remote units. 5.6.2 Wi-Fi and Femto Cells Wi-Fi can offload a large part of indoor traffic since a major part of global wireless data traffic are generated indoors and all smartphones and laptops are equipped with Wi-Fi connectivity. The indoor offload will connect users to the closest cell which reduces interference and transmission power and reducing battery consumption. Small Cell Deployment Options Wi-Fi is an important local area technology option for heterogeneous networks, comple- menting mobile technologies to enhance performance for the user as well as improving offload capacity. One of the criteria for Wi-Fi to become a successful part of the mobile network is technologies and procedures that enable efficient traffic steering between cellular and Wi-Fi, a seamless Wi-Fi/cellular access and therefore a better user experience. The use of Wi-Fi technology is the preferred means of offloading data from macro cells for users at home or in the office. Smartphones should use Wi-Fi where possible. For public Wi-Fi deployment, careful selection is crucial for effective offload while providing the best user experience. Outdoor Wi-Fi deployment has limited potential where mature macro networks are already installed. It also requires careful planning to limit interference sources from the unlicensed spectrum. Furthermore, many DSL lines are limited to less than 10 Mbps, which is slower than a typical LTE macro cell. Therefore, the practical Wi-Fi data rates may be lower than LTE data rates from the macro cell because of Wi-Fi backhaul limitations. Load-based traffic steering between macro, micro, pico clusters and Wi-Fi/femto layers will be needed in order to use the available spectrum efficiently. Furthermore, automatic authen- tication is needed for Wi-Fi offload to reach its full potential, because manual authentication will prevent some users from going through the registration process. Figure 5.9 shows an example of indoor data offloading to Wi-Fi cells in a macro and micro overlaid network. The graph shows th