Intelligent reflecting surface (IRSs) have recently played a crucial role for numerous application associated with unmanned aerial vehicle (UAV) communications. To provide good quality of service (QoS) for the users, it is necessary to study the IRS-aided UAV communication system with performance analysis. Thus, in this paper, a three-dimensional (3D) geometry-based stochastic multiple-input multiple-output (MIMO) channel model is developed to characterize the IRS-aided air-to-ground (A2G) propagation environments, which takes into account the multipath fading and height-dependent path loss effects. Based on the proposed channel model, the impact of some important system parameters on the outage probability (OP) is numerically investigated. One key insight from our analysis is the AIRS operating on mmWave frequencies is more suitable for high mobility scenarios. The obtained results can provide guidance for achieving better system performance optimization.

A recent study presented a new differential equation model, MultiVelo, which simultaneously performs on chromatin accessibility and gene expression from single-cell data to reveals regulatory network of epigenomic and transcriptomic changes. However, it is unclear how regulatory network changes with perturbations. Here, we extend the ordinal differential equation models to time-delay differential equation models with controller to investigate the stability of regulatory network with perturbations.

Recently, intelligent reflecting surface (IRS) has become a research focus for its capability of controlling the radio propagation environments. Compared to the conventional terrestrial IRS, aerial IRS (AIRS) exploiting unmanned aerial vehicle (UAV)/high-altitude platform (HAP) can provide better deployment flexibility. To this end, a three-dimensional (3D) one-cylinder model is first developed for AIRS-assisted multiple-input multiple-output (MIMO) narrowband channels. In order to change the wireless channel with AIRS and create a favorable propagation environment, we propose a novel method of designing the phase-shifts for the IRS elements. Based on the model, channel impulse response (CIR), space-time correlation function, and channel capacity are derived and thoroughly investigated. A key observation in this paper is that multipath and Doppler effects in radio propagation environments can be effectively mitigated via adjusting the phase-shifts of IRS. More specifically, for the special propagation environments in the absence of any scatterers, it is found that the effects of multipath fading can be completely eliminated by IRSs. While for the general propagation environments with multiple scatterers, a small number of IRS elements can also significantly reduce the Doppler spread and the deep fades of the channels. Based on the numerical investigation of channel correlations, it is shown that channel non-stationarity is not introduced into the time domain when the phase shift of IRS is linear related to the time. Moreover, the channel capacity can also be improved by the proposed methods. Finally, the model with non-ideal IRSs is considered and it is found that using non-ideal IRSs results in poor performances compared with using ideal IRSs. These conclusions will provide a fundamental support for developing intelligent and controllable propagation environments of the future sixth-generation (6G) wireless networks.