Research On MAC Protocol Of Chipless Multi-tag

Traditional RFID technology is applied to various fields of the social industry because of its superior performance advantages.However,behind its huge application value,expensive RFID tags limit the widespread promotion of this technology.The emergence of chipless RFID technology provides a reliable way for the resolution of this problem.As a low-cost alternative of traditional chip rfid techonlogy,multi-tag identification collision problem also exists in chipless RFID technology.Chipless tag does not contain chip which can be used to turn off their response,when the reader sends an interrogation signal through the transmitting antenna,multiple chipless tags within the recognition range will respond together,then the tags conflict will occur if the reader can not separate the tag response from the superimposed signal.Anti-collision identification of chipless multi-tag has important meaning for the application of the tag in the future.Due to the current chipless multi-tag identification system does not own corresponding MAC protocol mechanism,so this paper takes the multi-tag MAC protocol research as the ultimate goal to solve the multi-tag identification problem.First of all,the chipless tag which as the most important component of multi-tag identification system is studied in this paper,the main research content include the structural characteristics of tag and coding capacity of tag.Instead of the traditional way which scatters removal,we use short circuit of the scatters realize‘0'bit coding based on C-type chipless tag,improving the robustness of the tag response.At the same time,we design a±45°dual-polarized M-type chipless tag,through the polarization multiplexing technology,the coding capacity of the tag is increased to two times in the fixed band.According to the tag structure response characteristics,tag coding capacity is further expanded by use the frequency shift coding technology,the coding capacity of the C-type and M-type chipless tags are increased by one and three times respectively,the coding density of the M-type exceeds the existing tag far away and reaches to 11.1bits/cm~2.Next,we research the identification algorithm of single chipless tag based on the tag response of the previous chapter.On the basis of the singularity expansion method,using the martrix pencil method to extract the complex resonant frequency of tag.Analyzing error and verify the feasibility that martrix pencil method can be used to identify tag.Finally,conducting the research of the tag number in fixed channel and multi-tag scattering signal of chipless RFID system.On the basis of the former,we propose the MAC protocol of Chipless multi-tag and corresponding identification algorithm.The feasibility of the proposed multi-tag MAC protocol is verified by simulation analysis in final.