data that can be sent. Optical fibre systems have the widest bandwidth and therefore can support fastest transmission rates compared with copper-based and wireless systems. In turn, fixed and mobile wireless systems in general support faster transmission rates compared with a satellite system. Message transfer rates for a number of different telecommunications sys- tems are shown in Table 2.1: these systems are further discussed in detail in Chapters 9-11. Coverage Area Another parameter of importance for broadband telecommunication systems is coverage area or the maximum geographic extent within which a central serving node may serve a subscriber base. In the case of wireless communications, a transmission tower may send messages users over a radius of many kilometres. In fact, at times television and radio broadcast antennas cover entire cities. Mobile communications towers usually have a narrower coverage range of several hundred metres to several kilometres. Fixed, wired communications systems may also provide service to users many kilometres away, depending on the medium used for trans- mission and transmission rates. For example, twisted copper wires may be used for distances of tens of kilometres for telephony services whereas they can only be used for a maximum of 4 km or SO for DSL. Broadband residential/business optical fibre systems (as opposed to back- haul network) have unlimited coverage potential, but cost issues limit their deployment to hundreds of metres to several kilometres. Wireless systems, both fixed and mobile, can cover wide geographical areas of radius of tens of kilometres. Satellite systems can cover very large areas up to one-third of the Earth's surface (Table 2.2). The details of coverage calculation for satellite, fixed and wireless telecommunications systems are described in Chapters 9-11. Broadband Telecommunications Technologies and Management Table 2.2 Coverage area for commonly used telecommunications systems Telecommunications system Coverage Wireless - 3G ~10 km Wireless - 4