大规模无线传感器网络的路由协议研究

对于大规模无线传感器网络的路由协议进行了研究,提出了基于最小跳数的路由协议。详细介绍了最小跳数场的建立过程,从理论上证明了每个节点只会收到一个导致最小代价变小的信息包,分析了节点随机延时对跳数场建立的影响和相应的处理措施。该协议可以在大规模网络内使用,节点只要记忆自己的转发节点集,就可以沿着最短路径向网关发送数据。分析和仿真实验都证实了设计的正确性。     

基于NS-3的城市场景LoRaWAN网络性能研究

LoRaWAN作为低功耗广域网代表性技术之一,具有低功耗,长距离,免许可频段等特点,已逐渐成为推动智能物联网设备在城市中发展的关键因素.为解决城市场景下LoRaWAN基于Aloha协议接入信道导致数据包碰撞几率较大的问题,仿真基于NS-3网络模拟器,建立了城市信道损失模型,并引入干扰矩阵,提出冲突阈值判定算法.算法根据...     

一种高效节能的PR-MAC协议

为解决无线传感器网络能耗过大和效率不高的问题,提出一种功率控制和多速率自适应的PR-MAC协议。该协议采用功率控制和多速率自适应技术,在降低能耗的同时提高网络的吞吐量。仿真实验结果表明,该协议采用基于节点剩余能量和距离基站跳数的随机退避策略可提高网络效率,在选择节点发送数据上考虑节点的剩余能量和距离基站跳数等因素,能有效地平衡无线传感器网络的能量。     

一种动态簇头比的无线传感器网络多跳路由算法

通过分析LEACH协议的特点,提出了一种新的改进算法,网络根据存活的节点数动态改变簇头个数占节点总数的比例,并且根据数据传输的距离分别采用一跳和多跳的方式发送数据。仿真实验表明,新的算法在延长网络生命周期、单位能耗数据发送量、产生簇头个数、死亡节点的分布等方面均优于LEACH协议。     

IPv6与ZigBee互联网关的设计与实现

针对ZigBee无线传感网络和IPv6网络不能直接互联的问题,提出一种基于Contiki操作系统和cc2530硬件平台的嵌入式互联网关设计方案。将网关架构部署在ZigBee组网中的Sink节点上,利用6LoWPAN技术实现ZigBee网络和IPv6网络的互联互通。改进6LoWPAN适配层的报文压缩方法,实现接口层ZigBee协议与网络层IPv6协议的数据交换。仿真结果表明,在传输负载较大的情况下,该网关具有低延时和低功耗的特点,验证了该网关的有效性。     

WSN中节点覆盖分层下的多路径路由协议

为了解决无线传感器网络（WSN）的路由问题,在分析了单路径路由协议和多路径路由协议的基础上,提出了节点覆盖层次模型。该模型根据节点到sink节点的最小跳数将网络分成以sink节点为中心的层次结构,并将邻居节点分成父节点、兄弟节点和子节点3类。并设计了在此模型下的路由协议MP-NCL。在该协议中,节点总是将感应到的数据向父节点转发,实现了跳数最小、多路径的数据传递。分析和仿真结果表明,节点覆盖层次模型和MP-NCL路由协议在延时、耗能、可靠性和生命期方面有较好的性能。     

WSN中负载平衡的LEACH通信协议研究

LEACH协议是无线传感器网络中被广泛应用的聚类协议,但它存在负载不均衡的缺陷.通过分析LEACH协议聚类中节点的能耗情况,建立节点的能耗模型,找出了聚类之间以及节点之间负载不均衡的原因.基于原有协议,提出了一种新的LB-LEACH通信协议.使用OMNET 进行仿真实验,实验结果表明,新协议能够使聚类间的负载更加均衡,减少节点的过早死亡,延长整个网络的寿命.     

无线传感网络中的RPL路由协议研究

现有的低功耗有损网络路由协议RPL以跳数为唯一的路径选择度量,这样会导致Sink节点周边位置的节点数据压力过大,从而过早将其电量耗尽。为了更好地平衡网络能耗,缓解Sink周边节点的压力,文章在原路由协议的基础上,提出了考虑节点剩余能量的路径选择策略;即在路径选择时综合跳数和节点能量两方面因素,让数据尽量从能量充裕的节点传输。经计算机仿真验证:改进后的路由协议对平衡网络能耗、延长网络整体的生命长度具有较为显著的改善。     

动态延时的无线多播路由协议

在分析基于共享树的Ad Hoc网络多播路由协议MAODV的基础上,结合能量模型,提出了一种Ad Hoc网络基于动态延时的多播路由协议ECBMR。算法分析和仿真结果显示,在不增加算法复杂性的前提下,ECBMR明显地改善了MAODV协议的延时特性,节点的能量消耗比较均衡,一方面降低了系统的能耗,另一方面有效地延长了网络的存活时间,比较好地解决了Ad Hoc网络能量和延时相互矛盾的问题。     

