Component-interleaved Alamouti coding with rotated constellations for signal space diversity

A signal space diversity (SSD) scheme combined with Alamouti coding is investigated to achieve more diversity gain in fading channels. By approximating noise as a Gaussian distribution after Alamouti decoding, an exact expression for the SER for SSD schemes with Alamouti coding in Rayleigh fading channels can be derived for 4-QAM and 16-QAM. Using the formula derived by using upper bound approach, it can be confirmed that the diversity order is 4M_R, where 2 stems from SSD and 2M_R from Alamouti coding with receive MRC. Numerical evaluation performed using the formula developed for evaluating performance under various conditions indicated that the rotation angle affects the performance; this numerical evaluation had low computational complexity.