LTE-M and NB-IoT are Low Power Wide Area Networks (LPWAN) developed for IoT. These relatively new forms of connectivity come with the benefits of lower power consumption, deep penetration, smaller form factors and, maybe most importantly, reduced costs.
The decision of NB-IoT vs LTE-M is not a simple one. When I searched the internet for a clear answer, I quickly found contradictions and data based on ideal numbers and not the real world.
This article aims to make an unbiased and correct comparison of LTE-M and NB-IoT, cutting through the complexity with an easy-to-follow guide that makes your cellular connectivity decision easier.
Table of Contents
What is NB-IoT?
NB-IoT stands for NarrowBand-Internet of Things and, like LTE-M, is a low power wide area technology developed for IoT.
- Read more about our NB-IoT SIM cards.
- See our full list of available NB-IoT networks.
What is LTE-M?
LTE-M stands for Long Term Evolution for Machines and is the simplified term for eMTC LPWA (enhanced machine type communication low power wide area) technology.
- Read more about our LTE-M SIM cards.
- See our full list of available LTE-M networks.
What’s the difference between NB-IoT and LTE-M?
As we said before, NB-IoT and LTE-M are two key wireless technologies driving the IoT world, each with unique features making them suitable for different applications. Here’s a simplified breakdown of their main differences:
Comparison table: NB-IoT vs LTE-M
| NB-IoT | LTE-M | |
|---|---|---|
| Uplink and downlink speeds | Low (Kbit/s). LTE Cat NB2 offers max 159 Kbit/s uplink and 127 Kbit/s downlink. | High (Mbits/s). LTE Cat M2 offers max 7 Mbit/s uplink and 4 Mbit/s downlink. |
| Coverage/Penetration | Great coverage and penetration. | Great coverage and penetration. |
| Global availability | Good availability. Requires new infrastructure. Cheaper to roll-out than LTE. | Great availability where LTE already exists. Built on existing LTE technology. |
| Roaming capability | Technically possible, but basically non-existent in reality. Check regions of interest. | Good roaming availability. Check regions of interest. |
| Module costs | Typically cheaper than LTE-M. | Typically more expensive than NB-IoT. |
| Power saving features | PSM and eDRX support. | PSM and eDRX support. |
| Mobility | No handover when moving, only suitable for static devices. | Suitable for static and mobile devices. |
| Freedom to leave | Typically no SMS support. Not good for freedom to leave and eUICC (eSIM). | Supports freedom to leave and eUICC (eSIM). |
From the information above, you can see that LTE-M is just as good or better on every attribute except for the module cost.
Key Takeaways:
- NB-IoT is your go-to for cost-effective, low-data-rate applications where device mobility isn’t a concern.
- LTE-M shines in scenarios requiring higher data rates, mobility, and real-time communication.
If you are deploying static devices and need to reduce your BOM (Bill of materials) as much as possible, then NB-IoT might be right for you. Otherwise, LTE-M is most likely your best choice. Keep in mind, a lot depends on where you plan to deploy devices.
Now let’s take a look at the full story for a better understanding of the pros and cons of each technology.
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Penetration
If you ask the internet, you’ll generally hear that NB-IoT supports devices in deeper places than LTE-M.
But is this really the case? Recently, researchers and industry peers have shown this presumption is incorrect.
How is penetration measured?
To understand penetration, here are a couple of terms you need to be familiar with first: decibels, receiver sensitivity, link budget, and maximum coupling loss.
Decibels
We use decibels-milliWatt (dBm) to measure cellular signal strength. It’s logarithmic, and the typical range is -50 dBm to -110 dBm. The power in dBm comes from this equation:
P(dBm) = 10 · log10( P(W) / 1mW )
P(dBm) = Power expressed in dBm
P(W) = The absolute power measured in Watts
mW = milliWatts
log10 = Log base 10
Without getting further into the math, it’s good to know that every 3 dBm increase more-or-less doubles the signal strength, and roughly every 6 dBm increase doubles the coverage distance from the cell tower. You can read more on this topic here: How to measure signal strength.
Receiver sensitivity and link budget
A radio receiver’s sensitivity level indicates its capability to extract information from a weak signal and is denoted as the lowest signal level that can be useful. In this case, a lower sensitivity number means the receiver is better and has a higher sensitivity (-73 dB is better than -70 dB).
