When considering cellular connectivity, M2M has always been mainly about using low data rates. The aim for M2M solution designers has been to get the required information from a remote device using the least amount of bandwidth feasible for the job. Now that is beginning to change, but not in a uniform way. So why the interest in a high data rate technology like LTE?
In some markets there is now a forced move to 3G and even 4G as 2G networks are switched off to refarm the spectrum. As part of enabling this, higher bandwidths are being made available at low prices and this has raised the prospect in the market of creating richer M2M applications using more, cheap bandwidth rather than continuing the struggle to use the minimum.
There are growing instances of considerably more bandwidth now starting to be used by some M2M applications and there is every prospect that this will continue. As part of this, there is increasing interest in using LTE for these.
Most M2M applications do not need that higher bandwidth though. Then there is the idea of the Internet of Things – possibly billions of sensors producing huge amounts of data, but the bandwidth required for each sensor is tiny.
What is often overlooked is that LTE is not just about high data rates, but low ones too. Because it is based on OFDM (Orthogonal Frequency Division Multiplexing) and on IP, the air interface can be split into several narrow band channels having different bandwidths. Release 8 permits channel bandwidths of 1.4. 3, 5, 10, 15 and 20 MHz with no fundamental change to the radio architecture. Allowing bandwidth to be assigned in a very flexible way could make it ideal for M2M and IoT applications.
This is where LTE-M (the M is for M2M) is heading, as outlined at a recent event by Sierra Wireless who are very much involved in developments in this area, initially through their acquisition of part of Sagemcom. See here for the original EU-funded project covering this. This is increasingly being referred to as Cellular for IoT and – intriguingly – may also cover local mesh networking as well as traditional cellular switching, all aimed at being low cost, low power and low data rate.
There are still various options being discussed for this but the goal is for very low cost modules (under $5), very long battery life (more than 10 years) and low data rates... over existing cellular infrastructure. All of this can be two-way communication, unlike some other narrow band options. Too good to be true? We will have to see, but 2016 should see this start to come to market.