| Radio frequency identification(RFID) is one kind of automatic identification technology which has been widely used in military, industry, logistics and many other fields. A mobile radio frequency identification system consists of many passive moving tags and a battery-constrained portable reader. In such a mobile RFID system, massive tags continuously enter the interrogation zone of the reader, which must quickly and reliably identify all the tags before they leave its coverage area. To meet such performance requirement, in literature, a plethora of research works have been done in the design and optimization of anti-collision protocols, to enhance the system time efficiency and reduce the tag reading time as much as possible. However, as illustrated in this thesis, optimizing the time efficiency does not necessarily lead to maximizing the energy efficiency for the reader. In fact, to efficiently utilize the limited battery energy at the reader, tag reading process should be power-aware.In this thesis, we primarily study the tradeoff between the time and energy efficiencies for tag identification in a mobile RFID system. Specifically, we define the time and energy efficiency metrics for the system and analyze the impact of frame length on the two metrics and we also reveal the relation between the two metrics. Then we study the strategy to balance the time and energy efficiencies under two tag-moving models. With various tag density, moving velocity and prescribed identification constraint taken into consideration, we can efficiently reduce the energy consumption by adjusting the frame length while satisfying the reliability requirement at the same time. At last, we do lots of simulation on the system efficiency, the energy saving gain and percentage of unidentified tags with the strategy we propose. Extensive simulation results indicate that we can achieve as much as 11% improvement in energy efficiency while satisfying the identification reliability constraint. |
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