What about Near Field Communication technology? An ... - RFID Journal

What about Near Field Communication technology? An overview with possible future telemedicine applications.

Enrico M. Staderini Norwegian Centre for Telemedicine, Tromsø, Norway Correspondence: Nasjonalt Senter for Telemedisin, Postboks 35, N-9038 Tromsø, Norway (Fax: +47 7775 4098; Email: [email protected])

Summary Near Field Communication (NFC), jointly developed by giant players in the consumer electronics arena such as Philips and Sony, is the last in a series of ever evolving wireless networking technologies for data transfer. The impacts and the potential uses of this technology (ECMA-340 standard) in the medical device field, and telemedicine as well, are analyzed and compared with existing wireless technologies for data and signal transfer. The intrinsically very short range of NFC is all but a limiting factor indeed. Having the communicating devices to be placed intentionally close to communicate, an higher level of security is obtained: a must for medical privacy sensible data exchange. Furthermore, NFC data rate can go as fast as a few hundreds of thousands of bits per second so to provide a channel wide enough for real time biomedical signal transmission. The extremely low power required for NFC operation, which reaches zero on the target in the passive communication mode, is an extra bonus in modern battery operated, and very much battery life concerned, medical devices. It seems that NFC technology may enable new products having new functionalities and new man-machine interfaces in the future telemedicine systems to come.

Introduction Wireless technology started being appreciated by health care providers and medical devices manufacturers in the late ‘90s, just when mobile phone communications began skyrocketing. At that time, as well as today, competing existing standards, or announced standards to come, were one of the issues relenting the process of adopting or integrating wireless technology [1]. Over the time wireless medical devices evolved from the area of telemetry where the main issue was that of overcoming a distance which was simply not possible to cover with a cable, to that of guaranteeing mobility over short distances. In parallel, the needs for going wireless changed from the transmission of a signal having a clinical information in it (or one to one conventional telemetry), to the sharing of multimedia content, as text, images, and signals in a many to many architecture. As of today, systems are developed for vital signs transmission from wearable sensors [2], or from space flight simulated conditions [3], or from intelligent sensors avoiding large number of wired connections in medical laboratories [4]. Even infant incubators were connected into a wireless network for monitoring [5]. Another very interesting application, where wireless mode has its mandatory application, is capsule endoscopy using a miniature video camera that can be just swallowed to send live images from the gastrointestinal tract [6], [7]. More recently wireless technology in the health care revamped with applications in nursing [8], or in managing connectivity in medicine [9], or in hospital administration [10], [11], or for the global enhancement of patient care [12]. Present research activity, pushed forward by the academia, by the medical device industry and by the medical services providers as well, is focused on home health care services without direct health personnel involved in, that calls for e-home care. Homes are commonly part of a large network infrastructure like that composed of wired telephony, cable television or broadband connectivity. In this last case wireless technology is required to cover just the “last meter” from a home base station connected in the network to the biomedical sensor or device worn by the citizen free of moving into his/her home. Wireless technology drastically enabled and boosted e-home care applications and even more is expected in the future. The combining of personal computers, the internet and many biomedical digital transducers made feasible products and services never imagined before. But wireless technology geared up the applications more, giving the subject the freedom of movement and a normal access to everyday life while being monitored. Applications included diabetes screening [13], home cardiorespiratory telemonitoring [14], electrocardiography (ECG) monitoring [15], artificial ventilator monitoring in continuous positive airway pressure treatment (or CPAP) [16] and many others. The technologies span from WAP (Wireless Application Protocol) over GSM-GPRS mobile telephony networks, to Bluetooth, Wireless LAN, and the internet [17], [18]. With the advent of reliable and affordable telecommunication infrastructures [19] the wireless e-health concept recently has come to manage large healthcare information systems (HIS) in the hospitals [20] and long term care environments as well [21]. Now, in this already crowded wireless e-health arena, the last actor on the scene is the Near Field Communication technology having original performances and characteristics and with the possibilities to play strong and fast a role not just in a niche. As a matter of fact it may become the salt of many smart systems for they to be operated effortlessly in the medical field. It is therefore worthwhile for the reader to get acquainted with this not so strange, even somewhat exotic, new wireless gadget. The paper is organized in five parts. In the first NFC technology is explained in a very simple mean for the non-technical reader, then a more detailed presentation is done based on the 2

