Optimal Power Allocation and Active Interference Mitigation for Spatial Multiplexed MIMO Cognitive Systems

Abstract

This paper analytically studies an underlay MIMO cognitive radio system with spatial multiplexing at the secondary transmitter and zero‑forcing detection at the receiver. The system experiences interference from multiple randomly distributed single‑antenna primary users. The authors propose an optimal power allocation algorithm constrained by the interference temperature limits imposed by primary users. They derive a closed‑form expression for the secondary outage probability, consider special cases such as colocated PUs and massive MIMO, and develop an iterative antenna-reduction algorithm to actively mitigate excessive instantaneous interference. Analytical and simulation results confirm the proposed methods’ effectiveness.