Adaptive modulation scheme has been widely used in multiple-input multiple-output (MIMO) systems to enhance spectral efficiency while maintaining the bit error rate (BER) under a target level. We consider two MIMO schemes, orthogonal space-time block codes (OSTBC) and spatial multiplexing with zero-forcing receiver (SM-ZF), that apply adaptive modulation scheme and derive closed-form expressions of the average spectral efficiency and BER. Based on the closed-form expression of spectral efficiency, a low complexity switching method is utilized to obtain high spectral efficiency gain over an adaptive system using a single scheme.
['Jinliang Huang', 'Svante Signell']
Discrete Rate Spectral Efficiency Improvement by Scheme Switching for MIMO Systems