6LoWPAN多网关设计与实现

6LoWPAN是基于IEEE802.15.4标准的低功耗有损无线传感器网络承载IPv6协议的适配层技术。在6LoWPAN网络中,传感节点通过网关与Internet进行数据交互,导致靠近网关的节点与其他节点相比,能耗和负载严重不均衡。当前的6LoWPAN传感器网络协议不支持多网关路由功能。提出了一种基于rank值最小的多网关选择算法,在不增加额外信令的条件下,对现有6LoWPAN协议增加了多网关的支持,设计完成了6LoWPAN多网关系统方案,并在实际平台下实现。结果分析表明,该设计方案能够获得预期功能和性能,实现6LoWPAN节点能够自由选择网关,与Internet无缝互联互接。     

A Duty Cycle-Based Gateway Selection Algorithm for LoRaWAN Downlink Communication

Long Range Wide Area Network (LoRaWAN) has been developed to meet the requirements for the enormous device-to-device communication of Internet of Things (IoT) networks, which consist of a large number of participating devices spread over large coverage areas with low data rates and low power consumption. It supports communications in both directions, uplink, and downlink directions. However, the downlink communication in the current LoRaWAN raises the bottleneck issue at gateways due to the used gateway selection algorithm. This paper proposes a novel gateway selection algorithm based on the duty cycle time-off values for the existing gateways, Duty Cycle Gateway Selection (DCGS), to direct acknowledgment packets as downlink traffic towards the most suitable gateway. Thus, the proposed system avoids subsequent retransmission of previously sent traffic that leads to excessive traffic overloading the network. The proposed system avoids exhausting a gateway duty cycle with downlink traffic by distributing the downlink traffic among available gateways based on the duty cycle time off. DCGS is evaluated using FloRa and INET frameworks in the well-known network simulator OMNeT++. The result shows the superior performance of the proposed approach over the existing Signal-to-Noise ratio (SNR) based selection mechanism. It clearly indicates that the DCGS maintains a better confirmed packet delivery rate while reducing number of retransmissions, collisions, and power consumption.     

Real-time ECG monitoring using compressive sensing on a heterogeneous multicore edge-device

In a typical ambulatory health monitoring systems, wearable medical sensors are deployed on the human body to continuously collect and transmit physiological signals to a nearby gateway that forward the measured data to the cloud-based healthcare platform. However, this model often fails to respect the strict requirements of healthcare systems. Wearable medical sensors are very limited in terms of battery lifetime, in addition, the system reliance on a cloud makes it vulnerable to connectivity and latency issues. Compressive sensing (CS) theory has been widely deployed in electrocardiogramme ECG monitoring application to optimize the wearable sensors power consumption. The proposed solution in this paper aims to tackle these limitations by empowering a gateway-centric connected health solution, where the most power consuming tasks are performed locally on a multicore processor. This paper explores the efficiency of real-time CS-based recovery of ECG signals on an IoT-gateway embedded with ARM’s big.little™ multicore for different signal dimension and allocated computational resources. Experimental results show that the gateway is able to reconstruct ECG signals in real-time. Moreover, it demonstrates that using a high number of cores speeds up the execution time and it further optimizes energy consumption. The paper identifies the best configurations of resource allocation that provides the optimal performance. The paper concludes that multicore processors have the computational capacity and energy efficiency to promote gateway-centric solution rather than cloud-centric platforms.     

基于LoRaWAN的自适应多帧高效传输方法

针对LoRaWAN协议中LoRa网关与LoRa终端间数据多帧传输方式存在控制开销和传输时延较大的问题,提出一种基于LoRaWAN的自适应多帧高效传输方法（adaptive multi-frame efficient transmission,AMFET）,包含自适应多帧发送机制、自适应多帧接收确认机制和丢帧识别机制。自适应多帧发送机制对需确认数据消息设置优先等级,对高级需确认数据消息进行立即确认,对低级需确认数据消息在自适应发送模式结束后统一进行确认,同时将Fpending机制引入LoRaWAN上行多帧传输;自适应多帧接收确认机制通过位向量压缩技术记录已接收数据帧信息,从而单次对多个需确认数据消息进行合并确认;丢帧识别机制利用需确认帧编号（confirmed data identity,CDID）识别低级需确认消息是否丢失,避免终端异常进入休眠模式。通过数学分析和实验测试,分别对AMFET方法的性能进行了理论验证和实验验证,验证结果表明,相对于原LoRaWAN多帧传输方式,AMFET方法在保证数据传输可靠性的前提下,有效降低了数据传输时延和数据传输能耗。     

无线传感器网络中确保端到端传输质量的自适应调制缩放技术

在满足数据收集任务的时延要求及可靠性要求的前提下最小化能量消耗是传感嚣网络设计中的一个关键问题。选取不同的调制级数(即调制时的星座图大小,每符号位数)可以获得不同程度的能量节省,但引入不同程度的时延的同时也会造成不同程度的丢包。本文提出了一种优化模型在满足数据收集任务的时延要求及可靠性要求的前提下,最优选取各节点的调制级数以最小化网络能耗延长网络生命期。并在此基础之上提出了一个集中式控制算法以根据网络状况自适应地调节各节点的调制级数。实验表明本算法在所考查的各种网络环境下都能明显减少能耗,可以用该模型来确定时延及丢包率对能耗影响的敏感区。另外我们发现,如果将节点的服务率设置为与节点的包到达率近似成比例,在大多数情况下都能够获得好的节能效果。     

