Constant rate adaptive modulation with selection transmit diversity for broadband OFDM systems

Adaptive modulation combined with transmit diversity can achieve further increases in system´s capacity and bandwidth efficiency, as well as in QoS improvement in conventional OFDM systems. In this paper, we propose a constant rate adaptive modulation with selection transmit diversity for broadband OFDM wireless systems. By combining the adaptive modulation with the adaptive selection diversity according to the characteristics of the channel on each sub-carrier, the transmit diversity obtained by antenna selection is further maximized through adaptive bit assignment and power assignment on each sub-carrier under the constraint of power and overall bit rate. As a result, the proposed system can achieve better performance compared to that of the conventional selection transmit diversity based OFDM systems without adaptive modulation and conventional adaptive modulation based OFDM systems without selection transmit diversity over multipath fading channels.