High-altitude long endurance unmanned aerial vehicles (HALE UAVs) are military and strategic UAVs that fly above the ground in the stratosphere. The ability of stealth technology and long flight time, has led to use of these UAVs for various military missions such as interception and spying, control guidance, remote sensing, navigation, surveillance and others. In this paper, improving the performance of HALE UAVs communication through multiple input multiple output (MIMO) cooperative relay with amplitude-and-forward strategy is investigated. In clear sky (without rain), two-hop system with line of sight (LoS) channels from source to relay and relay to destination is considered. In LoS-MIMO channels, due to correlation between the sub-channels, neither high-rank MIMO channel nor maximum capacity are achieved. However, based on antennas optimum placement that provide orthogonally between the received signals, maximum capacity will be obtained. The proposed scheme in this paper dramatically increases capacity relative to LoS-SISO channel and dual-hop MIMO Rayleigh up to 6 b/s/Hz and 2 b/s/Hz respectively. Also, simulation results verify exactness analytical expressions. However, rain as one of the most important ambient conditions causes the signal to be scattered in different directions. Therefore, LoS channel is changed to fading (Rayleigh) channel by increasing rainfall. In this case, telecommunication range is proposed as a meaningful metric, and outage probability (P_outage) based on telecommunication range for N-hop channel is extracted. In rainy conditions, simulation results show, the telecommunication range dramatically increases by increasing the number of relay UAVs for specified outage probability so that in the long-range, the outage probability decreases up to 50% with the increasing number of relays.

高空长寿命无人机（HALE UAV）是在平流层上空飞行的军事和战略无人机。隐身技术的能力和较长的飞行时间已导致这些无人机用于各种军事任务，例如拦截和间谍，控制制导，遥感，导航，监视等。本文研究了采用幅度和转发策略通过多输入多输出（MIMO）协作中继提高HALE无人机的通信性能。在晴朗的天空（无雨）中，考虑了具有从源到中继以及从中继到目标的视线（LoS）通道的两跳系统。在LoS-MIMO信道中，由于子信道之间的相关性，无法实现高级MIMO信道或最大容量。然而，基于在接收信号之间正交提供的天线最佳放置，将获得最大容量。相对于LoS-SISO信道和双跳MIMO瑞利，本文提出的方案将容量显着提高，分别达到6 b / s / Hz和2 b / s / Hz。此外，仿真结果验证了准确性分析表达式。但是，雨水是最重要的环境条件之一，导致信号沿不同方向散射。因此，通过增加降雨将LoS信道更改为衰落（Rayleigh）信道。在这种情况下，建议将电信范围作为有意义的指标，并将中断概率（P 相对于LoS-SISO信道和双跳MIMO瑞利，本文提出的方案将容量显着提高，分别达到6 b / s / Hz和2 b / s / Hz。此外，仿真结果验证了准确性分析表达式。但是，雨水是最重要的环境条件之一，导致信号沿不同方向散射。因此，通过增加降雨将LoS信道更改为衰落（Rayleigh）信道。在这种情况下，建议将电信范围作为有意义的指标，并将中断概率（P 相对于LoS-SISO信道和双跳MIMO瑞利，本文提出的方案将容量显着提高，分别达到6 b / s / Hz和2 b / s / Hz。此外，仿真结果验证了准确性分析表达式。但是，雨水是最重要的环境条件之一，导致信号沿不同方向散射。因此，通过增加降雨将LoS信道更改为衰落（Rayleigh）信道。在这种情况下，建议将电信范围作为有意义的指标，并将中断概率（P 通过增加降雨，LoS频道变为衰落（Rayleigh）频道。在这种情况下，建议将电信范围作为有意义的度量标准，并将中断概率（P 通过增加降雨，LoS频道变为衰落（Rayleigh）频道。在这种情况下，建议将电信范围作为有意义的度量标准，并将中断概率（P提取基于N跳信道的电信范围的_中断）。仿真结果表明，在下雨天，通过增加指定停电概率的中继无人机的数量，电信范围会显着增加，因此在远距离情况下，随着中继数的增加，停电概率最多可降低50％。