High Power Efficient Quadrature Amplitude Modulation Soft Decision Algorithm

The quadrature amplitude modulation (QAM) is the basic technology on high speed broadband communication physical level symbol mapping. Systems requiring lower signal to noise ratio to achieve the same error probability are more power-efficient. The usage of high order modulation is limited due to its low power efficiency compared to lower order modulation. This paper combines the characteristics of Gray code symbol mapping for QAM constellation to design a soft decision algorithm based on signal diversity (div-log-MAP). The bottle-neck of the low power efficiency is overcome and highest power efficiency can be realized. The performance of div-log-MAP can beyond the performance of log maximum a posteriori probability algorithm. At the same time, the proposed algorithm is a more effective method to utilize high order QAM modulation on high speed broadband communication.