Practical acquisition issues for UMTS

When a UMTS mobile (UE) is powered-up it must first synchronise with a local Node B before it can use the network. Synchronisation must be achieved in the time, frequency and code domains. Time synchronisation is a two-part process, synchronising first to the primary synchronisation channel (PSCH) to find the power control period (PCP) boundaries, and then to the secondary synchronisation channel (SSCH) to establish the frame boundaries. Frequency synchronisation is performed to lock the UE's RF and data rates to those of the incoming rays. (These are not necessarily identical to those transmitted by the Node B due to the presence of Doppler effects for a moving UE.) Finally, code synchronisation must occur to match the scrambling and channelisation codes of the incoming broadcast channel (BCH) and downlink data channel (DLDCH). This paper considers practical aspects of acquisition relating to the time and frequency synchronisation stages, and presents an overview of algorithms that may be used together with working ranges and resolutions that need to be accommodated.