e total capacity in a radio network in terms of the number of sites is dependent upon two factors: transmission power and interference. The re-use of the BCCH TRX (which contains the signalling time slots) should be greater than that of the TCHs, since it should be the most interference-free. 2.4.7 Power Control The power that is transmitted both from the mobile equipment and from the base station has a far-reaching effect on efficient usage of the spectrum. Power control is an essential RADIO NETWORK PLANNING AND OPTIMISATION feature in mobile networks, in both the uplink and downlink directions. When a mobile transmits high power, there is enough fade margin in the critical uplink direction, but it can cause interference to other subscriber connections. The power should be kept to a level that the signal is received by the base station antenna above the required threshold without causing interference to other mobiles. Mobile stations thus have a feature such that their power of transmission can be controlled. This feature is generally controlled by the BSS. This control is based on an algorithm that computes the power received by the base station and, based on its assessment, it increases or decreases the power transmitted by the mobile station. 2.4.8 Handover Handover is the automatic transfer of the subscriber from one cell to another during the call process, without causing any hindrance to the call. There are two main aspects to this: the necessity to find a dedicated mode in the next cell as the mobile is on call, and the switching process being fast enough so as not to drop that call. So, how does the handover actually take place? There are many processes that can be used, but the one most used is based on power measurements. When a mobile is at the interface of two cells, the BSS measures the power that is received by the base stations of the two cells, and then the one that satisfies the criteria of enough power and least interference is selected. This kind of handover being directly related to power co