The link budget shows what happens to the signal between transmitter and receiver. It represents the change between the transmitted and received power at the receiver.
Maximum Coupling Loss (MCL)
Bringing this knowledge about dBm, link budget and receiver sensitivity together, 3GPP uses MCL to evaluate coverage.
In theory, it can be defined as the maximum loss in the conducted power level that a system can tolerate and still be operational (defined by a minimum acceptable received power level). A higher MCL means a more robust link between transmitter and receiver.
What is the MCL for NB-IoT and LTE-M?
3GPP’s website refers to the book Cellular Internet of Things (Second Edition) From Massive Deployments to Critical 5G Applications as a source for more information on Nb-IoT and LTE-M.
According to that book, the MCLs on 4G telecom technology are:
- LTE-M: 160.7 dB
- NB-IoT: 164 dB
In some 5G use cases, the requirements for NB-IoT and/or LTE-M may include a MCL of 164 dB and support for a connection density of 1,000,000 devices per km2, but this varies based on specific scenarios and use cases.
So, according to those MCLs, NB-IoT and LTE-M have the same penetration depth for 5G standards. For 4G standards, LTE-M falls behind the NB-IoT by 3.3 dB (160.7 dB).
What does research into LTE-M coverage show?
However, prominent companies in the telecom industry have conducted simulations based on the assumptions 3GPP has made. They researched the coverage for LTE-M and its suitability for IoT applications that need deep coverage: Whitepaper: Coverage Analysis of LTE-M Category-M1.
They found that LTE-M has a very similar penetration ability to other LPWA technologies.
“LTE-M supports a very similar if not better coverage enhancement compared to other LPWA technologies”
Gus Vos, Chief Engineer, Technology Standards, Sierra Wireless.
Why? It turns out the assumptions underlying 3GPP’s MCL calculations varied between technologies and thus was not a fair comparison.
These are the numbers used for calculating the MCL for LTE-M and NB-IoT in 3GPP standards:
| NB-IoT Downlink | NB-IoT Uplink | LTE-M Uplink | LTE-M Uplink | |
|---|---|---|---|---|
| Transmit Power | 46 dBm | 23 dBM | 43 dBm | 23 dBm |
| Noise Figure | 9 dB | 5 dB | 5 dB | 3 dB |
They went deep on the MCL calculations using typical LTE-M assumptions for the receiver noise figure and transmit power and found the penetration for LTE-M to be identical or better than NB-IoT.
How about real-world tests?
Jussi Ratilainen, CTO at Loopshore, is one example of someone who didn’t want to rely on what others said about the two standards.
He tested the NB-IoT vs LTE-M in practice using their Loopshore air quality sensing devices. The results surprised him “I assumed that Cat-NB would outperform Cat-M easily, I just wanted to know how much. But results hint that it might be the other way around.” (NB Cat-NB = NB-IoT and Cat-M = LTE-M)
The penetration conclusion
Both NB-IoT and LTE-M are well suited for deep penetration. Research shows that LTE-M is capable of attaining the same penetration depth as NB-IoT (but at the cost of extra power consumption? You can read more on this below).
However, it’s important to keep in mind that the parameters involved in tests and simulations around the penetration capabilities could vary a lot from device to device, cell tower to cell tower, etc.
As a final note, a disadvantage that NB-IoT has here compared to LTE-M is that NB-IoT is not available wholesale. Currently, your device will only have access to a subset of base stations in a country when using NB-IoT. LTE-M already has wholesale agreements available, meaning today it’s possible to attach to multiple LTE-M networks from one device, thus increasing the chance of finding a strong enough connection.
Global deployment and roaming
NB-IoT can be deployed on both 2G (GSM) and 4G (LTE) networks, while LTE-M is solely for 4G. However, LTE-M is already compatible with the existing LTE network, while NB-IoT uses DSSS modulation, which requires specific hardware. Both are planned to be available on 5G. These factors, plus some others, impact availability around the world.
Global availability
Fortunately, GSMA has a handy resource called the Mobile IoT Deployment Map. In it, you can see the global deployment of NB-IoT and LTE-M technologies.
Operators typically deployed LTE-M first in countries that had LTE coverage already (e.g. the US). It’s relatively easier to upgrade an existing LTE tower to support LTE-M than to add NB-IoT support.
