A new family of Linear Dispersion Code for fast Sphere Decoding

In this paper, a new family of linear dispersion codes (LDCs) that can be decoded using a fast sphere decoding (SD) algorithm in MIMO systems is proposed. The basic principle of this structure is to make the LDC to have as many as possible the rows orthogonal in the dispersion matrices. Monte Carlo simulation results show that the optimum LDCs with this orthogonal structure have nearly identical bit-error-rate (BER) performances as other optimal LDCs. We develop a simplified sphere decoding (SD) algorithm that can significantly reduce the decoding complexity in decoding the new LDCs with proposed orthogonal structure. Simulation results show that the complexity reduction is more significant for MIMO system transmitting higher level modulation. For 2times4 MIMO systems transmitting 4 64QAM and 256QAM symbols in a block length of 4, the reductions are about 71-83% and 76-88%, respectively.