Research On High-Speed LoRa Transmission Technology Based On Amplitude-Frequency Two-Dimensional Modulation

LoRa is a promising low-power wide-area network technology that can provide lowpower and long-range communication for millions of connected Io T devices.However,the maximum transmission rate of LoRa is just several Kbps,which not only limits the potential application scenarios,but also exacerbates the problem of data packet collision.In response to the above problems,this paper proposes a frequency-amplitude two-dimensional modulation technology aimed at improving the LoRa transmission rate.The main research content of this paper is as follows:Firstly,this paper starts with increasing the modulation dimension,and proposes to add the amplitude modulation to LoRa frequency modulation,so as to improve the LoRa transmission rate.The insight of amplitude modulation is to utilize a cyclic right-shifted ramp signal to modulate the LoRa symbol envelope.Different cyclic right shifts make the discontinuities of the envelope appear at different time.And the time stamp of the envelope discontinuity encodes data,realizing two-dimensional transmission of LoRa in both amplitude domain and frequency domain.Secondly,aiming at the problem of envelope nonlinear distortion and noise in amplitude modulation,a simple and effective denoising algorithm is proposed in this paper.The algorithm ensures that the noise interference is filtered out without affecting the amplitude decoding result.In addition,aiming at the problem that the noise appearing at the discontinuous point of the envelope reduces the accuracy of amplitude demodulation,a minimum assisted decoding algorithm is proposed in this paper.This algorithm can improve the anti-noise ability of amplitude modulation and reduce the bit error rate of amplitude demodulation by 15%～25%.Thirdly,this paper analyzes the performance of the proposed scheme in detail,including the lower limit of transmission rate,system energy overhead and efficiency,receiving sensitivity and compatibility with commercial systems.This paper presents a scheme to transform commercial LoRa nodes by adding an expansion board,and tests the key components to verify the feasibility of the scheme.Finally,this paper implements the prototype system of the proposed scheme on the software-defined radio platform,and conducts a comprehensive test and evaluation of the proposed scheme for both line-of-sight and non-line-of-sight scenarios.This paper evaluates the bit rate and bit error rate of the proposed scheme according to different parameters such as communication distance and spreading factor.A large number of results show that the communication rate of the proposed scheme can reach more than 2 times the communication rate of the existing LoRa technology.