What is typically the requirements (criteria) for a cell to be added/removed/replaced to/from/in the active set?

For addition (Event 1a), candidate cell needs to have an Ec/Io value that is within a T_ADD threshold of the primary/reference (usually the best) cell for a specify time hysteresis. For removal (event 1b), cell needs to have Ec/Io lower than T_DROP margin for a specific time hysteresis. For replacement (event 1c), cell needs to have an Ec/Io better than the worst cell in the active set by the T_REPLACE and for a specific time hysteresis.