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LTE MulteFire – Firing on all Cylinders, or Late to the LTE Party?

Jun 6, 2017

In the IoT world, there’s a new technology to be excited about every week, and unlike hype surrounding the latest Beyonce album or fidget toy, there is real-world substance behind the crowds of tittering IoT fans. MulteFire is the latest technology from Qualcomm, and builds upon a string of releases by the 3GPP that have attempted to serve a wider range of applications. When LPWAN technology burst onto the scene it made huge waves, but Low Power Wide Area Networks, despite their obvious benefits and many real world applications, have a drawback. For now at least they are not widespread enough for many use cases, and there is usually a hefty initial cost to build infrastructure that can support a non-cellular network. This is where things get interesting. Cellular alternatives to LPWAN technology have emerged to bridge the gap, creating a sort of hybrid connectivity that uses cellular coverage and gives M2M companies the low power consumption and increased range that they need. MulteFire is the latest iteration of this technology, and seems to offer some of the benefits of both cellular and non- whilst building upon the advances of earlier offerings.

The Big Cats: Cat-1 & Cat-0

With the completion of 3GPP Release 12 in 2015 came Category 1 (or Cat-1), which had been in the works since mid-2009. Cat-1 was intended as an LTE alternative to broadband, but with sub-3G performance levels, it is now used by developers who operate in an LTE coverage area but don’t want all that bandwidth. Cat-1 is already standardized, and experts predict that it will replace 3G for IoT devices once that band is sunsetted as well. The confusingly named Cat-0 is actually an upgrade of its predecessor which optimizes for cost, and as such has positioned itself as a great IoT alternative to Cat-1. Cat-0 has its bandwidth capped at 20MHz, and in doing so eliminates those M2M applications with higher data rates, keeping costs down and paving the way for more relevant cellular IoT connectivity.

The Cat that got the Cream

Cat-M, or Cat-M1, is the culmination of the previous two standards, and really narrows the criteria in favor of M2M communications. Cat-M caps its bandwidth to an almost Sigfox-level 1.4MHz, and as a result experiences speeds of 10mb/s, reducing power consumption and cost into the LPWAN league. Cat-M is clearly intended as an alternative to LPWAN that still operates in the licensed spectrum, and it could well become that alternative, reducing costs by using the LTE band and saving on infrastructure, and improving time-to-market significantly, as carriers are only required to upload new software for Cat-M to be available on the LTE band.

The Straight and NarrowBand

NarrowBand IoT (NB-IoT) was standardized in June 2016, and offers both benefits and drawbacks compared to the Cats. Working on a similar principle to the ultra-narrowband technology of LPWANs like Sigfox and Weightless, NB-IoT operates on the extreme ends of the LTE spectrum, using channels 98% narrower than those for LTE use, effectively taking traffic away from the main spectrum and moving it to the ‘guard-bands’ with little to no traffic. Unfortunately, because NB-IoT uses DSSS modulation to spread the signal and achieve the golden ‘low power: wide area’ ratio, this means that it is more difficult, and costly, to set up, and carriers will potentially have to upgrade infrastructure to access NB-IoT. The benefit of NB-IoT is that it sends all its data directly to the central server without aggregating it at a gateway, which cuts down the time between data exchanges, could decrease interference, and in reality may end up cheaper overall.

The Good, the Band, and the Unlicensed

  While all this data-slinging and spectrum wrangling has been going on, Qualcomm have been working on a way to subvert the busy and semi-exclusive licensed bands, allowing developers to create their own end-to-end solution without having to deal with operators or buy licensed bandwidth. LTE-U (LTE Unlicensed) and LAA (License Assisted Access) both have an ‘anchor’ in licensed spectrum, meaning that they rely on an LTE control channel, but all data passes through the unlicensed band occupied by WiFi and other non-radio communication. Amidst concerns of WiFi interference, Qualcomm confirmed that their un/licensed hybrids use a Listen-before-Talk system, which means the signals search for available space within the spectrum before transmitting, and if there is none available they adjust their on/off cycles to fit between existing WiFi signals. MulteFire is the next generation of these technologies, and only uses unlicensed spectrum, finishing what LTE-U and LAA started in terms of ease of deployment, cost, and global availability. This is a groundbreaking development, and means that those who do not own licensed spectrum can still be part of the IoT, and will allow carriers to ‘offload’ traffic from licensed bands, especially in high density areas. This technology may also have an added advantage, as further development to the authentication protocols could allow LTE devices to be deployed in a MulteFire network, opening a path between licensed and unlicensed spectrum.

Giant Killers or Pied Pipers?

The real question is whether or not these specifications can compete with the LPWAN goliath, which are still positioned to provide the perfect connectivity for industrial M2M technologies, or if they will just sweep up the leftovers that do not move to non-cellular. NB-IoT and Cat-M will certainly offer an alternative, with data and bandwidth caps ensuring that M2M companies can enjoy wide coverage and limited interference, thanks to ‘guard bands’ within LTE, but remote applications may not be covered by the LTE network. MulteFire will act as a medium between licensed and unlicensed spectrum, invaluable within an IoT ecosystem, but its ability to act as a node for LTE devices may restrict it to short range applications.

Can’t We All Just Get Along?

Perhaps then these technologies are not LPWAN alternatives, but should define their own territory for those cases where LPWAN is not viable. In this scenario, cellular options could develop independently, with Cat-1 and -0 picking up where 3G and 2G left off, Cat-M and NB-IoT picking up the applications that need the security of licensed spectrum and slightly larger range, and MulteFire providing a starting point without license issues and acting as a node for nearby LTE devices. This network of interoperable M2M connectivity is in fact what allows the IoT to function, and with a coherent ecosystem in which each connectivity type has its own place and coinciding applications, which can communicate with each other without competing to reach a universal standard, the IoT revolution will live up to its full potential.