3GPP—the industry expert behind the standardization of cellular systems—has recently introduced three new standards: LTE-MTC (no called LTE-M1), Narrowband (NB) LTE-M, and Narrowband (NB) IoT. These are the cellular industry's attempts at allowing devices that operate on carrier networks to be less expensive and more power efficient, thus making an impact on the Internet of Things (also called LTE IoT in the cellular space) and machine-to-machine (M2M) communications space. They are offered as an answer to the LoRa, LoRaWAN, and SIGFOX-type technologies. Each of these standards is fighting to become dominant, and they’re all a little different from one another. We’ll describe those differences and explain what you need to know about the technology and uses.
LTE-MTC (LTE-M or LTE Cat-M1)
LTE-M, which is an abbreviated version of LTE-MTC (or “machine-type communications”), is a part of 3GPP’s release 12 and 13, and was finalized in 2016. The LTE channel is made up of resource blocks of about 230 kHz of spectrum, and LTE-M is part of the 1.4 MHz block, comprised of six resource blocks. LTE-M is more energy efficient because of its extended discontinuous repetition cycle (eDRX), which means the endpoint can communicate with the tower or the network on how often it will wake up to listen for the downlink. This can be anywhere from 10s to 40 minutes or more. While promising, as of April 2017, eDRX had not been deployed on any LTE-M1 networks.
Update: Link Labs now supports LTE-M
LTE-PSM from Rel 12 (power-saving mode) had a similar feature, but extended sDRX was created specifically for LTE-M in Rel 13. PSM is an important part of LTE-M, since it allows devices to remain completely ideal, without having to re-join the network when it wakes up.
The advantage of LTE-MTC for M2M communications is that it works within the normal construct of LTE networks. In other words, a cellular carrier like Verizon or AT&T only have to upload new software onto its base stations to turn on LTE-M and won’t have to spend any money on new antennas. It’s also five times simpler than a category 4 receiver—like that found in user equipment like a cell phone—because it needs only to understand and digitize 1.4 MHz of the channel instead of 20 MHz.
Sequans is a leading provider of chips specifically for LTE-M. Certified modules for LTE-M cost around $15 or less.
LTE-M has a little higher data rate than NB-LTE-M and NB-IoT, but it is able to transmit fairly large chunks of data. Thus, it can be used for applications such as tracking objects, wearables, energy management, utility metering, and city infrastructure. The data rates are theoretically around 100kb/s up and down, but generally average at 64kb/s on today's Verizon network.
NB-LTE-M & NB-IoT
Like LTE-M, NB-LTE-M is another overlay of existing LTE structure. It is created by dedicating existing resource blocks to IoT traffic, through using smaller channels to make simpler receivers. NB-LTE-M proposes to refarm GSM by using a single ~200 kHz resource block.
Read More: Detailed post on Narrowband IOT
NB-LTE-M is unique in that instead of using 1.4 MHz spectrum and six resource blocks, it uses only one LTE resource block. This gives the user an effective throughput of about 200 kbps down and 144 kbps up.
NB-IoT is another 3GPP Rel 13 proposal which is not based on LTE, but instead on a DSSS modulation similar to the old Neul version of Weightless-W. The mode of complexity is even simpler than NB-LTE-M, and the chipsets will likely be lower cost. NB-IoT proponents, including Huawei, Ericsson, Qualcomm, and Vodafone, are actively involved in putting this standard together.
The problem with NB-IoT is its difficulty with deployability. Since it isn’t a part of LTE, it either needs to operate in a side band using different software—which may be costly for the carriers—or it needs to be deployed in deprecated GSP spectrum.
Comparison Of Narrowband Technologies
The real question here is which narrowband standard will be the predominant standard for smaller channel cellular IoT. Qualcomm, for example, thinks NB-IoT and LTE-M should be used, but NB-LTE-M should not . NB-IoT is “newer,” and potentially less expensive, but the carriers will not necessarily be able to use the same LTE radios they use for their data networks today.
NB-IoT and NB-LTE-M have differences from a technological standpoint, but they are being created to service similar use cases. For instance, they will both be ideal environmental monitoring, smart buildings, and sensor data monitoring. But, if both technologies are approved, cellular carriers will have to choose which technology to deploy to service narrowband applications. This may lead to some fracturing in the cell world. We’ll start seeing which of these standards is dominant in coming months and years.
If you need to go to market today with your solution, only limited LTE Cat-M is available. The NB-IOT chipsets are in the prototype stage, and no networks currently support them. NB-IOT likely won’t be rolled out for years.
If you’re looking to go to market soon, there are plenty of solutions that provide low power, wide-area network (LPWAN) coverage where you need it—like Symphony Link. But keep your eye on this space; there very well may be a cellular option that has the same cost and power performance as many LPWANs very soon.