Context-aware broadcasting approaches in mobile ad hoc networks

The aim of this paper is to compare different context-aware broadcasting approaches in mobile ad hoc networks (MANETs) and to evaluate their respective performances. Message broadcasting is one of the core challenges brought up by distributed systems and has therefore largely been studied in the context of traditional network structures, such as the Internet. With the emergence of MANETs, new broadcasting algorithms especially geared at these networks have been introduced. The goal of these broadcasting algorithms is to ensure that a maximum number of nodes deliver the broadcasted message (reliability), while ensuring that the minimum number of nodes retransmit the broadcasted message (efficiency), in order to save their resources, such as bandwidth or battery. In recent years, as more and more mobile devices have become context-aware, several broadcasting algorithms have been introduced that take advantage of contextual information in order to improve their performance. We distinguish four approaches with respect to context: (1) context-oblivious approaches, (2) network traffic-aware approaches, (3) power-aware approaches, and (4) location-aware approaches. This paper precisely aims at presenting these four different broadcasting approaches and at measuring the performance of algorithms built upon them.     

Cross-layering in mobile ad hoc network design

Mobile ad hoc network researchers face the challenge of achieving full functionality with good performance while linking the new technology to the rest of the Internet. A strict layered design is not flexible enough to cope with the dynamics of manet environments, however, and will prevent performance optimizations. The MobileMan cross-layer architecture offers an alternative to the pure layered approach that promotes stricter local interaction among protocols in a manet node.     

Adapting to route-demand and mobility in ad hoc network routing

We present adapting to route-demand and mobility (ARM), a control mechanism that allows any proactive routing protocol to dynamically adapt in a totally distributed manner to changes in node mobility and workload route-demands. Each node independently maintains a mobility metric indicating how fast its neighborhood is currently changing, and a route-demand metric indicating which destinations are currently involved in data forwarding. Control functions use these metrics to dynamically adjust the period and the content of routing updates. We apply ARM to the destination sequence distance vector (DSDV) protocol, coming up with ARM-DSDV. Simulations for various mobility and workload scenarios show that ARM-DSDV typically achieves better data delivery, while keeping the routing cost at reasonable levels, when compared to DSDV with update period optimized for the scenario.     

Optimizing communication in mobile ad hoc network clustering

Mobile ad hoc networks (MANETs) are gaining popularity in recent years due to their flexibility, the proliferation of smart computing devices, and developments in wireless communications. Clustering is an important research problem for MANETs because it enables efficient utilization of resources, and must strike a delicate balance between battery energy, mobility, node degree, etc. In this paper, we consider the typical communication workload of every mobile node as well as the additional communication workload of clusterheads in MANET clustering. We propose an algorithm that optimizes communication workload, power consumption, clusterhead lifetime, and node degree. Experiment results show that our clustering approach produces effectively balanced clusters over a diverse set of random scenarios.     

The performance of a hybrid routing intelligent algorithm in a mobile ad hoc network

End-to-end delay, power consumption, and communication cost are some of the most important metrics in a mobile ad hoc network (MANET) when routing from a source to a destination. Recent approaches using the swarm intelligence (SI) technique proved that the local interaction of several simple agents to meet a global goal has a significant impact on MANET routing. In this work, a hybrid routing intelligent algorithm that has an ant colony optimisation (ACO) algorithm and particle swarm optimisation (PSO) is used to improve the various metrics in MANET routing. The ACO algorithm uses mobile agents as ants to identify the most feasible and best path in a network. Additionally, the ACO algorithm helps to locate paths between two nodes in a network and provides input to the PSO technique, which is a metaheuristic approach in SI. The PSO finds the best solution for a particle’s position and velocity and minimises cost, power, and end-to-end delay. This hybrid routing intelligent algorithm has an improved performance when compared with the simple ACO algorithm in terms of delay, power consumption, and communication cost.     

