In this paper, a novel transmission scheme, referred to as difference-based spatial modulation (DBSM), is proposed to improve the performance of spatial modulation (SM) within multi-antenna systems. The DBSM delivers two adjacent symbols in an arbitrary transmission, where one of the two symbols is radiated from a single transmit antenna. Different from conventional SM, the DBSM selects the active transmit antenna based on the difference between the two adjacent symbols. Although the other symbol is not physically radiated, the information carried by it is conveyed not only through the radiated symbol but also through the selection of active transmit antenna. For the purpose of performance evaluation, the proposed DBSM is compared with conventional SM in terms of bit error rate for the same system settings and the same multi-antenna configurations. Illustrative simulation results substantiates that our DBSM outperforms conventional SM while achieving the same data rate, specifically in the systems with low-order modulation. © 2022 IEEE.