Multiple Symbol Differential Stack Algorithm for Unitary Space-Frequency Modulation

Differential unitary space-frequency modulation reduces the complexity of multiple-input multiple-output-orthogonal frequency division multiplexing (MIMO-OFDM) systems significantly. But the conventional single symbol differential detection (SSDD) results in a high error floor over a severe multipath spreading channel. To overcome this limitation, a multiple symbol differential stack algorithm is proposed by embedding a recursion of maximum-likelihood metric in the stack algorithm. The proposed algorithm is suitable for arbitrary nondiagonal unitary space-frequency constellations and enhances the flexibility to multipath spread compared with SSDD.