Adaptive modulation in MIMO system under power and QoS constraints

A bit loading and power allocation algorithm for multiple-input multiple-output (MIMO) systems under average transmit power and QoS constraints is proposed. The truncated right unitary matrix as precoder at transmitter and truncated left unitary matrix as decoder at receiver which are obtained by singular value decomposition (SVD) choose variable eigen-subchannels to carry Bell Laboratories Layered Space-Time (BLAST) codes with variable layers. We compare the average spectral efficiency (ASE) of our scheme with the other two adaptive modulation (AM) systems—continuous rate (CR) system and instantaneous power constraint (IPC) system. Performance is investigated by simulation results.