nd Convergence Carrier frequency set f2 is reused Carrier frequency sets Figure 13.13 Frequency reuse factor of 7 for 1G systems Tilted beams Little signal overlap at cell edge Figure 13.14 Antenna tilting to optimise coverage The 4G standards present yet a different set of challenges as the Orthogonal Frequency Division Multiple Access nature of resource allocation cannot work with a frequency reuse factor of 1. However, dynamic resource allocation ensures that each time/frequency slot is used as often as possible. In practice, a fractional frequency reuse factor of 1 and 3 as demonstrated in Figure 13.16 is used [15]. In these systems, a cell's central area uses all avail- able frequencies, but at cell-edge frequencies are dynamically allocated. Under full system utilisation, the cell edge is likely to have a frequency reuse factor of 3. Broadband Telecommunications Technologies and Management Old cell sites New cell site Figure 13.15 Introduction of a new base station Carrier frequencies Figure 13.16 Fractional frequency reuse in 4G systems In practice, frequency resource allocation for a 4G system is dynamic and time/subcarrier slot allocation is coordinated between advance base stations. This simplifies the design of cell configuration and allows for heterogeneous networks to coexist and operate. All these tasks are resource intensive, and many are outside the core competency of many operators. Therefore most operators outsource network planning to the specialist companies. A number of different organisations work together to plan and manage mobile communica- tions infrastructure. These include software companies which develop signal network design programmes, building and installation companies, real-estate management companies and SO on. A business system diagram of a network planning process is shown in Figure 13.17. Network planning companies which carry out or manage the above functions have become an integral part of infrastructure roll-out and therefore of great value to mobile operators. As Case Stud