the cell coverage areas are calculated again using the new parameters. All the preliminary BTS locations are gone through in the order the actual BTS locations are found and the coverage areas are always recalculated. Normally the plan is divided into smaller segments, each consisting of some base stations located close by. The segment can be drawn on the map as a geographically logical area, with the particular base stations inside the area. The aim is to find actual BTS locations segment by segment and to finalise the preliminary coverage plan one area at a time. When finding the actual base station locations it is important to reach the planning requirements. The coverage and capacity requirement needs to be reached with the actual BTS locations. When calculating the cell coverage with a planning tool the calculation range has to be wide, especially when the later interference estimation needs to be accurate. The common way to show the calculated Radio Network Planning and Optimisation Figure 2.18 Coverage area of a real cell coverage for a certain area is to view a composite plot with specified thresholds. In this type of presentation it is easy to see possible gaps in the coverage area. The contrary situation, when the overlapping areas between the cells are too large, can also be investigated. By fine tuning the planning parameters inside the given ranges can be made to fill the coverage gaps and reduce the unneeded overlapping; e.g. the BTS output power or antenna height, direction or down tilt can be changed. Another useful way to view the coverage is a dominance map. In this presentation each cell has a particular colour, which is used to show where this cell gives the dominant coverage. The coverage thresholds are therefore not used in this presentation. In practice the coverage borders are not this strict, because of the handover margin. When leaving the dominance area of one cell, another cell starts be to dominant - the handover is done only when the second cell's coverage is better than the handover