Design and USRP implementation of SISO and 2x2 multi-user OAM systems

Abstract

Orbital angular momentum (OAM) communication, a recent technology utilizing vortex beams, offers a new dimension in mobile communication by enabling high-speed data transmission through superposing multiple vortex waves, significantly increasing system capacity due to the orthogonal nature of different modes of OAM waves. However, imperfect orthogonality during OAM wave transmission can cause interchannel interference (ICI) leading to signal degradation. This dissertation proposes and implements 2×2 multi-user communication systems for OAM-based and plane-wave-based antennas. Design and implementation of these systems are based on Universal Software Radio Peripheral (USRP). In addition, a Single-Input Single-Output (SISO) communication system is also investigated to compare the bit error rate (BER) performance with the 2 × 2 multi-user scheme based on plane-wave and OAM wave. Furthermore, Zero-Forcing equalization are implemented by LabVIEW and MATLAB programs to study its capability to mitigate the ICI in 2×2 multi-user scheme. The BER analysis of diverse communication systems reveals that both OAM-based and plane-wave-based SISO communication systems exhibit similar BER trends with increasing signal-to-noise ratio (SNR), offering no significant advantage to OAM-based systems. In 2×2 scenarios, ICI causes negative impacts on both systems, but OAM-based systems are more robust and have better BER performance compared to 2×2 multi-user communication systems. Finally, it is shown that Zero-Forcing equalization can mitigate ICI and reduce BER effectively.