Transmission power control method and radio control apparatus in mobile packet communication system

Abstract

A downlink user data signal destined for a specific mobile station (-) is always transmitted from a single base station while a plurality of base stations (---, . . . ) being switched from one to another. A first downlink signal destined for the mobile station (-) is transmitted from one or a plurality of base stations through a first downlink radio channel (downlink A-DPCR). The transmission power of a second downlink radio channel (PDSCH, HS-SCCH) for transmitting a second downlink signal from the base station (-) to the mobile station (-) is provided with an offset relative to the transmission power of the first downlink radio channel from the base station (-) to the mobile station (-), thereby linking the transmission power of the second downlink radio channel with the transmission power of the first downlink radio channel. If the number of diversity branches, i.e., the number of base stations (--) simultaneously communicating with the mobile station (-) on the first downlink radio channel (downlink A-DPCH) is large, the offset for the transmission power of the second downlink radio channel (PDSCH, HS-SCCH) is increased. If the number of diversity branches is small, the offset for the transmission power of the second downlink radio channel is decreased. In this way, the offset is determined. As a result, in mobile packet communication that transmits user data for a plurality of mobile stations through a single radio channel by temporally multiplexing the data, the reception quality of the second downlink signal transmitted from the specific base station (-) on the second downlink radio channel (PDSCH, HS-SCCH) can always properly be maintained.