interfre- quency and inter-RAT measurements. That is, if the S parameter of the serving cell is above this threshold, the UE should not measure on intrafrequency and inter-RAT (unless it is not camping on its highest-priority RAT/frequency layer). This parameter is not needed when the UE is camping on a cell that is not of the highest-priority layer because, if the UE is camping on a lower-priority cell, it peri- odically searches for the highest-priority layer (see also Figure 4.21). The Thresh x,low parameter specifies the minimum level that must be fulfilled by a cell in order for it to be selectable. This value needs to be given for each RAT and frequency layer (x). Thresh x,high specifies the value that a higher-priority cell needs to fulfill in order for the UE to reselect to that cell. Thus, this parameter is not used when the UE is camping on its highest-priority layer. HigherPrioritySearch parameter is needed by UEs currently camping on cell that has lower than highest priority. These UEs need to look periodically for higher-priority cells. Because interfrequency and inter-RAT measurements © 2009 by Taylor & Francis Group, LLC Architecture and Protocol Support for RRM Parameter Meaning Comment Offset between serving and neighbor There may be two Qoffset values: layer specific Qoffset s,n cells in the R criterion. and cell specific. However, Qoffset is not needed in the priority-based scheme. The minimum level that must be fulfilled Assumes single (scalar) "S" value, for instance, Thresh low serving, for camping on a cell on the serving only signal strength or only signal quality. frequency layer (FFS: specific to the serving RAT?) If the measured (S) value is under this Thresh serving, high threshold, the UE shall start non-intra-frequency measurements. The minimum level that must be fulfilled An equivalent definition is: The minimum level that must be fulfilled for camping on a cell on a Thresh x, low for camping on a cell on a frequency/RAT frequency/RAT layer that has lower priority than layer. X spec