Reduced modulation modes for bit and power allocation in multi-carrier transmissions

A new scheme is proposed to optimally reduce the modulation modes for bit and power allocation algorithm in multi-carrier transmissions. By reducing the modulation modes, computational load and hardware complexity can be reduced without any performance degradation. When modulation modes for rectangular QAM are available at a transmitter, it is shown that the modulation modes for rectangular QAM can be reduced to those for square QAM which is the subset of rectangular QAM. After identifying a power allocation property of rectangular QAM, it is proved that the optimal allocation with square QAM has exactly the same performance as that with rectangular QAM. Numerical results show the reduction of computational load and verify our theoretic presentations.