Energy-Efficient Link Adaptation on Rayleigh Fading Channel for OSTBC MIMO System With Imperfect CSIT

We propose an energy-efficient adaptive transmission scheme for multiple-input-multiple-output (MIMO) beamforming systems with orthogonal space-time block coding (OSTBC) based on imperfect channel state information at the transmitter (CSIT). The transmission rate and transmit power are adapted to maximize the energy efficiency (EE) subject to an instantaneous bit-error-rate (I-BER) constraint. We solve this nonconcave problem based on the generalized convexity. Closed-form expressions of the energy-efficient transmission rate and transmit power for both modulations with constant power amplifier (PA) inefficiency and M-ary quadratic-amplitude modulation (MQAM) with nonconstant PA inefficiency are obtained. Based on these results, we also analyze four special cases: The circuit power dissipation is negligible, the CSIT is perfect, the CSIT is only channel distribution information (CDI), and the discrete rate adaptation policy is employed. Numerical results are also given to further illustrate the impact of CSIT imperfection to the transmitter EE.