Spatial modulation (SM) is a multiple antenna trans- mission approach that exploits the location of the transmitting antenna for conveying data information. In SM, only a single transmit antenna transmits at a time while all other antennas remain silent. The receiver estimates the transmitted symbol and the active transmit antenna index and uses both estimations to retrieve the original information bits. In this paper, two analytical approaches to symbol-error-ratio (SER) analysis of the SM algorithm in independent and identically distributed (i.i.d.) Rayleigh channels are developed. The validity of the approaches are discussed and the obtained analytical results are compared to Monte Carlo simulation results. I. INTRODUCTION