无线多跳Ad hoc网络中MAC机制的公平性与网络容量利用率

高效、公平的MAC协议是目前无线多跳Ad hoc网络研究的关键问题之一。该文在给出一种新的无线多跳Ad hoc网络的网络模型前提下,定义了MAC协议公平性、网络容量利用率两个性能参数。给出了一种能在竞争节点间公平共享无线信道并充分利用网络容量的MAC协议(FMAC),仿真比较了FMAC和IEEE 802.11 DCF的公平性和网络容量利用率。结果表明FMAC能在充分利用网络容量的前提下,实现无线信道在竞争节点间的公平共享。     

一种新的求解广义多跳洗牌网络平均跳距的计算模型

本文深入研究了用于波分复用光波通信的广义多跳洗牌网络的平均跳距性能。作者使用的广义洗牌网络概念最早见于洗牌环网络。基于上述定义的洗牌网络可以分为两类：附加级网络和缩减级网络。本文引用了计算附加级网络平均跳距的精确模型,并分析和推导了一种新的计算缩减级网络平均跳距的近似模型。     

基于随机网络演算的车联网边缘计算多跳任务卸载性能分析

车联网(IoV)边缘计算通过在网络边缘部署计算资源,可为车载用户提供低时延服务。该文通过随机网络演算(SNC)矩母函数(MGF)法分析车联网移动边缘计算的时延和数据积压性能。首先,分别对车辆高优先级和低优先级业务到达过程、单跳毫米波通信服务过程和边缘计算服务过程进行数学建模;其次,由服务级联定理获得不同优先级业务在多跳网络中的服务过程及其矩母函数表达式;接着,推导了车辆边缘网络不同优先级业务毫米波多跳通信任务卸载的时延和数据积压概率边界闭式解;最后通过蒙特卡罗仿真验证闭式解的准确性。     

一种基于多跳光旁路的IP over WDM节能网络设计方法

针对IP over WDM网络,基于多跳光旁路和流量疏导,以减少能耗为目标对网络链路配置进行设计;考虑多跳光旁路会增大业务传输距离的问题,分析了光路建立顺序对业务传输距离的影响;通过优先路由短距离业务和限制最大传输跳数来减少业务的平均传输跳数。仿真结果表明,优先建立短距离光路的启发式算法与Dijkstra算法相比可以减少25%～55%的能耗,业务平均物理跳数与Dijkstra算法相差在1跳之内。     

基于随机网络演算的无线多跳网延迟边界分析

端到端延迟作为无线多跳网QoS中最重要的参数之一,其边界分析的准确性直接影响到无线多跳网的QoS保障,而其中流量场景的复杂性导致了分析的难度大幅增加。在综合考虑了无线多跳网流量场景中存在流量直接传输,流量汇聚和流量分裂的特性后,该文运用3种流量算子对系统进行建模,并首次结合随机网络演算提出一种分析无线多跳网延迟边界的方法。仿真结果表明,理论边界可以准确地预测无线多跳网的延迟情况,且明显优于确定性延迟上界。     

基于分环多跳的无线传感网分簇路由算法

为了提高无线传感网在大区域情形下的能量效率,提出了一种分环多跳分簇路由算法RBMC(ring based multi-hop clustering routing algorithm).RBMC算法采用分环的方式实现簇头间的多跳通信,通过在不同环内构建大小不同的簇解决传感器网络中存在的"热点"问题,在不同的簇头选举策略下,能够同时满足节点能量同构及异构两种情形.仿真结果表明,在大区域环境下,分环多跳分簇路由算法能在很大程度上均衡节点能量消耗,延长网络的生命周期.     

