基于IEEE802.15.4的GTS调度算法优化

针对实时无线传感器网络(WSNs)系统对时延敏感的特点,对目前典型的IEEE802.15.4标准中保障时隙(GTS)调度算法进行了改进,提出一种基于时延优先级的GTS分配算法.根据网络微积分原理评估时延约束条件及GTS分配数目,按照优先级顺序响应GTS请求,并动态调整GTS中的时隙数量,确保实时传输和带宽利用率.通过在...     

基于IEEE 802.15.4的无线传感器网络性能分析*

通过将IEEE 802.15.4标准中的超帧与无线传感器网络的LEACH协议结合,在星型网络拓扑下,网络节点通过申请超帧中的GTS来进行无冲突的数据通信,对使用GTS传输数据的这一过程进行了研究,从理论上分析了无线传感器网络的网络性能.仿真结果说明了网络控制参数对网络性能的影响,为今后无线传感器网络应用中的参数配置提供了一定的理论基础.     

增强安全性的IEEE802.15.4协议研究

IEEE 802.15.4标准因其低速率、低成本、低功耗、高质量,被认为是无线传感器网络和无线个人域网络的理想实现技术。简要介绍了无线传感器网络及其主要特点和问题,及无线传感器网络的安全需求。提出了增强安全性的IEEE802.15.4协议SE-IEEE802.15.4研究,其中使用公钥加密算法ECC来实现IEEE802.15.4协议的数字签名。最后采用NS-2平台对其进行仿真,并进行了性能和安全性的分析。     

IEEE802.15.4的CC2530无线数据收发设计

基于TI公司的CC2530实现了IEEE 802.15.4(ZigBee)的无线传感器网络(Wireless Sensor Network,WSN)协议;在分析CSMA-CA算法的基础上,重点讨论了片内集成的命令选通/CSMA-CA处理器的工作机制,同时组建了一个小型星状网络.测试结果表明,在节点通信范围内,节点收发的...     

IEEE 802.15.4实时通信调度算法研究

IEEE 802.15.4是低功耗无线通信媒体接入控制协议,目前已广泛应用于医疗健康、工业控制和楼宇自动化等物联网领域。为满足不同应用需求,研究者提出了多种适用于IEEE 802.15.4协议的实时通信算法。根据带宽利用率、延时约束和能效性等特征,对这些实时通信调度算法进行分类、比较和性能分析,以助于在实际应用中合理部署。另外,对未来的研究工作进行了展望。     

IEEE802.15.4无线传感器网络仿真与性能评估

IEEE802.15.4标准是为满足低速率、低能耗、低成本需求而制定的无线个人区域网（LR_WPAN）规范。通过用网络仿真软件NS2对基于IEEE802.15.4的无线传感器网络的主要性能指标进行分析,较为详实地论述了IEEE802.15.4MAC层基于时槽的CSMA/CA机制,最后给出仿真环境及其结果,并进行度量分析和阐述各指标间的依赖关系。     

一种基于IEEE802.15.4无线智能化传感器网络实现探讨

介绍了IEEE802.15.4协议的特点、构件及体系结构、发展前景,分析了IEEE1451智能传感器模型,提出了一种基于IEEE802.15.4协议的无线智能传感器网络结构设计,并探讨了其实现。     

IEEE 802.15.4协议在GAINS-Z节点上的移植

本文基于CHIPCON公司提供的基于IEEE 802.15.4的MAC层和PHY层代码对中国科学院（宁波所）研发的GAINS-Z节点硬件进行了软件移植。并组建一星型拓扑无线传感器网络，实现网络协调器（PAN Coordinator）和设备节点（Device）之间的数据传输，验证了移植的正确性。     

IEEE 802.15.4 MAC 的分析与性能评估

本文针对无线传感网络中如何提高网络的传输性能的问题,提出了对不同的网络拓扑结构采用不同的传输方式。在分析了网络中两种不同的网络结构:"树形"结构及"网形"结构的基础上,运用NS2网络仿真软件,重点分析了在信标使能和非信标使能两种不同的传输方式下,通过改变发包速率来仿真两种不同网络结构中的分组投递率(丢包率)、平均端到端延时和路由开销等网络性能参数。实验结果表明,对不同的网络拓扑结构,有针对性地采用不同的传输方式确实可以提高其传输性能。     

支持异构数据通信的IEEE 802.15.4实时带宽分配算法

IEEE 802.15.4协议的GTS分配机制能够支持实时和延迟约束的应用,目前已经应用于医疗健康、工业控制和楼宇自动化等物联网领域。但是,在高速实时异构数据传输应用中仍然存在局限性,它不能解决多于7个设备需要实时服务、时延约束小于超帧长度以及不同周期异构数据传输等问题。为了摆脱这些限制,提出一种新的支持异构数据通信的IEEE 802.15.4实时带宽分配算法,其根据不同周期任务的数据传输信息,调整部分传输任务的发送时间。性能分析显示,该算法可以严格遵循时延约束条件,满足异构数据通信,提高带宽利用率,提升整个网络的性能。     

IEEE 802.15.4中信道利用率的分析与改进

在分析IEEE 802.15.4网络中为时延敏感应用提供的保护时隙(GTS)分配策略后,指出GTS分配中信道利用率低等不足。为此,对IEEE 802.15.4中的GTS进行改进。将GTS时隙再次划分为微时隙,与标准GTS申请命令不同,节点无须指定所需的GTS长度,而是提供需要发送的数据数量和数据长度,通过协调节点来决定所分配的GTS长度。仿真实验结果表明,改进后协议能提高信道利用率和网络吞吐量。     

