Realizing 100 kilometer wireless data link transmission belongs to the category of over the line of sight (BVLOS) communication, which usually cannot rely on single hop direct connection to achieve stable coverage. It requires the combination of specific frequency bands, high-power devices, relay technology, or Mesh self-organizing network solutions. The following are the core solutions and key elements based on the current level of technology:
1. Core technology solution
A. Mesh self-organizing network multi hop relay (the most mainstream solution)
Breaking through the distance limit of a single point through relay, suitable for complex terrains (mountainous areas, oceans, cities).
- Principle: A point signal ->B point relay ->C point reception. Each hop distance is about 30-50km, and 2-3 hops can cover 100km+.
- Advantages: It has the ability of self-healing links and can automatically switch paths in case of a single node failure; Support dynamic topology, suitable for drone clusters or mobile platforms.
Typical equipment parameters:
- Transmission power: A single node typically requires 10W-20W (40-43dBm).
- Networking capability: Supports decentralized self-organizing networks with up to 32-256 nodes.
- Delay: Multi hop cascade delay is usually controlled within 50ms-100ms.
B. Dedicated frequency band point-to-point/point to multipoint direct connection
In scenes with good visibility conditions (such as sea surfaces and plains) and no obstruction, high-power private network radio stations can be used for direct connection.
Preferred frequency band: 1.4GHz (1350-1450MHz) industrial private network.
- Reason: Compared to 2.4G/5.8G, 1.4GHz has a longer wavelength, stronger diffraction ability, and transmission loss is more than 40% lower, making it more suitable for long-distance and slightly obstructed environments.
Alternative frequency band: 600MHz -900MHz (with stronger penetration but lower bandwidth, suitable for pure data telemetry rather than high-definition video).
Performance indicators:
- Speed: Broadband image transmission can reach 10-90Mbps, supporting 1080P/60fps videos.
- Sensitivity: The receiving sensitivity needs to be below -110dBm to ensure weak signal decoding.
C. Ground fixed relay station scheme
Suitable for long-distance return between fixed infrastructure (such as offshore wind farms to land, border monitoring).
- Architecture: High gain directional antennas (parabolic or planar arrays) are installed at high points, utilizing line of sight transmission beyond the curvature of the Earth.
- Case: An offshore wind farm is located 100km away from the shore, and a relay station is set up on a high ground (such as a mountain tower) in the middle, using the 1.4G or 4-6GHz frequency band for two-stage transmission.
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2. Key Equipment Selection Guide
- Working frequency band: 1.4GHz or 600MHz. Avoid using crowded 2.4G/5.8G to ensure compliance and anti-interference capabilities.
- Transmission power: ≥ 10W (onboard/portable); ≥ 20W (ground fixed). Power is the key to overcoming free space loss, and 10W is the safety margin baseline for a 100km link.
- Modulation technology: COFDM/OFDM. Strong resistance to multipath effects and suitable for non line of sight (NLOS) and complex electromagnetic environments.
- Antenna type: High gain directional antenna. Parabolic antenna (high gain, strong directionality) or Yagi antenna, requiring precise alignment.
- Protection level: IP65/IP67, suitable for outdoor rain, dust, salt spray (sea scenes) and wide temperature environment (-40 ℃~+85 ℃).
3. Typical application scenarios and implementation suggestions
A. Industrial drone inspection (power/pipeline):
Solution: The drone is equipped with a 10W 1.4GHz image transmission radio and a ground station high gain antenna. If the terrain obstruction is severe, add a relay drone to hover at a high point for signal forwarding.
Attention: Sufficient Link Budget should be reserved, taking into account atmospheric attenuation and vegetation cover.
B. Maritime/Lake Communication:
Solution: Due to severe sea surface reflection, it is easy to generate multipath interference. It is recommended to use COFDM equipment with strong anti multipath algorithm. If the distance exceeds 50km, it is strongly recommended to set up a relay on an island or tower in the middle.
C. Emergency command/border patrol:
Solution: Deploy Mesh self-organizing network base stations (vehicle mounted or backpack mounted) to quickly build temporary communication networks. Support ‘in motion communication’, with automatic link reconstruction when the vehicle is in motion.
4. Common Misconceptions and Risk Warning
A. Don’t be superstitious about “single hop 100km”: unless on extremely open sea surfaces and using extremely high gain directional antennas, single hop 100km is highly susceptible to the effects of Earth curvature and small terrain undulations, leading to disconnection. Multi hop relay is a more robust engineering choice.
B. The trade-off between bandwidth and distance: the farther the distance, the lower the signal-to-noise ratio, and the smaller the available bandwidth. A 100km link may only maintain a stable speed of 4-10Mbps, making it difficult to support 4K high-definition video. It is recommended to compress it to 1080P or lower bitrate.
C. Regulatory compliance: Although the 1.4GHz frequency band is an industrial private network, it is still necessary to confirm the filing requirements of the local radio management committee to avoid illegal occupation of the frequency band.
5. Summary
For a 100 kilometer wireless data link, the combination of “1.4GHz frequency band+10W or more power+Mesh multi hop relay” is currently the most mature and reliable solution in the industry. If it is a fixed point to point transmission, it is possible to consider setting up directional relays at high points; If it is a mobile platform, it is necessary to choose self-organizing network devices that support fast self-healing.