy tree is obtained using a greedy algorithm in DTN connectivity graph. While there are some bad nodes such as disabled nodes or selfish nodes in delay tolerant networks, the nodes can choose the next p^oper intermediate node to transmit the mes- sage by comparing the location of neighboring nodes in the greedy tree. The single-copy routing method is very appropriate for energy-constrained, storage-constrained and bandwidth-constrained applications such as mobile wireless DTN networks. We show that delivery ratio is increased significantly by using the graph-based single-copy routing when bad nodes exist.
文摘In Delay Tolerant Networks （DTNs）, the offiine users can, through the encountering nodes, use the specific peer-to-peer message routing approach to deliver messages to the destination. Thus, it solves the problem that users have the demands to deliver messages while they are temporarily not able to connect to the Internet. Therefore, by the characteristics of DTNs, people who are not online can still query some location based information, with the help of users using the same service in the nearby area. In this paper, we proposed a location-based content search approach. Based on the concept of three-tier area and hybrid node types, we presented four strategies to solve the query problem, namely, Data Replication, Query Replication, Data Reply, and Data Synchronization strategies. Especially we proposed a Message Queue Selection algorithm for message transferring. The priority concept is set associated with every message such that the most ＂important＂ one could be sent first. In this way, it can increase the query success ratio and reduce the query delay time. Finally, we evaluated our approach, and compared with other routing schemes. The simulation results showed that our proposed approach had better query efficiency and shorter delay.
基金supported by the National Nature Science Foundation of China(61871388)
文摘The delay tolerant network(DTN) is an emerging concept, which is used to describe the network, where the communication link may disrupt frequently. To cope with this problem, the DTN uses the store-carry-forward(SCF) transmission mode. With this policy, the messages in the DTN are transmitted based on the nodes' cooperation. However, the nodes may be selfish, so the source has to pay certain rewards for others to get their help. This paper studies the optimal incentive policy to maximize the source's final utility. First, it models the message spreading process as several ordinary differential equations(ODEs) based on the meanfield approximation. Then, it mathematically gets the optimal policy and explores the structure of the policy. Finally, it checks the accuracy of the ODEs model and shows the advantages of the optimal policy through simulation and theoretical results respectively.
文摘Delay/disruption tolerant networking （DTN） is an approach to networking where intermittent connectivity exists： it is often afforded by a store and forward technique. Depending on the capability of intermediary nodes to carry and forward messages, messages can be eventually delivered to their destination by mobile nodes with an appropriate routing protocol. To have achieved a successful delivery, most DTN routing protocols use message duplication methods. Although messages are rapidly transferred to the destination, the redundancy in the number of message copies increases rapidly. This paper presents a new routing scheme based on a stochastic process for epidemic routing. Message redundancy is efficiently reduced and the number of message copies is controlled reasonably. During the contact process of nodes in the network, the number of message copies changes, and according to the variability in the number of copies, we construct a special Markov chain, birth and death process, on the number of message copies then calculate and obtain a stationary distribution of the birth and death process. Comparing the theoretical model with the simulation we have performed we see similar results. Our method improves on time-to-live （TTL） and antipacket methods, in both redundancy and delivery success efficiency.
基金supported by the National Natural Sciences Foundation of China(6113200261321061+3 种基金6123101161201183)the National Basic Research Program of China(2014CB340206)the Tsinghua University Initiative Scientific Research Program(2011Z05117)
文摘This paper investigates the maximum network through- put for resource-constrained space networks based on the delay and disruption-tolerant networking （DTN） architecture. Specifically, this paper proposes a methodology for calculating the maximum network throughput of multiple transmission tasks under storage and delay constraints over a space network. A mixed-integer linear programming （MILP） is formulated to solve this problem. Simula- tions results show that the proposed methodology can successfully calculate the optimal throughput of a space network under storage and delay constraints, as well as a clear, monotonic relationship between end-to-end delay and the maximum network throughput under storage constraints. At the same time, the optimization re- sults shine light on the routing and transport protocol design in space communication, which can be used to obtain the optimal network throughput.
基金Acknowledgments This work was supported by the National Natural Science Foundation of China （Grant No. 60873241 and 60673178） and the National High Technology Research and Development Program of China （863 Program, Grant No. 2008AA01 Z217 and 2007AA01A127）.
文摘针对容延容断网络(Delay/Disruption Tolerant Networks,DTN)不包含持续端到端连接、高传输时延及节点资源受限的特点,提出一种新的基于位置信息的喷射路由算法.该算法通过与GPRS网络结合形成平行网络结构,将GPRS作为DTN的一个通信频道以辅助路由,利用通信频道中已知的节点位置信息弥补DTN缺乏网络拓扑知识的不足,根据节点接触时的相遇角度调整Spray策略,减少无效信息副本的产生,Spray阶段完成后根据当前节点、目标节点及目的节点的位置和速度信息进行单副本路由,从而使传输过程中的信息路由具有方向性和目的性,减少对网络资源的消耗,降低传输时延并提高传输率.仿真结果表明本文所提出的算法是有效可行的,综合性能优于典型DTN路由算法Spray and wait和MaxProp.
文摘为了应对容迟网络中拓扑结构剧烈变化、节点间连接频繁中断等问题,报文通常采用"存储—携带—转发"的方式进行传输:节点将报文存储在缓存中,携带报文直到遇到合适的机会才将报文转发给其他节点.因为缓存有限,这样的传输方式会使节点缓存溢出,导致拥塞的发生.在容迟网络环境下提出一种基于生命游戏的拥塞控制策略(game of life based congestion control strategy in delay tolerant networks,GLCCS),并将其应用于Epidemic路由方式.GLCCS借鉴生命游戏的演化思想,依据邻居节点中持有特定报文的节点比例来决定节点本地缓存中相应报文的操作.同时还提出了基于全网信息的报文排队机制和丢弃策略,依据传递或者丢弃一个报文对整个网络投递成功率的影响,计算出报文的效用值,按照效用值对缓存中报文进行排队和丢弃.在机会网络模拟器ONE中对仿真移动模型和真实运动轨迹进行模拟,实验结果表明,GLCCS与其他拥塞控制策略相比提高了投递成功率,减小了网络时延、丢包率以及负载比率.
