Unlocking Potential in LEO Satellites Communications Through Spatial Modulation and Space Shift Keying

As future wireless networks demand higher throughput and lower latency, Low Earth Orbit (LEO) satellites have become essential to supplement terrestrial infrastructure. Meanwhile, ground-based systems alone often fail to fulfill these requirements, motivating the exploration of non-terrestrial solutions such as LEO-assisted advanced modulation techniques. This paper investigates the application of spatial modulation (SM) and space shift keying (SSK) techniques in LEO satellite-assisted wireless communication systems. A shadowed Rician fading model is employed to characterize the LEO-to-ground channel, incorporating realistic path loss, Doppler effects and others. Moreover, comprehensive analytical performance, with closed-form BER upper bounds, is derived for both LEO-SM and LEO-SSK schemes. To further enhance reliability, a gradient descent-based satellite elevation angle optimization method is proposed. Theoretical analysis and simulations confirm that the proposed schemes achieve improved error performance and reduced detection complexity compared to traditional modulation. Furthermore, trade-offs between spectral efficiency and complexity are analyzed and discussed, demonstrating the practical feasibility of applying SM/SSK to future LEO satellite- assisted wireless systems.