Quorum-based power-saving multicast protocols in the asynchronous ad hoc network

The asynchronous PS (Power-Saving) unicast protocol was designed for two PS wireless hosts to transmit the unicast message in the ad hoc network even their clocks are asynchronous. However, as regard to transmit a multicast message among more than two PS hosts, the protocol could not guarantee that all PS hosts can wake up at the same time. Some PS hosts may be in the PS mode when the multicast message is transmitted. Thus, the multicast message should be retransmitted again and again until all PS hosts receive the message. It will increase the energy consumption and the usage of the bandwidth. In this paper, we propose quorum-based PS multicast protocols for PS hosts to transmit multicast messages in the asynchronous ad hoc network. In those protocols, PS hosts use quorums to indicate their wakeup patterns. We introduce the rotation m-closure property to guarantee that m different quorums have the intersection even quorums are rotated due to asynchronous clocks. Thus, m PS hosts adopting m quorums satisfying the rotation m-closure property could wake up simultaneously and receive the multicast message even their clocks are asynchronous. We propose two quorum systems named the uniform k-arbiter and the CRT (Chinese Remainder Theorem) quorum system, which satisfy the rotation m-closure property. As shown in our analysis results, our quorum-based PS multicast protocols adopting those quorum systems can save more energy to transmit multicast messages.     

Ad hoc网络的局部最优路由选择策略

在Ad hoc网络中,由于节点的移动性及拓扑结构的易变性,路由成为最受关注的问题。提出了一种局部最优路由策略（LOR）。在该策略中,有两个节点需要通信时,根据节点存储的路由信息选择路径,如果有节点移动/删除,则就近选择合适的路径。仿真结果表明,LOR策略在工作过程中能使用较少的信息量和较小的时延来建立路径,明显提高了网络的性能。     

基于LoRa自组网无线传输技术实现用电信息采集系统设计

针对传统通信技术存在经济需求高、易被外界干扰、功率损耗高等问题,设计了一套非常适用的解决方案,该方案基于LoRa自组网无线传输技术,与A/D用电信息采集系统结合,组成一套很好的方案;通过LoRa扩频技术和低功耗技术来解决远距离无线通信易受到干扰和功率损耗高的问题,利用A/D用电信息采集系统解决大数据环境下传统采集方法准确率低的问题;经过仿真实验结果表明,该方案LoRa无线传输技术的远距离通信和低功耗能够实现,在大数据环境下A/D用电信息采集系统的准确率比WEB自动采集程序高达3%。     

An environment-aware mobility model for wireless ad hoc network

Simulation is a cost effective, fast and flexible alternative to test-beds or practical deployment for evaluating the characteristics and potential of mobile ad hoc networks. Since environmental context and mobility have a great impact on the accuracy and efficacy of performance measurement, it is of paramount importance how closely the mobility of a node resembles its movement pattern in a real-world scenario. The existing mobility models mostly assume either free space for deployment and random node movement or the movement pattern does not emulate real-world situation properly in the presence of obstacles because of their generation of restricted paths. This demands for the development of a node movement pattern with accurately representing any obstacle and existing path in a complex and realistic deployment scenario. In this paper, we propose a general mobility model capable of creating a more realistic node movement pattern by exploiting the concept of flexible positioning of anchors. Since the model places anchors depending upon the context of the environment through which nodes are guided to move towards the destination, it is capable of representing any terrain realistically. Furthermore, obstacles of arbitrary shapes with or without doorways and any existing pathways in full or part of the terrain can be incorporated which makes the simulation environment more realistic. A detailed computational complexity has been analyzed and the characteristics of the proposed mobility model in the presence of obstacles in a university campus map with and without signal attenuation are presented which illustrates its significant impact on performance evaluation of wireless ad hoc networks.     

Point-to-point voice over ad hoc networks: A survey

The dynamic topologies of mobile and wireless ad hoc networks affect voice communication applications. Difficult issues are wireless links with time-varying capacity and large loss rates, available bandwidth undergoing fast time-scale variations due to channel fading and physical obstacles, absence of centralized components assisting session set up and management, and instability of routes. The purpose of this paper is to survey research works that have been conducted to address these difficulties with an emphasis on the support of point-to-point voice sessions. The survey covers six complementary aspects: voice over ad hoc network architecture, route selection, bandwidth reservation and admission control, adaptive applications and security.     

