Resolving radio network interference using Ronja optical datalink

Wireless networks jammed by microwave ovens and other 2.45GHz equipment

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

Prevention. By building a network data link with Ronja from the beginning, you can be sure that neither microwave oven jamming nor jamming by another radio network will ever occur in the future.
Intervention. If a link gets jammed by a microwave oven or another wireless network, replacing the link with Ronja solves the situation immediately and forever.
Shorter deployment. To assess if a wireless radio network link will run without interference or will be jammed, you need a long test period. Microwave ovens are operated at unpredictable times. The same is valid for other wireless LAN's - their traffic flows irregularly and they can be turned on and off unpredictably. Ronja shortens this time to zero - with Ronja, after installation is complete, your network will operate , without any possibility of future interference.

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 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?

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.

Source: CHMI Recent Radar Data

Benefits of Ronja for solving the radar jamming problem

Ronja can prevent the problem. By using Ronja technology for building new links, you can be sure that radar jamming will never occur in the future.
Ronja can solve actual occurence of the problem. If your link is jamming a radar, replacing the radio link with Ronja will immediately fix the problem regardless of circumstances.
Ronja protects your investment. Operation of meteoradars is in the public interest: it's used for weather forecast, aviation, and research. The pictures show severe and persistent degradation of acquired images, which is seriously interfering with this service.
There is a risk that radar jamming will lead to operation of radio LAN equipment being excluded from this band to protect the public service. This could make existing equipment useless. The technical nature of free space optics guarantee that nothing like this will happen to a Ronja based link, making it a safer investment.