Fast searching a particular subset in a large number of products attached with radio frequency identification (RFID) tags is of practical importance for a variety of applications, but not yet thoroughly investigated. Since the cardinality of the products can be extremely large, collecting the tag information directly from each of those tags could be highly inefficient. To address the tag searching efficiency in large-scale RFID systems, this paper proposes several algorithms to meet the stringent delay requirement in developing fast tag searching protocols. We formally formulate the tag searching problem in large-scale RFID systems. We propose utilizing compact approximators to efficiently aggregate a large volume of RFID tag information and exchange such information with a two-phase approximation protocol. By estimating the intersection of two compact approximators, the proposed two-phase compact approximator-based tag searching protocol significantly reduces the searching time compared to all possible solutions we can directly borrow from existing studies. We further introduce a scalable cardinality range estimation method that provides inexpensive input for our tag searching protocol. We conduct comprehensive simulations to validate our design. The results demonstrate that the proposed tag searching protocol is highly efficient in terms of both time efficiency and transmission overhead, leading to good applicability and scalability for large-scale RFID systems.

/pdf/fast-tag-searching-protocol-for-large-scale-rfid-systems-12f4525fg5.pdf

Fast tag searching protocol for large-scale RFID systems

With the development of the industrial Internet of Things (IIoT), the existing IIoT platform has gradually formed a large-scale, heterogeneous distributed environment. How to ensure information security and achieve efficient product traceability is an urgent problem to be solved in the development of the steel IoT platform. In view of the low transparency of information traceability of current steel products and the defects of information islands, in this article the blockchain-based steel IoT quality traceability system is developed and adopted the alliance chain mode and the Hyperledger blockchain platform. Experimental tests prove that production companies, logistics, and consumers can participate in the information certification of steel products via the system. Consumers can understand the real product manufacturing process, effectively avoiding the incomplete information and low transparency in the traditional information traceability process, and effectively trace the quality of steel products. The system provides an effective scheme for promoting the transformation and upgrading of the steel industry .

Efficient Traceability Systems of Steel Products Using Blockchain-Based Industrial Internet of Things

Counting the number of radio frequency identification (RFID) tags, namely RFID counting, is needed by a wide array of important wireless applications. Motivated by its paramount practical importance, researchers have developed an impressive arsenal of techniques to improve the performance of RFID counting (i.e., to reduce the time needed to do the counting). This paper aims to gain deeper and fundamental insights in this subject to facilitate future research on this topic. As our central thesis, we find out that the overlooked key design aspect for RFID counting protocols to achieve near-optimal performance is a conceptual separation of a protocol into two phases. The first phase uses small overhead to obtain a rough estimate, and the second phase uses the rough estimate to further achieve an accuracy target. Our thesis also indicates that other performance-enhancing techniques or ideas proposed in the literature are only of secondary importance. Guided by our central thesis, we manage to design near-optimal protocols that are more efficient than existing ones and simultaneously simpler than most of them.

/pdf/understanding-rfid-counting-protocols-4avf3xn48z.pdf

Understanding RFID counting protocols

A distributed MIMO system consists of several access points connected to a central server and operating as a large distributed multi-antenna access point. In theory, such a system enjoys all the significant performance gains of a traditional MIMO system, and it may be deployed in an enterprise WiFi like setup. In this paper, we investigate the efficiency of such a system in practice. Specifically, we build upon our prior work on developing a distributed MIMO testbed, and study the performance of such a system when both full channel state information is available to the transmitters and when no channel state information is available. In the full channel state information scenario, we implement Zero-Forcing Beamforming (ZFBF) and Tomlinson-Harashima Precoding (THP) which is provably near-optimal in high SNR conditions. In the scenario where no channel information is available, we implement Blind Interference Alignment (BIA), which achieves a higher multiplexing gain (degrees of freedom) than conventional TDMA. Our experimental results show that the performance of our implementation is very close to the theoretically predicted performance and offers significant gains over optimal TDMA. We also discuss medium access layer issues in detail for both scenarios. To the best of our knowledge, this is the first time that the theoretical high data rates of multiuser MIMO systems have been showcased in a real world distributed MIMO testbed.

