A Novel Quadratic Programming Model for Soft-Input Soft-Output MIMO Detection

In this letter, we propose a novel quadratic programming model for soft-input soft-output (SISO) multiple-input multiple-output (MIMO) detection that is compact for QAM constellations and easy to analyze. A semidefinite relaxation for this model is derived that can be solved by the interior-point method. We also give the sufficient conditions and necessary conditions to speed up the interior-point method.