Spectral Efficiency Maximization in Pinching-Antenna-Enabled CR Networks

In this paper, we investigate a cognitive radio (CR) network underpinned by pinching antennas (PAs), in which both the primary transmitter (PT) and secondary transmitter (ST) employ a single waveguide and multiple PAs to support simultaneous spectrum sharing. A sum spectral efficiency (SE) maximization problem is formulated to jointly optimize the pinching beamforming at both the PT and ST, under constraints on the PA deployment. To solve this non-convex problem, a two-stage optimization algorithm is developed, which sequentially optimizes the PT and ST pinching beamforming. For each pinching beamforming optimization, the coarse positions of the PAs are first determined at the waveguide level, followed by wavelength-level refinements to achieve constructive signal combining at the target user and destructive superposition at the non-intended users. Simulation results demonstrate that PAs yield substantial SE gains compared to conventional fixed-position antennas.