When it comes to spectrum for M2M technologies, unlicensed doesn’t mean do-as-you-please

Matt Hatton, Director at Machina Research

Guest post by Matt Hatton, Director, Machina Research.

An increasingly diverse range of access technologies are being used for the M2M connectivity which will underpin the Internet of Things.

In a recent Machina Research report¹ we examined the plethora of standards that are being used for M2M. There has been a noticeable recent expansion to the already broad range of technologies available, including Bluetooth Low Energy and a range of low power wide area (LPWA) technologies from firms such as Neul and Sigfox which are being touted as the next big thing. At Machina Research we have been tracking these LPWA technologies for years. The market potential is huge: over 15 billion devices. What we’re also increasingly seeing is more demand for solutions based on multiple technologies, for instance using a combination of wide area technology to a hub and then short-range for local access. This set-up is nothing new, but with more and more diverse technologies available, there is an increasing number of possible permutations of different technologies.

This use of a growing array of technologies will inevitably have regulatory implications. Over the course of the last few months at Machina Research we have been reviewing the regulatory position in countries around the world with regard to M2M and IoT, looking at areas such as licensing, cellular roaming, and data sovereignty, amongst others². One of the more complex areas, with the most subtle variation, is spectrum.

In most cases the new technologies will make use of unlicensed spectrum, for instance at 433MHz, 868MHz, or 2.4GHz. They do so alongside more traditional technologies such as Bluetooth, WiFi or Zigbee. However, just because spectrum is unlicensed, does not mean that access is unrestricted, except in the most under-regulated markets. In most countries, use of the unlicensed bands has strict rules. There are limitations on factors such as power output, channel spacing and duty cycle. For those unfamiliar with duty cycle, it pertains to the proportion of the time that a device is sending or receiving. The aim of these restrictions is to ensure that devices do not interfere with each other; devices that are constantly blasting out a high power signal 100% of the time would use up all of the available bandwidth.

Regulation of these bands varies on a country-by-country basis. There is some harmonisation globally, but there are subtle variations. For instance, within Europe there is some harmonisation under the CEPT, but the availability of the 870-876MHz and 915-921MHz bands varies by country. Elsewhere, different bands are only available in certain regions. Furthermore, even where the bands are available, the power, duty cycle or channel spacing requirements may vary.

The implications of breaching the restrictions could also be significant. In one non-European country that we recently studied for our M2M and IoT Regulation Database, the key determining factor for a device categorisation was power. Anything with an EIRP above 100mW counted as ‘outdoor’, and required a specific licence. All others were ‘indoor’ and thus covered by a class licence for short range devices. The implications of being an outdoor device were quite significant, not least as it attracts a significant annual fee.

The key thing is that rules vary country by country and new technologies will need to cope with the idiosyncratic nature of national regulations. Neither service providers nor their customers should ignore the fact that devices will need to comply with a diverse range of regulatory restrictions if a solution can really be sold on a global basis.

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