基于无线自组网的灯光照明控制系统设计

目前,灯光照明主要依赖现场开关的手动控制为主,利用物联网技术实现灯光系统的无线遥控是一个新的发展趋势。该文利用无线自组网技术通过Openwrt路由器的串口输出配合Web页面来控制自组网模块的中心节点,继而对自带自组网模块的照明灯具进行无线控制,从而实现对灯光系统的无线遥控;再利用内网穿透技术将路由器的局域网延伸到广域互联网,就进一步实现对灯光系统的Web远程控制。该灯控方式无需在固定开关点进行操作,利用联网计算机或移动终端即可随时随地进行灯光远程控制,十分快捷方便。该系统在工厂、学校、楼宇和大型公共场所等场合的灯光照明系统集中控制及远程控制中具有实际应用价值。     

Cross-layer opportunistic adaptation for voice over ad hoc networks

The support of voice communication is fundamental in the deployment of an ad hoc network for the battlefield or emergency response. We use the QoS requirements of voice to identify factors influencing its communication, and validate their significance through statistical analysis. Based on the results, we propose an opportunistic protocol within a cross-layer framework that adapts these factors at different time scales. Hop-by-hop adaptation exploits the PHY/MAC interaction to improve the use of the spectral resources through opportunistic rate-control and packet bursts, while end-to-end adaptation exploits the LLC/application interaction to control the demand per call through voice coding and packet size selection. Our objective is to maximize the number of calls admitted while minimizing loss of quality. We evaluate the performance of the protocol in simulation with real audio traces using both quantitative and mean opinion score (MOS) audio quality metrics, comparing to several standard voice codecs. The results indicate that: (i) compression and packet-size selection play a critical role in supporting QoS over ad hoc networks; (ii) header compression is needed to limit the overhead per packet especially over longer paths; (iii) good voice quality is achieved even in strenuous network conditions.     

Investigating the performance of TCP in mobile ad hoc networks

Mobile ad hoc networks have several inherent characteristics (e.g. dynamic topology, time-varying and bandwidth constrained wireless channels, multi-hop routing, and distributed control and management). The goal of this work is to investigate the impact of these characteristics on the performance of TCP. First, we investigate throughput performance of TCP as a function of path length (i.e. multiple wireless hops), node mobility, and traffic intensity. Next, we examine the ‘fairness’ of the ad hoc network with regard to equal sharing of network bandwidth among multiple TCP flows. Third, we evaluate the impact of two on-demand routing protocols (i.e. AODV and DSR) on the throughput of TCP. Finally, a factorial design experiment is conducted to quantify the effects and interactions of three factors, which influence the throughput of TCP. These factors include routing, node speed, and node pause time. Two key results were observed. Results show that traffic intensity (e.g. number of concurrent flows) is significantly affects TCP throughput, suggesting the need for congestion control, scheduling and traffic management schemes. Second, source routing achieves higher throughputs while also generating significantly less routing overhead than AODV. Results also show that in some instances, the fairness of the network is very uneven among concurrent TCP flows, resulting in several sending stations achieving very little or no throughput.     

MANET路由协议及其性能研究

MANET(Mobile Ad Hoe Network)是由一组无线移动主机组成的一个没有任何建立好的基础设施或集中管理设备的临时网络。网络拓扑易变、带宽、能源有限是Ad Hoc移动网络的主要特点。重点介绍了Ad hoc网络的组网关键技术——路由协议,并对现在的具有代表性的协议性能进行了比较,研究了在不同环境下的各自路由协议仿真实验所体现出来的性能差别,对Ad hoc的组网具有指导意义。     

层状 Ad Hoc 网络的信息传播路由算法研究

讨论了层状移动AdHoc网络的一个信息传播路由算法和基于半马尔可夫过程的节点移动跟踪模型,通过该路由算法可以有效地解决层状子网络间的通信和信息交换。通过路由算法得到的中继节点的移动跟踪模型和计算机仿真,分析了层状移动AdHoc网络的传播性能和路由开销,并得出:当 0≤ρ≤ 1时,层状AdHoc网络的传播性能显著地受到移动呼叫率ρ的影响,当ρ>1时,层状AdHoc网络的传播性能主要取决于移动网络的节点总数、节点移动速度和加速度的结论。     

