Handover criteria and control in cellular and microcellular systems

Cellular system operation relies on frequency reuse, with cell sizes and reuse distances governed by receiver tolerance to cochannel interference. It is possible for a mobile unit to move away from the initial base station during communication, so the facility to handover the link to adjacent base stations is a necessary feature of the network. The complexity of the problem renders it difficult to quantitatively compare handover algorithms in a system design; hence a computer simulation tool has been developed to expedite this comparison. This has been used for handover criteria performance assessment within the model. A first order estimate of typical signalling loads anticipated in microcell based systems has been obtained. Simulation illustrates the excessive handover numbers compared with the number of cell boundary crossings, whenever the criteria chosen exhibit statistically indeterminate behaviour. However, the performance can approach that of a deterministically controlled system if the handover algorithm is modified. More sophisticated handover algorithms could magnify this effect