A dynamic channel assignment scheme for clustered multihop cellular networks

Whereas cellular systems have traditionally adopted single‐hop transmissions between the mobile station (MS) and the base station (BS), researchers expect multihop transmission to be utilised in the future. Cellular systems present several challenges, such as channel assignment, which are exacerbated by multimedia service traffic and an increasing number of subscribers. Recently, a clustered multihop cellular network (cMCN) architecture that complements traditional cellular systems has been proposed and studied using fixed channel assignment (FCA). However, the performance of FCA is limited when the traffic pattern varies in a service area. This paper proposes the use of dedicated information ports (DIPs) as clusterheads in cMCN, followed by a multihop dynamic channel assignment (mDCA) scheme. The mDCA works by assigning channels based on information about interference in surrounding cells. Two different channel searching strategies are developed and evaluated. Through computer simulation, we show that the proposed mDCA is able to achieve a significantly improved capacity which is maintained when the number of system channels is increased. Finally, issues regarding the implementation of the mDCA and future work on this topic are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

基于移动元胞自动机的网络舆情传播模型

为了准确刻画网络舆情的变化规律,针对经典元胞自动机存在的不足,考虑网络舆情主体的可移动因素,提出一种基于移动元胞自动机的网络舆情传播模型。首先对经典元胞自动机的工作原理进行分析,提出移动元胞自动机模型,然后根据网络舆情的特点,制定网络舆情主体状态转换规则和移动规则,建立移动元胞自动机的网络舆情传播模型,最后采用Matlab 2011对网络舆情演化过程进行仿真分析。仿真结果表明,舆情主体移动概率对网络舆情传播速度和同质化率影响比较大,移动元胞自动机模型可以很好地描述网络舆情的实际传播过程。     

OFDM双向多跳网络的新型比特和功率分配算法

结合新型双向多跳网络协议和正交频分复用技术,研究旨在保证通信质量情况下的自适应比特和功率分配算法,其目的是以较小发送功率和较高频谱效率完成通信。通过凸优化理论推导出最优功率分配算法,并提出一种基于贪婪原则的自适应比特分配算法,能够以较低的复杂度在实际工程中完成部署。仿真分析表明,提出的双向多跳算法是传统多跳协议频谱效率的2倍,所需发送功率是平均资源分配算法的1/3。     

Capacity planning framework for mobile network operator cloud using analytical performance model

A mobile network operator cloud (MNOC), solely or with the help of public clouds, provides the computational resources in the form of virtual machines on physical machines (PMs) to handle heavy tasks, which are offloaded by the subscribers. Definitely, cost is a constant source of worry for an MNOC. In fact, although a large number of used PMs of the MNOC and public clouds decreases the penalty cost of request rejection, other associated costs, such as infrastructure, power consumption, cooling, and virtual machine instances of public clouds, are imposed on the MNOC. Therefore, to minimize the overall cost, finding the optimal number of required PMs in all participant clouds, including the MNOC and public clouds, is recognized as an important issue. To deal with this issue, in the present paper, using analytical performance model of a MNOC, a capacity planning framework is proposed. Specifically, this framework solves a cost optimization problem using a simulated annealing algorithm. Numerical results demonstrate the ability of the proposed framework to identify the optimal solution within an acceptable duration of the time.     

Topology evolution model for ad hoc‐cellular hybrid networks based on complex network theory

Switching and routing are two important issues in the ad hoc‐cellular hybrid network. Frequently switching between different network modes will lead to the increase of time delay, and unreasonable routing will reduce information transmission efficiency and shorten the network life. In order to reduce the influence of these problems to the network, in this paper, we proposed a robust and efficient ad hoc network topology evolution model, which can reduce the switching probability and establish efficient transmission paths. In this model, the mobile users' residual energy, available channel quality, and the importance are taken into account. The model is based on Barrat, Barthelemy, and Vespignani model and the triad formation mechanism, which ensures the network topology have scale‐free and small‐world features. The topology construction process of the ad hoc network is composed of three parts: (i) new users join the network; (ii) new users establish connections with existing users; (iii) the connections between existing users were deleted because of the network optimization and the interference of cellular network. Simulation results show that the network built by this model with small‐world and scale‐free features has small average shortest path length and the robustness against random nodes failure, which will significantly improve the transmission efficiency and reduce the probability of switching between different transmission model. Copyright © 2016 John Wiley & Sons, Ltd.     

