Stochastic determination method of substream modulation levels for MIMO eigenbeam space division multiplexing

Multiple-input multiple-output (MIMO) eigenbeam space division multiplexing is a promising configuration to improve the transmission capacity and it uses adaptive modulation for the substreams. The modulation levels determined from the carrier-to-noise ratios, however, are sometimes optimistic and the use of the modulation levels results in transmission errors and transmission performance degradation. A novel determination method of substream modulation levels is proposed to alleviate the degradation. The proposed method calculates the expected bit error rates for possible modulations by mean of the delay profile. The simulation results show that the proposed modulation level determination method improves the transmission capacity by 30% compared with the conventional method.