A communication system that communicates over frequency channels set by dividing a frequency bandwidth assigned to the system, the communication system comprising: a transmitting device (151, 102b) that transmits a signal in which Inter-Channel Interference is allowed by purposely overlapping among the frequency channels adjacent to each other in a frequency domain; and a receiving device (103b, 104c) that receives the signal transmitted from the transmitting device (151, 102b), characterized by the transmitting device (151, 102b) comprising: a spectrum usage information and policy information acquiring portion that detects a bandwidth of a frequency channel that is not being currently used and determines usage status of other users frequency channels; and a pulse shape and symbol rate controller that determines a pulse waveform of a signal to be transmitted from the transmitting device (151, 102b) based upon the information acquired by the spectrum usage information and policy information acquiring portion, and that determines a center carrier frequency and a symbol rate of the signal to be transmitted from the transmitting device (151, 102b) based upon the pulse waveform determined, wherein the receiving device (103b, 104c) comprises ICI removal means that removes the Inter-Channel Interference, owing to overlapping adjacent frequency channels with each other, allowed at the signal transmitted, and wherein the pulse shape and symbol rate controller determines whether or not it is possible to overlap the frequency channel that is not currently used with an adjacent frequency channel, and when it is determined that the receiving device (103b, 104c) comprises the ICI removal means that removes the ICI generated by overlapping the frequency channel, the pulse shape and symbol rate controller determines the pulse waveform of the signal to be transmitted from the transmitting device (151, 102b) by overlapping the frequency channel that is not currently used with the adjacent frequency channel. a transmitting device (151, 102b) that transmits a signal in which Inter-Channel Interference is allowed by purposely overlapping among the frequency channels adjacent to each other in a frequency domain; and a receiving device (103b, 104c) that receives the signal transmitted from the transmitting device (151, 102b), characterized by the transmitting device (151, 102b) comprising: a spectrum usage information and policy information acquiring portion that detects a bandwidth of a frequency channel that is not being currently used and determines usage status of other users frequency channels; and a pulse shape and symbol rate controller that determines a pulse waveform of a signal to be transmitted from the transmitting device (151, 102b) based upon the information acquired by the spectrum usage information and policy information acquiring portion, and that determines a center carrier frequency and a symbol rate of the signal to be transmitted from the transmitting device (151, 102b) based upon the pulse waveform determined, wherein the receiving device (103b, 104c) comprises ICI removal means that removes the Inter-Channel Interference, owing to overlapping adjacent frequency channels with each other, allowed at the signal transmitted, and wherein the pulse shape and symbol rate controller determines whether or not it is possible to overlap the frequency channel that is not currently used with an adjacent frequency channel, and when it is determined that the receiving device (103b, 104c) comprises the ICI removal means that removes the ICI generated by overlapping the frequency channel, the pulse shape and symbol rate controller determines the pulse waveform of the signal to be transmitted from the transmitting device (151, 102b) by overlapping the frequency channel that is not currently used with the adjacent frequency channel. a spectrum usage information and policy information acquiring portion that detects a bandwidth of a frequency channel that is not being currently used and determines usage status of other users frequency channels; and a pulse shape and symbol rate controller that determines a pulse waveform of a signal to be transmitted from the transmitting device (151, 102b) based upon the information acquired by the spectrum usage information and policy information acquiring portion, and that determines a center carrier frequency and a symbol rate of the signal to be transmitted from the transmitting device (151, 102b) based upon the pulse waveform determined, wherein the receiving device (103b, 104c) comprises ICI removal means that removes the Inter-Channel Interference, owing to overlapping adjacent frequency channels with each other, allowed at the signal transmitted, and wherein the pulse shape and symbol rate controller determines whether or not it is possible to overlap the frequency channel that is not currently used with an adjacent frequency channel, and when it is determined that the receiving device (103b, 104c) comprises the ICI removal means that removes the ICI generated by overlapping the frequency channel, the pulse shape and symbol rate controller determines the pulse waveform of the signal to be transmitted from the transmitting device (151, 102b) by overlapping the frequency channel that is not currently used with the adjacent frequency channel.