Mimo Precoding for Rydberg Atomic Receivers Enabled Wireless Communications

Leveraging the strong atom-light interaction, Rydberg atomic receivers (RAREs) can measure radio waves with extreme sensitivity. Existing research primarily focuses on improving the signal detection capability of RAREs, while traditional signal processing methods at the transmitter side have remained unchanged, which leaves a large gap from the maximum channel capacity. To address this issue, we exploit the transmitter precoding in atomic multiple-input-multiple-output systems to achieve the channel capacity. To begin with, a strong-reference approximation is proposed to linearize the nonlinear magnitude-detection model of atomic receivers, allowing us to express the channel capacity analytically. Then, a new digital precoding technique, termed In-phase-and-Quadrature (IQ) aware precoding is presented, which features independent processing of I/Q data streams using four real-valued matrices. The design is shown to be capacity-achieving for the atomic MIMO system. For the case of large-scale MIMO, we extend the proposed design into the popular hybrid precoding architecture, which cascades a classical high-dimensional analog precoder with a low-dimensional version of the proposed IQ-aware digital precoder. By alternatively optimizing the digital and analog parts, the hybrid design is able to approach the performance of the optimal IQ-aware fully digital precoding. Simulation results validate the superiority of proposed IQ-aware precoding methods over existing techniques in atomic MIMO communication systems.