一种基于负载平衡树的多网关节点数据汇集路由算法

以均衡耗能为目标,考虑健壮性、可转发性和抗干扰性等因素,提出一种基于负载平衡树的多网关节点数据汇集路由算法(TBLB 算法).在多网关前提下,TBLB 算法结合节点能量和节点度形成以网关节点为根节点的负载平衡树,通过负载平衡树协调节点间的负载均衡,有效地降低节点的能量消耗.此外,节点根据路径性能评价因子W 进行路径选择和网关切换,进一步降低网络节点的通信开销,改善了网关节点的瓶颈问题.模拟实验结果表明,TBLB 算法能够有效均衡网络负载,对网络的能量消耗和网关节点接收到的数据包都有所改善.     

基于LoRaWAN的智慧农业系统

目前在智慧农业系统通信架构的实现上, 利用较多的往往是ZigBee、WiFi等技术, 虽然其基本能够实现较长距离传输、低功耗等需求, 但是在诸如抗干扰性、成本开销等方面上也还存在着许多缺点. 针对这些问题, 本文介绍了一种基于LoRaWAN技术设计的智慧农业系统. LoRa终端利用STM32单片机作为主控制器结合LoRa射频模块设计而成, 通过树莓派来搭建LoRa网关集中器进行数据转发, 在云服务器上部署ChirpStack服务与Flask Web应用实现了对农业作物生长环境的远程监测与管理功能, 并详细描述该LoRaWAN应用系统的工作原理以及系统设计. 最终所实现的系统数据传输稳定, 抗干扰性强, 同时也极大地降低了开发成本.     

An Improved Markov Model for IEEE 802.15.4 Slotted CSMA/CA Mechanism

IEEE 802.15.4 protocol is proposed to meet the low latency and energy consumption needs in low-rate wireless applications,however,few analytical models are tractable enough for comprehensive evaluation of the protocol.To evaluate the IEEE 802.15.4 slotted CSMA/CA channel access mechanism in this paper,we propose a practical and accurate discrete Markov chain model,which can dynamically represent different network loads.By computing the steady-state distribution probability of the Markov chain,we obtain a...     

Smart Mina: LoRaWAN Technology for Smart Fire Detection Application for Hajj Pilgrimage

The Long-Range Wide Area Network (LoRaWAN) is one of the used communication systems that serve and enables the deployment of the Internet of Things (IoT), which occasionally transmit small size data. As part of the Low Power Wide Area Network (LPWAN), LoRaWAN is characterized by its ability for low power consumption. In addition, it is built to provide more extended coverage and higher capacity with minimum cost. In this paper, we investigate the feasibility and scalability of LoRaWAN for the Mina area using a realistic network model. Mina, known as the world’s largest tent city, is a valley located in the east of Makkah city and surrounded by mountains. It accommodates up to 3 million pilgrims annually and contains more than 100000 tents. The performance was evaluated based on a fire detection-like application. Extensive simulations were conducted using the OMNeT++ simulator and Flora model to determine the delivery ratio, collision, and SF distribution for the simulated scenario with a network consisting of up to ten thousand end devices. The conducted simulations show a promising result for LoRaWAN technology for Mina city. It showed a consistent performance for LoRaWAN in most simulated scenarios when a high success ratio was achieved.     

能量均衡的无线传感器网络短路径路由算法

如何均衡地使用无线传感器网络节点的能量并产生较小的网络延迟是无线传感器网络研究的一个难点. 本文提出了一种能量均衡的无线传感器网络短路径路由算法EB-SPR (Energy-balanced short path routing). 首先将网络构造成层次结构, 节点根据上一层邻节点能量水平并优先使用剩余能量多的节点作为下一跳来转发数据包, 这种方式有效地平衡了网络能耗, 进而提高了网络生命周期. 另外, EB-SPR通过在路由中限制数据包在同一层被转发的次数来降低数据到达基站的跳数. 本文证明了EB-SPR下源数据包到达基站所经历的跳数最多为最短路径路由算法的2倍, 所以本文算法产生的网络延迟具有明确的上界. 模拟实验表明EB-SPR有效地延长了网络生命周期并能产生较小的网络延迟.     

分组敏感的无线传感器网络实时数据融合树算法

针对无线传感器网络中数据传输必须在指定时延约束下完成的特殊场景提出了一种能量有效的数据融合树算法,该算法首次将分组敏感的概念引入到传感器网络实时数据融合应用中,并通过特殊机制使得该算法在降低能耗水平的同时可以为实时数据动态地选择满足时延要求的路径。另外,针对该数据融合树算法设计了一种特殊的数据融合定时机制,从而进一步改善了该算法的性能。最后,通过仿真试验将该算法与已存在算法进行了比较,证明了该算法的优越性。