Relay reduction and disjoint routes construction for scatternet over Bluetooth radio system

Bluetooth is a new technology for low-cost, low-power, and short-range wireless communication. By constructing a piconet, Bluetooth device establishes link and communicates with other device in a master–slave manner. Relay is a Bluetooth device that joins two or more piconets and forwards data from one piconet to another, providing multi-hop (or inter-piconet) communication services. In a Bluetooth scatternet, the number of relays and the degree of each relay are factors that significantly affect the performance of entire network. Unnecessary relays raise the difficulty of scheduling, leading to frequent packet loss. Relay switching among several piconets in turns also creates guard time overhead and increases the transmission delay. This study presents an effective protocol that can dynamically adjust the network topology by reducing the unnecessary relays. An efficient scatternet environment thus can be constructed with characteristics of connected, high bandwidth utilization and low maintenance cost. Additionally, a routing protocol is developed to reduce the path length and generate two disjoint routes for any pair of source and destination devices located in different piconets. Experimental results demonstrate that the proposed protocols perform well in terms of route length, bandwidth consumption, and transmission delay.     

TARP: A traffic-aware restructuring protocol for Bluetooth radio networks

Bluetooth is a low-cost and short-range wireless communication technology. The Bluetooth device randomly searches and connects with other devices using the inquiry/inquiry scan and the page/page scan operations, resulting an uncontrolled scatternet topology. The unpredictable scatternet topology usually raises the problem of redundant traffic and causes inefficient communications. A traffic-aware restructuring protocol (TARP) is presented for partially restructuring a piconet or a pair of two neighboring piconets by applying role switch mechanism. The proposed TARP mainly consists of intra-piconet and inter-piconet restructuring protocols. According to the recent routes and their traffic load information, the intra-piconet restructuring protocol adjusts piconet structure by selecting the proper device to play a master role of a piconet and applies takeover operation to rapidly restructure the piconet topology. The inter-piconet restructuring protocol exchanges devices of two neighboring piconets to reduce the route length and thus improve the power and bandwidth consumptions and the end-to-end transmission delay. Performance results reveal that the proposed restructuring protocols reduce path length of recent routes and save power consumption, thus significantly improve the performance for a given connected scatternet.     

A scatternet formation algorithm for Bluetooth networks with a non-uniform distribution of devices

We address the problem of scatternet formation for network scenarios with a non-uniform distribution of Bluetooth devices. The assumption of having a non-uniform distribution of devices in a given area of interest is motivated by examples that can be encountered in real scenarios. We propose a new scatternet formation protocol called BlueHRT (Bluetooth Hybrid Ring Tree) that results in a hybrid ring tree topology. The proposed protocol operates in multiple phases that include node discovery, identification of a dense area within the network, role assignment with ring based piconets in the dense area and tree based piconets in the surrounding lightly loaded areas, and interconnection of the piconets to each other via slave–slave and master–slave bridges. General protocol design analysis and ns-2 simulation results are presented in order to highlight the main performance characteristics.     

DeviceNet现场总线中轮询协议的性能研究

基于DeviceNet协议生产者/消费者通信模型特点构建了其轮询通讯方式模型,轮询命令报文由主站广播至生产从站,轮询响应报文由生产从站通过主站周期地轮询每个生产从站广播至所有消费从站;文章采用Petri网的过程变迁TPN混合方法对DeviceNet总线协议进行了分析和研究,对其轮询通讯方式进行了模拟,讨论了响应时间、吞吐量等参数,分析了性能差异和响应快慢,根据文章的结论,现场总线的设计者可以很好的选择和设计满足自己需要的设计方案.     

