Near Field Communication

This page has been created because a friend sent me a Christmas message in the form of a personalised NFC (near field communication) tag in a card. At the time I could not read it, but I went out and bought a NFC reader, the model ACR122U-A9 from Advanced Card Systems. 

What is Near Field Communication (NFC)?

Start at the beginning with “The complete guide to Near Field Communication (NFC), how it works, what it does and much more”. NFC is a short-range radio technology based upon RFID (Radio Frequency Identification) standards. As a contactless ‘proximity card it uses electromagnetic induction between two loop antennas to exchange information in the radio frequency ISM (Industrial, Scientific and Medical) band at 13.56 MHz.

There are in fact several ISM bands. They were fixed internationally in 1947 for scientific equipment, experiments, etc. so that they would not interfering with other radio frequency devices (e.g. radio communication). For example, consumer microwave ovens operate in the ISM band of 2.45 GHz, because it is one of the absorption bands of the water molecule. Toys, wireless security systems, and wireless automatic meter reading systems all operate in the ISM 902-928 MHz band. NFC works in the ISM 13.56 MHz band otherwise reserved for aeronautical safety-of-life services. Given the very, very short operating range of NFC it does not interfere with air traffic control services operating along air routes. 

Originally the 13.56 MHz band was proposed because it was traditionally used for the rapid drying of glued joints in wood and the curing of rubber and plastics. At the time this drying and curing technology was relatively crude, with valves used as oscillators. The ‘oven’ of the machines formed a so-called LC or tank circuit in which the object to be cured became a dielectric which changed during processing. The machine actually introduced some frequency drift so that heat would buildup and fall away over several seconds as the LC circuit came into resonance.

NFC can be configured for both one-way and two-way communication, and can be found in contactless payment systemselectronic ticket smart cards, connection bootstrapping (e.g. establishing a Bluetooth connection), electronic identity documents, keycards, marketing and access tokens and tags, and mobile gaming

Today NFC is already deployed in nearly 100 countries around the world both for contactless payments of low-value transactions and transportation ticketing. Apple PaySamsung Pay and Google Pay all use a NFC antenna and a dedicated chip for storing encrypted payment information (an example of an eSE or embedded Secure Element which stores and protects card/cardholder data from malware attacks). It has been estimated that by 2020 there will be 3.9 billion NFC-enabled handsets worldwide. Mobile payments with NFC are as secure as chip-and-PIN security, and can be blocked in the same way banking cards can be blocked. 

On the other hand there is still much to do to pursued consumers to pay or travel using a mobile NFC device, although this may change if/when mobile wallets become more popular. So far it has been an uphill struggle since even quite sophisticated consumers are still concerned about security, and well over 50% of them don’t see the benefits of NFC-enabled payments or find it just as easy to pay cash or use a credit/debit card. 

Wikipedia mentions that there were earlier trials based upon the same basic idea, but they were proprietary systems that were outpaced by the introduction of barcodes and RFID tags. However, most experts think that the key advantage of NFC today is that it is both an evolution of RFID and is based upon a whole series of standards widely accepted by the industries involved. For example, NFC uses ISO/IEC 18000-3, which is an existing international standard that defines the way passive RFID items identify themselves using an air interface at 13.56 MHz. Other important international standards are ISO/IEC 7816 which defines smart cards, and ISO/IEC 14443 which defines proximity cards used for identification (e.g. as in biometric passports). ISO/IEC 18092 (2013) is the NFC standard for both active and passive communication modes, and it builds upon an earlier standard ISO/IEC 21481 (from 2005).   

How do NFC devices operate?

NFC can work in three different ways. 

The first way always involves an initiator (reader) and a target (tag). The initiator is said to actively generates a radio frequency (RF) field that can transfer power to a passive target. This enables NFC targets to be inexpensive and take on very simple physical forms such as tags, stickers, key fobs, or cards that do not require batteries. These tags can also be embedded into product labels and even into smart posters (for so-called proximity marketing). 

The simplest configuration consists of a basic or passive NFC tag containing an antenna and a microchip, which can be interrogated using a ‘reader’. The ‘reader’ is looking for NFC devices, and will activate any NFC tags that come within a few centimetres of it. The passive NFC tag does not have a power source, so the antenna has two functions, firstly to generate a voltage in the tag (capture energy), and secondly to transmit the tags identity and content (data telemetry, i.e. information). When an electrical conductor (the wire circuit of the antenna) moves in a magnetic field (created by the wire circuit of the antenna in the reader) an electromotive force is created in the tag’s antenna wire. This electromotive force is measured in volts, and acts just like a battery. Now electromagnetic induction is an example of the so-called near-field of an electromagnetic field

In the literature authors allocate considerable space to writing about the so-called near-field and the far-field. These are not really different fields, they simply describe physical areas where the magnetic and electric fields act differently. Far-field just means that the electromagnetic field can be seen (by a detector antenna) as a planar wave. Near field just means that we are too near to the source (emitting antenna) for the electric and magnetic fields to be in phase and of the same amplitude. We have to remember that electromagnetic waves are really a superposition of an electrical and a magnetic wave which co-propagate. So near-field electric field communication is used by RFID’s and Bluetooth and both rely on the conventional transmission of radio frequency signals between two antennas, the transmitter and receiver. The systems use an electric antenna (e.g dipole) which generates and transmits a propagated electromagnetic wave.

NFC is physically different because it is based upon magnetic induction, which relies on coupling of magnetic energy between two non-contacting magnetic antennas (e.g. loops). In NFC there is in fact no radio frequency signal propagation between the antennas but the transmitter and receiver are designed to resonate at the same angular frequency. It is this physical principle that favours a more secure communication over very short distances, and with reduced interference.

