if the spectrum is limited and the macro networks are fully developed. The cost efficiency is lower than with out-band micros. The frequency usage is considered in Reference 1. Selection of Small Cell Location It is highly important to place the small cell optimally in the network. The small cell placement needs to consider the RF propagation and the user locations. The small cell should preferably In-band Out-of-band Number of pico cells Figure 5.5 Co-channel (in-band) versus dedicated frequency (out-of-band) small cell LTE Small Cell Optimization have a clear dominance area to minimize the interference between small cell and macro cell. The small cell should also be located close to the users. The geolocation concept can be used to find out the locations of the users and identify the traffic hotspots in the macro network. Geolocation can be applied for the network troubleshooting, optimization and for the selection of the new small cell locations. Geolocation estimates are based on a number of information elements collected from the network: - Cell identity - Distance measurement from the round trip time information - Path loss from the signal level measurements - Observed time difference of arrival - GPS information from the UE The accuracy of geolocation estimates from round trip time is impacted by the non-line- of-sight propagation which makes the measured distance appear larger than the true distance between UE and the macro cell. Geolocation services can provide information about coverage holes, call drop locations, cell dominance areas, interference levels and voice and data traffic locations. The areas for the network optimization can be analyzed and the solutions can be implemented including parameter tuning, antenna optimization or adding a new small cell to provide better hotspot coverage and more capacity. An example output of geolocation calculations is shown in Figure 5.6. The advanced geolocation tools can also provide the traffic location information in three dimensions including the building fl