the use of an hdr system that is described from page 73 to page 75 in nikkei communication no 311 issued on feb 7 2000 by nikkei business publications inc the hdr system is a cellular radio communication system aiming high speeding of a data transfer rate without changing a basic parameter from a cdma 2000 1x system as a public standard in order to realize this high speeding a radio base station is ceased to be commonly used for both voice and data but is exclusively used for data and optimization thereof is achieved unlike voice communication data communication does not require a strict real time characteristic and the speed of data transfer is not always required to be constant either in general in the cellular radio system a transmitting environment varies depending on a traffic request in a service area various noises or the like however the hdr system improves its statistical throughput as a best effort type system by limiting exclusively its use to data transfer classification will be made below for features of the radio system for use in hdr 1 variable modulation system in general a radio wave is intense in the vicinity of a radio base station and an intensity of the radio wave is being attenuated as the wave travels far therefrom fig1 shows a state thereof since c i representing a ratio of the intensity of radio wave and an interference noise is high when the intensity of radio wave is high it is possible to increase a quantity of information capable of being transmitted for a unit time by allowing the modulation.