Green Bear - A LoRaWAN-based Human-in-the-Loop case-study for sustainable cities

Citizens are a crucial factor in the sustainability of the cities because they are one of the pillars for balancing their environment. Smart city projects can offer citizens an opportunity to understand how they contribute to their city’s sustainability. Furthermore, an interactive smart city system can create synergies that benefit both the citizens and the city itself. This paper presents the Green Bear smart city platform, an IoT Human-in-the-Loop system that uses LoRaWAN nodes to gather information on city green spaces, bike lanes, and recycling depots. A user-centered mobile application that allows for active user participation, feedback, and incentivization is used to close the loop with humans. This system allows citizens to evaluate their participation in aspects that improve the city’s sustainability through a gamification scheme, obtaining points for different activities in the city’s public spaces and personal activities to improve their quality of life. This solution is being implemented in the city of Coimbra, Portugal. After an overview of the system, the paper describes each main system module. The Green Bear prototype was subject to functional and technological assessment, and the results are presented and discussed.     

基于LBT-SA的LoRaWAN信道接入方法研究

标准LoRaWAN协议中定义的纯ALOHA信道接入方法在网络负载较大时会造成大量碰撞，使LoRa网络的可扩展性和可靠性受到极大挑战。为此提出了一种将先听后说与模拟退火相结合（Listen Before Talk combined with Simulated Annealing，LBT-SA）的LoRa信道接入方法。该方法通过在设备发送之前先监听信道，降低信道被同时接入的概率，并以成功传输所需退避时间为初始值，搜索更小的退避时间。仿真结果表明，LBT-SA和基于二元指数退避算法的先听后说（Listen Before Talk，LBT）方法在包成功传输率方面保持了高度的一致，并且LBT-SA在周期传输过程中逐渐减少了不必要的退避时间，从而减少了时延。在多达10 000个终端接入单个网关的场景中，该算法的平均退避时间至少降低了16.38%。     

电信运营商基于LoRaWAN的城域物联网组网方案

随着智慧城市的发展,基于LoRaWAN城域物联专网得到广泛重视。本文对LoRaWAN的架构和技术特点进行了研究,在此基础上从组网架构、频率使用和站址部署等方面提出了电信运营商基于LoRaWAN的组网方案建议。     

基于马尔科夫链的LoRaWAN网络节点性能分析

低功耗广域网LoRaWAN(Long Range Wide Area Network)能兼顾低功耗与远通信距离,已经应用于很多领域。本文分析了LoRaWAN协议中A类节点发送数据的过程,据此建立了包含各个状态转移概率的马尔科夫模型。然后,基于SX1278芯片的相关参数对协议模型进行了仿真,并分析了LoRaWAN网络中网关回复时机、节点数量、频段数、链路质量等因素对A类节点发送数据的延时和能耗的影响。仿真结果表明,在单网关且总信道数不变的情况下,减少频段数,延后网关确认回复可以缩短节点发送数据的延时,降低节点发送数据的能耗。这对提升LoRaWAN网络性能具有很强的参考性。     

LoRa广域网安全机制剖析

LoRa广域网（LoRaWAN）技术是目前主流的低功耗广域网技术。随着LoRa广域网技术越来越多地应用到各个垂直行业,网络安全变得越发重要。主要针对LoRa广域网技术的安全机制进行了分析,并且针对同类方案进行了技术对比分析。最后指出了LoRa广域网安全机制未来的技术发展方向。     

LoRaWAN中的公平数据速率分配和传输功率控制

文中对LoRaWAN单元内节点之间的数据速率公平性进行了研究。LoRaWAN数据提取速率不公平的原因在于:(1)分配给节点的数据速率不合理;(2)距离问题,LoRa/LoRaWAN表现出捕获效果,仅提取冲突信号中的较强信号。为解决上述问题,文中提出一种公平自适应数据速率分配和功率控制方案。通过在一个单元内部署每个数据速率的最公平比率并控制传输功率,降低捕获效果,无论其与网关之间的距离如何,都可以进行公平的数据提取。数值仿真结果表明,与现有的最新技术相比,文中方法在数据提取速率上实现了更高的公平性。同时,该方法可以不使用过高的传输功率来维持节点的生命周期,从而降低整个传输系统的整体能耗,符合绿色通信的理念。     

Experimental Evaluation of Trilateration-Based Outdoor Localization with LoRaWAN

Long Range Wide Area Network (LoRaWAN) in the Internet of Things (IoT) domain has been the subject of interest for researchers. There is an increasing demand to localize these IoT devices using LoRaWAN due to the quickly growing number of IoT devices. LoRaWAN is well suited to support localization applications in IoTs due to its low power consumption and long range. Multiple approaches have been proposed to solve the localization problem using LoRaWAN. The Expected Signal Power (ESP) based trilateration algorithm has the significant potential for localization because ESP can identify the signal’s energy below the noise floor with no additional hardware requirements and ease of implementation. This research article offers the technical evaluation of the trilateration technique, its efficiency, and its limitations for the localization using LoRa ESP in a large outdoor populated campus environment. Additionally, experimental evaluations are conducted to determine the effects of frequency hopping, outlier removal, and increasing the number of gateways on localization accuracy. Results obtained from the experiment show the importance of calculating the path loss exponent for every frequency to circumvent the high localization error because of the frequency hopping, thus improving the localization performance without the need of using only a single frequency.     

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.     

Two-Stage High-Efficiency Encryption Key Update Scheme for LoRaWAN Based IoT Environment

Secure data communication is an essential requirement for an Internet of Things (IoT) system. Especially in Industrial Internet of Things (IIoT) and Internet of Medical Things (IoMT) systems, when important data are hacked, it may induce property loss or life hazard. Even though many IoT-related communication protocols are equipped with secure policies, they still have some security weaknesses in their IoT systems. LoRaWAN is one of the low power wide-area network protocols, and it adopts Advanced Encryption Standard (AES) to provide message integrity and confidentiality. However, LoRaWAN's encryption key update scheme can be further improved. In this paper, a Two-stage High-efficiency LoRaWAN encryption key Update Scheme (THUS for short) is proposed to update LoRaWAN's root keys and session keys in a secure and efficient way. The THUS consists of two stages, i.e., the Root Key Update (RKU) stage and the Session Key Update (SKU) stage, and with different update frequencies, the RKU and SKU provide higher security level than the normal LoRaWAN specification does. A modified AES encryption/decryption process is also utilized in the THUS for enhancing the security of the THUS. The security analyses demonstrate that the THUS not only protects important parameter during key update stages, but also satisfies confidentiality, integrity, and mutual authentication. Moreover, The THUS can further resist replay and eavesdropping attacks.