It is important to stress the physical differences between both near-field and far-field, as well as the different between electric field (RFID and Bluetooth) and magnetic induction (NFC). In far-field the electric and magnetic fields propagate outward as an electromagnetic wave in which the two fields are perpendicular to each other and to the direction of propagation.   


If we start with the NFC operating frequency of 13.56 MHz, then the so-called radiative near-field region would be up to about 20 m from the antenna, and the so-called reactive near field below about 3.5 m. This also presumes that the half-wave dipole antenna would be about 11 m in length. If on the other hand we constrain the antenna to a loop of the size of a smartphone, then we can determine that the optimum ‘read range’ is about 0.7 times the loop radius (assuming that the reader coil and tag coil are placed in parallel to maximise the magnetic flux passing through the tag coil). We can improve somewhat on this by using a spiral loop antenna (in fact many smartphone antennas are more or less the size of the flat-side of the battery). Now in the reactive near field area the electric and magnetic fields are strongest and can be measured separately, and using a loop antenna the magnetic field is dominant. As such the loop antenna appears as the primary in a transformer because of the large magnetic field it generates. And in the near-field the strengths of the fields vary inversely with the cube of the distance from the antenna (in the far field the received power varies inversely with the square of the distance). We can see that the initiator (‘reader’) is the primary and the target (tag) the secondary of a transformer. The signal picked up by the tag is rectified and filtered into dc, providing power to the tag memory and transmitter. The transmitter sends the code from the memory for identification and further processing.

The physics of near field tells us that near-field signal power for a given antenna is higher than might be expected from the description of a far field, giving a better signal to noise ratio and better link quality. Near field power will drop quickly, so the range of communication is shorter than initially expected, but less prone to interception and therefore more secure. Equally, near-field will interfere less with other radio frequency systems.     


Principles of Inductive Near Field Communications for Internet of Things

By Johnson I. Agbinya

Unlike an active RFID tagpassive RFID don’t have their own source of power and therefore the tag reader is responsible for powering the communication with the tag. Power can be transferred in two different ways. The first one is magnetic induction method and second is electromagnetic wave transfer method by using the EM properties related with the RF antenna i.e. the near field and the far field. The transfer of power ranges from 10µW to 1mW depending on the type of tag. So these kinds of tags are used in the cases and in items where the tags are not used again and the cost of the tag is also not important. The operating frequency ranges of Passive tags are 128 KHz, 13.6 MHz, 915 MHz, or 2.45 GHz.


In the Near field technique the reader passes a large amount of a.c. current through the reading coil due to which an alternating magnetic field is created in the nearby region. If a tag is placed in this region of magnetic field, then alternating voltage will appear across it. This voltage is rectified and coupled to the capacitor and a pool of charge gathers, which can be used to power the tag chip.


Figure: Near Field Technique

La RFID est constituée d’un couple lecteur/étiquette. Le 

lecteur envoie une onde radio, l’étiquette envoie à son tour 

une trame d’identification. Une fois la puce alimentée, 

l’étiquette et le tag communiquent suivant le protocole TTF 

(Tag Talk First) ou ITF (Interogator Talk First). Dans le mode 

TTF l’étiquette transmet en premier les informations 

contenues dans la puce à l’interrogateur. En mode ITF, 

l’interrogateur envoie une requête à l’étiquette, et cette 

dernière répond par la suite. Il existe trois types d’étiquettes

les étiquettes passives, actives et semi-actives. Les premières 

n’ont pas leur propre source d’énergie : une petite quantité 

d’énergie leur est fournie par le champ magnétique induit par 

le lecteur au moment de l’identification. Les tags actifs sont 

quant à eux alimentés par piles, ils sont capables d’envoyer 

eux-mêmes des informations d’identification sans sollicitation 

d’un lecteurLes semi-actifs utilisent un mécanisme hybride 

auto-alimentés, ils ne s’activent qu’à la demande du lecteur, 

permettant une plus faible consommation d’énergie que les 

tags actifs. La distance de lecture des puces RFID varie de 

quelques cm à quelques mètres (10 m), et peut aller au-delà 

(200 m) avec des technologies de communication longue 

portée [31]. Le principe de fonctionnement de la technologie 

RFID est illustré dans la figure 

The active device or reader (this could be your smartphone) generally polls/looks for nearby NFC devices. The passive device or ‘tag’ begins to listen when it comes within a few centimetres of an active NFC device. The reader will then communicate with the tag.

 The antenna is a coil that picks up a magnetic field at very short range. The magnetic field not only provides communication. It also provides power to the microchip. Passive NFC tags can be built into anything, including credit cars and clothes.

work with induced electromagnetic fields over a very short distance, and they

The amount of information that you can store in an NFC tag is quite small. Usually, a small amount of text, such as your identity information. Most frequently, these tags are used as “keys” to unlock other forms of communication or authorize transactions. Near field communication transfers data a low rates. These rates are typically a few hundred kilobytes per second. Data storage is in the range of 50 to 2000 bytes, although this is increasing to 32 Kb.

If you are interested, you can read this detailed description of how NFC tags work.

NFC Tags – What can you do with them?

Quite a lot, actually. With NFC you can read a tag (small amount of data, slow communications) or exchange larger amounts of data faster between two NFC devices.

Here are some typical uses:

  • Simply touch your phone to promotional advertising and automatically transfer the information. Posters, signs and even magazine pages can be NFC enabled, replacing the QR code.
  • Touch your phone to the airport check-in kiosk to download your boarding pass.
  • Use your phone or NFC-enabled ID card as part of two-factor authentication.
  • Touch your phone to another NFC device to connect with it, or through it. You can now get routers with the “touch to connect” feature. Perhaps many IoT things will use NFC to connect to the cloud.

If you want to learn more and play with these NFC tags yourself, check out this beginners video.

