The optimization of spectrum efficiency will be a major concern for fourth generation wireless systems. In our view, the key principle that holds the promise for ultimate spectrum exploitation is the full-fledged use of diversity techniques. In particular, there is a definite trend towards the adoption of diversity in multiple domains. This trend is justified by the fact that the particular domain whereby diversity is implemented determines the benefit that should be expected in terms of impairments to be counteracted.
In this paper we will focus our attention onto Space-Time Coding (STC) techniques, where the domains of antenna diversity and time diversity are joined to yield unprecedented performance gains without increasing bandwidth requirements. The gains can be traded-off for an increase in the data rate, fixing power/interference requirements. Here, we analytically evaluate system performance in the presense of both ideal and realistic propagation conditions: Rice-lognormal and Rayleigh fading channels are considered with ideal and non-ideal channel state recovery. In this framework, a closed-form expression for the average bit error probability for space-time block coding systems has been achieved. In particular, when imperfect channel phase estimation is taking into account, bit error probability has been expressed as a function of the phase error statistical distribution. As a numerical example, the case of the Gaussian phase error model has been considered and the results have been validated through Monte-Carlo simulations.