基于移动蜂窝网的机器学习室外指纹定位方案

基于移动蜂窝网络技术的定位方案是提供网络优化、紧急救援、公安巡警和位置服务等应用的重要技术途径之一。传统的基于小区基站位置信息的定位方案定位精度低、定位误差大,无法满足某些定位应用需求。基于指纹定位的方案能够在基于小区粗定位方案基础上大幅度提升定位精度、节约计算成本、增强适用性,成为定位研究的热点。针对室外指纹定位的业务需求,深入研究分析了两种基于机器学习的栅格化和非栅格化室外指纹定位方案。通过参数加权、数据拟合等方法对于大规模指纹数据进行了清洗,提高数据源的有效性。通过划定研究区域、栅格化、构建指纹数据库、训练模型、修正模型、非栅格化、粗定位耦合、匹配参数、训练参数等子模块的实现,分析和优化了算法的运行效率和定位精度,确定了影响算法性能的关键指标。进而结合仿真结果,分析了两种基于指纹的定位方案的性能。最后介绍了基于机器学习的指纹定位方案在实际应用中的典型场景。     

基于细胞自动机模型电力网络攻击预测技术

传统电力网络攻击范围预测技术的预测范围不够广,导致电力网络安全性提升效果不明显。为此,提出基于细胞自动机模型的电力网络攻击预测技术。搭建电力细胞自动机模型,将细胞自动机中的细胞看作电力细胞,建立细胞活力值转换规则,将其与攻击者执行攻击概率相结合,预测电力细胞的发展变化。根据中心电力细胞及邻域电力细胞的变化趋势预测电力网络攻击。实验结果表明：在时间因素影响下,提出的基于细胞自动机模型电力网络攻击预测技术的预测攻击节点位置与原始节点基本一致,预测后负荷切除量始终在100 MW以下,本文所提技术的有效性更好。     

倾斜天线蜂窝系统的双向信道优化模型

地面基站天线倾斜是提高CDMA蜂窝系统容量和平衡小区负载的有效方法之一.本文通过对倾斜天线蜂窝系统的切换问题的研究,提出了在计算系统容量时,同时考虑前向信道和反向信道的双向信道分析方法,使得系统容量的计算更为合理.利用这一模型,得出了在用户均匀分布和非均匀分布情况下的最佳天线倾斜角度.仿真结果表明,利用本文的方法,系统的实际容量比单独考虑反向信道时有显著的提高.     

Capacity of FH wireless multi-hop networks

In this article, the capacity of wireless multi-hop networks with the frequency hopping (FH) technique is derived. Different from the previous work based on non- spread spectrum (SS) system, this study is based on frequency hopping spread spectrum (FHSS) and the retransmission mechanism. The analysis results show that the normalized transport capacity decreases as 1/(Mλ) , when the total available frequency band is divided into M sub-bands for frequency hopping and the nodes are randomly distributed in space according to a Poisson point process with intensity λ . In this work, the best transmission range per hop to get the maximum capacity is also derived. Besides, the results summarize how the capacity of FH wireless multihop networks is affected by the outage probability, target signal to interference plus noise ratio (SINR) and other system parameters.     

A new model for network traffic forecast based on user's mobility in cellular networks with highway stretches

Wireless communications have always faced the scarceness of bandwidth and until today the cellular division has solved this problem by making radio cells always smaller. However, as cell size is reduced, more users will probably require handoffs, and signaling can overload the system. Further, the decrease in cell dimension cannot ensure the best utilization of system resources, because user density in the cell is not constant over the time. Dynamic allocation might be the solution, but it is a complex task, basically due to complexity of the models for the mobility prediction, especially in those environments where users move very fast (e.g. highways). This last one is a typical environment where high mobility of vehicles does not allow small cell sizes and thus system capacity is intrinsically bounded. In this paper, we deploy an analytical model for a cellular network operating in a high mobility environment. Such a model is capable of representing and forecasting wireless system evolution in terms of channel occupancy, starting from the current state of the mobile network and road traffic. This model has been defined by integrating a vehicular traffic model with a wireless cellular communication one. With such approach the dynamic behaviour of the most critical mobile terminals, those associated with vehicles, are described in a very precise and specific way with respect to mobility. Many results obtained with specific simulation tools and herein reported show the good behaviour of our proposal. Copyright © 2004 John Wiley & Sons, Ltd.