ISO 14443 ISO 15693 FeliCa 

The reader deciphers the signals and is then prompted to do something. Some tags are re-writable so readers can actually update data.

When one of the connected devices has Internet connectivity, the other can exchange data with online services.

NFC tags are passive data stores which can be read, and under some circumstances written to, by an NFC device. They typically contain data (as of 2015 between 96 and 8,192 bytes) and are read-only in normal use, but may be rewritable. Applications include secure personal data storage (e.g. debit or credit card information, loyalty programdata, personal identification numbers (PINs), contacts). NFC tags can be custom-encoded by their manufacturers or use the industry specifications.

NFC tags contain data and are typically read-only, but may be writeable. They can be custom-encoded by their manufacturers or use NFC Forum specifications. The tags can securely store personal data such as debit and credit card information, loyalty program data, PINs and networking contacts, among other information. The NFC Forum defines four types of tags that provide different communication speeds and capabilities in terms of configurability, memory, security, data retention and write endurance. Tags currently offer between 96 and 4,096 bytes of memory.

The transmission frequency for data across NFC is 13.56 megahertz. You can send data at either 106, 212, or 424 kilobits per second. That’s is quick enough for a range of data transfers — from contact details to swapping pictures and music.

Read/write mode, on the other hand, is a one-way data transmission. The active device, possibly your smartphone, links up with another device in order to read information from it. NFC advert tags use this mode.

Tags can contain a URL code, and reader (phone) will jump automatically to url 

Reader mode
The “NFC Device” in reader mode behaves like a simple contactless card reader. It initiates communication by generating a magnetic field and then sending a command to the target. The target responds to the interrogator by retro-reflecting the incident wave as described in the definitions in §1.2.2). The specificity of NFC operating modes is that the target can be not only a tag or a contactless card, but also an “NFC Device" that behaves like a contactless card (in card emulation mode).Usages of reader mode are principally information reading, when “NFC Devices” is used to read data by waving it in front of electronic labels available on streets, bus stops, sightseeing monuments, ad banners, parcels, products or on business cards (vCard). 

Internet des objets et interopérabilité des flux logistiques : état de l'art et perspectives (PDF Download Available). Available from:'art_et_perspectives [accessed Mar 11 2018].

La technologie NFC est le résultat de plusieurs évolutions

des microcontrôleurs, des cartes à puce, et des

communications à courte portée [31]. NFC est basée sur le

même principe que la RFID, c'est-à-dire l’identification par

radio fréquence. Elle permet l’échange d’informations à

courte distance entre deux objets (un lecteur et une carte) sans

contact, et fonctionne suivant deux modes : le mode passif et

le mode actif. En mode passif, le terminal de l’utilisateur

émule une carte à puce et acquiert de l’énergie des radiations

Internet des objets et interopérabilité des flux logistiques : état de l'art et perspectives (PDF Download Available). Available from:'art_et_perspectives [accessed Mar 11 2018].

du lecteur (téléphone mobile par exemple). En mode actif, le

terminal se comporte comme un lecteur d’étiquettes

électroniques (code à barres, étiquettes 2D) et possède sa

propre source d’énergie [46] (une batterie embarquée par

exemple). NFC permet à l'utilisateur d’échanger des

informations avec son environnement, notamment dans le

domaine des transports, des loisirs, des achats, ou la lecture

d’informations sur des panneaux d’affichage. L’utilisation de

la NFC facilite la gestion des données de ventes dans la

chaîne logistique, la gestion et la validation de tickets de bus

dans le transport urbain [11]. Lorsqu’un utilisateur scanne un

tag NFC, il peut en outre avoir accès à des informations sur le

produit (origine, fabricant, contenu/ingrédients, procédé de

fabrication) [36].

Zigbee est un protocole de communication sans fil à bas

coût qui permet des échanges à courte distance entre les

nœuds d’un réseau WPAN (Wireless Personal Area

Networks). Ce protocole est basé sur la norme IEEE 802.15.4

qui spécifie les protocoles de communication entre les

couches physiques et liaison de données du modèle OSI, en

définissant trois types d’équipements : les FFD (Full Function

Devices) qui sont des équipements à fonctionnalité complète,

les RFD (Reduce Function Devices) équipements à

fonctionnalité réduite, et les coordinateurs de réseau. Les FFD

coordonnent l’ensemble du réseau, ce sont des coordinateurs

PAN (Personal Area Network), routeur ou dispositif relié à un

capteur. Les RFD sont conçue pour des applications simples

comme l’allumage d’une lampe. Les RFD ne peuvent

communiquer qu’avec un FFD [49]. Parmi les avantages que

procure ce protocole de communication, nous pouvons citer la

faible consommation d’énergie, l’utilisation optimale de la

bande passante, et son faible coût de mise en œuvre. Ces

avantages permettent d’adopter le protocole Zigbee dans les

environnements embarqués et les réseaux industriels, ou le

développement de nouveaux produits basés sur ce protocole


Internet des objets et interopérabilité des flux logistiques : état de l'art et perspectives (PDF Download Available). Available from:'art_et_perspectives [accessed Mar 11 2018].

XBee peut être utilisé pour la transmission de données

entre les objets logistiques (capteurs sur conteneurs, étiquettes

RFID sur les produits) et les environnements Cloud

(traitement de données, Big Data, Services Web).

Internet des objets et interopérabilité des flux logistiques : état de l'art et perspectives (PDF Download Available). Available from:'art_et_perspectives [accessed Mar 11 2018].

The second way NFC can work is peer-to-peer communication, provided both devices are powered. 

ISO 18092

Exchange business cards, email addresses, schedule meetings, 

  share music  

In a real life scenario an NFC equipped phone can act in an active or passive mode. As a payment method in a shop, the NFC equipped phone would act in the passive mode with the equipment at the checkout acting in the active mode. In an alternative scenario an NFC enabled phone might be used to scan a tag on a brochure or a card to retrieve more information, here the phone is acting in a active mode.

