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Efficient spectrum utilization is one of the most important issue in all mobile radio systems. Selective Handover for Traffic Balance (SHOT) is proposed which can improve the time domain frequency efficiency of cellular systems.If the traffic of a cell increases temporarily such that the resource utilization rate exceeds a threshold, SHOT compulsively hands some calls over to the appropriate adjacent cells. This results in balancing traffic loads among cells. Three algorithms are proposed and examined through computer simulations. The simulations reveal that SHOT improves the traffic performance by about 50% under the condition that offered traffic is uniformly distributed in the areas when the number of channel of each cell is 10.

SUMMARYIn mobile communication systems such as cordless telephones, it is extremely important to understand the service area if the base station is placed indoors. However, within a building, there exist walls, pillars, and partitions, so that accurate establishment of the propagation prediction formula has been difficult. A method that can accurately estimate the electric field intensity for a complex layout such as an indoor environment is the ray-tracing method. In this method, the electric field intensity can be estimated rather easily by deriving only the geometrical tracing between the transmitter and receiver. However, if the number of structural components such as walls, pillars, and partitions is increased, the processing time increases drastically. Therefore, it is indispensable to increase the processing speed in order to make this method practical. In the present paper we propose (1) the HY-RAYT method, (2) the ray-receiving model, and (3) the component search method, which allow high-speed processing via the ray-tracing method. The estimation accuracy and reduction of the computational effort are discussed.

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