The invention provides a central baseband processing unit for an indoor communication system. The central baseband processing unit is connected with a plurality of micro-power radio remote unit heads by fibers. Each micro-power radio remote unit head has a plurality of radio-frequency channels. The central baseband processing unit comprises a digital intermediate frequency processing module for modulating signals of all radio-frequency channels into ones with intermediate frequencies. A plurality of frequency bands corresponding to the multiple radio-frequency channels of one micro-power radio remote unit head are spaced from each other at a first frequency interval; and multiple frequency bands corresponding to the micro-power radio remote unit heads are separated from each other at a second frequency interval. Therefore, requirements of the coverage range and the capacity can be met; and the return stroke requirement is low. According to the invention, a novel topological structure can be realized and the arrangement cost of the network can be reduced.