documents of the ECMA standard. A comparison of NFC with existing wireless technologies is made before presenting all the possible applications in medicine, telecare and telehealth. Conclusion are taken considering possible technical and economical feasibility of NFC technology in the future. NFC explained to the people My grandmother was almost an addicted of television programs. I remember her, sitting on the sofa, watching to television for hours (or better just listening to, while hand-knitting wool items for her many nephews). She was all but a brainless or superficial spectator! Although quite aged, she was always commenting programs and often expressing clear and motivated criticisms. One day a program should have been particularly silly and she asked me to know if the local TV broadcasting company might “technically” notice the general disagreement of the people which may organize a protest consisting in suddenly switching off all the receiving TV sets in their area. Apart from the ingenuity of the action of protest, I was amused (and today I am) at the fact that my granny (well before interactive digital TV be invented) was looking for a way for sending information back to the TV broadcasting company (disagreement in this case) using just a receiver! While I was firmly replying “no” to her, I felt that may be I should say “yes”, if only the antennas should be close enough for the receiving one to disturb the near field (electromagnetic field) irradiated by the transmitting one. Energy in the far field will never interact any more with the transmitting antenna so the transmitter has no possibility to “know” whatever you make of that energy (unless you reflect it or backscatter), but, in the near field (defined as the region within one wavelength of an antenna, where the electric and magnetic fields are not related to each other solely by the characteristic impedance of free space [22], [23]) a field disturbance might be detected by the transmitter due to the mutual coupling with the receiver antenna. As a matter of fact, far field signal degradation with distance goes down as the inverse of distance squared while near field signal degradation follows a much harder function going down as the inverse of the distance to the third power. So the antennas must be in close proximity. After a couple of decades, this concept has been exploited to the RF-ID (RadioFrequency ID tags) technology and today to a full featured, protocol based, two way communication system and protocol: the NFC as in Figure 1. Near field communication technology is directly related to, and derived from, RF-ID which is nothing but an out of the lab practical application of the historical “grid dip meter”: a laboratory instrument used by radio amateurs and professional technicians since the beginning of wireless technology in the twenties of last century. This device was used to establish the exact frequency alignment of radio receivers’ and transmitters’ coils and actually “grid” stands for the grid of a triode vacuum tube oscillator which was employed at the time into the instrument. RF-ID systems have their main application in anti-theft devices used in shops, also known as EAS an acronym for electronic article surveillance systems. The operating principle is basically simple. A radiofrequency generator irradiates a RF field in a given area where an RF-ID tag may be located (typically at the shop’s exit). The RF-ID tag incorporates a resonant circuit which dissipates energy from the irradiated field induced on it. As a result of this effect the current into the irradiating coil of the generator decreases slightly although enough to detect the presence of the disturbing RF-ID coil. More practically the radiofrequency emitter is sending a frequency modulated signal around the RF-ID tag resonating frequency. If an RFID tag is in the area under surveillance then a “dip” in the voltage on the irradiating coil will be detected at the exact time the correct resonating frequency is emitted. If no dip is found, 3

no RF-ID tag is detected in the area. This kind of systems are also know as “1-bit transponders” as they, passive receivers without any power supply, can only communicate back to the emitter their “presence” or not in the area [24]. By the way doing, exactly, what my granny wanted to. For these systems to work, it is absolutely necessary the two coils be in close proximity so an electromagnetic coupling could take place between the two, nevertheless RF-ID tag can be realized in different ways and with slightly different working principles. While maintaining the “passive receiver feature” it is also possible to establish a two way communication channel. The receiver might use a small fraction of the electromagnetic field energy to power its own circuits and modulates its own resonance both in frequency and/or in amplitude so to send back not only information pertaining to its presence in the area, but other useful pay load information too [25]. This kind of transmission is often called, quite self-explanatory, as “load modulation”. Load modulation is the underlying physical principle of NFC. From the description depicted so far a few characteristics emerge: it is a very-close-proximity-based, an extra-low-power and a single-chip wireless technology. May be this technology could be compared to the mouse device in the everyday computer use. As the mouse enabled people to chose a virtual item on the computer screen by putting the cursor on it (click-it-to-select-it concept), so NFC will enable people to select an information content sender or receiver just by getting a NFC enabled device close to it, should it be a mobile phone, an MP3 player, a medical device such as a vital signs sensor or the like (approach-it-to-communicate-with concept). Therefore NFC is potentially as intuitive in transferring information as a computer mouse is in selecting an item on the screen as in Figure 1. NFC facts and figures The ECMA-340 Near Field Communication protocol technically defines the means and procedures by which two parties in the communication can exchange information in a peer-topeer link. The frequency used is in the unregulated band of 13.56 MHz so no restrictions are present nor licensing is required although each country may impose limitations to the maximum power emitted and the maximum out of band power from spurious emissions. In general any limitation is not about to impede a reliable communication over a 0 to 50 cm range. As a single frequency is allowed for use, a time division multiplexing must be employed thus asking for half-duplex operation as two devices can never transmit at the same time. As a consequence proper collision avoidance techniques are defined and adopted. The protocol differentiates an Initiator and a Target between the two wireless linked devices. The Initiator is responsible for initiating and controlling the exchange of data while the Target just answers the request from the Initiator. Furthermore the protocol defines two modes of operation: a passive mode and an active mode. In the first one only the Initiator is generating a RF electromagnetic field while in the active mode both the Initiator and the Target generate their own electromagnetic fields. In the passive mode of operation the Initiator sends information by modulating its own emitted electromagnetic field and the Target sends information by load modulating the field emitted by the Initiator (as a normal RF-ID tag works). In the active mode both devices transmit information by modulating their own emitted electromagnetic fields. Minimum and maximum unmodulated RF field are respectively set at Hmin=1.5 A/m and Hmax=7,5 A/m while the protocol prescribes the communication should start reliably as soon as a minimum field is detected by each of the devices surpassing a threshold of Hthreshold=0.1875 A/m. Bit duration and 4

