low or above the mean building heights [13,14]. In this case the base-station antenna height is near mean rooftop level, then: (2.37) The total transmission loss for the near rooftop case then becomes: (2.38) When hb m, hm = 10.5 m, X = 15 m, and b = 80 m, as typical in an urban and suburban environment, the above path loss expression reduces to a simple function of the transmitter to receiver distance R (km) and frequency f (MHz), L = =40log10(R)+30log1o(f)+49, (2.39) where R is the base station-mobile station separation in kilometres; f is the carrier fre- quency of 2000 in MHz for UMTS band application. L shall in no circumstances be less than free space loss. This model applies to the non-line-of-sight (NLOS) case only and describes worse case propagation assuming log-normal shadow fading with a standard deviation of 10 dB for outdoor users and 12 dB for indoor users. The average building penetration loss is 12 dB with a standard deviation of 8 dB [2]. A more detailed model uses a recursive approach [15] that calculates the path loss as a sum of LOS and NLOS segments. The shortest path along streets between the BS and the MS has to be found within the Manhattan environment and the path loss (dB) is given by: (2.40) The UMTS Network and Radio Access Technology where dn is the illusory distance, a is the wavelength, n is the number of straight street segments between BS and MS (along the shortest path). The illusory distance = sum of the street segments obtained recursively using the ex- pressions = and where C is a function of the street cross- ing, e.g. for a 90° street crossing c=0.5. Furthermore, Sn-1 = length in meters of the last (straight path) segment. We set the initial values as: ko= 1 and do = 0, and we get the illusory distance as the final dn when the last segment has been added. When extending the model to cover the micro cell dual slope behaviour, we express L as: where D(s)= = (2.41) Before the break point Xbr the slope is 2, after the break point it increases to 4. The break point Xbr is set to