Characterization of a mobile radio channel plays an important role in designing a reliable wireless communication system. Such channels are analyzed by two state model, namely satisfactory and outage state. This paper...Characterization of a mobile radio channel plays an important role in designing a reliable wireless communication system. Such channels are analyzed by two state model, namely satisfactory and outage state. This paper presents the analysis to estimate fading parameters of wireless channel with omission of certain outage durations which are considered as “Tolerance time”. Minimum outage duration which can be tolerated by a wireless fading channel to achieve desired packet error rate is defined as tolerance time. Normally a system with tolerable minimum outage time is analyzed based on Fade Duration Distribution (FDD) function over Rayleigh channel. In this paper Weibull function is used as FDD for varying tolerance time. The approach is simple and in general applicable from Rayleigh to Nakagami channels. The analysis is extended to study the effect of Tolerance time on channel fading statistics such as Average Fade Duration (AFD) and frequency of outage. Further the effects of various fade margin and Doppler spread on fading parameters are also investigated. The analysis can also be used in case of timeout expiration, connection resetting and congestion window control.展开更多
移动Ad Hoc网络是由若干个移动节点构成的无线网络。节点移动和无线传输环境给移动Ad Hoc网络的数据传输提出了挑战。为此,提出基于链路连通时间的移动Ad Hoc网络路由(Link Expiration Time-based routing protocol in Mobile Ad Hoc Ne...移动Ad Hoc网络是由若干个移动节点构成的无线网络。节点移动和无线传输环境给移动Ad Hoc网络的数据传输提出了挑战。为此,提出基于链路连通时间的移动Ad Hoc网络路由(Link Expiration Time-based routing protocol in Mobile Ad Hoc Networks,LET-RP)。先利用节点移动信息和信道衰减信息计算链路连通时间,然后再构建链路稳定函数,随后通过稳定函数设置定时器,从而选择最优的节点作为下一跳转发节点。实验数据仿真表明,提出的LET-RP路由有效地提高了吞吐量,降低了端到端传输时延。展开更多
认知无线电中频谱感知方法的性能与感知场景高度相关.研究表明,NakagamiGamma(KG)衰落信道模型能够可靠地描述无线通信信道.针对采样点数、接收信噪比、地理位置等多种性能影响因素各不相同的一组异构节点在KG衰落信道下的感知场景,提...认知无线电中频谱感知方法的性能与感知场景高度相关.研究表明,NakagamiGamma(KG)衰落信道模型能够可靠地描述无线通信信道.针对采样点数、接收信噪比、地理位置等多种性能影响因素各不相同的一组异构节点在KG衰落信道下的感知场景,提出了一种基于熵函数(based on entropy function,BEF)的合作感知方法.首先,根据异构节点的不同性能影响因素,通过定义的熵函数计算各节点的综合评价得分;然后,筛选出得分较高的节点进行标准化能量检测;最后,采用逻辑或(OR)准则进行融合判决.仿真结果表明,BEF方法有效地降低了系统的感知开销,在各个节点的目标虚警概率较低(Pf<0.1)时,显著提升了全局检测概率.展开更多
文摘Characterization of a mobile radio channel plays an important role in designing a reliable wireless communication system. Such channels are analyzed by two state model, namely satisfactory and outage state. This paper presents the analysis to estimate fading parameters of wireless channel with omission of certain outage durations which are considered as “Tolerance time”. Minimum outage duration which can be tolerated by a wireless fading channel to achieve desired packet error rate is defined as tolerance time. Normally a system with tolerable minimum outage time is analyzed based on Fade Duration Distribution (FDD) function over Rayleigh channel. In this paper Weibull function is used as FDD for varying tolerance time. The approach is simple and in general applicable from Rayleigh to Nakagami channels. The analysis is extended to study the effect of Tolerance time on channel fading statistics such as Average Fade Duration (AFD) and frequency of outage. Further the effects of various fade margin and Doppler spread on fading parameters are also investigated. The analysis can also be used in case of timeout expiration, connection resetting and congestion window control.
文摘移动Ad Hoc网络是由若干个移动节点构成的无线网络。节点移动和无线传输环境给移动Ad Hoc网络的数据传输提出了挑战。为此,提出基于链路连通时间的移动Ad Hoc网络路由(Link Expiration Time-based routing protocol in Mobile Ad Hoc Networks,LET-RP)。先利用节点移动信息和信道衰减信息计算链路连通时间,然后再构建链路稳定函数,随后通过稳定函数设置定时器,从而选择最优的节点作为下一跳转发节点。实验数据仿真表明,提出的LET-RP路由有效地提高了吞吐量,降低了端到端传输时延。
文摘认知无线电中频谱感知方法的性能与感知场景高度相关.研究表明,NakagamiGamma(KG)衰落信道模型能够可靠地描述无线通信信道.针对采样点数、接收信噪比、地理位置等多种性能影响因素各不相同的一组异构节点在KG衰落信道下的感知场景,提出了一种基于熵函数(based on entropy function,BEF)的合作感知方法.首先,根据异构节点的不同性能影响因素,通过定义的熵函数计算各节点的综合评价得分;然后,筛选出得分较高的节点进行标准化能量检测;最后,采用逻辑或(OR)准则进行融合判决.仿真结果表明,BEF方法有效地降低了系统的感知开销,在各个节点的目标虚警概率较低(Pf<0.1)时,显著提升了全局检测概率.
