Hello Experts.
My understanding is that UCI may carry SR, HARQ feedback, CSI reports.
There are short and long formats for PUCCH.
Does anyone know why we use the longer PUCCH formats for?
Why would UCI have so many bits?
I don’t know exact answer, but generally longer messages are used against poor coverage.
Most of the time Long PUCCH use in CA case (4CC to 8CC).
I have used in lab testing.
Long PUCCH can carry higher payload than short PUCCH.
Higher payload is required to transmit SR/HARQ/CSI together, as well as in case of carier aggregation.
Long PUCCH have benefit that, it can increase UL coverage, this is achived by lower code rate of PUCCH.
With long PUCCH, REs for PUCCH increase and hence it can be transmitted with lower code rate, hence more robust.
Also, long PUCCH can support more RRC connected users, by means of different parameter setting related to modulation, code rate multiplexing etc.