Abstract: A receiving device comprises a demodulating section for demodulating transmission signal into a demodulated signal having a digital speech signal and a error detecting code. The demodulating section divides the digital speech signal into first through N-th subframe speech signals and detects a received field intensities of the first through the N-th subframe speech signals to produce first through N-th field detection signals representative of the received field intensities of the first through the N-th subframe speech signals, respectively, where N represents a positive integer which is greater than one.

Abstract: A communication channel assigning system is disclosed, that comprises a mobile communication system having a plurality of radio base stations disposed in a plurality of radio zones, a plurality of mobile stations for communicating with the base stations using communication channels, and a radio base station controlling unit for controlling the radio base stations, a transmitting means for transmitting data corresponding to a code division multiple-access radio modulation system, a means for assigning a communication channel to the data transmitted by the transmitting means, and a means for using communication channels with a plurality of bandwidth in the same frequency band.