Practical NFC Range Limitations

Sadly, it can't always replace Bluetooth

Feb 24, 2017 - 4 minute read

Here at TapTrack, we regularly field inquiries about near-field communication applications that demand relatively long-range communication, such as indoor position tracking or anti-theft gates. Unfortunately, NFC usually is not a practical option for such uses due to its quite limited range.

NFC Range

Theoretically, for the 13.56MHz frequency used by NFC, the ‘near field’ ends at 3.5 metres from the antenna, but real-world range is a quite different topic. Since NFC tags draw their power from the reader’s field, the effective range is heavily influenced by the power of the field the reader is generating relative to the power the tag requires, which may vary depending on what the tag is trying to do. The antenna configuration of the tag plays a role in how effectively it can both harvest power from the field and communicate with the reader, so it is also very important. In general, tags with larger antennas perform better, but there is some interplay between the tag configuration and the reader configuration, so, strictly speaking, it is not always true that tags with larger antennas will always outperform tags with smaller antennas. Of course, like other forms of radio communication, NFC can also be affected by interference. Additionally, there are two different NFC standards, ISO14443 and ISO15693, that have slightly different electrical characteristics, resulting in a noticeable difference in range.

ISO14443

It is possible to communicate with 14443 tags from over 10 centimetres away, but this requires a both an extremely powerful reader and a quite sensitive tag. More typically, for a reasonably powerful reader and a normal tag, the maximum range is generally going to be somewhere in the 5-10cm range, while weaker readers are generally going to provide a maximum range of around 1-3cm. In the extreme case of a particularly weak reader trying to communicate with a very small tag, the maximum range can be reduced to a matter of millimetres. While many phones do fall into the ‘particularly weak’ category, there is a huge amount of variation between models. Some mobile devices, such as the 2014 Moto X, deliver performance that is superior to even some desktop readers. At the other end of the spectrum, we have observed the Nexus 9 tablet to provide extremely poor NFC performance, sometimes failing to communicate even at ranges of under a centimetre.

ISO15693

Tags conforming to the 15693 standard are intended to support applications that require detecting tags that are in the general vicinity of the reader, and thus they offer greater range than 14443 tags. Hypothetically, 15693 can provide ranges of significantly over a metre, but, like achieving the maximum range of 14443, actually doing so requires an extraordinarily powerful reader and a quite sensitive tag. However, it is quite possible to achieve maximum ranges between ten centimetres and a metre just using a decent 15693 tag and standard reader. Low-powered readers such as phones will also achieve longer ranges for 15693 than 14443, but it’s generally not a significant enough difference to enable any new use cases.

Conclusion

Both ISO15693 and ISO14443 tags provide useful features that can enable compelling applications, but they certainly have their limitations. If you intend to use phones as readers, you should probably not count on NFC to deliver anything more than a centimetre of range. For more powerful commercial readers, you can generally achieve 5-10 centimetres of range from 14443 tags or over ten centimetres from 15693 tags. With the highest power commercial readers, you should be able to achieve a bit over a metre from 15693 or a bit over ten centimetres from 14443. If your tags are particularly small or power hungry, your observed maximum range will be quite significantly lower than these approximations. So, you’ll probably want to do some testing of the reader and tag combination you intend to use if range is a topic of concern for your application. In any case, if you need reliable communication at ranges of several metres, you’re beyond the practical capabilities of NFC and should look into other technologies.

Luke Van Oort

Chief Developer, fan of immutable data structures and functional reactive programming. Guitar noodler and cycling enthusiast.

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