 site goes off-line. Under such a situation neighbouring cells detect the outage and balance their load to heal the network. Another aspect of self-organising network (SON) design is analysis of network signalling for optimisation. As noted above, driving tests were needed to examine the quality of coverage within a cell. These driving tests were effective to some extent, but could not give an accurate picture of reception quality inside buildings. However signalling mechanisms within 3G and 4G standards allow for reception signal strength to be fed back to the base station and to the mobile core network. A SON allows for this information to be analysed and used to identify and heal areas where reception is weak. Example 13.1 Celcite is a vendor of SON software for operating a heterogeneous network (HetNet). The software identifies operator's 2G/3G/4G network nodes and maps a multidimensional network coverage picture. Real-time network load is then analysed to balance the node of different cells. SON software is also used to allocate frequency and time-slot resources of the 4G net- work to ensure best resource utilisation. The software needs to analyse a large collection of information from base stations and subscriber signal strength feedback to map an optimal resource allocation solution for the users and the operator [20, 21, 22]. Network planning and roll-out, optimisation and maintenance has therefore become a problem for big data field, where an 'optimum' solution for a network at any particular time may be found. The role of network planning companies is minimised as cell planning and tuning can be done using vendor (e.g. Ericsson, Huawei) software installed within network equipment. The need for drive tests to analyse the network is also replaced by data analysis software based on information collected from subscribers. Broadband Telecommunications Technologies and Management Wireless service provision to a populated area is a function of subscriber density as well as standard specifics, as operators buil