# What type of modulation is used for PUCCH?

Hello Experts.

Wwhat type of modulation is used for PUCCH?

QPSK, I believe. Think all control channels are maximum QPSK.

Except for PHICH (BPSK), rest all are QPSK.
All Control CH.

Yes for the reason of robustness.

Thanks. Isn’t PHICH been ditched in 5G?

I was telling for 4G, not sure on 5G.
I’ll check.

For NR

• Pucch format 1: use either bpsk or qpsk
• Puuch format 2: always used qpsk
• Pucch format 3 and 4: can use either pie/2 bpsk or qpsk
• Pucch format 0: no modulation scheme used

Thank you very much.

Say I have 14 bits UCI should I use PUCCH format 3 because it’s long?
Let’s take an example of UCI of 14 bits. Can we have estimate of number of QPSK symbols?
What about the number of OFDM symbols and RBs that would carry the UCI.

Just wonder how 14 bits UCI would map to radio resources (RBs and symbols, slot) when it is transmitted.

I think PUCCH format 4 can be used in your case having 4 to 14 symbols in time domain and 1 RB in frequency domain.

How did you figure out the number of symbols and RBs?
Can we generalize it?
For example say it’s 28 bits, what happens?

With format 4 : 48 to 168 RE there available for usage to accommodate bits.

So say we have 100 bits and they are qpsk mod.

How can we figure out the number of RBs?

Is it possible to have 100 bits UCI?
Not sure…

Just an example, I agree with you.

I try to understand how to generalize any X bits.

I think it’s tricky but PUCCH format use control by parameter in gNB as per requirement.

Thabk you very much.
Can you give more details please?

Say I have 28 bit payload uci can I still use one RB?

I think you are confusing between two points: the RB and amount of bits that you can include. These are two independed things.

You can accumulate 1 RB by any amount of bit you want, but you need to care on your robust link.
Generally per 1 RB we have 256QAM or 1024bit.

Bits are translated to QPSK symbols and that fills up your RB.

I am considering UCI bits which are QPSK modulated.
And wanted to find out how much symbols and RBs they may require.

It’s per Spec definition.

Spec gives a range, right?

Say format 3 PUCCH allows 1 to 16 RBs.
How many RBs is actually needed? Is something else?