Space-time block coded OFDM with adaptive modulation and transmitter beamforming

We propose an optimum transmitting structure consisting of adaptive modulation, space-time block coding (STBC), and transmitter beamforming for orthogonal frequency division multiplexing (OFDM) systems to improve the data throughput and error performance. Using correlative properties of multi-input multi-output (MIMO) channels, we maximize the channel-to-noise ratio (CNR) based on a water-filling principle to optimally select the number of antenna beams and the power splitting ratio. The adaptive modulator employed is based on a lookup matrix adaptive bit and power allocation (LM-ABPA) scheme. As compared to non-adaptive systems, simulation results demonstrated that the proposed configuration achieves spectrally more efficient transmission under a constant error rate as well as better error rate performance under a constant data rate