基于连接认证的低功耗蓝牙泛洪攻击防御方案

针对低功耗蓝牙易受泛洪攻击的问题,提出了一种连接认证模型,基于该模型设计了低功耗蓝牙泛洪攻击防御方案。方案结合HMAC(Hash-based Message Authentication Code)运算速度快与蓝牙通信同步性强的特点,设计检测模块判断通信状态,利用挑战应答的方式设计连接请求认证协议,在蓝牙协议运行前进行主从设备双向认证,过滤掉攻击报文,保证低功耗蓝牙连接建立的安全。安全性分析和实验结果表明,方案能够有效防御泛洪攻击,同时具有较小的存储和计算开销,适合应用于低功耗蓝牙中。     

由Bluetooth实现的多媒体无线连接PC

Bluetooth技术能在短距离内用无线接口代替有线电缆连接。文中介绍了Bluetooth技术的基本特性，讨论了基于Bluetooth技术的多媒体无线连接PC(Multimedia Wireless Connection PC，MWCPC)的系统结构、通信协议软件栈，并对MWCPC的主／从单元连接建立和多MWCPC的从单元资源共享等问题进行了研究，实测效果良好。     

基于MicroCANopen的网络设计与实现

为了提高航天器CAN总线通讯系统各个节点的规范性、可维护性、可扩展性,研究了CAN总线的高层协议CANo-pen的一种经典开源协议栈MicroCANopen,设计与实现了MicroCANopen网络。软件方面,在VC6．0的开发环境下,采用并改进MicroCANopen从站协议栈代码,实现了主从站代码;硬件方面,利用IXXAT公司的USB-to-CAN的适配器作为底层硬件的支持,从而与PC机连接建立了一主多从的MicroCANopen网络。并且验证了通讯过程的正确性与设计的可行性。该网络可以应用在航天器地面测试系统中,为航天器地测通讯系统提供高层协议的统一标准。     

BlueCube: Constructing a hypercube parallel computing and communication environment over Bluetooth radio systems

In parallel computing structures, Hypercubes [P. J. Wan, L. W. Liu, Y. Yang, Optimal routing based on the super-topology in Hypercube WDM networks, 1999, pp. 142–149] and [Y. R. Leu, S. Y. Kuo, A fault-tolerant tree communication scheme for hypercube systems, IEEE Trans. Comput. 45(6) (1996) 643–650] have many advantages: they support parallel computing, provide disjoint paths, and tolerate faults. If devices with computing capabilities can be linked as a Hypercube by taking advantage of Bluetooth radio's features, then an efficient communication and high-performance computing environment can be established by applying currently used algorithms. A Bluetooth device randomly searches for and connects with other devices, using time-consuming inquiry/inquiry scan and page/page scan operation and hence, results in an uncontrolled scatternet topology and inefficient communications. The present work proposes a three-stage distributed construction protocol for rapidly organizing a Hypercube computing environment that was constructed from Bluetooth devices. The proposed protocol governs the construction of links, the assigning of roles and the formation of the scatternet in order to efficiently construct a Hypercube structure. The constructed scatternet easily enables Bluetooth devices to establish a routing path, tolerate faults and create disjoint paths, and thus, achieves parallel and distributed computing in a Bluetooth wireless environment. Experimental results reveal that the proposed protocol can set up a scatternet that is appropriate for parallel computing and communications.     

遗传算法在蓝牙scatternet组网中的应用

蓝牙a＆hoc网络包括微微网与散射网两种组网方式,可以实现短距离无线通信,并能较好的满足实际需求。其中,散射网的拓扑结构与组网方式很大程度上影响与制约着蓝牙技术的应用。为了提高蓝牙散射网的组网效率与性能,文中提出了基于遗传算法的组网方式,通过该算法可较好的改进散射网的形成速度。     

蓝牙4.2协议的一主多从防丢器APP设计

设计一款以蓝牙4.2协议为核心,可与多个从机进行通信的防丢器.将低功耗蓝牙芯片CC2541作为主控制器,结合在手机(主机)上开发的APP,通过蓝牙4.2相关协议,对配对成功的防丢器(从机)进行监控,当从机超出主机的监测范围后,主机和从机会同时启动报警装置,以便人们予以警觉.     