However, if LTE is not supported already, it is cheaper to put up new NB-IoT infrastructure.
Another factor to consider is that companies like Huawei are pretty invested in NB-IoT intellectual property (IP) and support its rollout. You can read more about this topic here: LTE-M vs NB-IoT: An Overview of Narrowband IoT.
Roaming agreements
Deployment is something you will need to consider if you are sending a device somewhere. And if that device is not staying in the same place forever or you’re not sure where in the world it will deploy, you’ll also need to consider the nuances of roaming with LTE-M and NB-IoT.
LTE-M has the advantage of having cellular roaming agreements already in place, while NB-IoT is far behind. Therefore roaming for NB-IoT is comparatively limited.
Global deployment and roaming conclusion
The decisions here depend on where your device will be situated and whether or not it will need roaming. If your device might need to roam, LTE-M is your natural choice.
If your device will be static in, e.g. China, then NB-IoT is currently the choice that makes sense.
Nevertheless, NB-IoT and LTE-M are still in their early days, and it’s currently helpful to have 2G or 4G fallback options, for example.
Power consumption
Traditional cellular standards are designed to function with voice and SMS, and so are always listening for incoming calls. But most IoT use cases don’t require that devices listen, which means traditional standards (2G, 3G, 4G) use more power than NB-IoT and LTE-M.
Most IoT applications focus on low-power applications. Energy efficiency and long battery lifetimes are essential. Think of use cases like smart cities, micromobility, and energy and utilities here.
NB-IoT and LTE-M represent a significant improvement in power consumption compared to other cellular standards. However, comparing the two IoT connectivity solutions is tricky due to the many factors that influence power consumption and battery lifetime.
NB-IoT and LTE-M have power-saving features
PSM (Power Saving Mode) and eDRX (Extended Discontinuous Reception) can dramatically extend the battery lifetimes of IoT devices using LTE-M or NB-IoT network technologies.
PSM is a power-saving mode that puts IoT devices in low-power mode for long periods of time and only wakes them up briefly to receive data or send a status update. This low-power mode saves the maximum amount of energy when the IoT device is not in use.
eDRX is an idle mode that typically uses shorter idle intervals than PSM. eDRX doesn’t reduce power usage as much as PSM, but it doesn’t require as much power to wake up and listen for messages.
PSM is generally used for devices that infrequently send data (like smart bin level monitoring), while eDRX is good for devices that need to listen, but don’t need to instantly react (like smart meters). Furthermore, by combining PSM and eDRX, as seen in the image below, you can further optimize the power consumption of devices.
However, in practice, it’s crucial that you thoroughly test these features on your device first. While they are great in theory, using them may not be straightforward.
We discussed this in a recent webinar with LightBug CEO and Founder Chris Guest. LightBug experienced difficulties in getting these power-saving features to work reliably and instead created their own “sleep” logic for their tracking devices.
Powered usage during transmission
The average transmission current of LTE-M is slightly higher than NB-IoT according to 3GPP 36.888 and 3GPP 45.820. But this potentially higher transmission current is often outweighed by the dramatically shorter transmission time that LTE-M has due to its higher uplink and downlink speeds. This is thanks to the generally higher bandwidth LTE-M operates at compared to NB-IoT.
| NB-IoT Downlink | NB-IoT Uplink | LTE-M Downlink | LTE-M Uplink | |
|---|---|---|---|---|
| Transmit Power | 46 dBm | 23 dBM | 43 dBm | 23 dBm |
| Max speed | 26 kbit/s | 66 kbit/s | 1 Mbit/s | 1 Mbit/s |
However, factors such as coupling loss (coverage conditions) will significantly affect the uplink/downlink speeds.
You could say that in good conditions, LTE-M will reap the rewards of faster data speeds. However, in bad conditions, NB-IoT may have faster data speeds.
See the graph below for an illustration of one study on NB-IoT and LTE-M (eMTC) power consumption.
Power consumption field test
Nordic Semiconductor conducted LTE-M and NB-IoT field tests using their nRF9160 System in Package which features a multi-mode modem offering both NB-IoT and LTE-M.
They found that LTE-M used less than half the energy (i.e. charge) from 4-10 km distance. This is thanks to it having less time in connection than the NB-IoT devices in the test. NB-IoT achieved similar results for up to 3 km and better results from 11 to 12 km because of poor conditions (natural obstructions).
