1、 Background and Requirements
Low altitude economy relies on various aircraft to carry out flight activities in airspace below kilometers, with communication services mainly focused on flight control and image transmission. Flight control data requires low latency and low speed, while image transmission services need to meet the bandwidth requirements for high-definition video feedback. The current ground mobile communication network lacks systematic evaluation and optimization methods for low altitude coverage, and a complete plan for coverage simulation prediction, quality assessment, and optimization improvement needs to be established for low altitude scenarios.
2、 Testing and simulation evaluation methods
Using drones equipped with professional testing terminals, conducting net pulling tests and single station coverage capability verification at different heights. Test to distinguish different frequency bands, beam configurations, and frequency locking modes, and synchronously record signal strength, signal-to-noise ratio, uplink and downlink rates, and switching performance. Network planning simulation is based on fine electronic maps and AI propagation models to predict multi frequency and multi height coverage of typical urban and suburban scenes, with a focus on evaluating the comprehensive compliance rate of reference signal reception power and signal-to-noise ratio, as well as the uplink speed of edge users.
3、 Main problem analysis
Coverage and interference characteristics: In low altitude scenarios, as the altitude increases, the signal coverage strength is still acceptable, but severe overlapping coverage leads to a deterioration of signal-to-noise ratio, becoming the main factor restricting network quality. The urban environment is particularly prominent, and the existing network structure lacks low altitude main coverage areas.
Differences in frequency band applicability: The coverage distance of the mid to high frequency band is relatively limited, but the bandwidth is sufficient, making it suitable for high-capacity demand scenarios in urban areas; The low-frequency band has a long propagation distance but is difficult to control interference, resulting in poor signal-to-noise ratio performance, making it unsuitable as the main carrier layer for low altitude in urban areas.
Air ground network conflict: When using multi-layer beam weights to enhance low altitude coverage, it will have a significant negative impact on ground network coverage and speed indicators, indicating that there is a contradiction in air ground co frequency networking that is difficult to balance.
4、 Optimization measures and planning strategies
Beam optimization: By using multi-layer beams (including negative inclination beams) to enhance targeted coverage of low altitude areas, it can improve low altitude signal quality and business stability, and reduce unnecessary switching.
Frequency strategy: In densely populated areas such as urban and county towns, it is recommended to prioritize the use of dedicated frequency bands for low altitude networking and implement cross frequency deployment with ground networks to avoid air ground co frequency interference from the source and ensure the uplink speed and reliability required for low altitude services.
Structural optimization: Strengthen the planning of low altitude main coverage areas, control overlapping coverage areas, optimize neighbor relationships, and carefully adjust power and antenna feed parameters to reduce the impact on ground networks.
Rural area plan: In rural areas with wide coverage, existing low-frequency station resources can be reused, and layered coverage between low altitude and ground can be achieved by deploying vertical dual beam antennas, which can meet the basic needs of low altitude communication while controlling costs.
5. Conclusion
The planning of low altitude communication networks should adopt a hierarchical strategy based on the differences in scenarios: urban areas should adopt a combination of dedicated network frequency bands, multi-layer beamforming, and fine structure optimization to ensure business quality; Rural areas can rely on existing low-frequency networks and use antenna layering technology to balance land coverage. The overall plan needs to strike a balance between enhancing low altitude coverage and minimizing ground network impact, and continuously optimize network configuration through precise simulation and iterative testing.