s is dependent on the load control and AC see below). Power Control Optimisation Efficient and fast power control is the key to success of WCDMA technology. As noted earlier, power control is based on the SIR. Power control has a direct effect on the coverage area. Another aspect related to power control is interference that may lead to capacity limitation. Both uplink and downlink power control is necessary, with downlink control 3G RADIO NETWORK PLANNING AND OPTIMISATION being the more critical. Power control of the common channels is necessary, the most important ones being the CPICH, AICH, PICH and CCPCH. However, this process is more one of control than of optimisation. Admission Control Optimisation The AC function is directly related to the load control process. The process is critical for both the RT and NRT traffic generators/users. As the AC function is power-based and throughput-based, parameters related to both those features are important for capacity and coverage optimisation. The two most important parameters are then the transmitted power and the received power, and orthogonality and throughput in both uplink and downlink directions. 3G Transmission Network Planning and Optimisation 8.1 BASICS OF TRANSMISSION NETWORK PLANNING 8.1.1 The Scope of Transmission Network Planning Transmission network planning encompasses the interfaces between the BS and RNC, between the RNC and CN, and between RNCs, i.e. the Iub, I (CS and PS) and Iur interfaces respectively (see Figure 8.1). fu-cs Ju-ps Iu-cs Internet Iu-ps Figure 8.1 Scope of transmission network planning in a third-generation system (WCDMA) Fundamentals of Cellular Network Planning & Optimisation A.R. Mishra. C 2004 John Wiley & Sons, Ltd. ISBN: 0-470-86267-X 3G TRANSMISSION NETWORK PLANNING AND OPTIMISATION 8.1.2 Elements in 3G Transmission Networks Base Station (Node B) Base stations play an important role in 3G transmission networks, and this role is different from GSM transmission networks. In the latter, if the number of tranceivers (TRXs) is k