v is defined in Table 15.1. As the second step, if the search of known frequencies and RATs is still unsuccessful after 10 seconds, the UE enters PLMN selection procedure [2]. In scenarios with high downlink interference (e.g. high buildings without indoor solution) the cell camping may also fail because broad- cast control channel (BCCH) decoding of system information fails repeatedly, leading to PLMN selection. This can be to some extent compensated by using lower channel coding rate for BCCH. In order for UE to camp on a cell the level and quality criteria must be fulfilled. The cell camping criteria (the so-called S criterion) in 3GPP Release 9 and later are based on reference Inter-layer Mobility Optimization Table 15.1 Maximum number of DRX cycles (Nserv) before triggering PLMN selection DRX cycle Nserv (number of length (s) DRX cycles) signal received power (RSRP) and (optionally) on reference signal received quality (RSRQ). The simplest form of the cell camping criteria read as measured RSRP - qRxLevMin > 0 measured RSRQ - qRxQualMin > 0 where qRxLevMin and qRxQualMin are broadcast in system information block one (SIB1). If the optional qRxQualMin is not broadcast the UE applies the default value of neg- ative infinity meaning that all cells satisfy the quality criterion. The cell camping cri- teria in Release 9 are based on both level and quality while cell reselection to a cell with different absolute priority is based on either level or quality; this is to be dis- cussed shortly. The above basic form assumes that the cell range should not be lim- ited because of UE transmit power limitation. If such uplink cell range limitation is desired (e.g. UEs having different maximum transmit powers in the network) UE maxi- mum transmit power can be optionally broadcast in SIB1. In this case the level criterion is modified as measured RSRP - qRxLevMin - P compensation > 0 where UE autonomously computes the positive number P compensation from maximum allowed UE transmit power in the cell and the UE power capabilit