嵌入式控制结点群上的一种通信方案设计

为解决现行RS485组网方式限制了通信节点数及网络扩展的问题,基于RS485总线提出了一种嵌入式控制结点群的组网方式及控制协议。通过在主控器与叶子节点间加入中继器,将485总线支持的节点数扩展到2.7万个,建立一对多控制的嵌入式结点集群。针对该网络特点,对Modbus协议进行扩展,增加了中继层规约。与传统单纯增加物理地址长度的方式不同,新扩展协议采用局部寻址方式,打破了Modbus地址长度对子节点数的限制,并引入节点扫描和差错反馈机制,从而实现了主控器对各网络节点的可靠控制;同时,控制协议保持了原Modbus协议的简单性,还具有易移植、可扩展的特点,便于在单片机上实现。在采用扩展协议时,一层中继器的引入导致周转延迟增加10.36%,而两层中继器则将延迟率增加了69.9%,并使总延迟较原始Modbus系统增加2.4倍左右,但实际中采用的两层中继系统将平均延迟控制在了70 ms以下。结果表明,该方案在牺牲一定系统实时性能的前提下,实现了嵌入式节点的集群化管理。     

电力线通讯中网络传输时延的研究

在电力线通讯网络中采用时分多路复用对网络传输时延会产生较大影响。本文采用OPNET网络仿真软件构建网络仿真模型,对使用时分多路复用技术的网络与未使用时分多路技术的网络进行性能比较。结果表明,时分多路复用对于网络负载小的情况,可以减少延时,提高传送效率;但是对于网络负载较大的情况,效果并不明显。     

Basestation collaboration in Bluetooth voice networks

In the near future Bluetooth may be embedded into many different types of mobile and portable devices [IEEE Personal Commun. 7 (1) (2000)]. This connectivity will enable a variety of future picocellular services such as real-time voice and data [Specification of the Bluetooth System 1.0b., Bluetooth Special Interest Group, 1999]. In this paper, we consider several Bluetooth-based telephony access point designs. Since the number of SCO links per Bluetooth node is very limited, the designs consider the use of multiple overlapping Bluetooth basestations or module coverage areas. The first scheme is a direct implementation of the telephony profile where the Bluetooth basestations/modules operate independently, without any coordination. The paper proposes several schemes which use a variety of techniques for reducing the call blocking rate using real-time communication between the basestations or Bluetooth modules. It is shown that significant improvements in blocking performance are possible using this approach. A constraint on the design of high-capacity voice access points is the potential packet loss experienced by overlapping SCO transmissions. The paper includes a worse-case characterization and discussion of Bluetooth’s shortcomings in this regard.     

带式输送机故障定位系统网关的设计

以带式输送机故障定位系统为应用背景,提出了一种基于STM32F103VE微处理器的CAN总线与Profibus-DP总线网关的设计方案。该网关在CAN网络中作为一个CAN通信节点,在Profibus-DP网络中作为一个从站;带式输送机沿线分布若干个CAN检测节点,每个节点负责检测其段内的4种传感器设备采集的实时数据,如果检测到故障信息,CAN检测节点就会向网关发送故障信息报文,网关接收CAN检测节点发送的报文并进行存储;当网关与Profibus-DP主站连通后,作为Profibus-DP从站的网关可以通过查询方式把故障信息报文传送到Profibus-DP主站中,从而实现故障定位功能。实际应用表明,该网关运行稳定、可靠,实现了带式输送机故障定位系统中CAN总线及Profibus-DP总线的互联。     

支持双网双主站的Modbus通信在继电保护中的应用

根据Modbus通信协议的特点以及继电保护装置中对通信可靠性的要求,提出了支持双通信网络、双主站的Modbus通信在继电保护装置中的应用。简介TModbus通信协议,系统冗余和单元冗余的概念。给出了双网双主站的通信方案,说明了为支持冗余在主站和子站设计上应该注意的问题,定量分析了采用单元冗余、系统冗余混合冗余的方式为系统可靠性提高带来的影响。说明了Modbus协议传输继电保护装置信息的数据交换过程和应当注意的问题,如镜像数据区定义,TCP粘连包的问题等。     

