Impact of transmit diversity on cell search in UMTS

In a CDMA cellular system, the process of the mobile station searching for a cell and achieving code and time synchronization to its downlink scrambling code is referred to as cell search. The 3GPP technical specification for UMTS introduces for that purpose two downlink channels (SCH, CPICH), which may also be transmitted in Tx diversity mode . This paper investigates the performance of cell search in general and the improvements by Tx diversity in particular. The diversity gain allows reduction of Tx power of SCH and CPICH as well. The power reduction of these signalling channels results in a network capacity increase, which is also discussed in this paper.