A microcell overlaid with umbrella cell system

The umbrella cell system, where the same radio system is used for microcells and overlaying macrocells, is the most promising strategy for deploying microcell service to cope with increased portable radio subscribers. A practical approach to implementing a microcell system overlaid with an existing macrocell system is proposed. There is no need to design the channel assignment and transmit power management for the microcell system by introducing the channel segregation, a self-organized dynamic channel assignment and the automatic transmit power control. The system channels are reused automatically between the macrocells and microcells. The interference from the macrocell to the microcell is compensated by slight increase of transmit power for the microcell system. It is shown by computer simulation that locally increased traffic is accommodated with the microcells laid under macrocells without any effort for channel management