Computational RFID Research Articles

Empowering the Blind: Contactless Activity Recognition with Commodity Software-Defined Radio and Ultra-High-Frequency Radio Frequency Identification.

This study presents a novel computational radio frequency identification (RFID) system designed specifically for assisting blind individuals, utilising software-defined radio (SDR) with coherent detection. The system employs battery-less ultra-high-frequency (UHF) tag arrays in Gen2 RFID systems, enhancing the transmission of sensed information beyond standard identification bits. Our method uses an SDR reader to efficiently manage multiple tags with Gen2 preambles implemented on a single transceiver card. The results highlight the system's real-time capability to detect movements and direction of walking within a four-meter range, indicating significant advances in contactless activity monitoring. This system not only handles the complexities of multiple tag scenarios but also delineates the influence of system parameters on RFID operational efficiency. This study contributes to assistive technology, provides a platform for future advancements aimed at addressing contemporary limitations in pseudo-localisation, and offers a practical, affordable assistance system for blind individuals.

SecuCode: Intrinsic PUF Entangled Secure Wireless Code Dissemination for Computational RFID Devices

The simplicity of deployment and perpetual operation of energy harvesting devices provides a compelling proposition for a new class of edge devices for the Internet of Things. In particular, Computational Radio Frequency Identification (CRFID) devices are an emerging class of battery-free, computational, sensing enhanced devices that harvest all of their energy for operation. Despite wireless connectivity and powering, secure wireless firmware updates remains an open challenge for CRFID devices due to: intermittent powering, limited computational capabilities, and the absence of a supervisory operating system. We present, for the first time, a secure wireless code dissemination (SecuCode) mechanism for CRFIDs by entangling a device intrinsic hardware security primitive Static Random Access Memory Physical Unclonable Function (SRAM PUF) to a firmware update protocol. The design of SecuCode: i) overcomes the resource-constrained and intermittently powered nature of the CRFID devices; ii) is fully compatible with existing communication protocols employed by CRFID devices in particular, ISO-18000-6C protocol; and ii) is built upon a standard and industry compliant firmware compilation and update method realized by extending a recent framework for firmware updates provided by Texas Instruments. We build an end-to-end SecuCode implementation and conduct extensive experiments to demonstrate standards compliance, evaluate performance and security.

Lama: Link characteristic aware multicast data dissemination for computational RFIDs

Computational radio frequency identification can be successfully employed in a range of applications. The efficient data dissemination is a building block for useful functions such as parameter configuration, code debug fixing, and wireless reprogramming. Many recent data dissemination protocols have adopted transmission methods from a reader to a single tag following EPC C1G2. Even if the same data need to be transmitted to multiple tags, they can only be distributed individually; however, tags in the reader antenna coverage area can hear commands from the reader, which motivates us to pursue a multicast data dissemination scheme that is compatible with the existing protocol. In this paper, we propose Lama, an efficient multicast data dissemination protocol that considers tag link characteristics (link quality and charging efficiency). This method improves the efficiency of data dissemination by selecting an appropriate master tag. Experiments based on a commercial reader demonstrate that Lama reduces the dissemination delay compared with state-of-the-art protocols.

Energy-aware rate adaptation for computational RFID

Rate adaptation is an effective method to maximise the transmission goodput, especially for the passive sensing systems with a more variable channel environment and unstable energy states. Most existing approaches share three common drawbacks: excessive energy consumption, not in real-time, and not taking into account the energy of computational radio frequency identification (CRFID). We propose an energy-aware rate adaptation algorithm for CRFID, which use new channel detection methods, and design an adaptive time window algorithm, also, we establish a model of data rate and required energy, considered the impact of different data rates on energy consumption, and design a new CRFID runtime mechanism. We implement an algorithm on the wireless identification sensing platform (WISP) CRFIDs and commercial RFID reader, compared to the state-of-the-art scheme, the goodput gain and energy efficiency of our design are much improved.

Energy-aware rate adaptation for computational RFID

Energy-aware rate adaptation for computational RFID

Modular Integration of a Passive RFID Sensor With Wearable Textile Antennas for Patient Monitoring

An integration and modularization solution for a passive computational radio frequency identification (RFID) module is proposed for wireless patient monitoring. In the proposed integrated configuration, all the electronic components are encapsulated within the cavity of a textile antenna. This forms a compact protected embodiment suitable for concealment in a hospital garment, with the aim of being unobtrusive to older patients. In addition, modularization of the sensor and textile antenna is introduced through a convenient snap-on attachment method for the computational RFID module. This is in harmony with simple assembly techniques and facilitates maintenance. Importantly, the resulting customizable configurations, for example, in terms of antenna form factor and materials, can be tailored to suit application requirements, such as performance and disposability. The experimental results demonstrate that the proposed wireless wearable sensor can operate with an antenna broadside gain of 2.74 dBi within a wide bandwidth extending over 893–964 MHz to support seamless worldwide operation across the ultrahigh-frequency (UHF) industrial, scientific, and medical (ISM) bands. The wearable sensor embodiment characterized in the context of a monitoring system attains excellent performance in terms of received signal strength, data read rate, and batteryless operational range.

