研究了FMIPv6(MIPv6 fast handovers)协议中移动节点在预测出错情况下的IP连接恢复问题,提出了一种基于冗余路由信息和预缓存策略的快速切换方法RIRS(router information redundancy scheme)。该方法通过构造冗余切换路由表来协助移动节点快速重构新的转交地址,并采用预缓存策略来保护切换过程中到达的数据分组。仿真结果表明,RIRS能够获得比FMIPv6更小的切换延迟及丢包率。
In this letter,we investigate the individual channel estimation for the classical distributed-space-time-coding(DSTC) based one-way relay network(OWRN) under the superimposed training framework.Without resorting to the composite channel estimation,as did in traditional work,we directly estimate the individual channels from the maximum likelihood(ML) and the maximum a posteriori(MAP) estimators.We derive the closed-form ML estimators with the orthogonal training designing.Due to the complicated structure of the MAP in-channel estimator,we design an iterative gradient descent estimation process to find the optimal solutions.Numerical results are provided to corroborate our studies.
A critical safe distance(CSD)model in V2V(vehicle-to-vehicle)communication systems was proposed to primarily enhance driving safety by disseminating warning notifications to vehicles when they approach calculated CSD.By elaborately analyzing the vehicular movement features especially when braking,our CSD definition was introduced and its configuration method was given through dividing radio range into different communication zones.Based on our definition,the needed message propagation delay was also derived which could be used to control the beacon frequency or duration.Next,the detailed CSD expressions were proposed in different mobility scenarios by fully considering the relative movement status between the front and rear vehicles.Numerical results show that our proposed model could provide reasonable CSD under different movement scenarios which eliminates the unnecessary reserved inter-vehicle distance and guarantee the safety at the same time.The compared time-headway model always shows a smaller CSD due to focusing on traffic efficiency whereas the traditional braking model generally outputs a larger CSD because it assumes that the following car drives with a constant speed and did not discuss the scenario when the leading car suddenly stops.Different from these two models,our proposed model could well balances the requirements between driving safety and traffic throughput efficiency by generating a CSD in between the values of the two models in most cases.
