A simplified adaptive modulation scheme for D-STTD systems with linear receivers

In this letter, we consider D-STTD (Double Space Time Transmit Diversity) with an adaptive modulation (AM) scheme. The simple criteria for AM are proposed according to linear receivers and the corresponding AM schemes are derived to minimize bit error rate under the constraint of the total data rate and total transmit power. The D-STTD system using the proposed AM scheme requires low computational complexity and small feedback information. The performance of D-STTD system using the proposed scheme is improved by 7 dB or more in signal to noise ratio corresponding to 10/sup -4/ bit error rate.