HARQ for SISO and MIMO system with constellation rearrangement

For higher order modulation, the reliabilities of the bits gray-mapped onto the modulated symbol vary from the most significant bits (MSBs) to the least significant bits (LSBs). This paper introduces one constellation rearrangement method for SISO (single-input single output) system. For MIMO (multiple-input multiple output) system, the constellation rearrangement works also for lower order modulation by the construction of spatial signal. One constellation remapping method for MIMO system is also introduced in the paper. The simulation results show the performance gain for the SISO constellation remapping method.