Design and implementation of enhanced IEEE 802.15.4 for supporting multimedia service in Wireless Sensor Networks

Recently, there has been a growing demand to incorporate multimedia content delivery over the Wireless Sensor Networks (WSNs). This feature could not only enhance several existing applications in the commercial, industrial, and medical domains, but could also spur an array of new applications. However, the efficient gathering of still images, audio, and video information in WSNs imposes stringent requirements on the throughput and energy consumption. Most wireless communication standards with high or moderate data throughputs do not focus primarily on energy efficiency. The IEEE 802.15.4 WPAN standard provides a widely accepted solution for low-cost and low-power wireless communication, with a potential to cater to many types of application scenarios. IEEE 802.15.4 MAC includes features such as its dual operational modes (Non-Beacon-enabled mode/Beacon-enabled mode), which make this standard more attractive for providing multimedia services over the networked sensors. Its Beacon-enabled mode can conserve energy by using the RF sleep mechanism, but it is limited by the lower data throughput. On the other hand, the Non-Beacon-enabled mode can offer higher data throughput but at the expense of significant energy consumption, mainly due to the idle listening problem. In order to overcome these issues, we propose an enhancement to IEEE 802.15.4, named TEA-15.4, which adaptively adjusts the active period based on traffic information. To detect data traffic in the network, the proposed scheme utilizes two techniques: Arbitrary Traffic Signal (ATS) and Traffic Time-Out (TTO). By utilizing these two techniques, the proposed TEA-15.4 can not only support enough data throughput to carry out multimedia communications, but also offer lower energy consumption for the sensing device in WSNs. For performance evaluations, we implement our proposed scheme and the IEEE 802.15.4 full-standard on the TinyOS. Based on the results gathered from testbed experiments and the TOSSIM simulator, TEA-15.4 is shown to be a suitable mechanism for Wireless Multimedia Sensor Networks (WMSNs).     

IEEE 802.15.4 MAC协议能耗与时延均衡的GTS调度新算法设计

简述了IEEE 802.15.4 MAC协议中超帧结构和保护时隙(GTS)分配机制,分析了星状网络中信标使能模式下设备节点利用GTS方式通信时超帧结构中各参数对能耗与时延性能的影响.在此基础上设计了一种GTS调度新算法,该调度算法对时延期限小的节点优先进行GTS分配并在满足其时延要求情况下,根据业务量调节超帧结构中的超帧序号SO与信标序号BO,使设备节点能耗降到最低,从而实现星状网络中各节点的能耗与时延均衡,并用NS2仿真评估了调度新算法性能,其研究可为无线传感网络的实时应用系统提供参考价值.     

Scheduling of wireless control networks based on IEEE 802.15.4 networks: Mixed traffic environment

This paper describes a scheduling method of wireless control networks for factory automation using IEEE 802.15.4 networks. The superframe of IEEE 802.15.4 is used for the transmission of real-time mixed data for wireless control systems. The schedulability of real-time data is defined, and scheduling algorithms are proposed for the efficient transmission of real-time mixed traffic. Simulation results show enhancements in the average network utilization and packet drop rate for real-time data.     

IEEE 802.15.4区分服务协议性能分析与建模

针对IEEE 802.15.4协议的无线传感网络不能提供数据流优先级区分的问题,提出一种基于区分服务的马尔可夫链模型以支持实时多媒体应用。该机制的主要思想是根据服务质量要求（时延敏感与否）为不同的数据流分配不同的优先级。不同优先级的数据采用不同的增长因子来更好地减少冲突。此外,为了弥补低优先级数据流,高优先级的数据流在第二次空闲信道评估发现信道空闲时并不立即接入信道而是以一定的概率竞争信道。数学分析表明,对不同数据流设置合理的增长因子和竞争概率能够显著提高高优先级数据流的性能并对低优先级数据影响较少。     

基于网络演算的簇树WSN性能上界分析

为保证WSN的服务质量(QoS),需精确求解其性能上界。对进入WSN节点的数据流进行漏桶管制,节点为数据流提供基于速率-延迟模型的服务保障,在已有簇状拓扑WSN性能模型研究基础上,利用确定性网络演算理论推导簇树WSN节点的有效带宽、缓冲区队列长度上界和数据流端到端延迟上界。     

Markov Chain-based performance analysis of multihop IEEE 802.15.4 wireless networks

In this paper, we propose a Markov chain-based analytical framework for modeling the behavior of the medium access control (MAC) protocol in IEEE 802.15.4 wireless networks. Two scenarios are of interest. First, we consider networks where the (sensor) nodes communicate directly to the network coordinator (the final sink). Then, we consider cluster-tree (CT) scenarios where the sources communicate to the coordinator through a series of intermediate relay, which forward the received packets and do not generate traffic on their own. In both scenarios, no acknowledgment messages are used to confirm successful data packet deliveries and communications are beaconed (i.e., they rely on synchronization packets denoted as “beacons”). In all cases, our focus is on networks where the sources and the relays have finite queues (denoted as buffers) to store data packets. The network performance is evaluated in terms of aggregate network throughput and packet delivery delay. The performance predicted by the proposed analytical framework is in very good agreement with realistic ns-2 simulation results.