Soft estimates for doubly iterative decoding of space-time turbo codes using M-ary Quadrature Amplitude Modulation

Quadrature Amplitude Modulation (QAM) is an important modulation scheme with many practical applications, including current and future wireless technologies. The performance of a mobile communication system can be improved by using a doubly iterative decoding scheme for space-time turbo codes with a large number of transmit and receive antennas, where the decoder uses preliminary soft values of the coded symbols. In this paper, the soft estimates for a high QAM order are derived and explained.