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UBC Theses and Dissertations

MIMO backscatter RFID systems : performance analysis, design and comparison He, Chen


Backscatter RFID systems are the most popular RFID systems deployed due to low cost and low complexity. However, they pose many design challenges due to their querying-fading-signaling-fading structure, which experiences deeper fading than conventional one-way channels. Recently, by simulations and measurements, researchers found that the MIMO setting can improve the performance of backscatter RFID systems. These simulations and measurements were based on simple signaling schemes and no rigorous mathematical analysis has been provided. In this thesis, we explore querying, STC, and diversity combining schemes over the three ends of the backscatter RFID systems and provide generalized performance analysis and design criteria. At the tag end, we show that the identical signaling scheme, which cannot improve the BER performance in conventional one-way channels, can significantly improve the BER performance of backscatter RFID. We also analytically study the performances of orthogonal STCs, with different sub-channel fading assumptions, and show that the diversity order depends only on the number of tag antennas. More interestingly, we show that the performance is more sensitive to the channel condition of the forward link than that of the backscattering link. In previous literature, the understanding of the query end is that the designs of query signals have no potential to improve the system performance. However, we show that some well-designed query signals can improve the system performance significantly. We propose a novel unitary query method in this thesis. Conventional measures of the physical layer performance cannot be obtained analytically in backscatter RFID channels with employing our unitary query. We thus provide a new performance measure to overcome the difficulty of conventional measures, and show that why the unitary query has superior performance. The multi-keyhole channel is another type of cascaded channel. The backscatter RFID channel and the multi-keyhole channels look similar, but are essentially different and there difference has not been clearly studied in previous literature. In the final part of this thesis, by investigating general STCs and revealing a few interesting properties of this channel in the MISO case, we show that the two channels achieves completely different diversity order and BER performance.

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Attribution-NonCommercial-NoDerivs 2.5 Canada