IoT connectivity and the choice of standards (Part I)
This article is the first of three about IoT connectivity and the choice of standards. In this part we emphasize on licensed vs. unlicensed radio technology standards and want to investigate into some common communication standards for Low Power Wide Area (LPWA) use cases to give you a better understanding what you should aim for, depending on the project you’re developing.
When developing IoT devices for mobile or outdoor use, well known technologies like the classic WIFI or Zigbee are out of the question. These protocols are made for indoor communication and are established mainly in the field of smart home solutions for the consumer market. Their power consumption and bandwidth usage are not made for devices that need to function in remote places or without any external power source over a longer period.
That pretty much leaves us with established but unlicensed standards such as LoRa or SigFox (just to name two) both utilizing the 868 MHz Band in Europe. They reach far, even through buildings, and are designed for low power consumption. One of the main reasons to choose license-free solutions is to be able to independently enable private networks that can be deployed everywhere. There is no external operator needed, at least for LoRaWAn Networks no fees to pay or no contracts to worry about. But this freedom comes with restrictions.
Imagine you want to market your product outside of Europe. The sub-GHz frequencies are not harmonized across different regions and are subject to a variety of spectrum bands. While Europe uses the 865-868 MHz Band, you’ll have to use 902-928 MHz in the U.S. and 923 MHz in Asia. That brings a lot more complexity in planning and developing your products.
It’s not just the frequencies themselves, the devil’s in the detail: Europe has a lower power limit than the US, a constraint that can impact your device range. Then there is the duty cycle in each of the sub-bands you must comply with in Europe. It only allows you to be on the air for 1% within an hour, so max 36 seconds every 60 minutes. The US in contrast doesn’t allow you to be on air any longer than 400 milliseconds for signal bandwidths lower than 500 kHz. So, you might need to utilize frequency hopping to get your data delivered.
Reliability of your device in each of the different regions is another point to consider when going for license-free networks. Interferences can have a heavy impact on your device’s reliability. While in Europe the 868 band is relatively interference-free since many other wireless solutions operate at 2.4 GHz or 433 MHz, the 900 MHz US band is significantly noisier. It’s been used for many other devices such as cell phones or baby monitors.
Then there is another obstacle, the different regulatory schemes: In the U.S. for example, the Federal Communications Commission (FCC) acts as a certifying body that does enforcement, testing, licensing, and compliance. Without their approval you won’t be able to sell your products there. Europe also requires you to comply to certain standards laid out by the European Telecommunication Standards Institute (ETSI) but contrary to the US you can certify yourself or via a 3rd party test house.
To get your data delivered to the cloud, a LoRaWan network requires additional dedicated gateways. Additional hardware means additional complexity and higher costs. Plus, while NB-IoT utilizes available cellular network coverage, with LoRa you will most likely need to install your own LoRaWan network since there is no comparable coverage given.
If you’re considering a global product, a product where reliability is crucial, you might want to consider going for licensed cellular communication. Besides the standards 2G, 3G, 4G which were mainly designed for human interaction or due to increasing bandwidth for multimedia purposes, there are also the new standards such as NB-IoT or LTE-M available specifically designed for communication between machines or devices.
The data capacity of NB-IoT or LTE-M is higher as with LoRa or SigFox. This is due to the previously mentioned limited number of messages that can be transmitted per day, especially in European networks. They are primarily designed to transport tens of bytes per hour rather than kilobytes. Still, NB-IoT or LTE-M can support similar device lifetimes of up to 5 to 10 years as well.
Finally, licensed cellular communication delivers a proven technology with high security standards. The existing licensed frequency spectrum enables higher QoS (Quality of Service).
With prices going down for licensed mobile communication it gets more and more attractive for IoT developers. One of the last obstacles are the multiple and sometimes often complex pricing models offered by various mobile operators. 1NCE developed the 1NCE IoT Flat Rate, a low-cost and fixed pricing model that allows mobile connectivity for just 10 Dollars over 10 years including 500 MB of data and 250 SMS. Partnering with German operator Deutsche Telekom and China Telecom Global we’re capable of delivering high quality mobile connectivity in over 100 countries worldwide. The obstacle of complex rates is an obstacle of the past.
However, with all advantages NB-IoT and LTE-M brings in terms of long battery life its availability is still in its infancy and worldwide coverage, especially under equal pricing conditions has yet to be improved. Luckily there are the other mobile standards that can be very useful in the meantime.
So far for our comparison of licensed vs unlicensed radio technology standards. In the second part of our three-part blog series we will take a deeper look into the available cellular network standards and explain how you can make best use of them for your individual IoT project.