Information Theory of Transmit Diversity and Space-Time Code Design
non-ergodic; channel; fast fading; transmit diversity; Alamouti; space-time code
We restate the achievable information rates for multiple transmit multiple receive antenna systems in fast fading channels. Then we consider non-ergodic channel, where we evaluate asymptotic expression for the outage probability and note its striking similarity with the error probability. After that, we consider a simple transmit diversity technique <i>Alamouti</i>, and evaluate its achievable information rate. We note that in the case of a single receiver antenna there is no loss in capacity if one reserves to this technique as a mean of exploiting transmit diversity. However, we note that in the case of multiple receivers there is a penalty in capacity. Also, we demonstrate that CDMA orthogonalisation between antennas results in capacity loss. Then we derive performance criterion for codes concatenated to the simple diversity technique. After that, we propose some high-rate space time codes which use multiple antennas in order to incerase the rate rather than improving communication reliability. At the end we note how some distance spectrum trimming can increase a performance of space-time codes without increasing computational complexity.
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