改进神经元PID无线拥塞研究

神经元PID算法能较好地控制瓶颈节点的队列长度,但当网络环境发生较大变化时,其控制效果往往难以保证。根据Ad Hoc网络环境参量时变的特点,推导了无线TCP/AQM离散模型,在神经元算法的加权系数中引入二次型性能指标。另外神经元增益K是系统敏感参数,而恒定的K值不易适应时变的无线自组织网络,据此设计了一种改进二次型性能指标神经元PID的AQM。仿真结果表明：在动态拓扑、突发流及链路容量变化的Ad Hoc网络中,该改进算法优于PI算法。     

Modelling and performance analysis of multi-hop ad hoc networks

Mobile ad hoc networks are becoming very attractive and useful in many kinds of communication and networking applications. Due to the advantage of numerical analysis, analytical modelling formalisms, such as stochastic Petri nets, queuing networks and stochastic process algebra have been widely used for performance analysis of communication systems. To the best of our knowledge, there is no previous analytical study that analyses the performance of multi-hop ad hoc networks, where mobile nodes move according to a random mobility model in terms of the end-to-end delay and throughput. This work presents a novel analytical framework developed using stochastic reward nets for modelling and analysis of multi-hop ad hoc networks, based on the IEEE 802.11 DCF MAC protocol, where mobile nodes move according to the random waypoint mobility model. The proposed framework is used to analyse the performance of multi-hop ad hoc networks as a function of network parameters such as the transmission range, carrier sensing range, interference range, number of nodes, network area size, packet size, and packet generation rate. The proposed framework is organized into several models to break up the complexity of modelling the complete network, and make it easier to analyse each model as required. The framework is based on the idea of decomposition and fixed point iteration of stochastic reward nets. The proposed models are validated using extensive simulations.     

Modeling and performance analysis of ad hoc broadcasting schemes

Broadcasting is a technique widely used for distributing control packets in ad hoc networks. The traditional flooding scheme has been proven to unnecessarily consume network capacity and may lead to severe packet collisions in high-density networks. New schemes have been proposed for alleviating this so-called broadcast storm problem and their efficiencies are usually analyzed and compared by ns-2 simulations. However, little work has been done on mathematical modeling and rigorous analysis. In this paper, we focus on two popular ad hoc broadcasting schemes and provide their detailed analysis in one-dimensional and two-dimensional ideal networks. The statistical results obtained have revealed new relationships between network parameters and the performance metrics. These results are useful for optimally setting network parameters in designing protocols. It is also expected that the analytical methods developed will lay a solid foundation for the development of mathematical models for other ad hoc broadcast and multicast schemes.     

一种Ad hoc网络按需路由协议的设计

Ad hoc网络中节点移动,网络拓扑不稳定,特别是对于节点高速移动的Adhoc网络来说网络性能下降问题更为突出.为此,设计了一种基于路径稳定率的按需路由的协议,新协议选择源目节点间稳定性高且跳数少的路径进行数据分组的转发.以经典的按需路由协议AODV为原型,并在此基础上进行改进,扩展为PS-AODV(Path Stability AODV).性能分析的结果表明.在节点高速运动的重负载Adhoc网络中,该协议显著减少了中断路由的修复时间,提高了端到端分组投递率,在端到端传输时延相近的情况下显著改善端到端时延抖动,对于那些时延敏感的应用有重要的参考价值.     

无人机集群编队自组网可靠性评估

针对无人机集群编队自组网的可靠性评估问题,考虑无人机集群编队在执行任务时对信息交互的时效性需求,提出一种自组网可靠性评估方案.首先,分析消息传输的可用时间;其次,通过排队论建立消息传输延迟模型以计算消息传输所需时间;然后,以消息传输所需时间小于可用时间的概率作为评估指标建立消息传输可靠性计算模型,进而为无人机集群编队提供一个动态可靠性评估框架以适应集群编队体系配置和环境变化的随机性与时变特性;最后,仿真分析在不同传输任务需求下,编队构型、无人机数量、编队缩放因子、传输速率、信息交互强度以及环境干扰对消息传输可靠性的影响.仿真结果可以为集群编队的队形设计以及集群编队的体系配置提供一定参考依据.