of carriers, and SO on before the cell sites are sufficiently apart SO the same subset of carriers can be reused. Frequency reuse factor is defined as the number of cells which do not use the same carrier frequency. A frequency reuse factor of 7 was used in 1G stan- dards as illustrated in Figure 10.13. This reuse regime resulted in a signal to interference ratio of approximately 30 dB, which was deemed sufficient for analogue voice communications. As noted above, cell size is determined by two factors. One factor is the maximum distance a signal may travel before its power falls below a certain threshold. Such calculations use path loss characteristics of the channel, which depend on the geographical as well as the built struc- ture of the cell area. A densely urban cell has a higher path loss as a function of distance, whereas a rural cell may be mostly characterised by line-of-sight communications. The other factor is the amount of expected traffic a user may generate and the user density in an area. Since the number of communications channels is limited, the number of users that may be served at any particular time is also limited. The cell area therefore must be designed with this Terrestrial Broadband Wireless Telecommunications Carrier frequency set f2 is reused Carrier frequency sets Figure 10.13 Frequency reuse factor of 7 for 1G systems limitation in mind. If a cell size is too large, the number of subscribers will be too many, and therefore connectivity demand on the base station will be larger than the capacity of the base station leading to unacceptable grades of service. Frequency Division Multiple Access Given a certain channel capacity in each cell a number of users may be connected to a base station. Several multiplexing technologies were developed over the first to fourth generations of mobile communications standards to connect multiple devices to a base station. The first generation of mobile telecommunications systems used a multiplexing technology known as Frequency Division Multiple Access 