Ajay Ogirala

Electromagnetic Interference of Cardiac Rhythmic Monitoring Devices to Radio Frequency Identification: Analytical Analysis and Mitigation Methodology

Increasing density of wireless communication and development of radio frequency identification (RFID) technology in particular have increased the susceptibility of patients equipped with cardiac rhythmic monitoring devices (CRMD) to environmental electro magnetic interference (EMI). Several organizations reported observing CRMD EMI from different sources. This paper focuses on mathematically analyzing the energy as perceived by the implanted device, i.e., voltage. Radio frequency (RF) energy transmitted by RFID interrogators is considered as an example. A simplified front-end equivalent circuit of a CRMD sensing circuitry is proposed for the analysis following extensive black-box testing of several commercial pacemakers and implantable defibrillators. After careful understanding of the mechanics of the CRMD signal processing in identifying the QRS complex of the heart-beat, a mitigation technique is proposed. The mitigation methodology introduced in this paper is logical in approach, simple to implement and is therefore applicable to all wireless communication protocols.

Interoperability Test Methodology for ISO 18000-7 Active RFID

Standards are developed by highly reputed organizations with a genuine intention that the document acts as a reference requirement and specification record for all manufacturers, and in this process the consumer is presented with a list of conforming products that are all interoperable. Active RFID tags and readers are designed with commercial intent by different manufacturers according to the ISO 18000-7 standard. Through intensive research and tests, it has come to our attention that it is possible to design two active RFID systems that in their entirety conform to the ISO 18000-7 standard and yet be not interoperable with each other. From this statement it can be inferred that conformance is not the sufficient condition for interoperability as is popularly believed, but only the necessary or minimum condition to satisfy interoperability. Therefore apart from preliminary conformance testing, it becomes absolutely essential to include additional and supplemental interoperability tests into the verification process of the production cycle. This research primarily establishes the requirement for interoperability testing giving instances where the standard fails to insure interoperable products. The traditional method to test interoperability currently in practice are investigated and their limitations are exposed. Further this research paper introduces an innovative and ingenious methodology to test active RFID systems for interoperability at the physical layer.

Automated Test System for ISO 18000-7 - Active RFID

When testing a system for compliance to a standard or interoperability with other systems compliant with a standard, the quality and repeatability of the testing methods is critical. This is especially true when the results are used to make a purchasing decision. The ideal test procedure will expose every device that is tested to the exact same stimuli, record the same measurements and evaluate those measurements using the same method. To this end the University of Pittsburgh RFID Center of Excellence has developed an automated test suite for testing compliance to and interoperability under ISO 18000-7, a leading active RFID standard. This automated system provides consistent input stimuli to all device and ensures that all results are calculated using the same method.

The impact of the internet of Things on implanted medical devices including pacemakers, and ICDs

The Internet of Things describes multiple distributed systems where all (or most) everyday items include embedded systems in order to connect to the internet. This paradigm has the potential to revolutionize global industry and daily life. Healthcare is once such industry where the Internet of Things may provide great advantages to patients, care givers, and medical institutions. As the number of radio frequency emitters increases under this new paradigm public health and safety must also be taken into account. This paper explores the electromagnetic interference on implantable cardiac rhythm management devices caused by RFID interrogators. A standard electromagnetic compatibility test framework is proposed in order to diagnose the possibility of interference. Also, a mitigation method is proposed and tested. It is shown that the proposed method can reduce the incidence of clinically significant interference by nearly 60%.

An alternative approach of operating a passive RFID device embedded on metallic implants

This paper presents a method of using volume conduction for communication with implanted passive RFID devices. Generating mainly electric field through human tissue, this method can reduce the interference with metallic implants when RFID devices are attached to the implants. Exterior and interior electrodes are designed for efficient energy and signal transmission. Experiments with a saline box are conducted to study the signal attenuation through biological tissue and the feasibility of using volume conduction for RFID devices close to in vivo metallic materials.