一种无线传感网与现场总线通信网关的设计与实现

设计了一种无线传感网与CAN总线、Modbus总线的通信网关。该装置以嵌入式微处理器STM32F207ZG为核心,采用无线通信模块CC2530作为无线传感网汇聚节点。在RS485通信的基础上实现了Modbus协议。STM32F207ZG内部CAN总线控制器配合CAN总线收发模块使网关可以接入CAN总线。试验表明:该网关分别接入Modbus总线、CAN总线均可实现总线监控网络与无线传感网的数据传输,且可以作为新型无线传感网监控系统扩充现场总线数据采集设备的接入点。     

高速跳频网络中时间同步的研究与实现

针对无线通信网络中各通信节点间守时存在较大的误差,提出了一种基于传感器网络时间同步协议TPSN双向时间同步算法,设计了一种小型化、模块化的高精度时统系统,可用于跳频同步和TDMA组网体制下的时隙同步。首先选取主机,仅当10 s内未收到校时呼叫的节点设置为主机;其次发送及应答,规定主机1 s内仅对一个从机请求作出应答;最后通过记录校时主从节点的发送时刻,扣除或补偿逻辑处理延迟、射频传输延迟、校时两端的频差等,计算节点间的同步误差。在不同条件下进行了仿真实验,节点间的同步误差可以精确到30 ns左右,表明该方案时间同步精度高、误差较小,可满足该无线通信网络中各节点间协同探测、协同攻击和协同干扰等战术目标的需要。     

基于冗余TTCAN的核电站报警窗改进设计

鉴于推行核电设备国产化以及核电报警系统的升级改造需求,对核电报警系统空气闸门报警窗的通信模块进行了改进研究。考虑到核电站场景的高安全性需求,报警窗通信模块的改进设计采用了实时性高、可预测性好、抗干扰性强的基于时间触发的控制器局域网络(TTCAN)总线,并以报警窗为主节点,各报警采集模块为从节点。在分析了主流TTCAN冗余方式的基础上,提出一种新的TTCAN冗余方式,应用了带有双路总线控制器的微控制单元(MCU)以及双通道互相独立的传输架构,搭建了TTCAN冗余网络,并提出了相应的新型冗余管理策略。试验证明,采用新型冗余TTCAN通信方式的报警窗总线利用率高、数据传输速率快、数据传输稳定、误码率低,具有高实时性和高可靠性,是TTCAN总线应用于核电仪控系统和报警系统的一次积极尝试。     

Usefulness of adaptive load sharing for parallel processing on networks of workstations

Networks of workstations (NOWs) can be used for parallel processing by using public domain software like PVM. However, NOW-based parallel processing suffers from node heterogeneity, background load variations, and high-latency, low-bandwidth communication network. Previous studies on load sharing in NOW-based systems have indicated that, for applications using the work-pile model, a simple load sharing scheme in which the master process gives a fixed amount of work to the slave processes performs as well as any other, more complex schemes. In this paper, we propose a new adaptive load sharing scheme and evaluate its performance using a Pentium-based NOW machine. The communication network used in the system consists of the standard 10 Mbps Ethernet and the 100 Mbps fast Ethernet. We use both these networks to study their impact on the performance of our new policy. The results presented here indicate that the new policy is useful for computation-intensive applications. Copyright © 1999 John Wiley & Sons, Ltd.     

基于TTCAN协议的井下通信网络研究

针对煤矿井下CAN通信网络中低优先级数据延迟较大而存在实时性与确定性较差的问题,提出了一种基于时间触发机制的TTCAN协议;给出了由主站节点和多个从站节点构成的TTCAN网络系统硬件结构,详细介绍了基于Level 1同步方式的TTCAN调度算法的设计。实验结果表明,与标准的CAN网络相比,TTCAN网络的最大响应时间和最大发送周期抖动指标几乎不受信息量的增加与优先级减小的影响,具有更好的实时性与确定性。