 of the process is transmission network planning. This phase is very important because the transmission network should be planned to provide the required protection against equipment failure. The network topology, transmission media and transmission equipment characteristics should be selected carefully in order to design a network having a high level of availability and resilience. Constraints about the network topology could affect the selection of radio base station sites; in these cases a trade-off is required between the selection of sites to meet the radio coverage objectives and network topology requirements. This is a simplified view of TETRA network planning, because each of the steps shown in Figure D.7 must be exploited and many of the different details need to be explored and resolved. The following section provides some more information about radio network planning. D.5.1 Radio Network Planning Radio network planning can be divided into various phases, starting from preliminary radio network planning and arriving at the detailed radio network. Preliminary radio planning is very useful for an initial dimensioning of the network and in this section an overview of this first step is given. TETRA Network Planning Downlink Uplink Formula TX Power TX Cable and Filter Loss TX Antenna Gain Peak Effective PBS - BBS + CBS PMS - BMS + CMS D=A-B+C Isotropic Radiated Power Propagation Loss Signal Level at PBS BBS + CBS PMS BMS + CMS F=D-E RX Antenna - - L RX Antenna Gain RX Cable Loss Receiver Input RBS = PBS-BBS RBS = PMS - BMS F+G-H Power CBS + GMS CMS L + GBS- NOTE: The BS antenna gain may be different for transmission and reception. This permits allowance to be made for techniques such as antenna diversity. Figure D.8 General radio link power budget from ETSI The preliminary radio network planning process begins with the definition of the radio coverage objectives. The area to be covered and the available services must be defined in the way that allows verification of the compliant of the project. Usually the