Differential spatial modulation (DSM) is an attractive multiple-input-multiple-output (MIMO) transmission technique in which spectral efficiency is boosted by transmitting additional data bits with antenna indexes. However, the flaw in the traditional DSM model affects how accurately fast-fading channel states are characterized. In this article, an enhanced DSM model and a related low-complexity detector based on the DFDD concept are proposed for DSM transmission in high-mobility scenarios. The proposed DSM model and detector enhance detection performance in fast-fading channels by differentiating the channel states in various time slots within a block. Simulation results show that the proposed DSM model and detector exhibit a noticeable performance boost over traditional ones.