3 ms·

LoRa would go much farther than Wifi on 2.4ghz. Lora uses Chirp Spread Spectrum (CSS) modulation while wifi uses OFDM (Orthogonal Frequency Division Multiplexin

LoRa would go much farther than Wifi on 2.4ghz. Lora uses Chirp Spread Spectrum (CSS) modulation while wifi uses OFDM (Orthogonal Frequency Division Multiplexing). The first being designed for extreme range while the latter for bandwidth. At 2.4ghz you could probably get LoRa connections up to 6 miles with the right antenna height.

lormayna 5mo ago
6 miles seems a very optimistic estimation: 2.4Ghz propagation is very reduced by obstacles like buildings or trees and at that frequency the atmospheric water (fog, rain, humidity) have a big impact on propagation. And you need also to consider that 2.4Ghz is a very polluted band, then the noise floor is significatevly higher than in the 865/915 Mhz. Moreover at 2.4Ghz the Fresnel window is smaller and the risk of multipath fading is higher.
- po1nt 5mo ago
  I did a test with my long range drone on ELRS and managed to get 6km (not miles) so it might be reachable with higher TX elevation.
- golem14 5mo ago
  The record seems to be 830 miles (with antennas at sea level, no less) https://www.thethingsnetwork.org/article/new-lora-world-record-1336-km-830-mi https://www.thethingsnetwork.org/article/new-lora-world-reco... But, that's receiving 3 of maybe thousands of packets. There's work on bouncing of LoRA signals off the moon: https://engprojects.tcnj.edu/lora-eme/ https://engprojects.tcnj.edu/lora-eme/ Yes, but Joe Shmoe won't see this on their home setup trying to talk to a buddy 2 miles away behind a hill.
- jauntywundrkind 5mo ago
  I have skepticism too. But also, from a recent LoRa thread, and talking about 900MHz here, but someone said: > Wifi HaLow 802.11ah. LoRa is another level. It works down to -146dBm. 802.11ah dies around -100dBm. https://news.ycombinator.com/item?id=47890598 https://news.ycombinator.com/item?id=47890598 LoRa looks like someone is dropping a saw wave on the spectrum. It so clearly looks like such a blunt force user of spectrum. Just wild.
- K0balt 5mo ago
  LORA uses a sub noise-floor link budget. It allows some pretty crazy performance, at the expense of massive speed losses. Like 203kbps for LoRa vs 1,376,000kbps for WiFi lol.(max phy speeds, ymmmv). WiFi sensitivity is about -90dB, while LoRa sensitivity is around-150dB…. So that’s about a million times more sensitive. So you need about a million times more signal strength to use low bandwidth WiFi (still impossibly fast by LoRa standards) than to use low bandwidth LoRa. Those are radio specifications. Real links require about 10db more to get any kind of reliability, but the comparison stands.
- KaiserPro 5mo ago
  > 2.4Ghz propagation is very reduced by obstacles like buildings I never did much 2.4ghz stuff because that was what rich people did, or people mad enough to modify microwave oven magnetrons. However I was always under the impression that freespace loss on 2.4 was terrible. but it turns out its "only" ~9db more than 865
  - Gibbon1 5mo ago
    Worth mentioning that 2.4GHz has a lot more attenuation due to clutter than 900MHz. Your problem is usually buildings and non line of site transmission paths. When the signal has to pass through and bounce off things your link budget takes a big hit. There is the idea of the path loss exponent. In a vacuum it's 2.0. 900Mhz with clutter it's -2.5 At 2.4 MHz it's -3 and -5.8 it's -3.5. Other downside for higher spreading factor spectrum is data rate drops which results in longer packets. Longer packets means more energy per packet and a higher chance someone else will blow your packet out of the water. You've been able to buy 900 and 2.4GHz transceivers for the last 20 years.
dheera 5mo ago
Just use Unifi Airfiber for 6 miles at gigabit speeds. If you're relying on line of sight then 2.4GHz is nonsense. And if you don't have line of sight then no you're not getting 6 miles
- mikeweiss 5mo ago
  Is UniFi Air fiber extremely low power and cheap to produce?
  - drgone 5mo ago
    yes, considering the options.
    - mikeweiss 5mo ago
      What are the options?
      - e12e 5mo ago
        Something like?: https://radionor.no/solution/cre-2-series/ https://radionor.no/solution/cre-2-series/
  - burnt-resistor 5mo ago
    $2000 minimum and closed source.
burnt-resistor 5mo ago
When I worked in the Trimble Navigation radio group, 2.4 GHz was tried but its real world range sucked compared to ~900 MHz and CB ~450 MHz bands of existing solutions. It's simply limitations of physics that lower frequencies propagate farther (at lower bandwidth) than higher frequencies.
- zobzu 5mo ago
  even 900mhz sux vs 433. the lower the better it penetrates matter for the same amplitude. lower than 430 you start to run into severe bandwidth issues though. and its not allowed to transmit lora/dss on 430 in the us without license hence the 900mhz at 2.4ghz the real world usage is limited. might as well use wifi. the only advantage is short range bandwidh while keeping lora compat.
ezwoodland 5mo ago
What makes OFDM inherently worse at long range? Don't you just lengthen your symbols and use the extra frequency bins until you have tolerable losses?

