- #1
Photo1234
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Why do Wi-Fi waves have such short distance and some microwaves are used for sending information through long distances?
Wi-Fi Waves: Why Short Range & Microwaves for Long Distances?
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Discussion Overview
The discussion centers on the differences in range between Wi-Fi waves and microwaves used for long-distance communication. It explores factors influencing these differences, including power levels, antenna types, and environmental considerations.
Discussion Character
- Technical explanation
- Debate/contested
Main Points Raised
- Some participants suggest that the differences in transmitted power levels and antenna types contribute to the short range of Wi-Fi compared to point-to-point microwave links.
- Others argue that point-to-point microwave links benefit from line of sight (LOS) conditions, which minimize signal attenuation.
- It is noted that point-to-point microwave links do not face obstacles like walls, and they utilize higher power and more directive antennas, potentially leading to better performance.
- One participant emphasizes that receiver sensitivity may be a more significant factor for range than output power, along with the frequencies used and associated path loss.
- Another participant highlights regulatory restrictions on Wi-Fi power levels, noting that typical maximum power is limited compared to point-to-point microwave communication, which can operate under different regulations.
- Discussion includes an example of S band satellite communication, which operates at frequencies between 2GHz to 4GHz and can communicate over vast distances, such as 36,000 km.
Areas of Agreement / Disagreement
Participants generally agree that factors such as output power, line of sight, receiver sensitivity, and antenna gain are important in determining communication range. However, there are competing views on the relative importance of these factors and the impact of regulatory limitations on Wi-Fi.
Contextual Notes
Limitations include the dependence on specific definitions of terms like "line of sight" and "receiver sensitivity," as well as unresolved details regarding the exact impact of frequency on path loss and range.
- #2
davenn
Science Advisor
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Hi there
welcome to PF
Also point to point microwave links will be line of sight (LOS) ... this provides the least attenuation possibleDave
welcome to PF
the difference in transmitted power levels and antennas ... simple as thatPhoto1234 said:
Also point to point microwave links will be line of sight (LOS) ... this provides the least attenuation possibleDave
Last edited:
- #3
DaveE
Science Advisor
Gold Member
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Point to point microwave links don't have to work through walls, have higher power, use much better (more directive) antennas, and might have better receivers. The communication networks also may have other redundant links to deal with drop-outs (thunderstorms etc.). Other than that they are pretty much the same thing.
- #4
HowardH
- 1
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It's not just a matter of output power. Like DaveE says, I have usually found that Receiver sensitivity is a bigger contributor to range than output power.
The frequencies used, and therefore the path loss also affect the range. Anything longer than ~ 8 miles also requires a higher elevation on the antennas.
The frequencies used, and therefore the path loss also affect the range. Anything longer than ~ 8 miles also requires a higher elevation on the antennas.
- #5
Anand Sivaram
- 90
- 43
As previous answers, output power, Line of Sight and receiver sensitivity do matter. Also the antenna gain. As WI-Fi uses unlicensed 2.4GHz band, there are power restrictions in most of the regions. Typical maximum 1W (30dBm) of actual power and 4W (36dBm) of EIRP which includes antenna gain. That means if 30dBm actual power is used maximum antenna gain must be 6dBm, where as if 26dBm power is used maximum antenna gain could be 10dBm.
Consider you have a highly directional 24dBi outdoor Wi-Fi grid antenna, then your actual power could be maximum of 12dBm, so the maximum power would be 36dBm. That limits the combination of high gain antenna and actual power.
Point to point microwave communication does not come under these regulations. They use much higher actual power coupled with a highly directional antenna.
One extreme use cases is S band satellite communication. S band is between 2GHz to 4GHz and it is used to communicate with Geostationary Satellites at 36000km away.
Where as
Consider you have a highly directional 24dBi outdoor Wi-Fi grid antenna, then your actual power could be maximum of 12dBm, so the maximum power would be 36dBm. That limits the combination of high gain antenna and actual power.
Point to point microwave communication does not come under these regulations. They use much higher actual power coupled with a highly directional antenna.
One extreme use cases is S band satellite communication. S band is between 2GHz to 4GHz and it is used to communicate with Geostationary Satellites at 36000km away.
Where as