Active Set, Monitored Set and Detected Set in WCDMA

Active Set Monitored Set Detected Set

The set of radio links simultaneously involved in the communication between a UE and a RBS is called active set. Up to three radio links can be included in the active set. In addition to measuring and evaluating the radio links (or cells) in the active set, the UE also continuously monitors and evaluates the signals from other surrounding cells.

The surrounding cells not part of the active set can either belong to the monitored set or the detected set. The monitored set are together with the active set the cells that the WCDMA RAN explicitly orders the UE to measure on, which normally are the defined neighbors to the cells in the active set (the abnormal case is described in the next paragraph). The detected set contains all cells that the UE detects that are not part of the active or monitored sets.

When the active set contains more than one cell, the monitored set will be a union of all defined neighbor relations for the cells in the active set. Since there is a limit of 32 intra-frequency cells in the active and the monitored sets, all the defined neighbors for all cells in the active set might not fit into the monitored Set. Those that do not are called unmonitored neighbors.