Perhaps the most common use in smartphones is the peer-to-peer mode. This allows two NFC-enabled devices to exchange various pieces of information between each other. In this mode both devices switch between active when sending data and passive when receiving.

Peer-to-Peer mode
This mode allows two “NFC Devices” with the same NFC performance to exchange the data with each other alternately. Each of these devices supports both interrogator and target communication modes, sending or receiving by turns the data.Communication in peer-to-peer mode is slower than in conventional reader / card emulation mode, because of the management of a heavier protocol, which is necessary for the repartition of roles between the two “NFC Devices.”
As of use cases:
This mode can be used to initiate gateways (pairing) with other technologies for data transfer at higher than NFC (Bluetooth, Wi-Fi or Wi-Fi Direct) data rates.

The third way is that the NFC-enabled device acts like a smart card. 

ISO 14443 

Behaves as a secure card credential - payment, loyalty card, access control, hotel room card, 

User control proximity 

Secure element - encrypted data special chip in nfc device acts as data vault all data encrypted, only accessible if you have the key, and keys are only held by a unique ‘trusted service manager’ 

NFC device (phone) contains a secure element (like SIM card), linked to an nfc controller to manage traffic and RF signals, and an nfc antenna

The final mode of operation is card emulation. The NFC device can function as a smart or contactless credit card and make payments or tap into public transport systems.

The introduction of host card emulation (HCE) in Android 4.4 (KitKat) and announcements by both Visa and MasterCard that they will support the new technology standard are yet two more signs the barriers to near field communication (NFC) adoption are quickly falling away.

What is Host Card Emulation?

Host card emulation creates a virtual and exact representation of a smart card using only software. HCE allows NFC applications to be hosted in the cloud as opposed to where it has traditionally existed, in the secure element on a SIM card. The secure element handles authentication and any financial institution that would like to roll out NFC mobile payment solutions would have to arrange it across multiple mobile networks, significantly increasing time to market.

HCE offers a software solution to this issue, allowing banks to offer a cloud-based solution without the need to coordinate with individual carriers. It also allows merchants to offer payment cards solutions more easily through mobile, closed-loop contactless payment solutions, real time distribution of payment cards, and an easy deployment scenario that does not require them to change the software inside their terminals.

And HCE is not just attractive to those looking to use it for payments. HCE potentially could be used for any NFC service. With HCE, NFC-enabled handsets are able to remove the physical secure element from the transaction, allowing services such as ticketing, identity and access control to be developed and implemented in a shorter amount of time.

According to Martin Cox, global head of Sales at Bell ID, inclusion of host-card emulation means that full NFC capability – including operation of the reader functionality of NFC handsets – would be made available to app developers. He told SecureID News that this would enable developers to create applications that can turn handsets into contactless card readers, a function that has potential in the mobile point-of-sale sector and a host of other markets.

How Does HCE Work?

As we discussed in Part 1 of this series, host card emulation (HCE) allows the transfer of information with near field communication (NFC) to happen between a terminal configured to exchange NFC radio information with an NFC card and a mobile device application configured to emulate the functional responses of an NFC card. HCE requires that the NFC protocol be routed to the main operating system of the mobile device instead of being routed to a local hardware-based secure element chip.

Here we look at exactly how HCE works from a technical perspective.

Host card emulation allows an application to emulate a card and talk directly to an NFC reader.

As explained on the Android developer site, when NFC card emulation is provided using the secure element, a user holds the device over an NFC terminal and the NFC controller in the device routes all data from the reader directly to the secure element (Figure 1). However, when an NFC card is emulated using host-based card emulation, the data is routed to the host CPU on which Android applications are running directly, instead of routing the NFC protocol frames to a secure element (Figure 2).

According to their website, Android 4.4 supports several NFC protocols that are common in the market today, including emulating cards that are based on the NFC-Forum ISO-DEP specification (based on ISO/IEC 14443-4) and process Application Protocol Data Units (APDUs) as defined in the ISO/IEC 7816-4 specification. Android mandates emulating ISO-DEP only on top of the Nfc-A (ISO/IEC 14443-3 Type A) technology. Support for Nfc-B (ISO/IEC 14443-4 Type B) technology is optional.

Although the mobile phone will still have to be NFC-enabled, with HCE support now coming prepackaged in Android 4.4. Anyone looking to deploy a payment system across multiple carriers will have a much easier solution to turn to.

Beyond the technical aspects, what are the real-world benefits of HCE?

The main benefit of HCE is that it is open source, allowing issuers (like banks and credit unions) and other payment providers to create NFC-enabled payment apps without needing permission from a mobile network operator (MNO) or dealing with complex trusted service managers (TSM). Managing payment credentials in the cloud will also be technically easier and less expensive. With an HCE-based solution, the complexity of managing the secure element, something that was hindering past NFC implementations, will no longer be an issue as the secure element will be in the cloud rather than part of the phone. With a software solution to the secure element, banks can offer cloud-based payments without the need to coordinate with individual carriers.  This means an organization can implement payment services globally rather than through the MNO.

The benefits to retailers are also very big. For most, HCE will require no change to the existing acceptance infrastructure. The technology also does not need network connectivity at the time of payment unlike many cloud services. And because HCE will interrogate the processor rather than the SIM on the phone, transaction speeds will be faster.

While the roll-out of HCE applications are just in their infancy, the technology does seem to be very promising and is being heralded as a game changer in the NFC space.

