  In contrast to terrestrial wireless networks, dynamic Unmanned Aerial Vehicle
(UAV) networks are susceptible to unexpected link failures arising from UAV
breakdowns or the depletion of its batteries. Drastic user rate fluctuations
and sum rate drops can occur due to the unexpected UAV link failures. Previous
research has focused primarily on re-establishing these links to maintain
service continuity, while neglecting overall system performance, including sum
rate and user rate fluctuations. This letter proposes a resilient UAV network
design utilizing the modern portfolio theory (MPT), which jointly optimizes the
bandwidth allocation, UAV-user association, and UAV trajectories to enhance the
overall service stability. Specifically, the design incorporates a novel
utility function based on MPT to achieve a better balance between the sum rate
and user rate fluctuations. To solve the joint optimization problem, we propose
an iterative algorithm based on alternating optimization (AO) and successive
convex approximation (SCA). Simulation results show that our scheme outperforms
the other two baselines in terms of sum rate and user rate fluctuations.
Furthermore, the resilience requirement in terms of sum rate, user rate
fluctuations and user fairness can be achieved by flexibly tuning weight factor
in our proposed algorithm.
