What is Antenna Port?

• An antenna port is in the 3GPP specifications an abstract concept that is a logical entity rather than a physical antenna.
• Each antenna port is associated with a specific set of reference signals such that the channel over which a symbol is transmitted on that antenna port can be distinguished from the channel over which another symbol is conveyed on the same antenna port.
• To understand this sentence we must recall certain aspects related to the channel estimation based on the reference signal.
• 5G NR contains a different type of reference signals, like DMRS for demodulation purpose & CSI-RS for channel status reporting, by way of explanation, we can understand that an antenna port is an indication of the type of reference signal that conveyed over the radio channel.
• So according to the antenna port is defined by its reference signal. This means each antenna port refers to a specific channel model, this in turn help in channel estimation and equalization at the receiver end.

Antenna Port for Downlink

● Antenna ports starting with 1000 for physical downlink shared channel (PDSCH) : Total up to 8 port for SU-MIMO and up to 12 port for MU-MIMO

Antenna Port for Uplink

Note: Antenna ports do not correspond to physical antennas, but rather are logical entities distinguished by their reference signals. A base the station can assign/map the antenna ports to the physical transmit antennas as per need.

Reference 3GPP 38.211,