# Low-Altitude Sensing Model: Analysis Leveraging ISAC in Real-World Environments
## 1 Introduction  
With the rapid development of technologies, the application of unmanned aerial vehicles (UAVs) in the low-altitude domain has become increasingly widespread, particularly in sectors such as transportation, logistics, and public utilities, where they show immense potential [1, 2, 3]. It is projected that by 2030, the global drone market will reach a scale ranging from $100 billion to $140 billion [4]. In this context, ensuring low-altitude flight safety and enabling effective UAV regulation have become critically important. The fusion of communication and sensing technologies for low-altitude networked sensing has emerged as the core solution to these challenges. It plays a significant role in building a safe and efficient low-altitude operational environment [5]. The integrated sensing and communication (ISAC) technology offers distinct advantages over traditional sensing methods. As one of the new native capabilities in next-generation wireless networks, ISAC allows for active environmental sensing while simultaneously supporting data transmission. Compared to traditional radar systems, ISAC basestations offer significant advantages in terms of cost, data transmission, coverage, and resource reuse. A major benefit of wireless sensing over radar is the ability to achieve contiguous coverage through large-scale networking. Although the ISAC technology provides a fresh perspective for low-altitude sensing, achieving wide-area sensing based on this technology still faces significant challenges [6; 7; 8; 9; 10]. A key challenge lies in the inherent differences in coverage characteristics between communication and sensing. Communication signals typically meet coverage needs through single-hop transmission, while sensing signals require reflection from targets, resulting in a multi-hop propagation process. This creates clear differences in coverage range and characteristics, making it difficult to achieve coordinated and ideal coverage during network deployment. Additionally, transitioning from traditional two-dimensional (2D) communication cellular networks to low-altitude three-dimensional (3D) sensing networks presents significant difficulties. The current 5G networks primarily focus on ground communication coverage, while low-altitude coverage and sensing capabilities have not been considered. The traditional hexagonal 2D cellular network model is not suitable for low-altitude environments. Base stations are limited by antenna performance, which prevents them from covering their own tower-top areas. Furthermore, low-altitude signal propagation is primarily line-of-sight (LOS), which is different from the non-line-of-sight (NLOS) propagation commonly found in urban areas. These differences render traditional network models unsuitable for low-altitude applications. Meanwhile, the low-altitude ISAC environment is complex and subject to various interferences, such as other communication devices and the impact of terrain, further complicating the construction of stable and efficient low-altitude networked sensing systems. Overcoming these challenges and building a network that meets the low-altitude \"wide-area, seamless, 3D\" sensing requirements has become an urgent and critical issue. This paper adopts Work Mode 1, as mentioned in IMT-2020, specifically, the single base station responsible for both the transmission and reception nodes [11; 12]. This approach was chosen due to its significant advantages. In Work Mode 1, base stations have independent sensing capabilities and do not rely on other base stations to complete sensing tasks. This eliminates the sensing errors caused by the asynchronous operation of the transmission and reception nodes, significantly improving sensing accuracy. In the complex low-altitude environment, this independent operational feature reduces reliance on other nodes, thus minimizing the risk of sensing failure due to network node faults or synchronization issues.