Spatial Modulation in MIMO Cognitive Radio Networks with Channel Estimation Errors and Primary Interference Constraint

This paper studies the use of spatial modulation (SM) in multiple-input multiple-output (MIMO) cognitive radio networks considering the primary receiver interference constraint and the maximum transmit power of the secondary transmitter. In particular, we investigate the effect of estimation errors on the secondary system performance, where a closed-form expression is derived for the average pairwise error probability (P̅E̅P̅) in Rayleigh fading environments. Based on this P̅E̅P̅ expression, a tight upper bounded average bit error probability is obtained using the union bound formula. In addition, an asymptotic analysis is conducted and simple approximate expressions are derived to get useful insights on the system diversity and estimation errors´ effects. Numerical results, which are validated through simulations, show that the SM is robust against estimation errors.