On mutual information and outage for extended Alamouti space-time block codes

Extended Alamouti codes have proven to exhibit very desirable properties which enable the implementation of simple receiver types. We show analytically that the mean mutual information for extended Alamouti codes in i.i.d. Rayleigh fading is invariant to the number of transmit antennas. Numerical investigation indicates that the variance of the mutual information decreases. Therefore, outage probability decreases with the number of transmit antennas. Finally, we observe that the mutual information due to fading can be closely approximated by a Gaussian random variable.