uently, the barriers and solutions are different for indoor and outdoor scenarios. 4.6.3.1 Site Locations For outdoor small cell deployments sourcing sufficient site locations is a significant barrier. With small cell inter-site distances of less than 100 m, compared with 0.5->1 km for a sub- urban macro cell, significantly more sites need to be found. A city center location will have street furniture, including, for example, streetlights and bus/tram stops. But equally a city center is likely to have three or four mobile operators looking for site locations. These site locations also need access to both power and backhaul connections. For indoor small cell deployments, the initial barrier is that the cooperation of the build- ing owner and possibly tenant are required. This is easier if the building owner is looking to improve their indoor coverage, but will still require an agreement between the build- ing owner and mobile operator over the installation costs and ownership of the installed equipment. These indoor locations will also typically require a server room, for hosting the connection back to the operator's network, and a good-quality connection from the server room to the indoor cell site locations. There are new initiatives designed to help overcome these barriers. The first is in the creation of relevant documentation: recommendations for footprints of small cells (Global 5G study) and what is required for new buildings to future-proof indoor installations (SCF 214). The second is the introduction of new small cell business and deployment models, specifically, neutral host small cells, which allow multiple operators to share the same site. 4.6.3.2 Scaling Up Deployment A challenge to the 5G vision for an ultra-dense network is the requirement to successfully deploy, maintain, and manage the network, and it is worth noting that one of the most expensive tasks in network management is to send an engineer to a cell site. To aid in the initial deployment task SONs are a key aspect and reduce the level of 