Communications, Radar & Electronic Warfare (201.. - Index of

250Communications, Radar and Electronic WarfareWantedsignal•Wantedbase stationIIIIIIIII•----r---:Interferencesignal•II. InterfererIIIIII*.Inte rferenceareaFigure 14.5An Interference scenario for 11l0bilc In a mobile network The onglllal wanted serv ice areaIS cIrcular, bUl the area closesl to the interferer suffers from IIlterfercnce.The analysis just described looks at interference on a base station, but it is alsopossible to jam mobiles in a network, even when their location is not explicitly known.Consider the system shown in Figure 14.2. Now, if an interferer of equal power isplaced 25 km away. Assuming the power of both systems fall off at the same rate, theirpower will be equal at half the distance, i.e. 12.5 km. This is illustrated in Figure 14.4.The interference to mobiles will not be equal over the whole service area. Anidealised case is shown in Figure 14.5. This ignores terrain and clutter. The wantedservice area is shown on the left, with circular coverage. Coverage to the same powerlevel for the interferer i