4G Connectivity - Cat-M1 vs NB-IoT, Coverage, Providers and Roaming

Many countries and network operators globally have rolled out or are in the process of rolling out Cat-M1/NB-IoT networks. We refer to Cat-M1, but it is often also called LTE-M1. NB-IoT is sometimes called NB1.

The benefits of these networks are covered here:
Understanding Cellular IoT in tracking

The GSMA provide an up to date list of what networks different mobile network operators have deployed.
GSMA - Mobile IoT Launches

Cat-M1 vs NB-IoT - key differences

Cat-M1 and NB-IoT are quite similar but have some key differences which make each network better suited to particular applications. There is no outright 'better' or 'worse' - the networks can be selected to suit the application. Our 4G device use the uBlox SARA R410M modem which supports both networks.

Note this does not mean that the device will choose whichever network is available (i.e. roam on both)

This is complicated for a number of technical reasons, and typically SIM cards are not yet available which will do both regardless.

Maturity, support, and DM's confidence

Digital Matter's experience with both Cat-M1 vs NB-IoT has shown Cat-M1 to be more mature and better supported. This may be due to the territories and networks operating there. In the US, AT&T coverage has been reliable and extensive. In Australia, Telstra coverage has also been reliable and extensive. In both the US and Australia, Cat-M1 has proven to be a suitable replacement for 3G, and we confidently supply devices for use on both networks.

NB-IoT has been more challenging. Europe is the primary driver for this technology, and each territory has different challenges. Global roaming SIM cards are more popular in these regions, and this poses a variety of challenges. NB-IoT roaming has not proven successful, so using a 'non-home network' SIM is risky. We hope this will change. Roaming triggers NB-IoT network scans, which are very battery intensive, and can be costly in applications where battery life is important.

Digital Matter confidence levels can be summarised as:

  1. Cat-M1, on the SIM's home network: highly confident and very well proven.
  2. Cat-M1, with a roaming SIM: with the right APN settings, confident, and well proven.
  3. NB-IoT, on the SIM's home network: experience varies greatly between networks and regions. Proceed with caution.
  4. NB-IoT, with a roaming SIM: we have not seen this work yet, but hope to have an update soon as network roaming agreements progress. Expect this not to work.

Bandwidth and Data Rate

NB-IoT uses a very narrow bandwidth (200 kHz), compared to Cat-M1 which uses 1.4 MHz. As a result the maximum data rate for NB-IoT is around 250 kb per second. Compared to Cat-M1 - up to 1 Mbps. 

The takeaway - Cat-M1 can support faster data transfer. This does not ultimately mean it is definitively better.

In many applications we are only sending little bits of data, so faster is not always necessary, or better. NB-IoT components can be built simpler and cheaper, which is well suited to deploying large numbers of devices. 

Cell tower handover

Cat-M1 supports cell tower handover - the connection will be maintained when the device is on the move and comes into range of a new tower. NB-IoT will drop the connection. 

For assets on the move such as vehicles, this gives Cat-M1 the edge. However for many asset tracking applications, the connection isn't maintained anyway. The device simply wakes up every few hours, does an upload, and goes back to sleep. 

Range and Battery Life

Both networks provide excellent range and penetration, particularly when compared to 3G or 2G networks. 

NB-IoT uses slightly less energy when the modem is running transferring data - however due to the slower speeds, uploads often take longer than Cat-M1. So in effect the same amount of energy ends up being used for larger uploads, since the device spends longer uploading.

Global Deployments

While they are both relatively new networks - from what we have seen Cat-M1 appears to be far more established globally. With many countries having excellent, commercially ready networks. The same can not be said for NB-IoT at this stage, this may change in future. 

Summary + Applications


  • Faster speeds, slightly less energy efficient than NB-IoT
  • Suited to tracking moving assets (due to cell tower handover)
  • Suitable for live tracking where data is sent regularly - e.g vehicles
  • Some applications which it is suited to:
    • Asset trackers such as vehicles, equipment, bins, tools
    • Telematics devices which send comparitively high amounts of data such as the tag lists on Digital Matter BLE enabled devices.
    • Cold chain monitoring, rental vehicles


  • Proceed with caution on home networks, and expect roaming networks not to work.
  • Low power
  • Low cost (supports deploying many thousands/millions)
  • Lower speed
  • No cell tower handover
  • It is well suited to applications which are not adversely impacted by the lower data rate or lack of handover - think stationary devices sending small bits of data infrequently such as:
    • Sensor monitoring - e.g Gas sensors in a basement
    • Ag Tech (farming sensor monitoring/data logging)

I want to use Digital Matter devices in my country, what do I do to get connected?

We produce devices which utilise a variety of networks:

  • 2G
  • 4G Cat-M1 and NB-IoT
  • LoRaWAN (all global regions)
  • Sigfox - RCZ1, RCZ2, RCZ4
  • 3G available subject to MOQ. 

See the complete range here

In order to determine which device will be right for your region we need to determine what networks are available. 

