Performance evaluation of priority CSMA-CA mechanism on ISA100.11a wireless network

The International Society of Automation recently released ISA100.11a as an open standard for reliable wireless networks for industrial automation. ISA100.11a uses the TDMA scheme in the medium access layer to provide deterministic services. However, ISA100.11a adopts the CSMA-CA mechanism with priorities for retransmission from failure on dedicated links, sporadic data, and network configuration.This paper evaluates ISA100.11a CSMA-CA by simulation, considering the effects of backoff procedures and priority settings to probability of collision and successful use of slots. It's demonstrated that a high number of priority classes enable better network utilization resulting in less number of packets exceeding their lifetime.     

基于ISA100.11a标准的工业物联网开发平台的设计与实现

工业物联网技术是未来几年工业自动化产品新的增长点。作者所在实验室作为Voting Member和ISA WCI工作组成员参加ISA100.11a标准的制定,研发了基于ISA100.11a的工业物联网通信协议栈软件、网络设备及终端设备,研制的ISA100.11a工业物联网开发平台具有完善的硬件、软件产品及技术支持,核心技术已经形成专利池,可广泛应用于智能工业、环境监测、智能电网等应用系统的开发,并已经在中国四联集团、韩国汉阳大学等单位得到应用。     

Improving simulation of wireless networked control systems based on WirelessHART

Recently, WirelessHART (2007) and ISA100.11a (2009) have been proposed as communication standard for a wireless fieldbus. However, Wireless Networked Control Systems performances are hard to verify in the real world, since test beds are expensive and difficult to implement.This paper proposes the use of a co-simulation framework based on the interaction of TrueTime, together with a cross layer wireless network simulator based on OMNET++. In particular, OMNET++ models show accurate aspects of network and devices, for improving overall coexistence management.A sample system controlled by a WirelessHART network has been considered; the analysis of the control performance and coexistence immunity of WirelessHART with respect to the traditional IEEE802.15.4, has been done.     

Real-time message scheduling for ISA100.11a networks

This paper proposes two new message scheduling methods on shared timeslots of the ISA100.11a standard to enhance real-time performance, namely, traffic-aware message scheduling (TAMS) and contention window size adjustment (CWSA). In TAMS, instead of competing to transmit sporadic messages in consecutive cycles, end-nodes are divided into groups, which then access the channel in specific cycles when the probability of timeslots getting involved in collisions exceeds a specified threshold. Conversely, in CWSA, the contention window is adjusted when the probability of timeslots getting involved in collisions exceeds the threshold. The results of simulations conducted indicate that these two proposed methods provide performance improvements in terms of success probability and end-to-end delay.     

面向最小延迟的无线mesh网络时隙分配问题研究

在基于IEEE802.15.4的工业无线传感器网络中,通过时分复用技术来实现节点间并行通信,以提高网络的吞吐量.通常,网络中的管理器根据全网拓扑对网络中的每个连接分配一个超帧中相应的时隙.不同的时隙分配方案中,连接在超帧中活动的顺序也不同,对网络性能的影响也不同.本文研究了不同时隙分配方案在网络吞吐量和数据延迟方面对网络的影响,定性分析了时隙分配方案与数据延迟的关系,并根据mesh结构的特点提出一种使用粒子群优化的算法,用于在网络管理器上对时隙分配进行优化,使得数据延迟最小化,以满足工业无线网络实时性应用的要求.     

小波网络在带噪声的混沌时间序列预测中的研究

在采用网络模型对带有噪声的混沌时间序列进行建模的过程中,噪声会影响模型的泛化能力。针对上述问题,本文提出了基于小波去噪的小波网络预测框架。在预处理阶段使用小波阈值方法抑制噪声,运用相空间重构理论确定嵌入维数和延迟时间,进而确定改进的小波网络模型的结构,结合BP算法和遗传算法对模型的参数进行学习。最后,在带噪声的Mackey-Glass混沌序列预测实验中验证了该框架的有效性。     

混合网络数据动态交换时隙再分配方法仿真

现有的混合网络数据动态交换时隙再分配方法,存在时延较大、时隙利用率较低等问题,提出基于WCDMA和数据链的交换时隙再分配方法,去除信道中的干扰信号,补偿由于数据传输造成的信号衰弱,通过信道的信干比估计,完成对信道的处理。当前分配时隙资源不能满足信息发送所需时,会在固定时隙内,周期性的发送时隙再分配消息给混合网络单元,并提出所需时隙资源,根据时隙动态分配方法,定制出混合网络时隙分配表,通过定制的时隙分配表,实现对混合网络数据动态交换的时隙再分配。仿真结果表明,所提方法能够在低时延、高时隙利用率的情况下,实现对混合网络数据动态交换时隙的再分配。     

