BER improved transmit power allocation for D-STTD systems with QR-based successive symbol detection

We propose a BER improved power allocation scheme for D-STTD systems over i.i.d. Rayleigh fading channels under the QR-based successive detection framework. Instead of relying on BER under a fixed channel realization, the adopted design criterion is the mean BER (assuming there is no inter-layer error propagation) averaged with respect to the channel distribution. Such a design metric has two-fold advantages: (i) It is analytically tractable and is closely related to a block error probability upper bound when inter-layer error propagation occurs, and (ii) There is no need for repeated feedback of the instantaneous channel information. By exploiting a distinctive channel matrix structure unique to D-STTD systems we derive a closed-form approximate upper bound of the considered BER metric; through minimization of this bound an optimal power allocation scheme is obtained. Numerical simulation is used to illustrate the performance of the proposed method.