DESIGN OF UNDERLAID MICROCELLS IN UMBRELLA CELL SYSTEM

The umbrella cell systems where the same radio system is used for micr ocells and overlaying macrocells, is a promising strategy for deployin g microcell service to cope with the locally increased radio traffic. The interference at microcells due to macrocells can be compensated by increasing the transmit power of microcell. In this paper, a practica l method to implementing a microcell system overlaid with an existing macrocell system is proposed. In order to engineer the radio resource planning for the underlaid microcells, transmit power design and appli cation of Channel Segregation, a self-organized dynamic channel assign ment, are proposed. By these techniques, the system channels are reuse d automatically while minimizing interference between macrocell and mi crocell systems, thereby communication quality of umbrella cell system can be improved. Furthermore, the prime advantage of the proposed met hod is that locally increased traffic is handled by the underlaid micr ocells without any extra effort for channel management.