Ronja Twibright Labs

Resolving wireless network interference using Ronja FSO link

Resolving radio network interference using Ronja optical datalink

Wireless networks jammed by microwave ovens and other 2.45GHz equipment

Spectrum of a microwave oven
Spectrum of a microwave oven
"I did some experiments with a RangeLAN2 PCMCIA card. A simple spectral analyzer is among the utilities shipped with the card,[...] I found a signal that doesn't have the character of a WiFi signal - it is 'sharp' and very strong. If the antenna is connected directly to the card, the card's input is so overloaded with this signal that the spectral analyzer shows nonsense.

After a while I found this to be a product of the microwave oven in our kitchen.[...] Then I tried other microwave ovens and found that this garbage is produced by more or less all of them.[...]"

Source: CZFree.NET forum thread "Microwave oven - an enemy of WiFi?"

The explanation is simple: "A microwave oven works by passing microwave radiation, usually at a frequency of 2450 MHz [...], through the food." (Wikipedia)2.45GHz lies just in the middle of the band used by 802.11b and 802.11g radio LAN equipment.

Not only microwave ovens can be a source of interference in the 2.45GHz band: "The 802.11b and 802.11g flavors of Wi-Fi use the unlicensed 2.4 GHz spectrum, which is crowded with other devices such as Bluetooth, microwave ovens, cordless phones " (Wikipedia)

Benefits of Ronja in solving microwave oven jamming

Meteorological radar being jammed by wireless LAN

A 5.4GHz band radio network link was operated in Pilsen, Czech Republic. The link was running in a licence-free band within legal power limits. The link jammed the meteorological radar CHMI Brdy (Czech Hydrometeorological Institute), because the radar was operating on the same frequency 5.66GHz. Radar output from 28th September 2005 demonstrates the interference.

Source: CZFree.Net forum thread "Meteoradar jamming"

radar imagejamming highlighted
Radar image with jamming The same image with jamming highlighted in red

This single incident has been resolved, but the problem was not fixed. With proliferation of 5.4GHz wireless network links, the situation gets rapidly worse. Currently it's possible to see interference on the radar images very often:

4 jammers in one picture?

4 jammers in one radar image?I found this image that appears to show as many as 4 interferences at the same time, but it is not the case. Note that Czech Republic is covered by 2 radars - Brdy 5.66GHz (left) and Skalky 5.652GHz (right). I got an information from Czech Hydrometeorological Institute that only (2) and (3) are real jammers. (1) and (4) are noise comming from the Sun. This is verified by the fact that both (1) and (4) point in exactly the same direction. The radar snapshot is from 4th January 2006, 15:00 UT

Other jamming examples follow. Note how the jamming stays at the same place, but it's intensity and gap pattern varies - this is caused by nonuniform nature of the data transmission.

3 jammers2 jammers2 jammers
2 jammers2 jammers1 jammer

Source: CHMI Recent Radar Data

Benefits of Ronja for solving the radar jamming problem

An expected information missing here?