er sufficient capacity and coverage. 2.1.2 Cell Shape In mobile networks we talk in terms of 'cells'. One base station can have many cells. In general, a cell can be defined as the area covered by one sector, i.e. one antenna system. The hexagonal nature of the cell is an artificial shape (Figure 2.1). This is the shape that is closest to being circular, which represents the ideal coverage of the power transmitted Fundamentals of Cellular Network Planning & Optimisation A.R. Mishra. © 2004 John Wiley & Sons, Ltd. ISBN: 0-470-86267-X RADIO NETWORK PLANNING AND OPTIMISATION Ater' Figure 2.1 The scope of radio network planning by the base station antenna. The circular shapes are themselves inconvenient as they have overlapping areas of coverage; but, in reality, their shapes look like the one shown in the 'practical' view in Figure 2.2. A practical network will have cells of nongeometric shapes, with some areas not having the required signal strength for various reasons. Coverage Un-Covered Base Station Ideal Practical Artificial Figure 2.2 Cell shapes 2.1.3 Elements in a Radio Network Mobile Station (MS) The mobile station is made up of two parts, as shown in Figure 2.3: the handset and the subscriber identity module (SIM). The SIM is personalised and is unique to the subscriber. The handset or the terminal equipment should have qualities similar to those of fixed phones in terms of quality, apart from being user friendly. The equipment also has functionalities BASICS OF RADIO NETWORK PLANNING Voice Channel Voice Encoding/ Ciphering/ Mod. + Amp. Encoding/ Encoding/ Decoding Decoding Decoding Deciphering Demodulation SIM card Figure 2.3 Block diagram of a GSM mobile station like GMSK modulation and demodulation up to channel coding/decoding. It needs to be dual-tone multi-frequency generation and should have a long-lasting battery. The SIM or SIM card is basically a microchip operating in conjunction with a memory card. The SIM card's major function is to store data for both the operator and subscriber. The SIM card