LTE Link Controller: RAI_UPDATE behaviour

RE: LTE Link Controller: RAI_UPDATE behaviour

Simonr — Wed, 04 Feb 2026 13:30:33 GMT

Hi Al

Since this is a slightly different topic than the original ticket, can you please create a new DevZone ticket for this issue. Please add information on:

What NCS and modem firmware version you're working on as well as what chipset/SiP you're working on.
Which country and network you're on, and if you're using a MVNO (mobile vitrual network operator).

You can potentially test the UDP sample, where PSM should be configured by default. https://docs.nordicsemi.com/bundle/ncs-3.2.1/page/nrf/samples/net/udp/README.html

Best regards,

Simon

RE: LTE Link Controller: RAI_UPDATE behaviour

Monkeytronics — Wed, 04 Feb 2026 08:38:12 GMT

Can I just ask for a bit of clarification around this. In addition to:

## PSM
CONFIG_LTE_PSM_REQ=y
CONFIG_LTE_LC_PSM_MODULE=y

## eDRX
CONFIG_LTE_EDRX_REQ=y
CONFIG_LTE_LC_EDRX_MODULE=y

## RAI
CONFIG_LTE_RAI_REQ=y
CONFIG_LTE_LC_RAI_MODULE=y

and adding the following code just after nrf_modem_lib_init() :

lte_lc_psm_param_set("00111000", "00000110");       // 24 hours &12 seconds
lte_lc_psm_req(true);

lte_lc_ptw_set(LTE_LC_LTE_MODE_LTEM, "0000");       // 1.28 seconds
lte_lc_edrx_param_set(LTE_LC_LTE_MODE_LTEM,"0000"); // 5.12 seconds
lte_lc_edrx_req(true);

rai_set();

What else needs to be done to set up PSM, eDRX and RAI? When I try this code, I'm running into some issues. The lte event handler is telling me that the network is rejecting the PSM paramaters (with active time = -1). And when I log the RAI stuff, it looks like this: MCC: 530, MNC: 5, AS RAI: false, CP RAI: false.

RE: LTE Link Controller: RAI_UPDATE behaviour

Simonr — Thu, 08 Jan 2026 09:59:38 GMT

We got a reply rather fast from the developers today, so here it is:

This is how the modem currently works, yes. In LTE-M during RRC connection establishment, the modem first sende the RAI notification with RAI disabled, and is followed by a second notification with RAI enabled.

Note that we do not clear cached information here. The Network first tells us that RAI won't be used, and then very quickly after enable it. The network may remember device capabilities and then enable AS-RAI at the connection establishment. This is especially the case with NB-IOT as connection establishment is the only place NV-IoT enables AS-RAI.

It might be possible to make a hacky solution with timers to hide these unnecessary reports, but we have decided against that as that could also introduce some other issues.

Best regards,

Simon

RE: LTE Link Controller: RAI_UPDATE behaviour

Simonr — Thu, 08 Jan 2026 08:05:11 GMT

Hi Jordan

Michal is out of office, and it took some time to get to this after the holiday season, so sorry about the late reply here.

I have now updated the internal ticket with your concerns and I agree with your points., We will get back to you when we hear from the devs on this.

Best regards,

Simon

RE: LTE Link Controller: RAI_UPDATE behaviour

JordanYates — Fri, 19 Dec 2025 23:29:20 GMT

> When modem wakes up from PSM, it selects a cell. When the cell has been selected, modem sends a RAI update with RAI not supported, because network communicates the support only in RRC connection establishment.

It seems odd that this behaviour occurs only for RAI, but no other information that could presumably change coming out of PSM. It seems like all other information is cached in the modem and only sent if it has actually changed, as indicated by the lack of other duplicate events notifying the cell tower, PSM parameters, etc.

I agree that this has minimal impact on the functioning of an application. But as it currently stands, using it for information/debug purposes will return the wrong value if the application is caching the support status and a query happens to arrive at the wrong time.

RE: LTE Link Controller: RAI_UPDATE behaviour

Michal — Fri, 19 Dec 2025 13:43:33 GMT

Hello again,

I have an update for you:

When modem wakes up from PSM, it selects a cell. When the cell has been selected, modem sends a RAI update with RAI not supported, because network communicates the support only in RRC connection establishment. At this point, modem does not know whether RAI is supported or not. When RRC connection has been established and RAI is supported, modem sends a new RAI update with RAI supported.

The extra RAI update with RAI not supported is not very useful, but that’s how the modem currently behaves. The RAI update is intended to be used for information/debug purposes, so this should not affect application behavior anyway. The application should always set the RAI socket options, regardless of what the RAI update indicates. Modem then uses RAI if it is supported by the network.

Best regards,

Michal

RE: LTE Link Controller: RAI_UPDATE behaviour

Michal — Mon, 15 Dec 2025 17:52:45 GMT

Sorry, just wanted to be on the same page.

I am checking internally for more information on that behavior.

Best regards,

Michal

RE: LTE Link Controller: RAI_UPDATE behaviour

JordanYates — Wed, 03 Dec 2025 23:27:59 GMT

My own fork of upstream Zephyr. I'm not sure why its relevant though, the events come directly from the modem library, its not like they are generated by the integration layer.

RE: LTE Link Controller: RAI_UPDATE behaviour

Michal — Wed, 03 Dec 2025 11:50:30 GMT

Are you using upstream Zephyr or some other kind of setup with just the nrfxlib?

RE: LTE Link Controller: RAI_UPDATE behaviour

JordanYates — Mon, 01 Dec 2025 04:27:48 GMT

I am not using NCS. The `nrfxlib` version is the v3.1.0 tag: github.com/.../v3.1.0

RE: LTE Link Controller: RAI_UPDATE behaviour

Michal — Mon, 01 Dec 2025 04:25:57 GMT

Hello,

I will check that internally and get back to you.

In the meantime, please also tell me your NCS version.

Best regards,

Michal