2.28 Using its expertise, Mason Communications independently designed a national network that would have delivered the same services as Airwave. Mason Communications used widely recognised modelling software to assess the number of radio sites needed for the comparator. Modelling radio coverage is a complex task where theoretical models have to be refined continually to take account of actual detailed terrain and other environments. Such modelling gives a reliable guide to the actual number of sites required, but the final number can only be determined after detailed on-site surveys of the sites, and hence the calculations in the comparator contained a margin for site errors. Mason Communications' approach resulted in an increased number of base stations in the comparator (3,415) over the number assumed in O2's design (3,012). Mason Communications considered that most of the difference was a consequence of the relatively short design timetable compared to that for O2, prohibiting the use of more sophisticated propagation modelling techniques that would have resulted in an optimum design. However, PITO considered that more refined modelling could just as easily have increased the number of sites, once factors such as detailed positioning and availability of sites were factored in.