o affects the propagation, although the mobile height is not usually a variable. used by cellular radio systems is affected by the terrain and by Predicting path loss is an essential part of radio planning, and buildings, trees and other features of the landscape. because of the large number of contributing factors, empirically based formulae are used. The most widely used formula is the Hata 47.3.2 Co-channel interference model (Hata, 1980) which is based on the propagation measurement results of Okumura et al. (1968). Generally, a mobile will receive a wanted carrier signal (C) from the Hata's basic formula for the total path loss, Lp, is given by base station serving the cell in which it is located, and in addition, Equation 47.2 where f is the carrier frequency in MHz, is the interfering signals (I) from other cells. The carrier to interference base station antenna height, h is the mobile antenna height, R is the ratio C/I is related to the re-use ratio D/R. Cellular radio systems are radial distance in kilometres, and a(hm) is the mobile antenna height designed to tolerate a certain amount of interference, but beyond correction factor. this, speech quality will be severely degraded. The TACS cellular system, for example, will work with a C/I down to around 17dB. Lp (dB) = 69.55 + (fc) 13.82 log (hb) This lower limit on C/I effectively sets the minimum D/R ratio that - a hm)+(44.9 -6.55 log(h))log R (47.2) can be used. The two key factors in ensuring that good quality transmission can occur between a mobile and base station are that the wanted signal Correction factors can be used to take into account the type of strength is sufficiently large, that is, above the receiver threshold terrain. sensitivity, and that the interference level is low enough to give an adequate C/I ratio. Both of these factors depend on the radio propa- 47.3.4 Practical radio planning gation between the mobile and base stations. Armed with a propagation model it is possible to calculate both the 47.3.3 Radio propagation wanted signal s