The physical signals of 5G NR can be divided into the following types according to its function: NR downlink physical signals include channel state information reference signal, demodulation reference signal, time-frequency tracking reference signal, phase noise tracking reference signal, RRM measurement reference signal, RLM measurement reference signal, etc. 5G NR uplink physical signals include sounding reference signals, demodulation reference signals, phase noise tracking reference signals, etc. And for all of these, the design of uplink DM-RS and PT-RS is basically the same as that of downlink.
Design specifications for 5G NR reference signals:
1. Avoid periodic signals that are continuously sent. The so-called continuous transmission means that it is sent without system configuration, and this kind of signal cannot be turned off, such as the CRS of LTE.
2. The time frequency resources occupied by physical signals should be configured flexibly.
3. Support large-scale beamforming transmission.
The physical channels of 5G NR correspond to a specific set of time/frequency resources, which are used to carry transport channels mapped by higher layers. Each transport channel is mapped to a physical channel. Some physical channels do not carry transport channels, which are called control channels. The physical downlink control channel carries downlink control information and is used to provide the UE with necessary information for downlink reception and uplink transmission, such as resource allocation information. The physical uplink control channel carries uplink control information and is used to report the state of the UE to the base station, such as the state of HARQ reception, channel state information, and so on.
The physical channels defined by 5G NR include the following:
The 5G NR physical downlink shared channel is mainly used for the transmission of downlink unicast data, and can also be used for the transmission of paging messages and system messages. PDSCH is transmitted on antenna ports 1000-1011. The physical broadcast channel carries a part of the minimum system information required by the UE to access the network. The antenna port of PBCH is 4000. The physical downlink control channel is used to transmit DCI, which is mainly the scheduling information required by the UE to receive PDSCH and transmit the physical uplink shared channel, and can also transmit time slot format indication and preemption indication. The antenna port of the PDCCH is 2000.
The physical uplink shared channel corresponds to the uplink physical channel of the PDSCH, and is used to transmit uplink service data, and can also be used to carry UCI. PUSCH is transmitted on antenna ports 1000-1003. The physical uplink control channel carries UCI, feeds back HARQ-ACK information, indicates whether the downlink transport block receives correctly; reports channel state information and requests uplink resources when uplink data arrives. The antenna port of PUCCH is 2000. The physical random access channel is used for the random access procedure, and the antenna port is 4000.
Summary: The control channel transmits signaling (control information), the shared channel transmits data (data information). The initial access channel (initial cell access).