oving slow or fast is decided and then the slow-moving MS is directed to lower layers. When a mobile is camping on a macro cell, for example, it reports downlink measurements of adjacent cells to the BSC. If the MS measures an adjacent cell with a 'good' level during a certain time, it is assumed that the MS is slow and an umbrella handover can be initiated towards the lower layer cell. In layer management, careful attention drives the choice of averaging window parameters. A small window size accelerates handover decisions for a fast MS, while a large window size will prevent unnecessary oscillation for a slow MS. Selection refers to the action of selecting a first cell when in idle mode and as soon as the mobile station is switched on. Reselection means the same action, but considers another cell when the mobile is already camping on a source cell either in idle or connected modes. Handover from macro to micro sites induces the use of cell selection and reselection criteria. C1 can be assimilated to the received level minus Rxlevaccessmin. It is used in cell selection as a ranking criterion. It can also be used in reselection with the introduction of a hysterisis. C2 criterion is used in cell reselection and introduces the consideration of a time dimension. When time is less than a certain value, an offset penalises the level of a cell and once the predefined time elapses, C1 criterion is improved with a certain offset. Radio Network Optimisation Finally, it is assumed that layer management is used in order to share traffic load in an optimised efficient way. Thus, when traffic is low on the macro layer, cell reselection offset is used to prevent unnecessary handovers to the lower layer. Handover Features Many handover features exist to allow faster handover decisions to be made and at the end contribute to call quality improvement. Turn around the corner MS and detection of rapid field drop features help to identify a mobile that quickly loses visibility with the micro cell antenna and commands an outgoing han