Nordic Semiconductor concludes that “under normal conditions using LTE-M will on average have a lower power consumption than NB-IoT, but if you have devices deployed a long distance away from the eNB or with a lot of obstructions, then NB-IoT technology would be to prefer.” You can read the full report here LTE-M vs NB-IoT Field Test: How Distance Affects Power Consumption.
Power consumption conclusion
Power consumption in NB-IoT and LTE-M is heavily dependant on your particular use case and the devices you use.
A straight comparison between the two technologies is complicated as many variables dictate power consumption (transmission frequency, transmission size, coupling loss).
Mobility
When moving, your device will need to switch between base stations (aka cell towers) frequently.
The image below is from a study by Fabien Sanglard and elegantly shows how his phone jumped between base stations while moving.
As you can see, there are a lot of handovers between base stations in a short journey. This handover process is about your device’s connection being seamlessly transferred from one base station to another.
NB-IoT isn’t capable of this kind of seamless handover. As a device moves out of cell tower range, it will increase the power (conductive Tx power) to stay connected. Once it becomes disconnected, it must register with the network again, causing a connectivity drop and increasing power consumption.
Mobility conclusion
It’s simple, use LTE-M for mobile devices.
The lack of handover between baste stations for NB-IoT makes it more suited to static applications.
Freedom to leave
Freedom to leave (aka freedom to operate) is not often discussed in our industry as it’s not commonly available. But it’s something that runs to the core of Onomondo (and is possible because of our network core), so it would be a shame not to look into the possibilities here for the two technologies as well.
In short, freedom to leave is about the ability to transfer an IoT SIM card to a new operator over the air (or load a new operator profile onto the SIM). If you don’t have freedom to leave and haven’t already got support for your desired operator on deployed SIMs, you’ll need to physically visit all of your devices to swap SIM cards to change operator. Visiting devices to switch SIMs is generally either very expensive or almost impossible.
Most will tell you this is not a problem with eUICC. But there is still an issue with vendor lock-in for eUICC thanks to eUICC platforms, meaning you don’t have total freedom to operate with your SIMs.
Read a thorough overview of eSIM/eUICC and existing lock-ins here: What are eSIMs?
Onomondo makes it possible to switch operators on regular UICC SIMs via over-the-air (OTA) updates. We can do this thanks to our network setup and our complete control over our SIMs’ IMSI, Ki and OPC keys, a vital part of switching operators.
NB-IoT and LTE-M SIM identity switching
Most operators don’t support SMS on NB-IoT. This means eUICC will not work in many networks, and Onomondo’s OTA operator updates are also not possible.
“Only some of the operators deploying NB-IoT will support SMS, thus no clear deployment recommendation can be provided at this time”
NB-IoT deployment guide, June 2019, GSMA
LTE-M supports OTA updates. Additionally, the higher bandwidths of LTE-M make the transmission of SIM profiles easier (or any software update for that matter).
Freedom to leave conclusion
If you are considering eUICC, then it’s best to go for LTE-M. eUICC most probably won’t work in your region(s) of interest on NB-IoT.
Additionally, NB-IoT is more of an operator lock-in risk as switching operators are generally not possible OTA.
LTE-M vs NB-IoT conclusion
Based on the above considerations, you can see that LTE-M and NB-IoT are both strong technology standards for IoT applications.
- Coverage/Penetration: In the real world, LTE-M is probably as good as NB-IoT.
- Global deployment and roaming: Roaming is better with LTE-M. However, it’s important to check availability in your region(s) of interest.
- Power consumption: This is a hard one to call. It appears that LTE-M is better in good to average coverage conditions, and NB-IoT is better in poor coverage conditions.
- Mobility: LTE-M is suitable for static and mobile devices, while NB-IoT is only suitable for static.
- Freedom to leave: LTE-M supports freedom to leave and eUICC, NB-IoT generally doesn’t.
My opinion is that LTE-M is overall the more robust choice for IoT solutions.
If you add that OTA firmware updates are easier with LTE-M and that it’s voice ready, it’s the more flexible solution of the two and represents a solid, future-proofed connectivity choice.
However, be sure to speak to your LTE-M SIM or NB-IoT SIM provider about regions of interest and technology availability before diving in. In many cases, the more ubiquitous LTE Cat 1 bis might be the best IoT connectivity option.
