Novel Hierarchical Tag-Recognition for RFID Systems

Abstract

In this paper, we propose a new hierarchical radio-frequency identification (RFID) tag- recognition method based on the graph-based automatic modulation classification (AMC) and direct-sequence spread-spectrum (DSSS). In our proposed method, RFID tags can be modulated using different modulation schemes according to different scenarios (e.g., different users or different devices). For each modulation scheme, the direct-sequence spread-spectrum strategy is employed to allow simultaneous transmissions of multiple tags. In the first hierarchy, different modulation types are employed to distinguish different users, the graph-based AMC is built upon the periodicity of the modulated signals. The cyclic spectrum of the received signal is first established. The graph representation is then constructed according to the cyclic spectrum. Ultimately, robust features are extracted from the graph representation. In the second hierarchy, the DSSS scheme is utilized to differentiate the control or sensed data carried by individual tags, the signature sequence set with low cross- correlations is generated from Gold and Kasami sequences. In the third hierarchy, the information data sequences are thus spread by these signature sequences. In our proposed new RFID framework, multiple tags can transmit the signals simultaneously in the same frequency band where the dominant tag signal will be identified and its carried information can be recovered. Monte Carlo simulation results demonstrate the promising performance of our proposed new scheme.