A faster ML sphere decoder with competing branches

A novel fast recursive sphere decoder with parallel competing branches (P-SD) is proposed for exact maximum-likelihood (ML) detection in multiple-input multiple-output (MIMO) systems. P-SD introduces a novel competition mechanism which makes P-SD dynamically choose the targeted branch to perform a bounded search among the competing parallel branches. In P-SD, the search radius shrinks to the minimum Euclidean distance as early as possible. Numerical results show that P-SD achieves considerable computational complexity reduction even compared with the Schnorr-Euchner enumeration (SEE) based sphere decoder (SE-SD).