TABLE OF CONTENTS This chapter gives examples of the most common Layer 1 procedures, enabling a better understanding of the practical usage of some of the physical channels described in Chapter 9.
Key Layer 1 procedures in the UE concern cell synchronization, power-control (TPC) and feedback (FBI) command generation, and a number of measurements used in cell-search and handover procedures (see Chapter 11). The performance of these procedures is highly dependent on the performance of the UE receiver architecture. Such architecture is not, however, specified in the standards with the purpose of enabling mobile manufactures to differentiate from each other in terms of performance and cost.
Figure 10.1 shows an example of a UE receiver. The front end of the receiver processes the RF signal and provides an analog baseband signal that is converted to the digital domain with an Analog-to-Digital Converter (ADC). At the output of the RRC filter, the Rake receiver attempts to separate multipath components and combine them based, for instance, on the MRC approach described in Chapter 5. The delay positions at which significant energy arrives are estimated by a path searcher algorithm using pilot symbols within the physical channels. These are also used by the Rake fingers to track the fast changing phase and amplitude values caused by the propagation channel, so that these effects are mitigated. The receiver operates in conjunction with the Automatic Gain Control (AGC) and the Automatic Frequency Control (AFC). The AGC improves the dynamic...
