nRF9151 DECT NR+ – PT association fails with MAC_STATUS_NO_RESOURCES (7) using official dect_shell sample

[Damntrak06]

Hello,

I am currently testing DECT NR+ communication between multiple nRF9151 SMA DK boards, but I am unable to establish a connection between an FT and a PT.

I initially observed the issue with my own application, so I decided to reproduce the test using the official Nordic dect_shell sample without any modifications.

Unfortunately, I can reproduce the association problem with the official sample as well.

Environment

• Hardware: nRF9151 SMA DK (multiple boards available for testing)
• nRF Connect SDK: v3.4.0
• Zephyr OS: v4.4.0-bf801e4e3d19
• Sample: nrf/samples/dect/dect_shell
• Board target: nrf9151dk/nrf9151/ns
• DECT NR+ modem firmware: mfw-nr+_nrf91x1_2.0.0
• Region: EU
• Band: 1

I configured one board as FT with Long RD ID 1 and another board as PT with Long RD ID 2.

FT configuration

dect sett --reset

dect sett -t 1 --dev_type FT

dect activate

dect connect

The FT successfully creates the network:

NET_EVENT_DECT_RSSI_SCAN_RESULT
RSSI scan result:
  Channel:                             1657
  All subslots free:                   yes
  Busy percentage:                     0%

NET_EVENT_DECT_CLUSTER_CREATED_RESULT
Cluster started/reconfigured at channel 1657.
FT: network created

NET_EVENT_DECT_NETWORK_STATUS:
  Network status: created

dect status reports:

DECT NR+ status:
  Modem FW version:             mfw-nr+_nrf91x1_2.0.0
  Modem activated:              yes
  Cluster running:              yes
  Cluster channel:              1657

I also tested starting the network beacon explicitly.

PT configuration

I first deactivate the modem before resetting/changing the settings:

dect deactivate
dect sett --reset
dect sett -t 2 --dev_type PT
dect activate
dect connect

The PT appears to discover the FT correctly, because it identifies Long RD ID 1 as its Parent, but the association fails with:

NET_EVENT_DECT_ASSOCIATION_CHANGED
 DECT_ASSOCIATION_REQ_FAILED_MDM:
  Association request failed in modem with long RD ID: 1
  Neighbor role:                                       Parent
  Modem cause:                                         No resources (7)

Network creation failed: 7 (No resources)

NET_EVENT_DECT_NETWORK_STATUS:
  Network status: failure 7 (No resources)

<err> dect_mdm: Modem operation failed for Association Response
with err MAC_STATUS_NO_RESOURCES (7) with long RD ID: 0x1

What is interesting is that immediately after this failure, dect cluster_info on the FT reports:

Cluster status information:
  Cluster channel:                 1657
  Number of Association requests:  0
  Number of Association failures:  0
  Number of neighbors:             0
  Number of FTPT neighbors:        0
  Number of received RACH PDCs:    0
  Number of RACH PCC CRC failures: 0

dect neighbor_list on the FT also reports:

No neighbors found.

Therefore, from the PT side it looks like the FT is discovered (Long RD ID 1 / Parent), but the association procedure fails with MAC_STATUS_NO_RESOURCES (7), while the FT does not appear to receive an association request at all.

I have multiple nRF9151 SMA DK boards available and can reproduce the issue after resetting the DECT settings. The boards are using the same modem firmware.

Could you please clarify:

1. What exactly does MAC_STATUS_NO_RESOURCES (7) mean during PT association in this context?
2. Is mfw-nr+_nrf91x1_2.0.0 the correct/recommended modem firmware for the dect_shell sample in NCS v3.4.0?
3. Is there any additional FT configuration required before a PT can associate (Network Beacon, RACH resources, association settings, etc.)?
4. Should the official dect_shell sample work with the simple FT/PT procedure above without any additional configuration?
5. Are there any additional modem/debug logs I can enable to determine why the PT reports NO_RESOURCES?

I can provide complete logs from both the FT and PT, as well as test with a third nRF9151 SMA DK if needed.

Thank you.