On the performance of spatial multiplexing MIMO cellular systems with adaptive modulation and scheduling

We analyze the forward link spectral efficiency (SE) of a spatial multiplexing cellular MIMO system using adaptive modulation and scheduling (opportunistic and proportional fair). With the channel state information (CSI) available only at the receiver side, the minimum mean square error (MMSE)-based ordered successive interference cancellation is employed for detection with either forward or reverse ordering. When the channel state information (CSI) is available at the transmitter, separate channels are obtained via singular value decomposition (SVD) of the channel matrix. The post processing SNR for each stream is fed back to the transmitter to adapt the modulation level corresponding to each stream. The multi-user diversity gain due to scheeduling is observed to be very significant especially without power control. The SE gain from the SVD scheme becomes negligible in a high SNR region which would not justify the complexity of having the CSI at the transmitter. The proportional fair scheduling is a good choice to compromise SE and fairness when the average channel conditions of users are different.