Georg Saxl

In recent years, RF identification (RFID) technology in the ultrahigh-frequency (UHF) range has become increasingly important in many applications, especially in the context of both the Internet of Things (IoT) and Industry 4.0. RFID is no longer simply a matter of identification; today, it is mainly concerned with recording data from the surrounding environment. As a result, researchers are working on the integration of sensors (or even small actuators) in passive RFID transponders (tags) for a variety of different applications and also on the localization and tracking of RFID tags attached to various objects and machinery. Another key aspect in UHF RFID technologies is security, as the data transmitted may be confidential and should not be shared with third parties. For the fast verification of novel algorithms in localization and novel protocols for security, wireless testbeds allow swift verification of these designs under real-world or real-time conditions [1]. Wireless testbeds are widely used in research and require scalability, modularity, and extendibility of the hardware and software. These needs can be achieved by using software-defined radios (SDRs). In the case of UHF RFID, SDR-based RFID readers have been developed and used as wireless testbeds for enhancements in UHF RFID systems.

Ultra high frequency radio frequency identification (UHF RFID) is seen as a key technology for future sensor and actuator devices in the Internet of Things. Therefore, improvements of read range and reliability of this technology is highly demanded. In this paper a novel reader is proposed to work on two frequencies simultaneously, intended to improve multipath fading behaviour and gain immunity to narrowband disturbance. The current legal situation is reviewed for the proposed device in the European Union and it is compared to existing multifrequency systems. The developed system is based on a software defined radio platform from National Instruments. In the measurement setup a commercially available transponder chip has been connected to the custom built reader which transmits a “Query” command on two frequencies -868 and 915. The results show, that the transponder replies on both channels. Further measurements in a real world multipath environment show the different fading behaviour of the chosen frequencies. Furthermore, it is demonstrated how dead zones can be avoided by using two different frequencies. Additionally, within the reader software a bitwise error correction for FM0 encoded data is implemented, which employs the redundant information on the two carriers. We are able show that a multicarrier system can be implemented with commercially available tags without restrictions in the European Union. Such a system could be used to improve successful read rates in harsh environments or increase reliability in critical applications. When upgrading from an existing UHF RFID system, only the interrogator needs to be exchanged by a new device working on multiple frequencies.

Ultra high frequency radio frequency identification (UHF RFID) is becoming a key technology in the Internet of Things. It allows the implementation of batteryless and wireless nodes, including sensors and actuators. Due to its possible transmission range of >10 m and potential to carry critical information, security is a highly important topic. For this reason, the International Organization for Standardization has published several crypto suites for UHF RFID within the ISO-29167 standard in 2014. Recently, research has focused on implementing those encryption features on the transponder side. However, currently no crypto enabled UHF RFID readers are available. In order to cope with the rapid development in this field, ‘open’ and flexible readers based on software defined radios are needed. They make it possible to quickly adapt the protocol and to test new functionalities such as encryption. This paper deals with the first implementation of the ISO 29167-19 standardized RAMON decryption on a software defined radio. The programming of this hardware is done in LabVIEW which allows for controlling the built-in transceiver modules. However, first measurements show that the decryption takes 51 s. This is because LabVIEW is not suitable for handling very large numbers like they are utilized in cryptography. Because such a long processing time is not feasible in experiments nor in a real-life scenarios, this method is not suitable for a prototyping platform. Thus, a different approach is chosen to optimize the decryption processing time. LabVIEW still provides the framework for handling the protocol and controlling the transceivers, but the decryption is performed in a Java application. In that way, the entire decryption process takes only about 2.2 ms, which is 23,318 times faster than the implementation in LabVIEW. Thus, this new approach meets the necessary timing requirements and is suitable for realistic application scenarios. The shown method allows development and testing of new functionalities in UHF RFID systems but may also be employed in any application that require long processing times in LabVIEW. Furthermore, the implementation of decryption features is the first necessary step towards a fully compliant, crypto enabled interrogator for UHF RFID, featuring a high adaptability.

The Internet of Things comprises the network of billions of devices. The need for wireless systems is leading to bandwidth becoming an extremely limited resource. For this reason, the spectral efficiency of radio systems is playing an increasingly important role. While active radios already use pulse shaping techniques to improve the efficiency, passive systems still make a little use of them. The reason for this is that the energy available for shaping is very low and would, therefore, massively influence the range. This paper presents a concept that enables pulse shaping especially for passive ”ultra-high-frequency radio frequency identification” transponders without significantly reducing the range at the same time. For this purpose, all approaches were designed to meet the requirements for chip integration. A 41-stage discrete Gaussian pulse was used which can be generated by a field-effect transistor. The transistor is controlled by a simple voltage divider which is operated by the digital part of the transponder. The total power consumption of the concept with simultaneously acceptable space requirement is estimated with 200 nW. The results of both the simulation and the measurements show that even a small number of steps improve the spectral efficiency. In adjacent channels, less energy is radiated compared with a rectangular pulse. According to the measurements, the adjacent channel power ratio in the directly adjacent channel for the discrete Gaussian is 7.5 dBc lower than for the rectangular shape. This effect is more pronounced with an increasing distance and is already 32 dBc for the fourth adjacent channel.

This paper deals with the development of an ultra-low-power local oscillator for use in passive UHF RFID tags. The oscillator is intended to provide the clock signal for digital processing and serves as the basis for generating the backscatter link frequency (BLF). The BLF must be adjustable depending on the reader query and be within specified tolerances to comply with the EPCglobal Gen2v2 standard. Besides the main requirement of the oscillator, an extremely low power consumption is essential. To meet this challenge, the design uses a current-starved, three-stage ring oscillator. Since the circuit is to be integrated in 55 nm technology from Globalfoundries, this topology offers the advantage of not requiring passive components that would be difficult to integrate. To provide the bias voltages for the current-starving, a reference circuit is utilized. The results of the simulations show a low power consumption of about 381nW at an oscillation frequency of 5.82 MHz.

Besides identifying objects ultra high frequency radio frequency identification (UHF RFID) can be used to control actuators like a simple transistor. The big problem of such scenarios is the minimal available energy for the switching operation and leads to a massive influence of the reading distance on the actuation time. The presented measurements, calculations and simulations show that it is generally feasible to control a transistor using a UHF RFID tag. The measured actuation time ranges from 339 μs at 2.5 m up to 0.222 s at 10 m. Based on this technology applications like a zero watt standby module can be implemented.

This paper deals with the development of a random number generator for cryptographic key generation. The proposed implementation is designed for the use in a passive UHF RFID Tag and is based on a 55 nm semiconductor process. Since passive RFID Tags are not equipped with an autonomous power supply, the circuit is designed for minimal power consumption. However, the design should still generate a sufficient randomness. When generating keys for cryptographic applications, it must be ensured that there is no way of predicting them. Therefore, a true random number generator (TRNG) is used. The proposed TRNG is based on several ring oscillators, which are subject to random phase noise (jitter). By comparing the positions of the phases, the extraction of the randomness can be performed. Additionally, a post-processing unit is deployed, to increase the randomness of the circuit. To evaluate the randomness of the bit sequences generated by simulation, the NIST Statistical Test Suite is used. The results show a minimal dependence on the randomness of the thermal effects within the specified range. Furthermore, they suggest a likely sufficient randomness of all tested bit sequences. According to simulations, the maximum power consumption of the entire circuit is 270 nW at 27 °C.