About NFC

Tom explains the purposeful design of NFC, its limitations, and what benefits it holds over over similar technologies.

Featuring Tom Merritt.

MP3

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Episode Transcript:

I want to pay for things with my phone that looks so cool.
But my friend says my phone has to have NFC.
I’ve always preferred AFC teams!
Confused?
Don’t be.
Let’s help you know a little more about NFC.
NFC in this case stands for Near Field Communication, NOT the National Football Conference.
It’s a set of protocols for electronic communication over a distance of about 10 centimeters or so. Really short.
Because it is such a short distance it’s useful for things you do up close like contactless payments, keycards and identity cards.
NFC uses radio waves to broadcast its information at 13.56 megahertz. And it’s a little slow by data transmission standards. You can send data at either 106, 212, or 424 kilobits per second. So you’re not going to stream video over it.
But it can be used for sharing small files, like contact lists, and provide a kickoff point for sharing larger files over a separate connection. So if you’ve seen NFC touted to share video files, it’s because NFC is used to connect two devices then hand off the file transfer to something else, like Bluetooth, then shut off the something else like Bluetooth once the file transfer is done.
NFC’s communication protocols are based on the existing radio-frequency identification — or RFID standards. RFID is a much older technology, that was developed for things like security cards that get you into the office or those toll booth transmitters you stick on the windshield of a car.
Now we say NFC can work at around 10 centimeters but that’s the number for reliable use. If you are worried about someone trying to steal the info sent by NFC by eavesdropping you don’t care about reliability just possibility. A passive device that doesn’t broadcast its own signal can be read up to a meter away. An active one that’s broadcasting– like the one in your phone– can be read up to 10 meters away.
That still means the attacker would have to be pretty close but it’s far enough away for them to hide. Most NFC transmissions, especially ones around payment, are encrypted. Even passive tags can have an authentication scheme by generating a new unique number every time they’re read to help a server uncover duplicates and counterfeits.
So now we know what they’re used for. But you probably hear NFC used to refer to your phone, a watch , a piece of clothing, a bus pass. How does that work? Does that cute green tank have to have a battery in it to power its NFC tag? No. They’re all NFC but they’re all not the same KIND of NFC. There are three different modes of NFC. An NFC chip can act as one or more of these three modes.
Mode one is called card emulation, which, as you might guess from the name, acts like a smart card. Usually this is used for payments or ticketing and even transit passes for buses and trains in more and more locations. Japan uses a version of NFC called FELICA for its transit cards, meaning you can use an NFC-enabled smart watch to get yourself into a train station.
Mode number two is Reader/writer mode. I bet you can guess but it can read information, and sometimes Write information, stored in NFC tags that are embedded in things like clothing labels, or smart posters. The Nintendo game consoles use NFC in reader mode to detect Amiibo.
And the third mode is peer-to-peer mode, which lets devices send and receive information to each other. This can be used for trading contact info or anything where the two NFC devices need to exchange information.
NFC takes up very little space in a device and uses very little energy.
So how does it work? How does that tiny little grain of rice transfer data?
An NFC chip can be active or passive. Active needs a power source. Passive does not. That’s how you can have an NFC tag in that cute green tank top without it carrying around a battery.
When two active NFC devices are in range, they detect each other’s radio waves and automatically start communicating. They may do nothing other than say “Hey I’m a phone with Apple Pay” and “Hey I’m a point of sale system” If the user doesn’t take any action they leave it at that. Just two chips passing in the night. But if the user taps the right buttons they might exchange payment information or ticket validity or some such other thing.
A passive NFC tag, as I said, doesn’t even need a power source. It gets its power from the air man. Specifically from another NFC device trying to read it. It works by induction- the radio waves from the active NFC chip induce an electric current in the passive tag– which, side note is the same thing a Qi wireless charging pad does just on a much greater scale. The transmission from an NFC reader like your phone is enough to power the tag and let it report the data it has stored. Like the price of the green tank top you’re thinking of buying for instance. When the reading stops it just goes inert. Without an active NFC device, NFC tags just sit there doing nothing. But don’t worry they were literally MADE for that life. They’re happy.
The two big phone operating systems both support NFC in different ways.
Apple used to limit NFC to just Apple Pay but starting with the iOS13 Apple devices can read tags and label them using an NFC app.
Android 4.0 started supporting NFC for payments on Google and Samsung Pay and Android 4.4 to Android 9.0 supported Android Beam for exchanging information, but that was retired in favor of Nearby Share which does not use NFC.
That brings up an interesting point. Why use NFC when there’s Bluetooth Low Energy? The biggest reason is that NFC uses less power. A lot less power. You can’t have passive Bluetooth tags. Bluetooth always needs power.
Bluetooth on the other hand has much greater range and can transfer data at a much faster speed. As we mentioned earlier NFC tops out at 424 kilobits per second. Bluetooth can reach 1 MEGABIT per second for Low Energy and 2.1 Mb/s for Bluetooth 2.1
But that’s how fast Bluetooth is after it’s up and running. Bluetooth does take longer to establish its connection. Anyone pairing headphones or cars to your phone knows this. NFC takes less than a tenth of a second to establish a connection.
Another challenger for NFC’s crown for low power short range communication is UltraWide Band, though that also requires power. See our episode of Know A Little More called About Ultra Wide Band – for more on what Ultra Wide Band is used for.
So there you have it. That little chip hidden in your phone is a low power way to pay and play and more.
In other words, I hope you Know a Little More about Near Field Communication.