UCI

Hello, GuiDance.
For your first question:
1. LTE uses flexible frequency domain scheduling (OFDM technology) to improve performance, which requires measuring a large number of channels and transmitting resource allocation signaling.
2. The application of MIMO leads to a large increase in reference signals and control signaling.
For the second question:
UCI is transmitted in PUCCH and PUSCH.
PUCCH: dedicated transmission channel for control signaling, which is only used when the UE has no data.
PUSCH: signaling along with the channel, sent with the uplink data.
Thanks！