After the bwp-InactivityTimer expiry, which BWP is activated / switched?

Hello 5G NR PHY experts.

After the bwp-InactivityTimer expiry, which BWP is activated / switched?


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Normally, default bwp is also initial bwp.

After BWP inactivity timer , UE switch its active DL bandwidth part to a default DL bandwidth part


For NR within active BWP it’s mentioned UE complete BWP switching using DCI 0_1 and 1_1.

Which field indicates it?

What is role of bwp inactivity timer not able to seen same in logs.

WP inactivity timer is seen as a backup mechanism for bwp switching through DCI.

Backup mechanism at UE to switch to default bwp after some time when it misses decoding the dci carrying bwp switch indicator.

How is it configured to UE?

Isn’t it given from gNB to UE?

It is given in RRC reconfig.

I checked it, not able to see such timer…

Supplier don’t support BWP as of now for eg. Ericsson.

I think Huawei supports multi BWP by default.

Yes agree seen BWP concept only theoretical yet.

Not implemented practically due to limitation.

What is the limitation?

BWP used when there is scenario like gNB support 400 MHz, but UE support less BW, ex 100 MHz.

Seems as of now such scenario not tested or do not exist.

Supporting Bandwidth limited UEs is just one use case.

There is one more important use case wrt battery saving where UEs with less need of data will be shifted to smaller BWPs with longer pdcch monitoring periodicity.

I think this is why Huawei has multi BWP support by default even for FR1 (we tested this in lab).

Other infras seem to yet catch up

Thanks good info :+1:

  • with different BWP different SCS can be also configured - Another use case of BWP.

BWP Inactivity timer facilitates UE to switch to default BWP if conigured, If not, it switches to InitialBWP. I always wonder, Is this BwpInactivitytimer is maintained by Network as well ? because if BWPInactivity timer gets expired, UE swtiches the BWP, If network doesn’t track this, How does network know UE has swtiched to the default BWP ?

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