Patent ID: 8270525

Claim:
A digital radio communications method using a multi-level modulation scheme for use in a digital radio communications system including: a transmitter which transmits a signal modulated with the multi-level modulation scheme in which a single symbol is transmitted using a plurality of bits; and a receiver which demodulates the reception signal received from the transmitter by means of performing a symbol evaluation, said digital radio communications method comprising: on the transmitter, performing a coding process of coding an information series to be transmitted, to generate multiple codes which are different in significance; performing a bit correction process of controlling bit arrangement such that a code having high significance, out of said multiple codes obtained by said coding process, is allocated with high priority to a bit having a tendency such that the likelihood of the bit at the symbol evaluation performed on the receiver becomes large; performing a multi-level modulation process of allocating the code to said plurality of bits in accordance with a bit arrangement obtained in said bit correction process to perform the multi-level modulation of the information series at a predetermined symbol arrangement on a complex plane; and performing a symbol arrangement control process of controlling the symbol arrangement so as to change the positions of symbols on the complex plane arranged regularly such that at least a part of the symbols are arranged irregularly in accordance with a ratio of the codes different in significance in said bit correction process, while maintaining a transmission power before and after the control of the symbol arrangement, on the receiver, demodulating a signal received from the transmitter based on information relating to the controlled symbol arrangement; and performing decoding the demodulated signal to obtain the information series.