Handoff techniques in universal mobile communications

Global personal communications will be realized from the combination of terrestrial and space mobile networks. Thus, if handoff between these networks is intended, the satellite network must be part of the overall system. This means that the satellite ground infrastructure has to be interconnected with the mobile station centers and the public land mobile networks. Such interconnection would be rather complex and perhaps difficult to coordinate due to limits of national boundaries. Thus, an ideal alternative to combined coverage is an automatic scheme of selection and re-selection of cells and beams while the mobile terminal is idle. Within this prospect, the present work uses power attenuation characteristics to determine a dynamic criterion that allows smooth transition from space to terrestrial networks. The analysis includes a hybrid channel that combines Rician, Rayleigh and Log Normal fading characteristics. The criterion is based on the fact that a mobile equipment performs initial measurements of the radio environment, then selects a network according to a programmed list of allowed networks before it indicates service availability. An important limit used to classify the network list is the power level at the receiver, which in part depends on the transmission effects influenced by shadowing and fading.