Large RFID Systems Research Articles

Time-Efficient Range Detection in Commodity RFID Systems

RFID is becoming ubiquitously available in our daily life. After RFID tags are deployed to make attached objects identifiable, a natural next step is to communicate with the tags and collect their information for the purpose of tracking tagged objects or monitoring their surroundings in real-time. In this paper, we study an under-investigated problem range detection in a commodity RFID system, which aims to check if there are any tags with the data between an upper and lower boundary in a time-efficient way. This is important especially in a large RFID system, which can help users quickly pinpoint the target tags (if any) and give an early warning to users for taking urgent actions and reducing the potential risk in the nascent stage. We propose two tailored protocols, selective query and range query, to achieve range detection within the scope of the C1G2 standard. The novelty is that, instead of querying each tag, we exploit the capability of C1G2-compatible selection and quickly separate target tags from others by silencing most of tags. The final result is that range query is able to achieve a range detection with only one query command. We implement the proposed protocols in commodity RFID systems, with no need for any hardware modifications. Extensive experiments show that range query is able to improve the time efficiency by an order of magnitude, compared with the baseline.

Efficient RFID Grouping Protocols

The grouping problem in RFID systems is to efficiently group all tags according to a given partition such that tags in the same group will have the same group ID. Unlike previous research on unicast transmission from a reader to a tag, grouping provides a fundamental mechanism for efficient multicast transmissions and aggregate queries in large RFID-enabled applications. A message can be transmitted to a group of $m$ tags simultaneously in multicast, which improves the efficiency by $m$ times when comparing with unicast. This paper studies this practically important but not yet thoroughly investigated grouping problem in large RFID system. We start with a straightforward solution called the Enhanced Polling Grouping (EPG) protocol. We then propose a time-efficient Filter Grouping (FIG) protocol that uses Bloom filters to remove the costly ID transmissions. We point out the limitation of the Bloom-filter based solution due to its intrinsic false positive problem, which leads to our final ConCurrent Grouping (CCG) protocol. With a drastically different design, CCG is able to outperform FIG by exploiting collisions to inform multiple tags of their group ID simultaneously and by removing any wasteful slots in its frame-based execution. We further enhance CCG to make it perform better with very large groups. Simulation results demonstrate that our best protocol CCG can reduce the execution time by a factor of 11 when comparing with a baseline polling protocol.

Tag-Ordering Polling Protocols in RFID Systems

Future RFID technologies will go far beyond today's widely used passive tags. Battery-powered active tags are likely to gain more popularity due to their long operational ranges and richer on-tag resources. With integrated sensors, these tags can provide not only static identification numbers but also dynamic, real-time information such as sensor readings. This paper studies a general problem of how to design efficient polling protocols to collect such real-time information from a subset M of tags in a large RFID system. We show that the standard, straightforward polling design is not energy-efficient because each tag has to continuously monitor the wireless channel and receive O(|M|) tag IDs, which is energy-consuming. Existing work is able to cut the amount of data each tag has to receive by half through a coding design. In this paper, we propose a tag-ordering polling protocol (TOP) that can reduce per-tag energy consumption by more than an order of magnitude. We also reveal an energy-time tradeoff in the protocol design: per-tag energy consumption can be reduced to O(1) at the expense of longer execution time of the protocol. We then apply partitioned Bloom filters to enhance the performance of TOP, such that it can achieve much better energy efficiency without degradation in protocol execution time. Finally, we show how to configure the new protocols for time-constrained energy minimization.

A Secure RFID Identity Reporting Protocol for Physical Attack Resistance

RFID tags will exist pervasively in our daily life in a near future. In RFID systems, privacy and security are of critical importance to avoid potential tracking abuse and privacy violations. Many protocols have been proposed to address privacy and security issues in RFID systems. Physical attacks receive few considerations from the current research. Through physically attacks, attackers can get the secret identification-related information stored on RFID tags, and can later use the obtained information to impersonate legitimate readers for illegal tracking. In this paper we describe a threat model of RFID systems and present a detailed analysis of physical attacks on RFID tags and other security threats. We propose a secure identity reporting protocol to address these threats. Our security and performance analysis show that the proposed protocol can defeat physical attacks, in addition to other security threats, and scale well to large RFID systems.