Antenna Coding Design for Multi-User Transmissions Using Pixel Antennas

This work investigates exploiting the potential of pixel antennas, which are a reconfigurable antenna technology that can flexibly adjust the antenna characteristics through antenna coding, in multi-user transmissions. To that end, we propose a multi-user multi-input single-output (MISO) pixel antenna system, which deploys the pixel antenna at users, and develop the system model including pixel antenna with antenna coding and multi-user beamspace channels. Aiming at maximizing the sum rate performance, we first propose an algorithm to alternatively design the precoding at the transmitter and the antenna coding at users, which explores the performance boundary for the proposed multi-user MISO pixel antenna system. To reduce the computational complexity, we propose a codebook-based antenna coding design algorithm, where the antenna coder is online optimized from an offline codebook. To further enhance the computation efficiency, we propose a hierarchical codebook-based antenna coding design that uses a multi-layer hierarchical search to achieve a better performance-complexity trade-off. Simulation results show that, adopting the proposed algorithms, the multi-user MISO pixel antenna system can always outperform conventional multi-user MISO systems with fixed antennas. More importantly, results validate that the proposed (hierarchical) codebook-based algorithms can significantly reduce the computational complexity while maintaining a satisfactory sum rate performance.