Space Shift Keying (SSK) for LOS Communication at mmWave Frequencies

We use space shift keying (SSK), which is the simplest form of spatial modulation (SM), to present and analyze the idea of spatial modulation in line-of-sight (LOS) conditions. We show that SSK can operate effectively in LOS conditions provided that the antennas are properly placed at TX and RX such that a high-rank LOS-MIMO channel is constructed. The operating conditions for LOS-SSK with parallel uniform linear arrays are established and two schemes, namely orthogonal SSK and bi-orthogonal SSK, are introduced. The bit error probabilities for both methods are derived and given in closed form. It is shown that LOS-SSK (more generally LOS-SM) is a promising technique and might especially be attractive in millimeter-wave communications which, due to its high frequency and small wavelength, inherently prefers LOS transmission and also enables packing of a large number of antennas in terminals.