Large-scale RFID Systems Research Articles

PET: Probabilistic Estimating Tree for Large-Scale RFID Estimation

Estimating the number of RFID tags in the region of interest is an important task in many RFID applications. In this paper, we propose a novel approach for efficiently estimating the approximate number of RFID tags. Compared with existing approaches, the proposed Probabilistic Estimating Tree (PET) protocol achieves {\cal O}(\log \log n) estimation efficiency, which remarkably reduces the estimation time while meeting the accuracy requirement. PET also largely reduces the computation and memory overhead at RFID tags. As a result, we are able to apply PET with passive RFID tags and provide scalable and inexpensive solutions for large-scale RFID systems. We validate the efficacy and effectiveness of PET through theoretical analysis as well as extensive simulations. Our results suggest that PET outperforms existing approaches in terms of estimation accuracy, efficiency, and overhead.

Scalable RFID Systems: A Privacy-Preserving Protocol with Constant-Time Identification

In RFID literature, most “privacy-preserving” protocols require the reader to search all tags in the system in order to identify a single tag. In another class of protocols, the search complexity is reduced to be logarithmic in the number of tags, but it comes with two major drawbacks: it requires a large communication overhead over the fragile wireless channel, and the compromise of a tag in the system reveals secret information about other, uncompromised, tags in the same system. In this work, we take a different approach to address time complexity of private identification in large-scale RFID systems. We utilize the special architecture of RFID systems to propose a symmetric-key privacy-preserving authentication protocol for RFID systems with constant-time identification. Instead of increasing communication overhead, the existence of a large storage device in RFID systems, the database, is utilized for improving the time efficiency of tag identification.

Smart Trend-Traversal Protocol for RFID Tag Arbitration

A self-learning Smart Trend-Traversal (STT) protocol for tag arbitration is proposed in this work, which effectively reduces the collision overhead occurred in large-scale RFID systems. The protocol dynamically issues queries according to the adaptively learned tag density and distribution; and therefore, it significantly reduces delay and energy consumption. The optimality of STT does not rely on any presumed network conditions, which is in sharp contrast to other available schemes and renders it a highly desirable and practical solution.

Adaptive collision resolution for efficient RFID tag identification

Abstract In large-scale RFID systems, all of the communications between readers and tags are via a shared wireless channel. When a reader intends to collect all IDs from numerous existing tags, a tag identification process is invoked by the reader to collect the tags' IDs. This phenomenon results in tag-to-reader signal collisions which may suppress the system performance greatly. To solve this problem, we design an efficient tag identification protocol in which a significant gain is obtained in terms of both identification delay and communication overhead. A k-ary tree-based abstract is adopted in our proposed tag identification protocol as underlying architecture for collision resolution. Instead of just recognizing whether tag collision happens at each interrogation time period, the reader can further obtain the reason of why the collision occurs in the current tag inquiry operation. With this valuable information, we can reduce tag signal collisions significantly and at the same time avoid all of the tag idle scenarios during a tag identification session. The rigorous performance analysis and evaluation show that our proposed tag identification protocol outperforms existing tree-based schemes.

Cardinality Estimation for Large-Scale RFID Systems

Counting the number of RFID tags (cardinality) is a fundamental problem for large-scale RFID systems. Not only does it satisfy some real application requirements, it also acts as an important aid for RFID identification. Due to the extremely long processing time, slotted ALOHA-based or tree-based arbitration protocols are often impractical for many applications, because tags are usually attached to moving objects and they may have left the readers interrogation region before being counted. Recently, estimation schemes have been proposed to count the approximate number of tags. Most of them, however, suffer from two scalability problems: time inefficiency and multiple-reading. Without resolving these problems, large-scale RFID systems cannot easily apply the estimation scheme as well as the corresponding identification. In this paper, we present the Lottery Frame (LoF) estimation scheme, which can achieve high accuracy, low latency, and scalability. LoF estimates the tag numbers by utilizing the collision information. We show the significant advantages, e.g., high accuracy, short processing time, and low overhead, of the proposed LoF scheme through analysis and simulations.

Cardinality Estimation for Large-Scale RFID Systems

Counting the number of RFID tags (cardinality) is a fundamental problem for large-scale RFID systems. Not only does it satisfy some real application requirements, it also acts as an important aid f...

