Age-of-Information Analysis of UAV-Ground Uplink Transmission with HARQ and MUI

Unmanned aerial vehicles (UAVs) have emerged as indispensable tools for addressing emergency communication challenges due to their mobility, agility, and accessibility. With the growing demand for real-time applications, the age of information(AoI) in UAV-ground communication has gained traction. This paper focuses on a UAV-ground communication system comprising a UAV (U) and ground transmitters (Sn). Considering the randomness of whether Sn sends packets or not when Sn and $U$ communicate via code-division multiple access, the outage performances of the Automatic Repeat reQuest (ARQ) and Hybrid Automatic Repeat reQuest (HARQ) schemes are investigated separately. In detail, the corresponding closed-form analytical expressions for the outage probability are introduced to analyze the AoI of the different schemes in this system, i.e., their impact on packet freshness. Finally, some numerical results are given to validate the proposed analytical model.