An adaptive power allocation scheme for space-time block coded MIMO systems

Receive diversity yields a higher signal-to-noise ratio (SNR) than transmit diversity when the total transmitted power and diversity order are the same. However, if the transmitter has complete or partial knowledge of channel, the SNR gap between these two schemes can be reduced. This paper introduces an adaptive power allocation scheme for space-time block coded (STBC) multiple-antenna systems to improve system performance. For any set of channel fading coefficients, the transmit power scaling factors are controlled by a single design parameter u. The proposed adaptive power allocation scheme improves the instantaneous SNR at the receiver. Special choices of u result in some existing STBC schemes. Performance gain of the proposed scheme over the conventional equal-power scheme under the condition of perfect and imperfect feedback is studied. The maximum achievable SNR gain limit over the conventional scheme is also derived.