How UE send ACK/NACK when change band in 5G NSA?

5G NR
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Hi Experts.

In NSA, when the UL user plan switches from NR to LTE (L1800), how the UE send the ACK/NACK of 3500 band PDSCH?

How UE send ACK/NACK when change band in 5G NSA
How UE send ACK/NACK when change band in 5G NSA745×750 106 KB

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I remember i read somewhere that even though UL is switched to LTE, NR PUCCH is still transmitted and ACK/NACK for PUSCH can be transmitted through NR PUCCH.

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Every leg is handling its own MAC layer, so for DL ACK is transmitted on PUCCH on the same leg where PDCCH grant delivered to the same MAC layer.

So for example if PDCCH delivered from the 1800 ACK will be sent on PUCCH on the same leg and same for NR 3500.

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4

Yes, right.

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But when the switching happen, Uplink is on L1800 band.

So how the UE will send ACK/NACK on 3500 band.

Is the UE is simltaneously connected to both L1800 and NR 3500 band on Uplink?

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In ENDC the UE is simultaneously connected all the time (listening on PDCCH on both leg NR & LTE).

So when data switch from one leg to another from LTE to NR for example means PDCP will redirect all the packet from LTE RLC to NR RLC.

But the UE will still listen to PDCCH from both leg in case some packet routed again.

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