Cellular IoT – The Dust Slowly Settles – MTC, NB-IOT and Things In Between – Part 1

I haven’t written a lot about the Internet of Things (IoT) so far as there are so many different approaches discussed, specified, prototypes tested and proprietary solutions rolled out these days. In other words, it’s not easy to keep an overview and to get a feeling which solutions might might become popular and which will fade away over time. But it looks like 3GPP is finally getting their act together with LTE enhancements in Release 12 and 13 for a wide variety of different Machine Type Communication (MTC) scenarios and the Internet of Things (IoT). While I’ve found information about many different things in many different places I couldn’t find an overview that sets all of these things in perspective. So I decided to do it here. Read on for the details.

In this post I will focus on 3GPP defined solutions and completely disregard other proprietary systems such as Sigfox, Loran, etc.

Why Pure LTE Is Not Ideal for the Internet of Things

When LTE was designed it addressed one main requirement: It has to be fast. While this is great for mobile broadband purposes it doesn’t work so well for other applications like wearables, industrial sensors, home appliances, etc. etc. Such devices devices that have to be very small, only come with a very small battery and are often put into places like basements where cellular network coverage is weak or even non-existent today. In many cases, IoT devices in home environments can make use of a local area networks or a central IoT hub close by that interacts with small IoT devices and forwards the data over Wifi, cable, DSL and fiber. In other cases that’s not possible, e.g. a power monitoring device in the basement or for industrial applications. In many cases it could therefore be beneficial to use a cellular network as backhaul.

LTE and the Internet of Things

While GSM was and is still used today for many machine to machine applications, it’s legacy technology and many network operators would like to switch it off rather sooner than later. That leaves LTE networks as a connectivity option in the future for such devices. However, LTE was never designed to be power efficient, to handle potentially tens of thousands of such devices per cell or to support low complexity and cheap devices that only transport little data. Over the past few years, 3GPP has thus specified a number of enhancements for LTE from simple to radically new to enable connectivity for IoT devices with the following goals in mind:

• Low cost radios in devices, $5 or less
• Deep indoor and long range coverage not possible with LTE today
• Support up to 50.000 devices per cell that only transmit a few bytes a day.
• Ultra low power consumption, battery life of up to 10 years for devices that only transmit a few bytes a day
• Efficiently support devices with low data rates, i.e. a few hundred kilobits per second maximum throughput in exchange for simplicity and low cost ($5 or less) and significantly increased radio sensitivity (deep indoor coverage)

Obviously one kind of IoT radio doesn’t fit all potential use cases. Some IoT applications might want to transmit data quite frequently and at a bit rate such as a few hundred kilobits per seconds while they can compromise on power efficiency and indoor coverage in return. Other IoT applications might only want to exchange fifty bytes a day but must do so from very far away from a base station or are installed in a basement into which 10 or 20 MHz channels used by LTE today simply do not reach into. To cater for anything between those two extremes, 3GPP specifications now offer the following enhancements:

• LTE Category 1 devices with speeds up to 10 Mbit/s
• LTE Category 0 devices with speeds up to 1 Mbit/s
• LTE Category M1 with speeds up to 1 Mbit/s with power efficiency enhancements
• LTE Category NB1 (previously referred to as Cat M2), also referred to as Narrow-Band IoT (NB-IoT) with speeds of a few hundred kbit/s with significant power efficiency enhancements and deep indoor coverage extensions.

One thing they all have in common is that they can communicate with the LTE infrastructure that is already in place today once base station and core network software has been updated. The important point is that a base station can simultaneously handle traditional LTE and LTE-Advanced mobile broadband access and the new device categories. In other words, no dedicated infrastructure is required for Machine Type Communication (MTC) or the Internet of Things (IoT).

So much for today. In the following parts I’ll go into some of the details for each of the new device categories and which features have been standardized for them.