The dawn of Cellular IoT - LTE-Cat M (Cat-M1)

Mobile communications has been the base for the explosion in smartphones. Enormous consumer demand for mobile wireless broadband services has driven the last decade of telecom standards resulting in the LTE-Advanced 4G multi-mode devices that we take for granted today. Beyond serving the needs of smartphones, mobile operators are increasingly thinking about what role they can play in delivering IoT. The IoT market is still considered to be in its infancy, but according to industry analyst firm Gartner by 2020 we can expect over 26 billion ‘things’ or devices to be connected to the internet, the majority of those likely to be served via wireless connections.

IoT devices will connect to the Internet through wired and wireless communication technologies. The wireless technologies could be both cellular and non-cellular. In the case of the local area unlicensed band standards, for example Bluetooth and WiFi, a router is needed to reach the Internet. The LTE Cat-M (Cat-M1) standard is a cellular standard and has a number of benefits compared to the non-cellular technologies. One obvious benefit is the existing infrastructure for LTE, where operators around the world have been rolling out this technology since 2009. According to GSA, there are now 480 LTE networks launched in 157 countries and Ericsson predicts that more than 70% of the world population will have LTE access by 2020.

There are several key additions to the Cat-M (Cat-M1) specification in 3GPP release 13 providing lower cost and power consumption.

The first LTE specification in release 8 specified 4 categories, with Cat-4 as the highest category supporting up to 150Mbits/s in the downlink. The modem complexity is derived from this category and normalized to it. Cat-0 was specified in release 12 as an intermediate step towards a competitive LTE specification for IoT applications. The complexity of LTE Cat-0 vs LTE Cat-4 is estimated to be reduced by 40% mainly due to lower data rates but also from the change in duplex mode, where half duplex mode eliminates the need of a duplexer and so saves cost. LTE Cat-M (Cat-M1) is an optimized IoT version of Cat-0 where the major change is the system bandwidth reduction from 20MHz to 1.4Mhz. Another important change is the transmit power reduction to 20dBm. This reduction eliminates the need for an external power amplifier and enables a single chip solution, again reducing cost. NB-IoT (Cat-M2) is the next step with a lower bandwidth of 200kHz will further reduce the cost and power consumption.

Mistbase and Arm have written a paper where we have investigated how the new 3GPP Rel-13 standard is enabling IoT, both from a HW/SW architecture point of view as well as from a performance point of view. In this paper we focus on LTE Cat-M (Cat-M1) and look ahead on NB-IoT (Cat-M2) which is Mistbase core business.

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