Modulation method and radio communication system

Abstract

An input digital signal is periodically and alternately subjected to first modulation and second modulation, being thereby converted into a pair of a baseband I signal and a baseband Q signal. The first modulation and the second modulation are different from each other. The pair of the baseband I signal and the baseband Q signal are outputted. The first modulation may be at least 8-signal-point modulation while the second modulation may be phase shift keying.

1 . A method for wireless transmission comprising the steps of:
 generating a first modulation signal by modulating first data;   generating a second modulation signal by modulating second data, which is different from the first data, using a modulation scheme which changes a mapping pattern based on the first data; and   outputting the first modulation signal and the second modulation signal.   
     
     
         2 . The method according to  claim 1 , wherein:
 the second modulation signal is a signal generated by using the mapping pattern of the modulation scheme based on a position of the first modulation signal on an IQ plane.   
     
     
         3 . The method according to  claim 1 , wherein:
 the first modulation signal is a signal modulated by a PSK scheme; and   the second modulation signal is a signal modulated by a QAM scheme.   
     
     
         4 . The method according to  claim 1 , wherein:
 the second modulation signal is generated by using one of a plurality of mapping patterns which are obtained by changing phase components of modulation signal points on an IQ plane, the modulation signal points being composed of the phase components and amplitude components.   
     
     
         5 . The method according to  claim 1 , wherein:
 a signal point of the first modulation signal is a signal point arranged on an I axis or a Q axis of an IQ plane.   
     
     
         6 . The method according to  claim 1 , wherein:
 the first modulation signal is a modulation signal modulated by a QPSK modulation scheme.   
     
     
         7 . A wireless transmitter, comprising:
 a first modulator that generates a first modulation signal by modulating first data;   a second modulator that generates a second modulation signal by modulating second data, which is different from the first data, using a modulation scheme which changes a mapping pattern based on the first data; and   a transmitter that outputs the first modulation signal and the second modulation signal.   
     
     
         8 . The wireless transmitter according to  claim 7 , wherein:
 the second modulation signal is a signal generated by using the mapping pattern of the modulation scheme based on a position of the first modulation signal on an IQ plane.   
     
     
         9 . The wireless transmitter according to  claim 7 , wherein:
 the first modulation signal is a signal modulated by a PSK scheme; and   the second modulation signal is a signal modulated by a QAM scheme.   
     
     
         10 . The wireless transmitter according to  claim 7 , wherein:
 the second modulation signal is generated by using one a plurality of mapping patterns which are obtained by changing phase components of the modulation signal points on an IQ plane, the modulation signal points being composed of the phase components and amplitude components.   
     
     
         11 . The wireless transmitter according to  claim 7 , wherein:
 a signal point of the first modulation signal is a signal point arranged on an I axis or a Q axis of an IQ plane.   
     
     
         12 . The wireless transmitter according to  claim 7 , wherein:
 the first modulation signal is a modulation signal modulated by a QPSK modulation scheme.