hence data rate is a function of RF frequency and it is calculated with the for128 mula: bit duration = where f c = 13.56 MHz and D is a power of 2 from 1 to 64. ThereD ! fc fore data rates can be obtained from 106 kbps up to (theoretically) 6.78 Mbps. Practical implementations reach data rates as high as 424 kbps with a 847 kbps speed to be delivered in the near future. All data rates are allowed for the active mode of communication while only 106, 212 and 424 kbps are allowed for passive mode too. Modulations and bit encoding schemes generally depend on speed and thus the Initiator sets the rules of the game when starting a transaction. Transmission is terminated under a command or when the devices go out of range (i.e. Hreceived < Hthreshold). Most used modulation type is ASK (Amplitude Shift Keying) with 10% deepness and bit encoding is the common Manchester coding. The protocol is just a transport protocol defining low level communication, therefore responsibility for any higher level network protocol or layer security procedures is given to each particular implementation. Security threats of NFC communication are mainly those already present into RF-ID business and are an open problem yet. They can be summarized just considering the need to establish a trusted channel of communication. This means the NFC devices should trust each other. Mutual authentication provides a measure of trust but session hijacking and replay attacks are also concerns [26]. To this end, having proved vulnerability by relay attacks of RF-ID security [27], common public key cryptography systems are to be implemented into NFC systems. Technical characteristics of NFC communications can be summarized in a few very unique points [28], [29], [30], [31]. • It is a very short range wireless link. It might be considered a definitive disadvantage to have a range in the order of tens of centimetres. Instead it is a unique feature which gives an inherent degree of security to the protocol against unintended connections. Furthermore the establishment of a connection just by approaching the two devices simplifies as it is not relying on particular network identification procedures. • It supports a passive mode of communication. When energy saving is a strategic need, having only one of the two devices to provide energy for communication, is a definite advantage. Although the device which is not irradiating energy has to be anyway powered for its own working, nevertheless a consistent increase in battery life-time should be expected on this side. • It can be used in connection with other protocols. This aspect is quite important considering the effort often required to establish a connection between two devices using links like Bluetooth or Wireless LAN. An NFC link could establish the exchange of parameters and identification parameters for subsequent longer range communication. • It is compatible with already widespread smart card protocols like FeliCaTM [32] and MifareTM [33] so that an NFC device can be used instead of a smart card and a smart card can be seen by an NFC enabled device as well. • Security/privacy issues are directly addressed and solved by the fact that extremely low range of operation is an intrinsic security level, at least because any attack device need to be very close and thus at risk to be easily identified. Further security procedures and protocols must be added as for other communication systems i.e. internet for implementing a secure channel. NFC compared with other wireless technologies

