This thesis analyzes a hybrid architecture that integrates spread-spectrum delay multiplexing (SSDM), and symbol-wavelength-spaced antennas to enhance capacity, and mitigate multi-user interference (MUI) in High Altitude Platform (HAP) communication systems. The optimal spatial decorrelation in line-of-sight (LOS) channels is achieved by an odd value of spreading factor, and symbol-wavelength-spaced antennas as evidenced by the analysis of determinant, norm, and condition number. Symbol-wavelength-spaced antennas and spread spectrum delay multiplexing are combined to evaluate their impact on system capacity, interference, and spectrum efficiency. To determine the stability, and effectiveness of the system, the study analyzes important performance measures, such as determinants, norms, and condition number. To enhance signal quality, and reduce multi-user interference, a zero-forcing approach is used. The results demonstrate that antenna spacing at symbol wavelength intervals provides the best performance, especially in LOS communication situations.
https://www.ece.unb.ca/petersen/pubs/theses/students/Lu25/