ing priority order: 1. Home PLMN 2. User controlled PLMN list (SIM) 3. Operator controlled PLMN list (SIM) 4. Randomly one of the PLMNs (RSCP > -95 dBm) 5. The best of the other found PLMNs (highest RSCP) The frequency with which the mobile searches its home PLMN can be set by a parameter: Home- PLMNSeachPeriodTime Cell Search During the cell search, the UE searches for a cell and determines the downlink scrambling code and common channel frame synchronisation of that cell. The cell search is performed in idle mode when the UE makes an initial cell selection or when the mobile makes a cell re-selection. The search procedure consists of three phases: scanning for the primary synchronisation channel, detecting the secondary Radio Network Planning and Optimisation synchronisation channel and detecting the cell primary scrambling code using CPICH. The cell search uses primary (P-SCH) and secondary (S-SCH) synchronisation channels, which are transmitted in all cells in the network with the same code sequence. The P-SCH and S-SCH are the only channels not scrambled with the cell primary scrambling code. In addition to synchronisation channels the CPICH is used to find the correct scrambling code of a particular cell. Scanning for the Primary Synchronisation Channel (P-SCH) The primary synchronisation channel carries the P-SCH code (PSC). The same code is repeated at the beginning of every slot. Every cell sends an identical code. The receiver correlates the received signal on the selected carrier frequency with the P-SCH code. Each correlation peak corresponds to one cell and each cell transmits the same P-SCH code. The UE selects the strongest peak, which gives the slot synchronisation to the transmitting cell. Detecting the Secondary Synchronisation Channel (S-SCH) Sequence At the same time as the P-SCH is transmitting the P-SCH code the S-SCH transmits one of 16 different S-SCH codes. The S-SCH codes are repeated in a predefined sequence. The UE detects the S-SCH codes and correlates the detected S-SCH sequence to p