dBm or better compared to the C2 value of the current cell. Another exception rule is the situation where the new cell and old cell belong to different location areas. In this case the C2 of the new cell has to be higher with CellReselectHysteresis for a time of 5 seconds time or more. The CellReselectionOffset parameter can be used for prioritization, with certain cells having a higher offset, making selection easier. TemporaryOffset is applied for the cells added to the comparison list. PenaltyTime is the time controlling the TemporaryOffset usage. The timing advance (TA) parameter is used to indicate how far the MS is from the BTS. The actual measure is time - how much time it takes for the signal to travel the distance from the BTS to the MS. The speed of the RF signal is equal to the speed of light, and in this way the distance can be calculated. The maximum cell radius of a normal GSM cell is 35 km. This radius is divided into 64 equal TA steps. Each step is then approximately 550 m. For example, the TA value for a mobile that is 1500 metres distance from the BTS is 2. For other examples see Table 2.17. Location update is a procedure that makes the network aware of the MS location. This is a prerequisite for mobility where the MS movement can be tracked and its position known in the case of incoming calls, short message services (SMSs), etc. The network is always sending parameter information via broadcasting to the MS, as one part there is also LAC. The MS keeps this information and incase of change in location area or PLMN compared to the previous information the MS makes a request for a location update. On the network side the location update changes the MS to be assigned to the new VLR, which informs the HLR about the update. The old VLR re-sets the information related to the MS. The parameter IMSIAttach defines the location update procedure to be automatic. If IMSIAttach is activated when the mobile is powered it informs the network to be active. A very similar parameter is IMSIDetach, Radio Network Pl