Design and implementation of a volume conduction based RFID system for smart implants

As the population ages, knee and hip replacement surgeries are more and more popular, and embedding an RFID (radio frequency identification) tag on these implants for identification becomes an important issue. Traditional operation of an RFID tag by wireless means will not work on the implantable knees or hips which are made of metal because of the interference caused by metallic objects degrading the field strength near the RFID tag. This paper proposes a method of operating an RFID tag using volume conduction while avoiding the RF interference in a metallic environment. To increase the efficiency of power transmission, electrodes in this paper are designed and optimized for a real knee implant. Experiments using saline have been conducted and the results have shown that volume conduction has a better performance than wireless methods in that signal attenuation is far less in metallic environments. Finally, the experiment on reading an implanted RFID tag through pig skin shows that volume conduction is an effective method to operate an RFID tag embedded on a metallic implant.

Anti-collision policy for RFID systems: fast predict tags in field algorithm

Passive radio frequency identification (RFID) technology is developed and designed to identify many items that are ‘tagged’ within range as quickly as possible. To explain the identification process briefly, the interrogator issues a command that it is ready to listen and allots T time slots for tags to respond in. The tags that received the command pick a time slot between 0 to T –1 and respond in that time slot. Considering this one frame of communication; the entire identification process usually requires multiple frames to complete identifying all tags in field. Assuming a fairly random distribution of the time slots selected by all the tags in the field ( N ), the value of T should be ideally equal to N to complete identification of all N tags in minimum time while minimising idle and collision slots and maximising single reply slots. Establishing a value of T not knowing N is a challenge. The research documented in this article describes the conception of a new fast predict tags in field algorithm (FPTFA), the hardware complexity and processor overhead involved in its implementation and compares it with popular anti-collision algorithms that are in practice.

Impact of ISO 18000 Series RF Signals on CRMDS: A Unified Approach

Abstract Radio Frequency Identification technology in recent times is finding several application in the health care industry. With the increase in integration of RFID in daily hospital routines, there is a growing concern about its impact on infirmary equipment and implantable devices. Several organizations have published results on this issue developing individual test procedures but few have tried to generalize the testing procedures. This article is a sincere attempt to understand the science that is unexplored and unreasoned behind the raw results provided; to unify the data sources and present a direction for future research in this branch of engineering. RF sources conforming to ISO 18000 series and impact on Cardiac Rhythmic Medical Devices are presented as an embodiment to summarize the results of testing completed at the RFID Center of Excellence, University of Pittsburgh. The discussion and results presented in this article can be interpolated and extrapolated to the RF communication and Active Implantable Medical Devices.

In Vitro Test Modelling for Electromagnetic Compatibility Evaluation between CRMDS and RFID Systems

Abstract Radio frequency identification (RFID) technology has enjoyed substantial market growth in the past few years, gaining footholds in a wide array of consumer, industrial, and medical applications. Also, over the past few decades the number of patients requiring cardiac rhythm management devices (CRMDs), such as implantable cardiac pacemakers and implantable cardioverter defibrillators, has been steadily increasing due to advances in pacing technology as well as the aging populace of many countries around the world. The prevalence of these trends underscores the importance of proper electromagnetic compatibility (EMC) testing between RFID and CRMDs, in order to ensure a safe environment for the CRMD implanted patient. Though there are several results claiming the negative impact of RFID on CRMDs, there are no definitive test procedures for experimentation. This article proposes a comprehensive testing model in order to assess the electromagnetic compatibility of CRMDs when exposed to radio frequency (RF) signals at various RFID frequencies. While building upon previous, ad hoc approaches to EMC testing of CRMDs, this framework attempts to expand these techniques to include testing to determine the fundamental, interfering characteristics of RF signals. It is the opinion of the authors that current publications claiming that RFID interferes with CRMD operation cannot be validated until the test procedures executed are transparently disclosed and approved.

Serial Data Driven Cyclic Redundancy Check Generator for Low Power RFID Applications

Cyclic Redundancy Checks (CRCs) are commonly used for their effective error-detecting capabilities in various wireless transceivers, digital networks, data storage devices, embedded designs, RFID systems, etc. The conventional clock-driven and combinational logic based CRC hardware implementations are known to consume considerable power especially those used in wireless passive devices. This paper proposes a low-power implementation of a novel serial data driven CRC for passive RFID tags. This CRC design is not explicitly clocked, but driven by the incoming encoded data as opposed to clock recovery. The associated CRC computations are done in parallel to the data decoding procedure unlike the traditional shift register implementations. Simulation results of the data driven CRC-16 design show significant reduction in power consumption and the area occupied as compared to the typical CRC-16 implementations used in RFID applications.