On the Performance of SSK Modulation over Multiple-Access Rayleigh Fading Channels

Spatial Modulation (SM) is a recently proposed joint coding and modulation scheme for Multiple-Input-Multiple-Output (MIMO) wireless systems, which is receiving a growing interest. SM offers a low-complexity alternative to the design of MIMO wireless systems, which avoids multiple Radio Frequency (RF) chains at the transmitter and high-complexity interference cancellation algorithms at the receiver, but still guarantees a multiplexing gain that only depends on the number of antennas at the transmitter. This makes this technology especially suitable for the downlink with low-complexity mobile units. So far, the feasibility and performance of SM have been assessed and studied only for point-to-point communication systems, i.e., the single-user scenario. However, the performance achievable by the vast majority of wireless communication networks is interference limited, due to the simultaneous transmission of various users over the same physical wireless channel. Therefore, the adoption of SM in the next generation of wireless communication systems requires a deep understanding of its performance over interference channels. Motivated by this consideration, in this paper we study the performance of SM over the reference multiple-access fading channel composed by two transmitters and one receiver. Two detectors at the receiver are studied, i.e., the single- and the multi-user detector. In particular, analysis and Monte Carlo simulations show that the single-user detector does not offer, in general, good error performance for arbitrary channel conditions, while the multi-user detector achieves error performance very close to the single-user lower-bound. These results clearly highlight that SM can be adopted for enabling data transmission over multiple-access fading channels as well.