In this thesis, we revisit differential and non-coherent transmission techniques over fading channels. In particular, we consider receiver design for differential space-time modulation (DSTM) over correlated multiple-input multiple-output (MIMO) fading channels and the performance analysis of differential phase shift keying (DPSK) and non-coherent frequency shift keying (FSK) in generalized K-fading. For DSTM over spatially correlated MIMO channels, we derive a multiple-symbol differential detection (MSDD) and a novel MSDD-based decision-feedback differential detection (MS-DFDD) receiver. We show that MS-DFDD outperforms previously proposed decision-feedback differential detection (DFDD) schemes that are based on scalar and vector predict...