| In recent years,with the rapid development of the Internet of Things(Io T)technology,various wireless technologies,and wireless protocols have emerged,providing favorable support for the cur-rent smart Io T.Especially low-power wide-area network technology(LPWAN),due to its long trans-mission distance,wide communication coverage,and low power cost,is widely used in factories,farms,and other scenarios to meet the intelligent control of equipment and monitoring the environ-ment.However,LPWAN technology also faces the problem of the coexistence of a large number of end nodes in the network,which further leads to competition for network resources.The deploy-ment of large-scale communication nodes will bring about the problem of channel congestion and the overloaded channel,and the signal collisions are more likely to occur,leading to the decline of the reliability and throughput of the network.As one of the representative low-power wide-area network technologies developed in recent years,LoRa has become an attractive communication platform for the Internet of Things.However,LoRa also faces the problem of signal collisions and heavy network load.We consider the problem of concurrent transmission collisions in the LoRa network and propose and verify the demodulation mechanism for LoRa signal collisions under the burst traffic of LoRa.For the wireless signal collision problem,the current solutions are mainly designed from the phys-ical layer and medium access control(MAC)layer of the wireless network.For LPWAN technologies such as LoRa,due to limited device power consumption and device ability,the sophisticated MAC ap-proaches are not feasible to operate in practice,and the simple MAC layer mechanisms cannot achieve the great concurrent transmission of large amounts of devices.The existing physical layer solutions usually utilize the features of wireless signals to identify and separate collided data packets.How-ever,in practical deployment,the current solutions are limited to solving the problem of concurrent transmission collision due to unstable signal features and large concurrency issues.To this end,we consider the challenges faced by LoRa networks in practice and propose a new demodulation mechanism to solve the LoRa signal collision based on multi-dimensional features of the physical layer.First,we explore the performance of the features of the LoRa physical layer in the real environment to test the feasibility of different features for distinguishing collided packets.Second,we comprehensively leverage the frequency feature and amplitude feature of the LoRa signal to distinguish different data packets.The multi-dimensional features improve the identification of data packets in burst traffic.In addition,we also consider practical factors such as channel fading,similar symbol boundaries,and spectral leakage,and achieve more accurate and reliable packet demodulation in practice through the design of cumulative tracking multi-dimensional features.The design of this paper does not need to modify the hardware or firmware of commercial devices,which allows the design of this paper to be quickly deployed on the practical LoRa network.The design of this paper starts from the LoRa physical layer and is independent of the MAC layer of the network,so the scheme in this paper does not conflict with the MAC mechanism.In order to verify the design in this paper,we deploy it on the commercial LoRa chip SX1278 and software-defined radio equipment USRP B210 and conducted extensive verification under different scenarios and RF parameters.To sum up,we propose a new design to resolve the collision problem and separate packets by leveraging multi-dimensional features of the physical layer to relieve the pressure of the base station in the LoRa network in processing concurrent data packets and improve the load capacity of the net-work.In this paper,the proposed design is verified on a real platform.The experimental results show that,compared with the existing methods,the proposed design in this paper achieves higher network throughput in various settings and scenarios.The research results of this paper will help to improve the network performance of LPWAN,thereby further improving the quality of service and develop-ment of various LPWAN applications. |
