 explosive growth in mobile broadband data communications due to widespread usage of smart phones, operator networks are under significant loading constraints. The amount of capacity required is growing at a very fast rate and networks are struggling to cope with this demand. One strategy in reducing this traffic is to off-load traffic to the wireless LAN systems. In this configuration, wireless LAN systems provide connectivity to mobile devices in dense subscriber demand areas such as shopping centres and central business areas. As a user moves away from an area covered by a wireless LAN, connectivity is provided by the mobile network using a 3G/4G technology as illustrated in Figure 13.19. Many operators have partnered with wireless LAN operators or rolled out one of their own to cope with the increasing demand on their mobile network. One such example is the Japanese operator Docomo who has a network of 150 000 hotspots throughout metropolitan areas [16]. The network subscribers can connect to any of these networks at a small monthly fee. Hierarchical and Overlay Cell Design As different distributions of population density, and traffic needs lead to cell designs with var- ious degrees of cell radius, a mixture of macro-, micro-and picocells are required to design a network with adequate coverage and user capacity. These structures may use different stan- dards (2G/3G/4G) and frequency spectrum. When the same frequency and technology are used, dynamic resource technologies can be used to minimise interference. This approach is Broadband Telecommunications Technologies and Management Voice, SMS Public 3G/4G Core networks Wireless services Packet data gateway Figure 13.19 Hybrid networking using macrocells and wireless LAN access points Microcell Umbrella macrocell Figure 13.20 Umbrella cell structure useful in a dynamic roll-out of a wireless network: as the number of subscribers and traffic increases, more cell sites may be deployed in areas of large traffic concentration. One solution is to use an overlay stru