Design of underlaid microcells in umbrella cell system

The umbrella cell system, where the same radio system is used for microcells and overlaying macrocells, is a promising strategy for deploying 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 practical 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 application of Channel Segregation, a self-organized dynamic channel assignment, are proposed. By these techniques, the system channels are reused automatically while minimizing interference between macrocell and microcell systems, thereby communication quality of umbrella cell system can be improved. Furthermore, the prime advantage of the proposed method is that locally increased traffic is handled by the underlaid microcells without any extra effort for channel management.