necessary adjacencies is the geography and the location of sites. The case of adding new neighbours will first be considered. If a relation is missing between two close cells, the statistics will not detect this anomaly. In fact, statistics are picked on already existing neighbours and are blind towards missing declarations. This is why considering the use of a map is very important in the detection of missing neighbours. For the case of deletion of unnecessary relations, it has been exposed previously that the process of selection takes place through statistics. Therefore, after selection of unwanted neighbours and before the deletion, it is worth checking on a map to see whether there is enough overlapping with other neighbours to cover the whole geographical area. Statistics Handover performance is crucial for quality of service and mobility. Drive testing allows localising handover disfunctioning. The NMS gives statistics on handover performance to let operators identify bad performing cells and areas in the handover mechanism. The main KPI that qualifies handover on a network is the HSR. Hereafter, a clear definition of HSR will be given. Two other main notions are also important to understand: handover cause and failure cause. By identifying these two elements, troubleshooting becomes easier. Handover Success Rate The HSR indicates the percentage of successful handover attempts in accordance with the total number of attempts. Generally a value of 95-98 % is acceptable. Bellow this range, the optimisation engineer should look for the origin of the problem and try to find solutions. The HSR is measured on a cell or area basis considering all outgoing successful handover attempts. If the HSR is not good enough then there should be a detailed consideration of all adjacencies cell-to-cell in order to highlight the worse performing couples. Handover Causes In the handover troubleshooting process, causes are important to consider. In fact, for several reasons the network can initiate one handover. A high percentag