Opportunistic networks are self-organizing networks that do not require a complete path between the source node and the destination node as it uses encounter opportunities brought by nodes movement to achieve network ...Opportunistic networks are self-organizing networks that do not require a complete path between the source node and the destination node as it uses encounter opportunities brought by nodes movement to achieve network communication.Opportunistic networks routing algorithms are numerous and can be roughly divided into four categories based on different forwarding strategies.The Prophet routing algorithm is an important routing algorithm in opportunistic networks.It forwards messages based on the encounter probability between nodes,and has good innovation significance and optimization potential.However,the Prophet routing algorithm does not consider the impact of the historical throughput of the node on message transmission,nor does it consider the impact of the encounter duration between nodes on message transmission.Therefore,to improve the transmission efficiency of opportunistic networks,this paper based on the Prophet routing algorithm,fuses the impact of the historical throughput of the node and the encounter duration between nodes on message transmission at the same time,and proposes the Prophet_TD routing algorithm based on the historical throughput and the encounter duration.This paper uses the Opportunistic Networks Environment v1.6.0(the ONE v1.6.0)as the simulation platform,controls the change of running time and the number of nodes respectively,conducts simulation experiments on the Prophet_TD routing algorithm.The simulation results show that compared to the traditional Prophet routing algorithm,on the whole,the Prophet_TD routing algorithm has a higher message delivery rate and a lower network overhead rate,and its average latency is also lower when node density is large.展开更多
It is of great significance to study the encounter possibility of typhoon and plum rain in the Taihu Lake Basin in order to adjust the schemes of design storm and utilize flood resource and make the decision of real-t...It is of great significance to study the encounter possibility of typhoon and plum rain in the Taihu Lake Basin in order to adjust the schemes of design storm and utilize flood resource and make the decision of real-time scheduling for flood control in the Basin. Based upon the existing research findings of description of encounter phenomena of typhoon and plum rain, the initial time of typhoon affecting the Taihu Lake Basin, the start time of plum rain season and the end time of plum rain season were selected as the characteristic indices of typhoon and plum rain, respectively. According to their synchronous data from 1954 to 2009, the distribution functions of the above-mentioned three random variables were identified and a formula expressing the encounter possibility of typhoon and plum rain was derived. In view of the complexity and solution of this formula, joint distribution functions of typhoon and plum rain were constructed by the use of Gumbel Copula function on the basis of the adaptability comparison among three functions (Gumbel Copula, Clayton Copula and Frank Copula) in Archimedean functions. For the characteristics of the formula with the joint distribution functions based on Gumbel Copula function, two methods, i.e., numerical integration and Monte Carlo simulation, were selected to solve the encounter probability, and the validity of the computed results was analyzed finally.展开更多
基金The authors wish to thank the Natural Science Foundation of China under Grant Nos.61841109,61662054Natural Science Foundation of Inner Mongolia under Grand No.2019MS06031.
文摘Opportunistic networks are self-organizing networks that do not require a complete path between the source node and the destination node as it uses encounter opportunities brought by nodes movement to achieve network communication.Opportunistic networks routing algorithms are numerous and can be roughly divided into four categories based on different forwarding strategies.The Prophet routing algorithm is an important routing algorithm in opportunistic networks.It forwards messages based on the encounter probability between nodes,and has good innovation significance and optimization potential.However,the Prophet routing algorithm does not consider the impact of the historical throughput of the node on message transmission,nor does it consider the impact of the encounter duration between nodes on message transmission.Therefore,to improve the transmission efficiency of opportunistic networks,this paper based on the Prophet routing algorithm,fuses the impact of the historical throughput of the node and the encounter duration between nodes on message transmission at the same time,and proposes the Prophet_TD routing algorithm based on the historical throughput and the encounter duration.This paper uses the Opportunistic Networks Environment v1.6.0(the ONE v1.6.0)as the simulation platform,controls the change of running time and the number of nodes respectively,conducts simulation experiments on the Prophet_TD routing algorithm.The simulation results show that compared to the traditional Prophet routing algorithm,on the whole,the Prophet_TD routing algorithm has a higher message delivery rate and a lower network overhead rate,and its average latency is also lower when node density is large.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50909063 and 51079037)Modern Water Science and Technology Innovation Project (Grant No. XDS2007-04)Non-Profit Special Industry Research Project both funded by the Ministry Water Resources of China (Grant Nos. 200901044 and 200901030)
文摘It is of great significance to study the encounter possibility of typhoon and plum rain in the Taihu Lake Basin in order to adjust the schemes of design storm and utilize flood resource and make the decision of real-time scheduling for flood control in the Basin. Based upon the existing research findings of description of encounter phenomena of typhoon and plum rain, the initial time of typhoon affecting the Taihu Lake Basin, the start time of plum rain season and the end time of plum rain season were selected as the characteristic indices of typhoon and plum rain, respectively. According to their synchronous data from 1954 to 2009, the distribution functions of the above-mentioned three random variables were identified and a formula expressing the encounter possibility of typhoon and plum rain was derived. In view of the complexity and solution of this formula, joint distribution functions of typhoon and plum rain were constructed by the use of Gumbel Copula function on the basis of the adaptability comparison among three functions (Gumbel Copula, Clayton Copula and Frank Copula) in Archimedean functions. For the characteristics of the formula with the joint distribution functions based on Gumbel Copula function, two methods, i.e., numerical integration and Monte Carlo simulation, were selected to solve the encounter probability, and the validity of the computed results was analyzed finally.