Optimal data transmission in backscatter communication for passive sensing systems

Computational Radio Frequency IDentification (CRFID) is a device that integrates passive sensing and computing applications, which is powered by electromagnetic waves and read by the off-the-shelf Ultra High Frequency Radio Frequency IDentification (UHF RFID) readers. Traditional RFID only identifies the ID of the tag, and CRFID is different from traditional RFID. CRFID needs to transmit a large amount of sensing and computing data in the mobile sensing scene. However, the current Electronic Product Code, Class-1 Generation-2 (EPC C1G2) protocol mainly aims at the transmission of multi-tag and minor data. When a large amount of data need to be fed back, a more reliable communication mechanism must be used to ensure the efficiency of data exchange. The main strategy of this paper is to adjust the data frame length of the CRFID response dynamically to improve the efficiency and reliability of CRFID backscattering communication according to energy acquisition and channel complexity. This is done by constructing a dynamic data frame length model and optimizing the command set of the interface protocol. Then, according to the actual situation of the uplink, a dynamic data validation method is designed, which reduces the data transmission delay and the probability of retransmitting, and improves the throughput. The simulation results show that the proposed scheme is superior to the existing methods. Under different energy harvesting and channel conditions, the dynamic data frame length and verification method can approach the theoretical optimum.

A theoretical and experimental study of passive computational radio frequency identification tags

AbstractThe investigation and optimization of the RF frontend of radio frequency identification (RFID) tags represents a crucial topic when looking for an increased tag performance. This work studies the RF frontend of three state‐of‐the‐art passive computational RFID tags: AMS SL900a Dev Kit, Farsens Spider Eval, and WISP 5.1. Given a module‐based approach, the antenna, the matching network, the RF energy harvesting, and the load modulation are reviewed both theoretically and experimentally. The influence of a set of properties, corresponding to these modules, on the overall RFID tag performance is evaluated using a tag read range measurement.

Fast and Reliable Burst Data Transmission for Backscatter Communications.

Computational radio frequency identification (CRFID) sensors are able to transfer potentially large amounts of data to the reader in the radio frequency range. However, the existing EPC C1G2 protocol is inefficient when there are abundant critical and emergency data to be transmitted and cannot adapt to changing energy-harvesting and channel conditions. In this paper, we propose a fast and reliable method for burst data transmission by fragmenting large data packets into blocks and we introduce a burst transmission mechanism to optimize the EPC C1G2 communication procedure for burst transmission when there are critical and emergency data to be transmitted. In addition, we utilize erasure codes to reduce Acknowledgement (ACK) delay and to improve system reliability. Our results show that our proposed scheme significantly outperforms the current fixed frame length approach and the dynamic frame length and charging time adaptation scheme (DFCA) and that the goodput is close to the theoretically optimal value under different energy-harvesting and channel conditions.

Selecting Impedance States in a Passive Computational RFID Tag Backscattering in PSK

A methodology to carefully select the impedance states of a backscatter phase-shift keying (PSK) load modulator in a passive computational ultrahigh-frequency (UHF) radio frequency identification (RFID) tag is presented. Considering the most significant tag read range limitations reader sensitivity, power transmission and bit error rate (BER), the proposed selection results in constant power transmission to the energy harvester and thus in an increase of the average power at the input of the energy harvester during tag-to-reader communication. A graphical tool to select the modulator impedance states using a Smith chart is proposed.

On the Synchronization of Computational RFIDs

Battery-free computational RFID platforms, such as WISP (Wireless Identification and Sensing Platform), are intermittently-powered devices designed for replacing existing sensor networks. Accordingly, synchronization appears as one of the crucial building blocks for collaborative and coordinated actions in these platforms. However, intermittent power leads to frequent loss of computational state and short-term clock frequency instability that makes synchronization challenging. In this article, we introduce the WISP-Sync protocol that provides synchronization among WISP tags in the communication range of an RFID reader. WISP-Sync overcomes the aforementioned challenges by employing a Proportional-Integral (PI) controller-inspired algorithm which (i) is adaptive—reactive to short-term clock instabilities; (ii) requires only a few computation steps—suitable for limited harvested energy; and (iii) keeps a few variables to hold the synchronization state—minimum overhead to recover from power interrupts. Evaluations in our testbed showed that WISP-Sync ensured an average synchronization error of approximately 1 ms among the tags with an average energy overhead of 1.85 $\mu$μJ per synchronization round.

Protocol for Streaming Data from an RFID Sensor Network †.

