e ratio indicates the main cause for outgoing attempts from a certain cell. It also gives hints on possible optimisation needs. For example, a cell that performs with a high ratio of interference handovers may in reality be experiencing external interference. Therefore the frequency plan of the area needs to be reconsidered. Possible causes for outgoing handover can be power budget, quality, interference, level, slow-moving MS, congestion, turnaround corner, distance, Handover Failures A handover failure refers to an unsuccessful handover attempt either while trying to move to the target cell or while returning back to the origin cell. Field drive tests highlight handover failure problems, especially when they simultaneously give information on other indicators such as the serving and neighbouring cell level, quality, base station identity code (BSIC) decoding and location area code. We talk about handover blocking when there is some factor preventing the call being transferred to the target cell. Usual Checks and Corrections As handover is a crucial operation that ensures mobility on cellular networks, more attention is paid to define coherence precisely. An adjacency is defined by the target cell location area code, cell identity, Radio Network Optimisation BCCH frequency, BSIC network colour code and BSIC broadcast colour code. Any change in one of these identifiers requires an update in the adjacency definition from neighbour cells towards this target cell. Updating such information is intended to be transparent and automatic, but verification is better than assumption. One cell in the adjacent list may be declared with a false BCCH, BCC or NCC that differs from the actual values. In this case no handover can succeed towards this cell. The only solution remains to correct the parameters in the adjacent database. In general, neighbouring relationships are symmetric. A handover may occur from cell A to cell B and from cell B to cell A. There may be an error if an adjacency is not symmetric unless explicitly wan