Connectivity is a critical component to any IoT application, without it, IoT devices are just Things. In this article, I’ll examine NB-IoT, some of its recent advancements, and the applications where it really shines.
NB-IoT (which stands for Narrowband IoT) is a LPWAN technology that operates at a licensed frequency 200kHZ. It’s called a narrowband frequency because it operates with a very small difference between the highest and lowest frequency.
The operating frequency determines a couple of things, including how much data can be transmitted, power consumption required to operate, and the range at which data can be transmitted. NB-IoT operates at a higher frequency than LoRa and Sigfox, so it has a higher data rate, but less effective range. But a lower frequency than LTE-M which means it has a lower data rate, but larger effective range. Each frequency that a device transmits on consumes power, so narrowband technologies have a lower power consumption than non-narrowband technologies.
And because the spectrum is licensed and managed by the FCC, it is expected to be more reliable and have less noise.
NB-IoT is a subset of the LTE-M standard and is managed by the 3GPP (3rd Generation Partnership Program). Release 14 was frozen in June of 2017 and brought a lot of improvements to NB-IoT. The reason that we are talking about NB-IoT now, 3 years later, is because technology has advanced and devices that meet the 14th release have become widely available.
The first key improvement that was made from v13 to v14 is the addition of a 14 dBm device transmit power added to the spec. dBm, Decibel-milliwatts, is a power ratio expressed in decibels (dB) with reference to one milliwatt (mW). What this boils down to is the lower the dBm, the less power in mW used by the device. The other 2 transmit power supported in v13 are 20 dBm, and 23 dBm. The additional support of 14dBm is a significant reduction in power consumption when the device is sending and receiving data and thus extending battery life.
The second improvement was a massive increase to the data rate - from 26 to 127 kbit/s Downlink and 66 to 159 kbit/s uplink. This improvement speaks for itself, being able to upload and download data from the device faster will allow for a reduction in battery consumption.
The third improvement was to support Observed Time Difference Of Arrival (OTDOA) and Enhanced Cell ID (E-CID) positioning methods. These methods use the signal strength, and a time of arrival calculation to use multilateration to calculate the position of a device. This method can be used indoors or when a device does not support GPS.
The last improvements I want to touch on are multicast transmission mode and the multi-carrier mode. The multicast transmission mode enables firmware and other updates to be done on a large number of devices simultaneously, drastically reducing the headache involved in device management. And multi-carrier mode allows you to set an anchor carrier to be used for initial setup and data communication and non-anchor carriers for data transfer.
NB-IoT is a great solution for any device that is going to be deployed for any period of time, and left in the field. Though it has its own set of constraints, it is very efficient in terms of battery power, and can last several years or longer.