Spatial Modulation With Energy Detection: Diversity Analysis and Experimental Evaluation

In this paper, we present a non-coherent energy detection scheme for spatial modulation (SM)
systems. In particular, the use of SM is motivated by its low-complexity implementation in comparison
to multiple-input multiple-output (MIMO) systems, achieved through the activation of a single antenna
during transmission. Moreover, energy detection-based communications restrict the knowledge of the
channel state information to the magnitude of the fading gains. This consideration makes the design
applicable for low-cost low-powered devices since phase estimation and its associated circuitry are
avoided. We derive an energy detection metric for a multi-antenna receiver based on the maximumlikelihood
(ML) criterion. By considering a biased pulse amplitude modulation design, we develop an
accurate analytical framework for the error rate at high signal-to-noise ratios. Numerical results show
that the diversity order is proportional to half the number of receive antennas; this result stems from
having partial receiver channel knowledge. In addition, we compare the performance of the proposed
scheme with that of the coherent ML receiver design and show that the SM energy detector outperforms
its coherent counterpart in certain scenarios, particularly when utilizing non-negative constellations.
Ultimately, we implement an SM testbed using software-defined radio devices and provide experimental
error rate measurements that validate our theoretical contribution.