A
base station, a
mobile station, a
radio communications system, and a
radio transmission method are disclosed. The
base station includes a control information determining unit configured to determine control information that includes a
spreading factor, the number of
chip repetitions, and a phase unique to the
mobile station, based on at least one of information about the type of
cell environments in which the
mobile station is present, information about the number of mobile stations that are present in the
cell, information about information rate required by the mobile
station, information about a type of traffic, information about a radio parameter of the mobile
station, information about a propagation
path condition, and information about interference from an adjacent
cell, and configured to transmit the
spreading factor, the number of
chip repetitions, and the unique phase of the mobile
station that is determined to the mobile station.