太赫兹无线个域网高时隙利用率跨PAN数据传输协议

针对现有跨PAN数据传输机制存在的业务量分布不均衡造成的时隙浪费、协调超帧开始时刻不明确、超帧统一机制所需控制开销较大等问题,提出了一种高时隙利用率太赫兹无线个域网跨PAN数据传输机制HTSU-PAN（high time slot utilization cross PAN data transmission protocol for Terahertz wireless personal area network）。该协议通过采用隐式TDMA时隙分配、基于无beacon的空闲时段启用以及基于网桥节点超帧统一这三种新机制,有效提高时隙利用率,降低数据传输时延从而提升网络吞吐量。     

适用于飞行自组网的闲置时隙预约TDMA协议

在飞行自组网中,固定时隙分配时分多址接入（TDMA）协议存在闲置时隙无法成功使用的问题。通过对TDMA协议引入闲置时隙预约机制,提出一种支持业务优先级传输机制的闲置时隙预约TDMA协议。采用短帧长的方式满足协同与控制业务的低时延传输需求,并利用闲置时隙预约机制允许节点使用闲置时隙传输感知业务,从而满足感知业务的高吞吐量传输性能要求。仿真结果表明,与CF-MAC和CTMAC协议相比,该协议能够在降低传输时延的同时,有效提高信道利用率和网络吞吐量。     

多宿点无线传感器网络时分多址时隙优化分配算法

针对单宿点无线传感器网络的时延大、容易出现传输瓶颈等问题,提出了多宿点无线传感器网络模型以及该模型的基于遗传算法(GA)的时分多址(TDMA)时隙分配算法。该算法根据宿点的数量以及位置将整个传感器网络划分成多个小传感器网络,并采用遗传算法对时隙分配结果进行优化。仿真结果表明,基于遗传算法的多宿点无线传感器网络TDMA时隙分配算法得到的时隙分配结果在时隙分配帧长度、数据包平均时延以及节点平均能耗方面均要优于图着色算法。     

WSN中利用蚁群路径优化的时隙选择重排算法

针对无线传感器网络(WSN)汇聚传输中的数据传输时间和功耗问题,提出了考虑时间同步和唤醒延迟的汇聚传输时隙选择重排算法。将时分多址接入(TDMA)用作介质访问协议,并允许每个节点在传输时隙期间可以发送或接收数据;设计新的WSN数据收集树模型,将传感器节点生成的数据通过无线链路形成的多跳网络发送到汇聚节点,在数据收集树的每条链路上分析时隙顺序,优化时隙选择,并基于蚁群算法优化路径选择,减少传输能量消耗和均衡簇头能量。实验结果表明,提出的算法可以实现显著的数据传输性能提高和功耗节约。     

An efficient broadcast scheduling algorithm for TDMA ad-hoc networks

In this paper, we propose an efficient algorithm to find a collision-free time slot schedule in a time division multiple access frame. In order to minimize the system delay, the optimal schedule must be defined as the one that has the minimum frame length and provides the maximum slot utilization. The proposed algorithm is based on the sequential vertex coloring algorithm. Numerical examples and comparisons with the algorithm in previous research have shown that the proposed algorithm can find near-optimal solutions in respect of the system delay.Scope and purposeAn ad-hoc network was introduced in order to apply packet switching communication to a shared radio channel. Using a radio channel as the broadcast medium to interconnect users, an ad-hoc network provides flexible data communication services among a large number of geographically distributed, possibly mobile, radio units. In an ad-hoc network, since all users share a single channel by multiple access protocol, unconstrained transmission may lead to the time overlap of two or more packet receptions, called collision, resulting in damaged useless packets at the destination. Collided packets increase the system delay because they must be retransmitted. Therefore, the transmission for each station must be scheduled to avoid any collision, that is, collision-free transmission should be guaranteed. The time division multiple access (TDMA) technology can be used to schedule collision-free transmission. In this paper, we propose an efficient algorithm to find a collision-free time slot schedule in a TDMA ad-hoc network.     

工业无线技术在大型石油化工罐区自动化的应用

随着无线技术的迅速发展，在工业自动化领域的应用越来越广泛。本文介绍工业无线技术标准ISA100．11a及无线解决方案，霍尼韦尔基于ISA100．11a工业无线标准的解决方案在大型石油化工罐区自动化的应用。     

LoRa无线网络的多模式时隙分配算法研究

针对LoRa自组网络传输过程中动态改变指定区域所有节点的传输频率、所有区域内或指定区域中A类传感器采集数据传输频率的需求,在LoRa无线网络MAC协议的基础上,提出一种基于LoRa的多模式时隙分配算法,将时隙接入阶段分为普通模式和观察模式。其中,普通模式主要为正常情况下的传输任务分配时隙,观察模式同时要为正常情况下的传输任务和动态增加的传输任务分配时隙。实验结果表明,该分配算法在应对传输频率多变的情况时,提升了通信过程中的时隙利用率,降低了通信过程中的平均时延。     

