Is support for nRF91 "Full modem FOTA update" required by Nordic or cellular carriers?

[droberson]

Hello,

We are in the feasibility phase of updating a product to include a nRF9151 modem connected to a nRF52840 via a single UART. The modem will operate in SLM (Serial LTE Modem) mode. This must fit on our existing PCB board size which is already quite small, so board space is limited. In regard to nRF91 modem FOTA, my understanding is that in order to perform a "full modem" FOTA update (as opposed to delta FOTA update), an external flash of 4 MB or larger is required to be connected directly to the nRF91 modem to store the downloaded firmware image. It is also my understanding that delta FOTA updates support updating only from one minor version to another (For example, 1.1.1 to 1.1.2), and full modem updates are required to update from one major version to another (For example, 1.1.x to 1.2.x). We are trying to determine if we can do away with the 4 MB flash and the need to support full modem FOTA updates, and only support delta FOTA updates.

Question: Is there some requirement by Nordic or cellular carriers to support full modem FOTA updates?

For example, will a carrier required bugfix ever require a major firmware version change (full modem FOTA update)?

Question: If full modem FOTA is not required, do you see any issues with not supporting it?

For example, will Nordic stop providing bugfixes for products stuck on an old 'major' firmware version that would otherwise require an update to a new 'major' version?

We don't necessarily care about new features, just bugfixes. For FDA approved products, they are required to have the ability to apply any new critical bugfixes that are deemed a cybersecurity threat.

Thanks,

Derek

[dejans]

Hi,

Question: Is there some requirement by Nordic or cellular carriers to support full modem FOTA updates?

For example, will a carrier required bugfix ever require a major firmware version change (full modem FOTA update)?

There are no such requirements from the carrier. On our side there are no 2 modem firmware versions with different major version number which can be run on the same device.

Question: If full modem FOTA is not required, do you see any issues with not supporting it?

For example, will Nordic stop providing bugfixes for products stuck on an old 'major' firmware version that would otherwise require an update to a new 'major' version?

We provide fixes only in the bugfix versions, not in the new major firmware versions. Delta firmware updates are provided for these bugfix versions. 

Best regards,
Dejan

[droberson]

Hey Dejan,

dejans said:

On our side there are no 2 modem firmware versions with different major version number which can be run on the same device.

Using the nRF9160 as an example, it does indeed have 2 or more modem firmware versions with a different major version that can run on the same device.

Some nRF9160 firmware versions include:

1.1.5

1.2.8

1.3.7

The major version jumps from 1 to 2 then to 3. What am I missing in regard to your comment? From my understanding, Nordic uses the second number (in bold above) as the "major" version, and not the first number per industry standard.

Source: https://docs.nordicsemi.com/bundle/comp_matrix_nrf9160/page/COMP/nrf9160/nrf9160_modem_fw.html

"Nordic's current nrF91 modem FOTA is designed to fix bugs and corrections to keep devices in the field running. These are differential updates that can update minor updates, i.e from 1.1.x to 1.1.x+1. It is correct that this will not cover major updates and feature additions, i.e transitions from 1.1.x to 1.2.x."

Source: https://devzone.nordicsemi.com/f/nordic-q-a/56357/nrf9160-modem-fw-fota-updates

"This means you can't jump from a minor version to major one. So from 1.3.x to 1.4.x you would need to do a full modem FOTA"

Source: https://devzone.nordicsemi.com/f/nordic-q-a/98169/nrf9160-fota-modem-updates/417859

Thanks,

Derek

[dejans]

Hi Derek,

I am sorry for confusion. The versioning is done in the form Major.Minor.Bugfix. Modem firmware versions do not follow semantic versioning, meaning that new features can be added to a firmware between "bugfix" version changes.  Delta modem firmware update files are available for minor versions. 

Best regards,
Dejan

[droberson]

For anyone that comes across this in the future, I reached out to Nordic directly via email for additional clarification on the versioning scheme.

From Martin Lesund in cellular:

-------------------------------------------------------

The modem firmware is configured as follows: v<major>.<minor>.<patch>.

Delta FOTA is supported for patch versions, which typically include bug fixes or maintenance updates. For new projects using the nRF9160, it is advisable to start with the latest version, v1.3.x. Regardless of the modem firmware selection, Nordic is required to provide patch updates to address critical bugs as needed.

Full Modem FOTA, which requires external memory, is applicable for updates between minor releases (e.g., from v1.2.x to v1.3.x). This capability was introduced specifically for the nRF9160 to facilitate upgrades to the v1.3.x path, as this version is supported globally by carriers, whereas versions v1.1.x and v1.2.x have more regional support and are not recommended for new designs.

For the nRF9151, we are on version v2.0.x, there are no plans to introduce new minor releases. Instead, ongoing support will be provided through patch releases, ensuring full compatibility with Delta FOTA (no ext. flash needed).

The recommended approach is to use the latest v1.3.x for the nRF9160 and v2.0.x for the nRF9151, thereby eliminating the need for a full modem FOTA (and ext. flash).

FOTA between major releases is not supported, as v1.x.x is supported only on nRF9160, and v2.x.x is only supported on nRF91x1.

-------------------------------------------------------

Based on my research, one caveat to the above is the following scenario:

What if the nRF9151 modem is on firmware 2.0.1 and we want to update it to a potential future version of 2.0.7? Can we simply jump from 2.0.1 to 2.0.7, or do we need to go from 2.0.1 to 2.0.2, then from 2.0.2 to 2.0.3, then from 2.0.3 to 2.0.4, etc. up until 2.0.7?

Answer:

If using delta updates (no external flash), you must go from 2.0.1 to 2.0.2, then from 2.0.2 to 2.0.3, then from 2.0.3 to 2.0.4, etc. up until 2.0.7. Otherwise, external flash is needed to jump from 2.0.1 directly to 2.0.7.

Source:  nRF9160 Delta update 1.3.1 -> 1.3.5 

Incremental updates are required in order when using the delta update method which doesn't seem practical in practice when updating thousands of devices in the field unless you are on top of every new update that comes out. In my experience, I usually don't update something unless I have to (If it isn't broke don't fix it). By the time I realize I have to update something, the latest firmware is many versions ahead of the current firmware I am on. In this scenario, jumping from 2.0.1 to 2.0.7 for example would be much easier and straightforward than performing 6 separate delta firmware updates for each device.

Based on the above, I personally wouldn't recommend building a device without external flash (full modem FOTA capability) unless you are willing to accept and handle this caveat accordingly. This is my stance unless Nordic tells me otherwise.