lormayna 5mo ago

6 miles seems a very optimistic estimation: 2.4Ghz propagation is very reduced by obstacles like buildings or trees and at that frequency the atmospheric water (fog, rain, humidity) have a big impact on propagation. And you need also to consider that 2.4Ghz is a very polluted band, then the noise floor is significatevly higher than in the 865/915 Mhz. Moreover at 2.4Ghz the Fresnel window is smaller and the risk of multipath fading is higher.

po1nt 5mo ago
I did a test with my long range drone on ELRS and managed to get 6km (not miles) so it might be reachable with higher TX elevation.
golem14 5mo ago
The record seems to be 830 miles (with antennas at sea level, no less) https://www.thethingsnetwork.org/article/new-lora-world-record-1336-km-830-mi https://www.thethingsnetwork.org/article/new-lora-world-reco... But, that's receiving 3 of maybe thousands of packets. There's work on bouncing of LoRA signals off the moon: https://engprojects.tcnj.edu/lora-eme/ https://engprojects.tcnj.edu/lora-eme/ Yes, but Joe Shmoe won't see this on their home setup trying to talk to a buddy 2 miles away behind a hill.
jauntywundrkind 5mo ago
I have skepticism too. But also, from a recent LoRa thread, and talking about 900MHz here, but someone said: > Wifi HaLow 802.11ah. LoRa is another level. It works down to -146dBm. 802.11ah dies around -100dBm. https://news.ycombinator.com/item?id=47890598 https://news.ycombinator.com/item?id=47890598 LoRa looks like someone is dropping a saw wave on the spectrum. It so clearly looks like such a blunt force user of spectrum. Just wild.
K0balt 5mo ago
LORA uses a sub noise-floor link budget. It allows some pretty crazy performance, at the expense of massive speed losses. Like 203kbps for LoRa vs 1,376,000kbps for WiFi lol.(max phy speeds, ymmmv). WiFi sensitivity is about -90dB, while LoRa sensitivity is around-150dB…. So that’s about a million times more sensitive. So you need about a million times more signal strength to use low bandwidth WiFi (still impossibly fast by LoRa standards) than to use low bandwidth LoRa. Those are radio specifications. Real links require about 10db more to get any kind of reliability, but the comparison stands.
KaiserPro 5mo ago
> 2.4Ghz propagation is very reduced by obstacles like buildings I never did much 2.4ghz stuff because that was what rich people did, or people mad enough to modify microwave oven magnetrons. However I was always under the impression that freespace loss on 2.4 was terrible. but it turns out its "only" ~9db more than 865
- Gibbon1 5mo ago
  Worth mentioning that 2.4GHz has a lot more attenuation due to clutter than 900MHz. Your problem is usually buildings and non line of site transmission paths. When the signal has to pass through and bounce off things your link budget takes a big hit. There is the idea of the path loss exponent. In a vacuum it's 2.0. 900Mhz with clutter it's -2.5 At 2.4 MHz it's -3 and -5.8 it's -3.5. Other downside for higher spreading factor spectrum is data rate drops which results in longer packets. Longer packets means more energy per packet and a higher chance someone else will blow your packet out of the water. You've been able to buy 900 and 2.4GHz transceivers for the last 20 years.

dheera 5mo ago

Just use Unifi Airfiber for 6 miles at gigabit speeds. If you're relying on line of sight then 2.4GHz is nonsense. And if you don't have line of sight then no you're not getting 6 miles

mikeweiss 5mo ago
Is UniFi Air fiber extremely low power and cheap to produce?
- drgone 5mo ago
  yes, considering the options.
  - mikeweiss 5mo ago
    What are the options?
    - e12e 5mo ago
      Something like?: https://radionor.no/solution/cre-2-series/ https://radionor.no/solution/cre-2-series/
- burnt-resistor 5mo ago
  $2000 minimum and closed source.

burnt-resistor 5mo ago

When I worked in the Trimble Navigation radio group, 2.4 GHz was tried but its real world range sucked compared to ~900 MHz and CB ~450 MHz bands of existing solutions. It's simply limitations of physics that lower frequencies propagate farther (at lower bandwidth) than higher frequencies.

zobzu 5mo ago
even 900mhz sux vs 433. the lower the better it penetrates matter for the same amplitude. lower than 430 you start to run into severe bandwidth issues though. and its not allowed to transmit lora/dss on 430 in the us without license hence the 900mhz at 2.4ghz the real world usage is limited. might as well use wifi. the only advantage is short range bandwidh while keeping lora compat.

ezwoodland 5mo ago

What makes OFDM inherently worse at long range? Don't you just lengthen your symbols and use the extra frequency bins until you have tolerable losses?