Currently, there is an increasing interest in the use of Radio Frequency Identification (RFID) tags which incorporate passive or battery-less sensors. These systems are known as computational RFID (CRFID). Several CRFID tags together with a reader set up an RFID sensor network. The reader powers up the tags’ microcontroller and their attached sensor using radio frequency waves, and tags backscatter, not only their EPC code but also the value of those sensors. The current standard for interrogating these CRFID tags is the EPC global Class 1 Generation 2 (EPC C1G2). When several tags are located inside the reader interrogation area, the EPC C1G2 results in very poor performance to obtain sensor data values. To solve this problem, a novel protocol called Sensor Frmed Slotted Aloha (sFSA) for streaming sensor data dealing with the tag collisions is presented. The proposed protocol increases the Sensor Read Rate (SRR), defined as the number of sensor data reads per second, compared to the standard. Additionally, this paper presents a prototype of an RFID sensor network to compare the proposed sFSA with the standard, increasing the SRR by more than five times on average. Additionally, the proposed protocol keeps a constant sensor sampling frequency for a suitable streaming of these tag sensors.

Lightweight (Reverse) Fuzzy Extractor With Multiple Reference PUF Responses

A physical unclonable function (PUF), like a fingerprint, exploits manufacturing randomness to endow each physical item with a unique identifier. One primary PUF application is the secure derivation of volatile cryptographic keys using a fuzzy extractor (FE) comprising: 1) a secure sketch and 2) an entropy extractor. Although the entropy extractor can be lightweight, the overhead of the secure sketch responsible for correcting naturally noisy PUF responses is usually high. We observe that, in general, response unreliability with respect to an enrolled reference measurement increases with increasing differences between the in-the-field PUF operating condition and the operating condition used in evaluating the enrolled reference response. For the first time, we exploit such an inadvertent but important observation. In contrast to the conventional single reference response enrollment, we propose enrolling multiple reference responses (MRRs) subject to the same challenge but under multiple distinct operating conditions. The critical observation here is that one of the reference operating conditions is likely to be closer to the operating condition of the field deployed PUF, thus resulting in minimizing the expected unreliability when compared to the single reference under the nominal condition. As a consequence, MRR greatly reduces the demand for the expected number of erroneous bits requiring correction and, subsequently, achieves a significant reduction in the error correction overhead. The significant implementation efficiency gains from the proposed MRR method are demonstrated from software implementations of FEs on batteryless resource constraint computational radio frequency identification devices, where realistic PUF data are collected from intrinsic static random access memory PUFs.

LILAC: computable capabilities based high performance protocol for CRFID

Compared with traditional radio frequency identification (RFID), computational RFID (CRFID) tag has more powerful computing capability, but it shows poor performance when it follows EPC Class-1 Generation-2 protocol especially transmitting large amounts of data. In fact, the operation of the CRFID tag entirely depends on the state of energy. For this point, this study proposes an optimised protocol called LILAC. LILAC allows tags to select the communication time slot according to their current voltage value measured by using an analogue-to-digital converter rather than randomly selecting, the authors proposed a more reasonable time slot mapping algorithm for LILAC that increases the success rate of tag responding. In addition, they design a data transmission format that can be retransmitted to improve the uplink throughput. Finally, they implemented LILAC on a CRFID platform and practically measured several parameters to compare with the existing well-known protocol. The results of experiments show that LILAC increases the maximum communication distance by more than half in the access phase and doubles the goodput of the backscatter link in both the inventory and access phase.

Joint Information and Power Transfer in SWIPT-Enabled CRFID Networks

Computational radio frequency identification (CRFID) tags sense the environment and transmit the sensed data using the received energy from readers. To operate CRFID tags, both information and energy need to be delivered appropriately. Simultaneous wireless information and power transfer (SWIPT) can be useful for such CRFID applications. However, in a SWIPT network, undesired signals may be harmful or helpful from the information decoding or energy harvesting perspective. In this letter, we focus on the performance of joint information and power transfer for CRFID tags. We model a SWIPT-enabled CRFID network with the Poisson point process (PPP). The joint probability for simultaneously receiving both information and power is derived using the properties of the PPP, which determines the optimal transmission probability and the optimal power splitting factor in a SWIPT-enabled CRFID network.

