an value for building separation (b) is calculated from the centre of one building to the centre of another building and is also given in metres. The Walfish-Ikegami model separates into two cases, which are the line-of-sight (LOS) and non-line- of-sight situations. The formula for path loss prediction in the LOS condition can be written as L = 42.6+26logd+20log f (2.29) where d is distance (km) and f frequency (MHz). When no line-of-sight condition exists, the path loss formula can be written as (2.30) hroof Figure 2.12 Parameters in the Walfish-Ikegami model Radio Network Planning and Optimisation where Lrts is the rooftop-street diffraction and scatter loss while Lmsd is the multiscreen diffraction loss. The path loss in the non-line-of-sight situation actually consists of three components: rooftop-street diffraction and scatter loss, multiscreen diffraction loss and free space loss: L0 =32.4+20logd+20logf = (2.31) The rule follows: Lmsd : Lits + Lmsd > 0 Lrts + L msd <0 (2.32) The rooftop-street diffraction and scatter loss is the loss occurring when the radio wave propagates from the closest rooftop to the receiver: (2.33) where Lori is the street orientation loss: 1-10 - 0.354q for 0   35° - for :35 < < < 55 (2.34) 4.0-0.114(4 -55) - 55 << < 90° The multiscreen diffraction loss is caused by propagation from the BTS to the rooftop, which is closest to the MS: - log (2.35) where hroof) hroof (2.36) hBTs<hhoot hBTS > h throof - hroof) : d >0.5km and hBTs Throof (2.37) (hBTS - d < 0.5 km and hBTs Throof (2.38) medium sized city and suburban centres (2.39) urban centres The parameter ka increases the path loss in case the BTS is below the rooftop. The parameters kd and kf are for adjusting the correlation between the distance and frequency with multiscreen diffraction. The Walfish-Ikegami model is valid for the frequency range 800-200 MHz. The range for the base station antenna height is from 4 to 50 metres, mobile antenna height from 1 to 3 metres and distance between the transmitter and receiver from 20 to 500