Large-scale active RFID system utilizing ZigBee networks

As the era of the ubiquitous computing is ushered in, consumers have been primed for a variety of automation applications. Active RFIDs can be used for a number of automation applications because it may also have other sensors to extend its applications. An active RFID instinctively focuses on a long communication range. Nevertheless, active RFIDs cannot be applied to a large-scale area due to their limited radio communication and obstacles. This paper introduces a large-scale active RFID system based on multi-hop deployment utilizing dual radio frequency to overcome radio shadow areas that do not reach signals from the RFID reader. The proposed system consists of multiple RFID readers deployed in an ad hoc pattern. It uses a multihop collection scheme utilizing ZigBee networks to extend the coverage of the RFID reader and collect RFID tags outside its communication range. This paper also includes an experiment evaluating performance of the proposed method, using an implemented RFID system that complies with the standard for 433 MHz active RFIDs based on ISO/IEC 18000-7.

Threshold jumping and wrap-around scan techniques toward efficient tag identification in high density RFID systems

With the emergence of wireless RFID technologies, the problem of Anti-Collision has been arousing attention and instigated researchers to propose different heuristic algorithms for advancing RFID systems operated in more efficient manner. However, there still have challenges on enhancing the system throughput and stability due to the underlying technologies had faced different limitation in system performance when network density is high. In this paper, we present a Threshold Jumping (TJ) and a Wrap-Around Scan (WAS) techniques, which are query tree based approaches, aiming to coordinate simultaneous communications in high density RFID environments, to speedup tag identification, to increase the overall read rate and to improve system throughput in large-scale RFID systems. The main idea of the Threshold Jumping is to limit the number of collisions. When the number of collisions exceeds a predefined threshold, it reveals that tag density in RF field is too high. To avoid unnecessary enquiry messages, the prefix matching will be moved to next level of the query tree, alleviating the collision problems. The method of setting frequency bound indeed improves the efficiency in high density and randomly deployed RFID systems. However, in irregular or imbalanced RFID networks, inefficient situation may happen. The problem is that the prefix matching is performed in single direction level-order scheme, which may cause an imbalance query tree on which the right sub-tree always not been examined if the identification process goes to next level before scan the right sub-tree due to threshold jumping. By scanning the query tree from right to left in alternative levels, i.e., wrap-around, this flaw cold be ameliorated. To evaluate the performance of proposed techniques, we have implemented the TJ and the WAS method along with the query tree protocol. The simulation results show that the proposed techniques provide superior performance in high density environments. It is shown that the TJ and WAS are effective in terms of increasing system throughput and minimizing identification delay.

A hybrid approach for privacy-preserving RFID tags

Recently, there have been a considerable amount of works for privacy-preserving RFID tags. However, most existing schemes have a common, inherent problem in the fact that in order to identify only one single tag they require a linear computational complexity on the system side. This problem makes use of the schemes impractical in large-scale RFID deployments. We propose a new scheme for privacy-preserving RFID tags which combines the classical challenge-response mechanism with the idea of one-time pads in a simple but practical way. Our technique has a number of crucial advantages. It supports mutual authentication between reader and tag. It also supports untraceability with no information leakage. Furthermore, the scheme we present requires only one cryptographic operation to identify one device among N, which is an important benefit in large-scale RFID systems.

Performance-Effective and Low-Complexity Redundant Reader Detection in Wireless RFID Networks

The problems of redundant RFID reader detection and coverage have instigated researchers to propose different optimization heuristics due to the rapid advance of technologies in large-scale RFID systems. In this paper, we present a layered elimination optimization (LEO) which is an algorithm-independent technique aims to detect maximum amount of redundant readers that could be safely removed or turned off with preserving original RFID network coverage. A significant improvement of the LEO scheme is that amount of "write-to-tag" operations could be largely reduced during the redundant reader identification phase. Moreover, LEO is a distributed approach which does not need to collect global information for centralizing control, leading to no communications or synchronizations among RFID readers. To evaluate the performance of the proposed techniques, we have implemented the LEO technique along with other methods. Both theoretical analysis and experimental results show that the LEO is reliable, effective, and efficient. The proposed techniques can provide reliable performance with detecting higher redundancy and has lower algorithm overheads.