lower. A typical macro cell in a rural area might offer a range of 15 km. Both the free space loss and loss due to obstacles also depend on the signal frequency. I infer frequency from the network type. For example, GSM signal is delivered in 900 or 1800 MHz frequency bands in most parts of the world. Typically the spectrum is divided into bands that are allocated for different service providers by a national regulator. To approximate the frequency, I use the frequency bands that the mobile network providers have reported in the Mobile World Live website, together with information on how the frequency bands are divided between operators. In this procedure, I use the same parameter values for all cell towers. In reality, all the parameters are likely to vary substantially depending on the propagation environment (e.g. urban vs rural) and operator (Parsons 2000). 27