Research On High Scalability Transmission Optimization Mechanism In Low-power Wide-area Networks

Low-Power Wide-Area Networks are narrowband Io T technologies for long-range and low-energy wireless communication requirements.They are cutting-edge technologies widely adopted in smart cities,intelligent manufacturing,and other fields.The typical ones are LoRa and NB-Io T.Compared with other technologies,LoRa has more unique advantages:miniaturization,easy deployment,on-demand networking and autonomous control.It is especially suitable for scenarios with complex environments,special locations,operator signals not covered,or cost sensitivity,capturing considerable attention from scientific and industrial communities.With the continuous upgrading and evolution of the application mode,the small data generated by the Io T on-site large connection continues to grow explosively,posing a more severe challenge to the concurrent transmission capability between end-devices and the gateway of the existing LoRa networks.Therefore,the optimization of high scalability transmission in LoRa networks has attracted wide attention in the academic community and is the current research hotspot.The existing literature is summarized into the following two categories: PHY-layer approaches and MAC-layer approaches.The PHY-layer approaches examine the signal characteristics from different LoRa devices,so that they could resolve collided transmissions.These techniques require direct access to PHY samples and are not feasible on commodity chips,which makes the high scalability transmission optimization technology based on MAC-layer become the focus of research.However,the existing studies based on MAC-layer still cannot adapt to the requirements of LPWAN scenarios,which may introduce excessive communication overhead,end-devices cost,power consumption,or hardware complexity.Thus,it is of utmost important to improve the concurrent transmission capability in LPWAN applications by leveraging the traffic characteristics of LPWAN applications,combining the transmission features between LoRa end-devices and gateways,optimizing the utilization of channel resources,and designing a highly cost-effective transmission optimization mechanism.This dissertation studies high scalability transmission optimization mechanisms based on two practical scenarios of the single-gateway and multi-gateway to improve the concurrent transmission capability of LoRa end-devices.Firstly,aiming at the imperfect orthogonality of LoRa signals with different spreading factors,we propose an imperfect-orthogonality spreading factor awareness mechanism for the single-gateway scenarios.Meanwhile,aiming at the distinct feature from single-gateway scenarios that uplink transmission collision and the corresponding packet reception capability,we propose an uplink transmission collision awareness mechanism for the multi-gateway scenarios.Secondly,for the single-gateway scenarios,we propose the optimal and suboptimal channel scheduling strategies for the ideal and actual LoRa spreading factor channels,respectively,to reduce the concurrent transmission collision of end-devices,so as to achieve high scalability transmission for small-scale enddevices.Thirdly,for the multi-gateway scenarios,we propose the corresponding uplink channel optimization scheduling strategies with the uplink transmission collision awareness mechanism according to the strict and loose periodic transmission characteristics of LoRa end-devices.On the basis,we design an online downlink channel scheduling strategy by leveraging the information of end-devices within the communication range of each gateway,to avoid the downlink concurrent transmission collision,so as to achieve high scalability transmission for large-scale end-devices.Finally,we design and implement the transmission optimization system supporting the high scalability transmission in low-power wide-area networks,and deploy the system in various real-world environments,to evaluate and verify the effectiveness and performance of the theoretical approaches in the dissertation.Overall,a series of transmission optimization mechanisms are explored in this dissertation to support high concurrent transmission in LoRa networks,and meet the requirements of largescale Io T applications.With the popularity of LPWANs,the proposed techniques can be applied for the efficient and energy-saving data transmission generated by massive end-devices in LoRa networks,and is able to support important applications such as urban governance,intelligent transportation,and intelligent manufacturing,with wide application prospects.