 Card emulation mode
In card emulation mode, the “NFC Device” behaves like a contactless smart card. It is functioning as a target in a passive mode (cf. definitions in §1.2.2).While a contactless card is powered by the magnetic field generated by the interrogator, an “NFC Device” may require more energy to operate. Indeed, an NFC application on a mobile phone, a tablet or a consumer device may benefit from other features than just NFC (screen, applications, security, internal communications, etc.). Access to these features requires an internal power source, a battery or power supply. 

What is the difference between RFID and NFC?

Kind of. It transmits data, but the amount of data transmitted is generally considerably less and the power needed to transfer the data is too a lot less.

NFC offers more security than Bluetooth and there is no need to ‘pair’ devices. NFC is just a tap.

This marks the one major difference between NFC and Bluetooth/WiFi. The former can be used to induce electric currents within passive components as well as just send data. This means that passive devices don’t require their own power supply. They can instead be powered by the electromagnetic field produced by an active NFC component when it comes into range. Unfortunately, NFC technology does not command enough inductance to charge our smartphones, but QI charging is based on the same principle.

What is the Difference Between an NFC Tag and an HF RFID Tag?

An RFID tag uses proprietary data storage methods, usually just storing data in specific blocks that are defined by the developer. An NFC/RFID reader would need to know how the data is stored to interpret it.

An NFC tag uses the NFC Data Exchange Format (NDEF) to store data in tags according to the NDEF standards. This allows any NFC-enabled devices to read the data from any NFC tag and interpret it. Most applications on NFC-enabled smartphones use NDEF when reading or writing data to NFC tags.

Why is NDEF Used? What Advantages Does NDEF Provide?

The concept of NDEF is to create a universal format for how to store data across all NFC tags. This allows NFC devices such as smartphones to have a standard for how to read data across each NFC technology type despite varying memory structures and features.

The advantage of using NDEF is that any NFC-compliant device is able to read and write to an NDEF formatted tag allowing for excellent interoperability with a large number of devices and tags in the market.

NDEF should be leveraged for applications in which any of the following is desired:

  • Compatibility with NFC-enabled devices in the market
  • Display of information (text, URL, contact information, and so on) in an easily readable format

NDEF may not be an ideal choice for some applications such as:




• •

Proprietary closed-loop applications
Applications in which raw unformatted data should be transferred over NFC 

Is NFC just an alternative to QR codes?


Yes and No.

It is like a QR code that once scanned it tells your reader to do something. From opening a web page to adding contact details to your phone.

NFC tags seen in public places are too often roughly the same size as QR codes.

However unlike a QR code you do not need to always switch on or open a reader. NFC is often an always on technology. Simply tap the two NFC products and your away.

What about WiFi, Bluetooth, etc.?

Above we have a table that summarises the differences between Bluetooth (and the low-energy Bluetooth LE), WiFi (or WiFi Direct), and NFC. All are standards-based radio transmission (wireless) data transmission technologies, but there are a number of major differences. Bluetooth is one well-known peer-to-peer technology used for the personal area network, connecting computers, smartphones, tablets, video games, etc. together (with their accessories), and eventually uplinking them to an Internet gateway. WiFi, and in particular the recent WiFi Direct, connects devices together without using a wireless access point. In many ways it is a more modern alternative to Bluetooth, although new versions of Bluetooth are emerging, e.g. Bluetooth 5.0

In the table it shows NFC as operating over <0.2 m, but the reality is that it usually functions over about 3-4 cm, i.e. almost touching. As such it is not usually included as a technology for personal area networks (like Bluetooth) nor for body area networks (which requires data rates up to 10 Mbps and the application of strict non-interference guidelines). NFC is found in contactless payment systems, in the contactless smart card in biometric passports, in keycards/smartcards, and as a way to share contacts, photos, files, etc.

While we have answered the question “What is NFC?”, how does it compare with other wireless technologies? You might think that NFC is bit unnecessary, considering that Bluetooth has been more widely available for many years. However, there are several important technological differences between the two that gives NFC some significant benefits in certain circumstances. The major argument in favor of NFC is that it requires much less power consumption than Bluetooth. This makes NFC perfect for passive devices, such as the advertising tags mentioned earlier, as they can operate without a major power source.

However, this power saving does have some major drawbacks. Most notably, the range of transmission is much shorter than Bluetooth. While NFC has a range of around 10 cm, just a few inches, Bluetooth connections can transmit data up to 10 meters or more from the source. Another drawback is that NFC is quite a bit slower than Bluetooth. It transmits data at a maximum speed of just 424 kbit/s, compared to 2.1 Mbit/s with Bluetooth 2.1 or around 1 Mbit/s with Bluetooth Low Energy.

But NFC does have one major advantage: faster connectivity. Due to the use of inductive coupling, and the absence of manual pairing, it takes less than one tenth of a second to establish a connection between two devices. While modern Bluetooth connects pretty fast, NFC is still super handy for certain scenarios. Namely mobile payments.

Samsung Pay, Android Pay, and even Apple Pay use NFC technology — though Samsung Pay works a bit differently than the others. While Bluetooth works better for connecting devices together for file transfers, sharing connections to speakers, and more, we anticipate that NFC will always have a place in this world thanks to mobile payments — a quickly expanding technology.

Simplicité d'utilisation: Contraitement au Bluetooth ou au Wifi, pour effectuer une communication par NFC, un simple rapprochement de deux appareils suffit. Il n'y a pas de clé ou autres mots de passe à fournir. De plus, un opérage en NFC s'effectue en quelque milli-secondes là ou le bluetooth en met plusieurs.

Une technologie répendue: Le NFC est de plus en plus présent sur les smartphones, téléviseurs et de nombreux autres équipements de la vie de tous les jours.

De nombreux cas d’utilisations: On peut imaginer un très grand nombre de cas d'utilisation du NFC (carte bancaire, badge pour portail automatique, tags pour passeport...).

What exactly is the tag and how does it work? 



