Fast RFID Sensory Data Collection: Trade-off Between Computation and Communication Costs

This paper studies the important sensory data collection problem in the sensor-augmented RFID systems, which is to quickly and accurately collect sensory data from a predefined set of target tags with the coexistence of unexpected tags. The existing RFID data collection schemes suffer from either low time-efficiency due to tag-collisions or serious data corruption issue due to interference of unexpected tags. To overcome these limitations, we propose the hierarchical-hashing data collection (HDC) protocol, which can not only significantly improve the utilization of RFID wireless communication channel by establishing bijective mapping between <inline-formula> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> target tags and the first <inline-formula> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> slots in time frame, but also effectively filter out the serious interference of unexpected tags. Although HDC has attractive advantages, the theoretical analysis reveals that the computation cost involved in it is as huge as <inline-formula> <tex-math notation="LaTeX">$\mathcal {O}(k2^{k})$ </tex-math></inline-formula>, where <inline-formula> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> is normally large in practice. By making some modifications to the basic HDC protocol, we propose the multi-framed hierarchical-hashing data collection (MHDC) protocol to effectively reduce the involved computation complexity. Unlike HDC that only issues a single time frame, MHDC uses multiple time frames to collaboratively collect sensory data from the <inline-formula> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> target tags. It can be understood as that a big computation task is disintegrated into multiple small pieces and then shared by multiple time frames. As a result, the computation cost involved in MHDC is reduced to <inline-formula> <tex-math notation="LaTeX">$\mathcal {O}(k2^{n})$ </tex-math></inline-formula>, where <inline-formula> <tex-math notation="LaTeX">$n\ll k$ </tex-math></inline-formula> is the expected number of target tags that each time frame handles. Theoretical analysis is given to jointly consider the communication cost and computation cost thereby maximizing the overall time-efficiency of MHDC. Extensive simulation results reveal that the proposed MHDC protocol can correctly collect all sensory data and is always about more than <inline-formula> <tex-math notation="LaTeX">$2\times $ </tex-math></inline-formula> faster than the state-of-the-art RFID sensory data collection protocols.