R 3

Computational Radio Frequency Identification (CRFID) tags operate solely on harvested energy and have emerged as viable platforms for a variety of ubiquitous sensing and computation applications. Due to their battery-less nature, these tags can be permanently deployed in hard-to-reach places where the possibility of tag access is eliminated. In such scenarios, maintaining and upgrading the tag’s firmware becomes infeasible because programming tools, including wired interface and PC-based software, are required to erase, modify, or reprogram the microcontroller unit’s memory. Such limitations necessitate the demand for an over-the-air (OTA) scheme, which can wirelessly reprogram or upgrade the firmware in CRFID tags. In this article, we present R 3 —a reliable OTA reprogramming scheme that is compliant with EPC protocol and requires no hardware upgrade to RFID reader or CRFID tag. We demonstrate our scheme on three platforms, which include both software-defined as well as chip-based CRFID tags, that is, WISP5.1 and Optimized WISP (Opt-WISP), and Spider tag, respectively. The selection also includes both the FLASH- and FRAM-based microcontrollers. We extensively evaluate our scheme in terms of several metrics, including overall system delay, time and energy overhead, and success rate in line with interrogation range. We foresee our endeavor to offer the viability of OTA reprogramming and firmware upgrade for CRFID tokens under practical situations.

Remote Firmware Execution Control in Computational RFID Systems

Computational RFID (CRFID) tags are an emerging class of UHF RFID tags, which are capable of communication, sensing, and computation. However, their computational units are pre-programmed to execute a specific task and cannot change their execution flow during runtime. They require a wired interface to reinstall a new firmware, which strictly limits their use. We address this issue by remotely changing the behavior of CRFIDs by switching their firmware during runtime through commercial RFID reader, without any modification to either CRFID tags or EPC protocol. We present the design, implementation, and evaluation of FirmSwitch-a wireless scheme that equips CRFIDs with the capability of switching amongst pre-installed firmwares during runtime. To achieve this goal, we wirelessly pass the encoded instructions to CRFID tag through RFID reader, which leverages the CRFID tags to switch among firmwares and execute them for intended cycles. For concept validation, three prototype tags belonging to two CRFID categories are evaluated. The results show that FirmSwitch incurs an overall switching delay of 5–35.7 ms, and a minimal energy overhead of $48.7~n\text{J}$ – $69.3~\mu \text{J}$ . The success rate of 95% is achieved at the interrogation range of a half meter with no retransmission.

Read Bulk Data From Computational RFIDs

Without the need of local energy supply, computational RFID (CRFID) sensors are emerging as important platforms enabling a variety of sensing and computing applications. Nevertheless, the data throughput of CRFIDs is very low. This paper aims at efficiently reading bulk data from CRFIDs using commodity RFID readers. We carry out thorough experiment studies to investigate the root cause of the low data throughput of CRFIDs. The experiment results suggest that the fundamental problem of data transfer stems from the mismatch between the stringent timing requirement of commodity standard and the limited packet handling capability of CRFIDs. We further propose several simple yet effective techniques to allow CRFIDs to meet stringent timing requirement of commodity RFID readers and achieve efficient data transfer. We implement a prototype system based on the WISP CRFIDs and commercial off-the-self RFID readers. We carry out extensive experiments on the prototype systems, which show that the proposed scheme works well with the commodity RFID readers.

Goodput optimization via dynamic frame length and charging time adaptation for backscatter communication

Computational radio frequency identification (CRFID) sensors present a new frontier for pervasive sensing and computing. They exploit ambient light or radio frequency (RF) for energy and use backscatter communication with an RFID reader for data transfer. Unlike conventional RFID tags that only transmit identifiers, CRFID sensors need to transfer potentially large amounts of data to a reader during each contact. Existing EPC Gen2 protocol is inefficient in dealing with a small number of CRFID sensors transferring a large amount of buffered data to the RFID reader and it has no specific design for adaptation to dynamic energy harvesting and channel conditions. In this article, we propose to adopt dynamic frame length and charging time for CRFID backscatter communication, aiming to adapt to the changing energy harvesting and channel conditions and improve the system goodput. First, optimal frame length and charging time that maximizes the goodput are obtained by solving the formulated goodput optimization problem. Then we propose a dynamic frame length and charging time adaptation scheme (DFCA) that increase or decrease the frame length and charging time at runtime based on the goodput measurement. Simulations show that our proposed DFCA scheme outperforms current fixed-frame-length approach and can converge to theoretically optimal under different energy harvesting and channel conditions.

Fully-Coherent Reader With Commodity SDR for Gen2 FM0 and Computational RFID

There has been a continuously growing interest in radio frequency identification (RFID) and more recently, in computational RFID, i.e. battery-less sensors that piggyback sensed information, rather than a constant ID bit stream, utilizing Gen2, the physical layer of commercial RFID systems. This work offers a complete software-defined radio (SDR) reader with 1) coherent detection without rate degradation, by exploiting already present preambles in Gen2; 2) full exploitation of FM0 line coding memory in Gen2 tags; 3) careful handling of symbol synchronization and departure of commercial tags from nominal bit duration; and 4) implementation and testing of Gen2 in a commodity SDR, utilizing a single transceiver card. Continuing recent work, this contribution offers an updated prototyping tool that could further unlock the potential of computational RFID and relevant battery-less sensor networks.