Performance analysis of <i>α</i> − <i>μ</i> distributed MIMO wireless links using coherent terahertz technology

Coherent terahertz (THz) communications are characterized by high frequency, large bandwidth, and low energy consumption and can maintain high transmission performance even in complex environments. However, THz wave propagation in the atmosphere is subject to significant attenuation and interference, affecting its coherent transmission performance in complex transmission environments. In this study, a coherent terahertz communication framework is established by employing a multiple-input multiple-output (MIMO) configuration to overcome the limitations of a single-input single-output system. A model is used to solve the non-line-of-sight problem of the communication link, and an expression for the signal-to-noise ratio (SNR) at the receiving terminal using the air-detection method is derived. The channel model is constructed, and a <i>α</i> - <i>μ</i> turbulence model is introduced to derive the probability density function of the SNR for the composite <i>α</i> - <i>μ</i> turbulence model by combining the static attenuation and random attenuation suffered by THz waves. Subsequently, the SNR expressions for coherent THz communication systems with maximum ratio combining (MRC) and equal gain combining (EGC) diversity are derived. The bit error rate (BER) expressions for the two diversity techniques are computed using multilevel pulse modulation and multilevel differential pulse position modulation. Finally, the outage probability under the two diversity techniques is computed using the moment generating function, and the results obtained are verified by Monte Carlo simulation. The effects of modulation parameters (<i>M</i>), number of channels (<i>L</i>), communication distance (<i>d</i>), and beam width <i>ω</i>_<i>z</i>/<i>r</i> on BER performance are quantitatively analyzed under both MRC and EGC. Additionally, the outage probablity (OP) performance for both techniques is assessed. The results show that for the same parameter settings, the BER performance is positively correlated with the OP. The performance indicators of the studied coherent THz system provide guidance for future THz communication research.