The NFC tag like the one shown above consists of an NFC chip near the centre bonded to a loop antenna. The antenna is designed to resonate at 13.56 MHz, and at the resonant frequency the current inside the antenna and the voltage delivered to the NFC chip are maximum (which also maximises the communication distance). The larger the antenna, the better the performance for a given magnetic field. The thickness of the antenna does not affect its performance, so the tags can be made exceeding thin. However, the bond between the NFC chip and the antenna is the weak point, and constrains the physical construction. Nevertheless antennas and therefore tags can be designed with different shapes. 

The passive RFID tags do not have any power source and hence they have indistinct operational life span. The power needed for functioning is taken from the reader when the tag comes in the vicinity of the reader. They are available in a variety of sizes ranging from sizes which can fit into adhesive label. The passive RFID is basically made up of three parts: Antenna which is responsible for capturing energy and transferring the tag ID, Semiconductor chip appended to the antenna and an encapsulation which maintains the tag integrity. The encapsulation protects the antenna and chip from harsh environmental conditions. These encapsulations can be made up of small glass vial or from a laminar plastic substrate with adhesive on one side so that it can be easily attached to the goods.


Unlike an active RFID tagpassive RFID don’t have their own source of power and therefore the tag reader is responsible for powering the communication with the tag. Power can be transferred in two different ways. The first one is magnetic induction method and second is electromagnetic wave transfer method by using the EM properties related with the RF antenna i.e. the near field and the far field. The transfer of power ranges from 10µW to 1mW depending on the type of tag. So these kinds of tags are used in the cases and in items where the tags are not used again and the cost of the tag is also not important. The operating frequency ranges of Passive tags are 128 KHz, 13.6 MHz, 915 MHz, or 2.45 GHz.


In the Near field technique the reader passes a large amount of a.c. current through the reading coil due to which an alternating magnetic field is created in the nearby region. If a tag is placed in this region of magnetic field, then alternating voltage will appear across it. This voltage is rectified and coupled to the capacitor and a pool of charge gathers, which can be used to power the tag chip.


Figure: Near Field Technique 

In the far field technique, the tag captures EM waves transmitted from the dipole antenna which is attached to the reader. The small dipole antenna receives this energy in the form of alternating potential difference that appears across the arms of the dipole. After the rectification it is linked to the capacitor which results in accumulation of energy in order to supply power to the tags.


Figure: Far Field Technique


There can be one more method to transmit the signal from the tag that is when passive RFID tag stores the energy of the signal from the reader in an onboard capacitor. The tag uses the energy of the capacitor when it is fully charged.


The passive tags can be used in forming the identification cards for building access, credit cards, identity cards, bus fares, on the purchasable items etc where just a small tag of size as small as quarter is required to fulfill the needs and the reader reads the information from the tags and supply us the information of the items that are stored in the tags.

Les deux principaux éléments que l'on retrouve sur tous les périphériques NFC sont : - Une antenne RF ( Radio Fréquence ) : Elle permet d'envoyer les ondes radio dans l'air à différentes fréquences. Cette antenne doit être au standard NFC. - Une puce électronique NFC : Cette puce électronique, va transformer un signal numérique en un signal analogique qui sera ensuite transmit à l'antenne pour être envoyé. La problématique étant la suivante : Les équipements actuels (ordinateurs, cartes électroniques etc) utilisent tous le même langage, le langage binaire (composé uniquement de 0 et de 1). Pour représenter ce langage, nous utilisons un signal électrique dit numérique. Le problème est qu'un signal électronique numérique ne peut être transmit dans l'air par onde radio. Il faut donc au préalable le convertir en signal analogique qui lui peut être envoyé par onde radio. C’est le rôle de la puce NFC.

La puce NFC: Elle va transformer le signal numérique à envoyer en signal analogique. Inversement elle transforme un signal analogique reçu en signal numérique. La transformation du signal numérique en signal analogique est appelé modulation, tandis que l'opération inverse est appelé démodulation. La partie de la puce qui effectue cette opération est généralement appelée Modem (pour Modulateur / Démodulateur).

NFC operates at 13.56 MHz on ISO/IEC 18000-3 air interface and at rates ranging from 106 kbit/s to 424 kbit/s. 

As with proximity card technology, near-field communication uses electromagnetic induction between two loop antennas located within each other's near field, effectively forming an air-core transformer. It operates within the globally available and unlicensed radio frequency ISM band of 13.56 MHz. Most of the RF energy is concentrated in the allowed ±7 kHz bandwidth range, but the spectral mask for the main lobeis as wide as 1.8 MHz.[35]

Theoretical working distance with compact standard antennas: up to 20 cm (practical working distance of about 10 cm).

Supported data rates: 106, 212 or 424 kbit/s (the bit rate 848 kbit/s is not compliant with the standard ISO/IEC 18092)

The two modes are:


The initiator device provides a carrier field and the target device answers by modulating the existing field. In this mode, the target device may draw its operating power from the initiator-provided electromagnetic field, thus making the target device a transponder.


Both initiator and target device communicate by alternately generating their own fields. A device deactivates its RF field while it is waiting for data. In this mode, both devices typically have power supplies.

As with proximity card technology, near-field communication uses electromagnetic induction between two loop antennas located within each other's near field, effectively forming an air-core transformer. It operates within the globally available and unlicensed radio frequency ISM band of 13.56 MHz. Most of the RF energy is concentrated in the allowed ±7 kHz bandwidth range, but the spectral mask for the main lobeis as wide as 1.8 MHz.[35]

Theoretical working distance with compact standard antennas: up to 20 cm (practical working distance of about 10 cm).