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Perhaps the reader will be much more interested in considering NFC technology through comparisons with other, more or less well known, wireless technologies. Data rate and range are the main parameters a communication technology exhibits in a technical comparison, although other, more mundane, characteristics like power consumption and cost are also of importance. Six technologies were considered in the comparison: Bluetooth, 3G, ZigBee, UWB, the 802.11 family and NFC. Many of these systems are used, or their use has been considered/evaluated, in medical applications. Bluetooth and 802.11 (802.11b also known as WiFi or Wireless LAN) wireless communication in telemedicine has been tested and reviewed in [17] especially to the end of assessing the possible coexistence of the two standard into a health care environment. 3G (also known as UMTS, although not equivalent) mobile telephony standard has been proposed and used in medical applications considering the possibility to make video stream communication [34], [35], [36]. Bluetooth applications in medicine are becoming almost countless due to this system is approaching maturity along with a widespread use into mobile phone and palmtop computers. Bluetooth enabled systems were proposed for sensor to mobile phone connection [37], [38], [39], [41], [42], while concerns regarding interference with existing systems were evaluated too [40], [43]. ZigBee (WBAN wireless body area network) communication systems were also employed in computer assisted physical rehabilitation [44], and UWB systems were developed as communication devices and as sensor for vital parameters monitoring as well [45]. It is worthwhile considering why a brand new communication technology should be introduced into the medical devices arena and what improvements and drawbacks should be expected from. A Power vs. DataRate bubble plot is depicted in Figure 2. In the last figure as well as in the followings, the areas of bubbles should encompass the most part of the implementations of each given technology. WiFi family (IEEE 802.11 standards) are quite power expensive although they provide the best data rate along with UWB systems (which received a written standard from ECMA only recently as ECMA-368 and ECMA-369, after apparent stalling of IEEE 802.15.3a group). NFC’s data rate is comparable to 3G and Bluetooth while power consumption touches zero. It has been already said that NFC is, much more than UWB, a very short range communication system. As a matter of fact NFC’s range is in the order of 10 to 50 centimeters. No surprise in a EnergyEfficiency vs. Range bubble plot as that shown in Figure 3, NFC is topping on the left side while longer distance, power hungry systems are bottoming on the right. As NFC technology can be an intrinsically zero power communication system, one can surmise that it can be implemented with a few passive components and some active ones (which may even be powered by the RF field itself). This may lead to a low cost of production and this is exactly what happens as depicted in Figure 4: NFC appears to be even cheaper than UWB. From the comparisons in the Figures 2 to 4 it results that NFC has the highest data rate to power ratio with an acceptable data rate and a nominal power consumption down to zero. On the other part NFC’s range is extremely short and this hampers expectations of those who are in search of the ideal longest distance, lowest power, highest data rate communication channel. As a matter of fact, NFC’s short range gives NFC the right place where it can be used profitably. NFC is not just a communications link born to reduce wire connections, as Bluetooth was. Sony, Philips and other companies are implementing NFC applications to the end of producing what it is called “electronic wallet” a sort of credit card which can be used directly by the owner just approaching his NFC enabled mobile phone or palmtop computer to a suitable device so that a secure payment is possible. E-ticketing is another obvious applica6

tion as well. A “communication on demand” system, as in Figure 1, is now available for the people to use, play and brainstorming on. So let’s see what can be the potential applications in connection with medical devices and telemedicine. NFC applications in biomedicine and telemedicine A NFC communication network to work from/to/in the human body will consider two or more NFC enabled devices which will be placed in close distance between each other. It is clear that one or more of those devices will be connected by wire or other non-NFC wireless communication to an appropriate network like Internet or the like. In the following we will overview many of the possible future applications in telemedicine and telecare where NFC enabled systems might be a new driving force to succeed. The field of body area networks and wearable computing. Wearable computers can be differentiated from portable ones as they can be operated continuously and hands-free. Wearable computers differ in input-output devices as well, as they should be operated using speech and with head-mount or eyeglass-based display [48]. To cope with continuous operation requirement, wearable computers need to be very much power savers and very low power is budgeted to establish a communication link. Useful communication range is as much as tens of centimeters for a reliable body area network to operate and communication by approaching is as intuitive as possible for a human being. This is why NFC is perfectly suited in the field of body area networking and wearable computing. The field of wearable sensors. Vital signs monitors are considered today for remotely checking health and well being of people at home who suffer from some sort of chronic and possibly life threatening disease. Most interesting wearable sensors include activity detectors, heart rate monitors, breath rate monitors, blood pressure and pulse oximeters. Using NFC in a body area network the various sensors can be simply be battery operated and put in different places on the body without attention on an inexistent cabling. The field of implanted medical sensors. Implanted sensors are where bioengineers’ skills are driven to the top. Miniaturization, material biocompatibility and energy budget are the three main issues of the game. NFC systems are very good for complying with miniaturization issues as radiofrequency parts are reduced to a minimum along with zero power on the RF link. Probably the main advantage from NFC technology might be achieved by the so called wireless capsule endoscopy: a technique by which real high quality images of the gastrointestinal tract are sent by a miniaturized capsule, containing a microcamera, during its voyage after being swallowed by the subject. At present a conventional, although miniaturized, transmitting method is used while the adoption of NFC might increase the number of images transmitted with the same energy budget or decrease the size of the pill. Moreover, the receiver outside the patient might be realized in a less cumbersome way, without the many antennas and wires around. Implantable physiological monitors will also benefit from NFC technology. They are mostly used for research purposes to monitor temperature or other physiological parameters. Often they are used on model animals and in this case miniaturization and low power are a must. 7

