Cell Reselection enables a UE to continuously monitor the signal quality of neighboring cells, and determine the most suitable cell to camp on. This ensures that the UE camps on the cell that can provide the best possible service and signal quality.

This can be within the same Radio Access Technology (RAT), e.g., 4G cell to 4G cell. Or it can be between different RATs, e.g., 5G cell to 4G cell.

Cell Reselection is primarily performed while the UE is in IDLE state, where the UE locally decides it shall camp on which cell, according to received signal quality.

Network operator can optimise the parameters that the UE uses in cell selection, so that it balances network load, coverage, and user experience.