Supported data rates: 106, 212 or 424 kbit/s (the bit rate 848 kbit/s is not compliant with the standard ISO/IEC 18092)

As an aside a NFC transmitter-responder can easily be put together using standard components. For example, the TI MSP430F2370 Is a low-power micro controller used in RFID devices, and TI TRF7970A is a custom NFC/RFID transceiver. All you need is to match them to a NFC antenna (following this design guide) and you have the basis for a standards-compliant NFC reader-writer. The FAQ on the TRF7970A is a mine of useful information for those wishing to build a NFC transponder.


Inductive coupling

The technology involved is deceptively simple. Evolved from radio frequency identification system, an NFC chip functions as a way of the wireless link. After activating this by another chip, amounts of information within two devices are accessible.

NFC follows the inductive coupling principle, where electrons move through conductors generating a magnetic field, while change occurs in a magnetic field, it can generate an electric field, this process is called inductive coupling.

RFID chip works on the mechanism of inductive coupling, RFID is an electronic chip, which includes some specific information related to it. While we take RFID tags near to magnetic field, it induces electricity with tag. The changing in the field then identified by the reader and decoded to interpret the information secured in the RFID tag.

Data Transfer

NFC employs two different codings to transfer data. If an active device transfers data at 106 kbit/s, a modified Miller coding with 100% modulation is used. In all other cases Manchester coding is used with a modulation ratio of 10%.

NFC devices are full-duplex—they are able to receive and transmit data at the same time. Thus, they can check for potential collisions if the received signal frequency does not match the transmitted signal's frequency.

Although the range of NFC is limited to a few centimeters, plain NFC does not ensure secure communications. In 2006, Ernst Haselsteiner and Klemens Breitfuß described possible attacks and detailed how to leverage NFC's resistance to man-in-the-middle attacks to establish a specific key.[36] As this technique is not part of the ISO standard, NFC offers no protection against eavesdropping and can be vulnerable to data modifications. Applications may use higher-layer cryptographic protocols (e.g. SSL) to establish a secure channel.

The RF signal for the wireless data transfer can be picked up with antennas. The distance from which an attacker is able to eavesdrop the RF signal depends on multiple parameters, but is typically less than 10 meters.[37] Also, eavesdropping is highly affected by the communication mode. A passive device that doesn't generate its own RF field is much harder to eavesdrop on than an active device. An attacker can typically eavesdrop within 10 m and 1 m for active devices and passive devices, respectively.[36]

Because NFC devices usually include ISO/IEC 14443 protocols, relay attacks are feasible.[38][39][page needed] For this attack the adversary forwards the request of the reader to the victim and relays its answer to the reader in real time, pretending to be the owner of the victim's smart card. This is similar to a man-in-the-middle attack.[40] One libnfccode example demonstrates a relay attack using two stock commercial NFC devices. This attack can be implemented using only two NFC-enabled mobile phones.[41]

NFC, Le software

Les couches protocolaire

Comme précisé en introduction, le NFC n'est pas une nouvelle technologie à part entière. Il s'appuie sur des normes existantes. Le NFC apporte réellement 3 couches protocolaires qui vont venir en surcouches des normes ISO sur lesquelles il se base.


Si nous partons du bas de l'architecture logicielle, nous trouvons dans un premier temps les couches ISO-14443 et Felica. Ces couches sont les normes sur lesquelles s'appuie le NFC. Elles permettent de piloter directement le hardware (gestion du champ magnétique, fréquence des ondes émises, émissions des données dans l'air...). Nous retrouvons ensuite les 3 couches protocolaires amenées par le NFC: DEPLLCPSNEP,

Data exchange protocol

Le NFC-DEP est un protocole d'échange de données bas niveau. Il peut s'appuyer soit sur la couche physique NFC-A (ISO 14 443 - A) ou bien sur la couche NFC-F (Felica). Dans le protocole DEP, l'équipement qui initie la connexion est appelé Initiator tandis que l'équipement cible est appelé Target. Les messages respectant DEP suivent le format suivant :


Start of Data (SOD) : Dans ce protocole, le début d'un message doit indiquer la taille totale du message. La taille des données doit être comprise entre 3 et 255 octets. 
Payload : Le champ Payload contient la commande DEP à effectuer suivi du corps du message à envoyer au périphérique distant. 
End of Data (EOD) : Le champ End of Data contient des octets de contrôle permettant de vérifier qu'il n'y a pas eu d'erreurs de transmission.

Principales commandes 




La commande Attribute Request permet d'activer une connexion DEP entre deux périphériques. Elle permet également de définir les paramètres de communication tels que la vitesse de communication, la taille maximale d'un message etc. Sans cette activation, il est impossible d'échanger des messages à travers le Protocol DEP.


La commande Parameter Selection Request permet de changer les paramètres de connexion définis lors de la commande ATR_REQ. Cette commande est notamment utilisée lorsqu'un Initiator effectue une demande de connexion avec un périphérique et que celui-ci ne supporte pas les paramètres de connexion demandés. L'Initiator effectue alors un PLS_REQ pour redéfinir les paramètres si cela est possible.


La commande Data exchange protocol request est la commande permettant d'échanger des données avec un périphérique distant.


La commande Deselect Request est la commande permettant de désélectionner un périphérique NFC précédemment activé. Une fois désélectionné, il reste en attente de reconnexion.


La commande Release Request est la commande permettant de fermer une connexion avec un périphérique NFC précédemment activé. Une fois la connexion fermée, le périphérique distant n'est plus en attente d'aucun message.

En résumé, le couche DEP permet de paramétrer un lien entre deux périphériques et ainsi de définir la façon de communiquer (vitesses, temps de réponse...).

