Research On Signal Detection Algorithm Of Ambient Backscatter System Based On Multi-antenna Tag

Internet of things(Internet of Things,IoT)technology has been widely used in our lives,such as intelligent logistics,intelligent medical care,intelligent agriculture and so on.However,the current communication technologies of the Internet of things use active radio frequency units,which have high power consumption.The emergence of backscattering technology has solved the problem of high energy consumption.with the increase of the competitive pressure of spectrum resources,improving the spectrum efficiency of backscattering technology has become an urgent problem to be solved.The emergence of ambient backscatter communication(Ambient Backscatter Communication,AmBC)technology solves the problems of backscattering technology,which uses the electromagnetic signals in the environment for communication,and no longer needs to occupy additional spectrum resources.It brings new opportunities for the development of the Internet of things.AmBC technology realizes the debugging of the signal through the reflection equipment by adjusting the impedance matching network,and then realizes the communication with the receiving equipment.Due to the uncertainty of the environmental signal,it is difficult for the receiving equipment to separate the signal reflected by the label from the mixed signal.The existing research is to improve the efficiency of signal detection by sacrificing the communication rate.However,many application scenarios have high real-time requirements,so it is very important to improve the communication rate of AmBC technology to promote the development and application of AmBC technology.In order to improve the communication rate,this paper studies from two aspects: the theoretical design of multi-antenna tag and the design of signal detection algorithm.The main contents are as follows:1)the theoretical design of multi-antenna tag: this paper designs a multi-antenna tag model,which contains three antennas,in which antenna 1 and antenna 2 are communication antennas and communicate with the reader at the same time,which can improve the communication rate.Antenna 3 is an energy antenna,which is responsible for collecting energy from the environment.In order to prevent the antenna 3 from interfering with the antenna 1 and the antenna 2,the antenna 1 and the antenna 2 are designed to communicate with the receiving equipment in the same frequency band,and the antenna 3 acquires energy for the use of the tag in another frequency band.2)signal detection: the traditional signal detection methods are carried out under the condition of constant carrier signal.In order to make up for the shortcomings of the existing schemes,this paper proposes a signal detection algorithm based on k-means clustering analysis for multi-antenna tag AmBC system.Because the radio frequency carrier signal of AmBC system is unpredictable,it is difficult to detect the signal by envelope detection,so the signal detection problem is transformed into data classification problem in this paper.The multiantenna tag uses two antennas to communicate,and the signal received by the receiving equipment has four states.The k-means algorithm is used for clustering analysis in the IQ domain to decode the signal.In addition,in view of the shortcomings of the k-means algorithm,according to the time correlation,a queue-based algorithm to calculate the cluster center kmeans-q(Queue of k-means)algorithm is proposed,which reduces the bit error rate.The two algorithms are compared through simulation experiments.