The field of implanted stimulators. One kind of the most promising implanted stimulators are those performing deep brain stimulation (DBS). This is a surgical procedure used to treat a variety of disabling neurological symptoms – most commonly the debilitating symptoms of Parkinson’s disease (PD), such as tremor, rigidity, stiffness, slowed movement, and walking problems. Although at present, the procedure is used only for patients whose symptoms cannot be adequately controlled with medications, research is being conducted to assess it clinically and methodologically. In the future implanted neurostimulator for treating PD might be controlled externally using NFC technology. The same might be considered for controlling and exchanging data with cardiac pacemakers and implantable cardioverter/defibrillator (ICD). Other kind of stimulators of current use should have to employ feasibility of NFC. Bladder control devices are used for people suffering from urine incontinence. They are also used as rehabilitation system in biofeedback based training exercises. Cochlea implants used to treat deep deafness might employ NFC for controlling and receiving signal from external microphone. The field of implanted actuators. Finally, in the implanted actuators group, insulin pumps should be cited. Although the problem of developing an artificial pancreas is now approached using nanotechnologies or genetic engineering techniques, insulin pumps to be refilled by external injection or, in general, drug pumps employing NFC systems should be controlled and operated at a distance without cables or direct contact. What about safety? As long as no literature is present regarding safety or potential health risks deriving from RFID or NFC emissions, one is only forced to discuss RF level emitted by NFC systems and comparing them with the standards. According to the US Federal Communication Commission a limit of 0.16 A/m is tolerated for people non professionally exposed to fields in the NFC frequency of 13.56 MHz. European standard, as of 1999/519/CE recommendation, sets a maximum to 0.073 A/m in the same conditions. Various European countries have set even lower thresholds (0.05 A/m). As already stated before a minimum magnetic field value of 0.1875 A/m is set as threshold for NFC systems to start operate. This means that in close proximity to the human body, as explained so far, NFC systems are exceeding standard thresholds. This fact should not be considered as a definite stop to using NFC. Mobile phones too exceed in the same fashion the standard thresholds. By the way it should be noted that standard levels are generally measured on a six minutes average thus a short burst of data coming from a NFC device should be in compliance with the law even more than widespread mobile phones. What about interference robustness? Near field (radio) communication is less susceptible to eavesdropping and interference than far field communication due to propagation properties of the two: an isotropic radio transmitter propagates energy with a signal strength that decreases with distance squared, whereas near field strength goes down with distance cubed. In addition, the earth is expected to shunt the electric field, further attenuating the signal and making NFC more difficult to intercept. Conclusions

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This paper highlights the potentially substantial impact on medical technology of a new shortrange communication protocol known as Near Field Communication or NFC, which enables electronic devices to automatically exchange information simply by bringing them close together. NFC has been pushed forward by Sony and Philips to optimize user-friendliness of consumer devices by allowing users to communicate by approaching devices each other in an intuitive way, similar to people shaking hands. It is quite difficult at present to consider the cost of this technology in respect to existing wireless solutions. Based on aspects like chip number, chip complexity, firmware requirements, antenna manufacturing, assembling, power supply, etc. it seems possible to surmise the cost of incorporating this technology in new devices will be almost virtual. Nevertheless existing technologies have already entered the stage of maturity in which costs slow down faster and reliability is at the top so cost comparison is not as easy as it may appear. Anyway it may be expected this technology will play a significant role into the medical devices arena of the future. References 1 2 3 4 5 6 7 8 9 10 11 12 13

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Fig. 1: Comparing intuitiveness of use between computer mouse and NFC communication Image used with permission from ViVOtech Inc. (http://www.vivotech.com/)

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Fig. 2: Power consumption versus data rate for most common wireless technologies (modified and adapted from [46])

Fig. 3: Useful range versus energy efficiency for most common wireless technologies (modified and adapted from [46])

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Fig. 4: Cost per unit versus data rate for most common wireless technologies (modified and adapted from [46])

Fig. 5: NFC body area network linked using NFC a) or Bluetooth b) to an external network

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Fig. 6: NFC body area network connected via Bluetooth to broadband network

Fig. 7: When NFC is used to link to an external network, the NFC transceiver is strategically placed in a site the user approaches seamlessly, as a door jamb in this case

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