基于分簇的无线传感器网络MAC节能算法

为减少节点能耗和提高信道利用率,提出一种基于分簇结构的无线传感器网络MAC节能算法(EEC-MAC)。在TDMA机制的基础上,采用时隙系数动态调整簇内节点的时隙大小,降低数据的传输时延。对于部分不需要数据传输的节点不分配时隙,使其拥有较长的睡眠时间来节约能量。簇内节点按其剩余能量系数形成时隙分配顺序,减少状态转换的能耗。簇间节点采用基于CSMA/CA机制的随机分配策略实现通信。仿真结果表明,EEC-MAC节能效果较好,具有较小的平均通信时延和较长的网络生命周期。     

Diagnosis mechanism for accurate monitoring in critical infrastructure protection

Wide-area situational awareness for critical infrastructure protection has become a topic of interest in recent years. As part of this interest, we propose in this paper a smart mechanism to: control real states of the observed infrastructure from anywhere and at any time, respond to emergency situations and assess the degree of accuracy of the entire control system. Particularly, the mechanism is based on a hierarchical configuration of sensors for control, the ISA100.11a standard for prioritization and alarm management, and the F-Measure technique to study the level of accuracy of a sensor inside a neighborhood.     

基于强化学习的无人机网络资源分配研究

以无人机网络的资源分配为研究对象,研究了基于强化学习的多无人机网络动态时隙分配方案,在无人机网络中,合理地分配时隙资源对改善无人机资源利用率具有重要意义;针对动态时隙分配问题,根据调度问题的限制条件,建立了多无人机网络时隙分配模型,提出了一种基于近端策略优化(PPO)强化学习算法的时隙分配方案,并进行强化学习算法的环境映射,建立马尔可夫决策过程(MDP)模型与强化学习算法接口相匹配;在gym仿真环境下进行模型训练,对提出的时隙分配方案进行验证,仿真结果验证了基于近端策略优化强化学习算法的时隙分配方案在多无人机网络环境下可以高效进行时隙分配,提高网络信道利用率,提出的方案可以根据实际需求适当缩短训练时间得到较优分配结果。     

A hybrid neural network model for rule generation and its application to process fault detection and diagnosis

In this paper, a hybrid neural network model, based on the integration of fuzzy ARTMAP (FAM) and the rectangular basis function network (RecBFN), which is capable of learning and revealing fuzzy rules is proposed. The hybrid network is able to classify data samples incrementally and, at the same time, to extract rules directly from the network weights for justifying its predictions. With regards to process systems engineering, the proposed network is applied to a fault detection and diagnosis task in a power generation station. Specifically, the efficiency of the network in monitoring the operating conditions of a circulating water (CW) system is evaluated by using a set of real sensor measurements collected from the power station. The rules extracted are analyzed, discussed, and compared with those from a rule extraction method of FAM. From the comparison results, it is observed that the proposed network is able to extract more meaningful rules with a lower degree of rule redundancy and higher interpretability within the neural network framework. The extracted rules are also in agreement with experts’ opinions for maintaining the CW system in the power generation plant.     

一种采用时隙对准方式的TDMA自组网同步协议

通过对TDMA方式下的同步协议STS和TISS进行研究,提出一种基于时隙对准方式的TDMA自组网同步协议MFSS。该协议以工作周期为自组网节点之间同步的标准,在节点初入网时采用双向交互和时隙对准方法,消除了传输时延误差和初始时间偏差,从而实现了快速初始同步;随后通过监测过程保证了节点之间产生的时钟漂移误差可自适应控制,同时减小了重新同步带来的开销。仿真结果证明,相比于STS协议和TISS协议,MFSS协议在同步收敛速度、同步精度以及同步开销上都取得了更好的性能。     

基于NTP的Ad Hoc网络时隙同步算法

基于无线Ad Hoc网络时分多址接入机制,设计一种多信道时隙结构。根据网络时间协议(NTP)的基本原理,提出基于该时隙结构的全网时隙同步算法。该算法继承了点对多点无线通信系统的时隙同步方式,在完成时隙主从同步调整后,实现全网时隙的初始对齐,然后进入时隙互同步调整阶段,根据网络节点时钟偏差、节点移动速度和保护时隙的长度,设置合理的互同步调整周期,既不增加网络流量负荷,又可保证各节点发射时隙不碰撞。仿真结果表明,该算法具有较小的时间同步偏差,能快速实现全网的时隙同步,可应用于基于TDMA方式的Ad Hoc网络。