mobile device and billing. Different 1G-4G standards perform these functions at network nodes referred to as the core network. Different terminologies are used in different standards, from base station controller (BSC) and mobile switching centre (MSC) in a 1G standard, to radio network controller (RNC) in several 2G and 3G standards to enhanced Node-B in a 4G standard. The functionalities are very similar: a BSC determined which mobile phones were allowed to communicate with a base station and an MSC relayed the voice traffic onward to the fixed telecommunications network. Similar functions are carried out by RNCs or enhanced Node-Bs. A base station transmit signals to (and receives from) mobile devices within a coverage area known as a 'cell'. The radius of this area is determined by the maximum range of transmission as found through a link budget analysis as well as the amount of traffic generated to/from mo- bile devices. Based on this a 'cellular' network is constructed to cover entire populated areas. The size of a cell is smaller in densely populated urban areas compared with suburban and rural areas because the offered traffic amount, and path loss is larger. A typical metropolitan area may be covered by cells with a radius of ~500 m in a central business district area, and 3-4 km in outer suburbs. A typical configuration may appear as shown in Figure 10.11. Each cell has a base station which serves the mobiles that roam within its borders. Resource Allocation The frequency spectrum is a limited resource and is used for a number of services, from public emergency, police and military wireless communications applications, to radio, TV, and amateur radio and SO on. Governments control the allocation of the spectrum within their jurisdiction and ensure that different services do not interfere with each other. Each mobile operator is allocated a certain portion of the spectrum, within which it provides mobile Broadband Telecommunications Technologies and Management Interference Interference Signal Signal Figu