Logical link control protocol

La couche LLCP est un protocole d'échange de données offrant différents services de contrôle et permet l'utilisation d'un mode connecté ou non connecté. L'utilisation du protocole SNEP nécessite d'utiliser LLCP en mode connecté uniquement. C'est donc ce mode que est générallement implémenté. Dans ce mode, LLCP utilise un mode de communication half duplex (Question/Réponse). On ne peut envoyer qu'une trame à la fois, celle-ci devant être suivie obligatoirement d'une trame réponse dans les délais impartis. L'échange de trames doit être permanant même lorsqu'il n'y a pas de données utiles à envoyer. Cet échange permanant permet de détecter les pertes de connexions. Un message Llcp suit le format suivant :


Dsap : Destination Service Access Point. Sur un même équipement, plusieurs applications peuvent utiliser Llcp simultanément. Le champ dsap est un numéro d'identification attribué à un service (une application) utilisant llcp. Il permet de déterminer à qui le message est destiné. 
Type : PDU type. Ce champ représente la commande LLCP à effectuer. 
Ssap : Source Service Access Point. Le champ dsap est un numéro d'identification attribué à un service (une application) utilisant llcp. Il permet de déterminer de qui le message provient. 
Sequence : Sequence number. Un numéro de séquence est attribué à chaque message envoyé. Il permet d'effectuer un contrôle afin de vérifier qu'aucun message n'a été perdu en route. 
Information : Le champ information contient le corps du message en lui même.

Principales commandes 



Symmetry Pdu

Cette commande permet de respecter le balancement 1 trame envoyé, 1 trame reçue ... Elle doit être utilisé lorsqu'aucune autre commande ne peut être envoyé en réponse d'une trame reçue.


Cette commande permet d'effectuer une demande de connexion d'un service local vers un service distant à travers un lien llcp . La commande Connect permet d'échanger également différents paramètres tels que la version de la librairie, les services supportés, le timeout de la connexion . . .


Cette commande permet de terminer une connexion ou de désactiver un lien llcp.

Connection Complete

Commande en réponse à la commande Connect confirmant que la connexion à bien été établie.


Cette commande permet d'échanger des données à travers la connexion établie. Elle permet également d'acquitter des messages reçues grâce au champ Séquence.

En résumé, la couche LLCP permet de maintenir une connexion entre deux périphériques et de détecter lorsque l'un des deux ne répond plus. Elle fournit également du contrôle de données grâce aux numéros de séquences attribués aux messages permettant de vérifier qu'ils ont bien tous été reçus.

Simple NDEF exchange protocol

Le protocole SNEP permet d'échanger des messages dans un format particulier (NDEF). Il est notamment utilisé en surcouche de LLCP par le BEAM des smartphone Android. Ce protocole est assez simple.


Version: Ce champ correspond à la version de SNEP utilisée. 
Request: Ce champ correspond à la commande SNEP à effectuer. 
Length: Ce champ correspond à la taille du message à transmettre 
Information : Le champ information contient le corps du message en lui même.

Principales commandes 




Cette commande est utilisée après avoir reçu un PUT ou un GET. Elle doit être utilisée lorsque la commande reçue ne tient pas en une seule trame pour confirmer la capacité à recevoir le reste du message.


Cette commande permet de demander à un périphérique de nous envoyer un Ndef message en particulier.


Cette commande permet d'envoyer à un périphérique un Ndef message.


Cette commande est utilisée après avoir reçu un PUT ou un GET. Elle doit être utilisée lorsque la commande reçue ne tient pas en une seule trame pour préciser que l'on ne peut pas recevoir la suite du message.

En résumé, SNEP fournit une interface de programmation pour envoyer des messages en NFC simple à utiliser pour les développeurs. Elle permet une fois toutes les couches implémentées de profiter de tous leurs avantages (contrôle de données, paramétrage de connexions etc) sans avoir à se soucier de quoi que ce soit, le travail étant effectué par les couches inférieurs à SNEP.

Different types of NFC tags

There are several types of NFC chips, each with its own characteristics.  Each varies in the amount of data they hold, whether they can be made read-only or can be re-written, the performance of the chip and any other special features.

The biggest determining factor is the amount of memory each NFC tag has. You need to choose the right NFC tag for the application or purpose you intend to use it for.

You do also need to consider whether the tags are going to be used inside or outside, attached to metal and what devices are going to be scanning the NFC tag as at the time of writing different brands of phone can have trouble with different types of tags.

  • Ultralights (UL) – Good for a short URL or phone number (64 bytes)
  • Ultralight Cs (ULC) – Have a bit more data storage and are good for a long URL or a small contact card (192 bytes)
  • Standard 1K – Can store more data so they can handle a large contact card but are more expensive (1024 bytes)
  • NTAG203 – Like ULC but are a new chip type with better responsiveness (168 bytes)
  • Anti-Metal Tags – Can be stuck onto metal surfaces.

The Ultralight C (ULC) and NTAG are the most popular.

You will often see words such as MIFARE, DESFire and Classic amongst others. Don’t worry too much about this unless you want to get really technical, concentrate on the type of tag and the memory capacity as shown above.

Do be aware the Blackberry devices tend to have problems reading the 1k tags.

Once you have decided upon the tag type required you then need to consider the size of the tag/sticker and the colour.

The NFC-enabled phone is seen as the wallet of tomorrow (or today). It contains access cards, loyalty cards, credit cards, shopping cards, transport tickets, identification, drive licence, cash and possibly keys. All of this will disappear inside the smartphone. Younger users (18-49) always carry their smartphones, and on average detect its loss within 13 minutes or less. Smartphones are already multipurpose devices, with music and videos, photos and camera, email/Internet, so a smart wallet has a good chance. 

These technologies, and there are a multitude of others out there as well, all focus on the Internet-of-Things (body area networks and vehicle-to-vehicle come to mind). 

We have mentioned the Internet-of-Things, but is there anything beyond that? Yes, it’s the Internet-of-Everything.  
  © Bernard Smith 2017-18