To see whether Cat-M1/NB-IoT will be suitable, 

  1. Check if you have a Cat-M1 or NB-IoT network in your country here: GSMA - Mobile IoT Launches
  2. You will need to find a SIM provider that will let you get on one of these networks.
    Options are:
    1. Enquire directly with the network listed in the link above
    2. Find another local SIM provider that supplies cards which utilise one of these networks
    3. Find a roaming SIM provider who's cards will roam on the above networks. Note that some networks reserve the right to kick roaming SIMs off their network which stay attached for too long (often around 6 months). This may pose a risk to your deployment.

Getting Connected - the tricky bits

You may be used to setting APNs on devices in order to get them online. APN stands for Access Point Name. The APN provides the device with all the information that it needs to connect to the network - e.g which ports to use, what IP address etc. 

On our 2G and 3G devices, a list of APNs is stored in device FW. When a SIM is inserted, it reports its IMSI - International Mobile Subscriber Identity. Then if there is an APN against this IMSI this is used and the device can join the network. If the right APN isn't in the list, it needs to be set. This can be done via SMS easily on 2G and 3G, as SMSes can be received even if the device isn't connected to the network. 

On our 4G devices, we also have the Auto-APN feature, where a device will automatically detect the settings to use. Typically most devices come online with most SIMs without any input. On top of this, when specific SIM cards are detected, we apply the best possible modem settings (as advised by the mobile networks) to allow for the best connection speeds. However not every network is the same, and sometimes APNs and network settings need to be applied manually.

4G networks networks use a flat architecture where all communication is sent via the data network - so the device must be online to receive an SMS. This makes setting an APN directly via SMS impossible! We have developed other methods to achieve this which are covered here:
4G APN - How do I set the APN so I can get connected to the network?

The issue is that if you do not have access to the device and it won't connect - settings can't be changed to rectify the situation without retrieving the device. This can make roaming difficult.

Roaming on Cat-M1 and NB-IoT - Do DM devices roam?

Digital Matter devices are able to roam between countries and join different networks. There is nothing specific to the device which will enable/prevent this. It is typically down to whether or not the SIM card in the device can successfully attach to various networks in different countries. That being said, there are some issues with roaming.

  1. Rollout of 4G Networks
    4G Cat-M1 and NB-IoT networks are still quite new. Many countries are rapidly rolling these networks out along with 5G networks. However there are still many countries around the world (particularly developing countries) which do not have 4G Cat-M1 or NB-IoT coverage, and may not for some time.
    On top of this, given how new the networks are, many operators are still getting roaming agreements in place. 2G and 3G networks have been long established so this has all been put in place.
    More and more 4G Cat-M1/NB-IoT enabled roaming SIM cards are becoming available as time progresses. NB-IoT roaming is very new and has not been demonstrated successfully at this time, so proceed with caution.
    Generally though they will still have 2G or 3G coverage, and we can provide devices which operate on these networks.
  2. Network settings
    While a SIM card may be able to roam to multiple countries and use networks in these locations, the specific mobile networks may require advanced or specific configuration in regards to what APN is set, and what LTE bands the devices connect on. This is hard to manage if each country requires a different set up, as then we cannot use the same set up to ensure connectivity is maintained in all countries.
  3. Our Experiences
    See Digital Matter network confidence levels above for our experience and results with Cat-M1 and NB-IoT networks when using roaming SIM cards.
    In short, we have seen Cat-M1 roaming SIMs perform well when the right APN settings are used.
    We have not seen NB-IoT SIMs work properly.

So what's the bottom line?

  • If roaming on 4G is required, you must ensure there is a 4G network available in all countries the device may end up. Due to the relative infancy of 4G compared to 2G and 3G, this might not be easy - giving the edge (at least for now) to 2G/3G for roaming applications - purely since they are more widespread.
  • Go for a Cat-M1 roaming SIM rather than Nb-IoT.
    Although our devices can use either Cat-M1 or NB-IoT, they won't automatically switch between what is available. So this make the above point even more relevant, as even for the countries rolling out 4G - they may not be rolling out Cat-M1 and NB-IoT together, meaning even the countries you want to operate in all have 4G, they may not all be on M1, or NB-IoT, meaning roaming isn't possible.
  • TEST


The latest ublox modem update enabled ePCO on the SARA R410M-02B. Many NB-IoT networks do not yet support ePCO, and offer PCO instead, despite ePCO being part of the NB-IoT spec. This effectively means that DNS does not work, so the devices cannot resolve the IP address for sX.oemserver.com. To fix the DNS on these networks you need to update the modem's internal network profiles, and enable PCO support in your network settings, as described in this article.

Other Resources

  • For help in choosing a SIM to get online, see SIM Providers: LTE-M/Nb-IoT + Roaming, and Setup
  • Sick of hearing us bang on about networks? Check out the webinar M2M One (Australian SIM Provider) did on the topic - Link Here. This provides some great answers to common questions, related to networks in Australia (note it is not specific to DM devices but just general info)

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