Whats is Beam Tracking in 5G?

Hello dears,

Whats is Beam Tracking in 5G?

For purposes of beam tracking, UE will measure RSRP of CSI-RS or SSB and report it to the gNB as a part of Uplink Control Information (UCI).

  • if beam refinement is disabled, UE will report SBRI-RSRP measurement of a single best beam

  • if beam refinement is enabled, UE will report CRI-RSRP measurement of 2 best beams.

Beam switch will take place when filtered RSRP of a new beam is larger than RSRP of the source beam by a certain threshold.

A 5G-UE may be notified about the upcoming beam change with Beam Change Indicator (BCI) message.



The literal meaning of Beam Tracking would be obvious. It is a mechanism that transmitter and reciever chasing a specific beam (a specific direction) that gives the best communication performance.
The question is ‘why we need Beam Tracking in 5G ?’. Unlike LTE, 5G is designed to use Beam Forming (meaning Beam Shaped signal propagation rather than omni direction (or semi omni directional) which imply that the reciever would lose signal if its Rx direction is not aligned with Tx beam direction. In Cellular communication, the user device tend to move around. As it moves around, the mobile device and NW has to find other beam that give the better performance for the changed position.
The most important question and most difficult question is how this beam tracking really happens ? This cannot be explained in short… you may check my note :