co-exist for some time with all types of deployment scenarios. However, complete interoperability will not necessarily occur at the introduction of UMTS, but will follow a gradual process. Thus, in this section we mainly discuss essential handover issues with GSM. Handover with other systems such as MC-CDMA and IS-136, e.g. will not be cover at this time. We introduce inter-system handover based on the handover recommendations from GSM to UMTS. Specifications in this area continue at this writing. Thus, here we look at it primarily from the requirement side. The handover may consist of the following aspects [19]: cell selection/reselection and handover features. 4.3.15.1 Cell Selection/Reselection Requirements The MS compares GSM quality with UMTS neighbour cells to determine the most ap- propriate cell for cell selection/reselection. The MS in a GSM cell obtains system in- formation of its UMTS neighbour cells through BSC broadcasting all the required in- formation in the GSM cell. Broadcasting UMTS cell information depends on the defini- tion of new system information messages or the adaptation of existing system informa- tion messages together with the transmission of area-based UMTS system information (e.g. UTRAN frequency/ies used in LA) [19]. 4.3.15.2 Handover Requirements The requirements for GSM to UMTS handover as an extract from [19] can be outlined as follows: 1. Synchronization requirements a MS will synchronize with a UTRAN cell using GSM idle frame(s) a MS will be capable of blind detection; thus, it will not reject a handover com- mand to an UMTS or GSM cell which it has not reported and to which it is not synchronized 2. GSM MS requirements R99 and newer MSs will support a 'blind handover' to GSM or UMTS when a handover fails, the MS will remain camped onto the original cell, and con- tinue its measurement reporting as defined prior to the attempted handover. GSM BSC requirements the call will go to the most suitable cell for the service that the user requested The UTRA Physical Layer Design the B