Achieving high data rates in a distributed MIMO system

Device-free localization, which does not require any device attached to the target, is playing a critical role in many applications, such as intrusion detection, elderly monitoring and so on. This paper introduces D-Watch, a device-free system built on the top of low cost commodity-off-the-shelf RFID hardware. Unlike previous works which consider multipaths detrimental, D-Watch leverages the “bad” multipaths to provide a decimeter-level localization accuracy without offline training. D-Watch harnesses the angle-of-arrival information from the RFID tags’ backscatter signals. The key intuition is that whenever a target blocks a signal’s propagation path, the signal power experiences a drop which can be accurately detected by the proposed novel P-MUSIC algorithm. The proposed wireless phase calibration scheme does not interrupt the ongoing data communication and thus reduces the deployment burden. We implement and evaluate D-Watch with extensive experiments in three different environments. D-Watch achieves a median accuracy of 16.5 cm for library, 25.5 cm for laboratory, and 31.2 cm for hall environment, outperforming the state-of-the-art systems. In a table area of 2 $\text{m}\times 2$ m, D-Watch can track a user’s fist at a median accuracy of 5.8 cm. D-Watch is also capable of localizing multiple targets which is well known to be challenging in passive localization.

https://ink.library.smu.edu.sg/cgi/viewcontent.cgi?article=4842&context=sis_research

D-Watch: Embracing “Bad” Multipaths for Device-Free Localization With COTS RFID Devices

Counting the number of RFID tags, or RFID counting, is needed by a wide array of important wireless applications. Motivated by its paramount practical importance, researchers have developed an impressive arsenal of techniques to improve the performance of RFID counting (i.e., to reduce the time needed to do the counting). This paper aims to gain deeper and fundamental insights in this subject to facilitate future research on this topic. As our central thesis, we find out that the overlooked key design aspect for RFID counting protocols to achieve near-optimal performance is a conceptual separation of a protocol into two phases. The first phase uses small overhead to obtain a rough estimate, and the second phase uses the rough estimate to further achieve an accuracy target. Our thesis also indicates that other performance-enhancing techniques or ideas proposed in the literature are only of secondary importance. Guided by our central thesis, we manage to design near-optimal protocols that are more efficient than existing ones and simultaneously simpler than most of them.

/pdf/understanding-rfid-counting-protocols-m1tbhgt194.pdf

Motivated by recent emerging systems that can leverage partially correct packets in wireless networks, this paper investigates the novel concept of error estimating codes (EEC). Without correcting the errors in the packet, EEC enables the receiver of the packet to estimate the packet's bit error rate, which is perhaps the most important meta-information of a partially correct packet. Our EEC algorithm provides provable estimation quality, with rather low redundancy and computational overhead. To demonstrate the utility of EEC, we exploit and implement EEC in two wireless network applications, Wi-Fi rate adaptation and real-time video streaming. Our real-world experiments show that these applications can significantly benefit from EEC.

/pdf/efficient-error-estimating-coding-feasibility-and-13m1vv6nt1.pdf

Efficient error estimating coding: feasibility and applications

Motivated by recent emerging systems that can leverage partially correct packets in wireless networks, this paper proposes the novel concept of error estimating coding (EEC). Without correcting the errors in the packet, EEC enables the receiver of the packet to estimate the packet's bit error rate, which is perhaps the most important meta-information of a partially correct packet. Our EEC design provides provable estimation quality with rather low redundancy and computational overhead. To demonstrate the utility of EEC, we exploit and implement EEC in two wireless network applications, Wi-Fi rate adaptation and real-time video streaming. Our real-world experiments show that these applications can significantly benefit from EEC.

/pdf/efficient-error-estimating-coding-feasibility-and-4xv7oocfjn.pdf

For many applications that use RFID technology, it is important to count the number of RFID tags accurately. However, the wireless channel between the RFID tags and readers can introduce communication errors, and the error rate may vary significantly over time. No existing protocol can perform RFID counting robustly (i.e., maintaining the estimation quality) over time-varying channels. In this paper, we design RRC, a Robust RFID Counting protocol that offers provable guarantees on estimation quality over time-varying channels. Specifically, regardless of how the communication errors occur, the final output generated by RRC is always a standard (e, δ) estimate of the correct count n. Furthermore, the expected amount of time needed by RRC is O(Y + 1/2 + (log log n)2) for a constant 6, where Y is the number of communication errors encountered by RRC. This makes the efficiency of RRC asymptotically near-optimal.

Ziling Zhou

Papers

Understanding RFID counting protocols

Understanding RFID counting protocols

Efficient error estimating coding: feasibility and applications

Efficient error estimating coding: feasibility and applications

RFID Counting over Time-Varying Channels