Code against wifi jammers

The frequency bands for wireless Internet via WLAN are increasingly overloaded. US researchers have now developed a software-based solution that can bypass signal jammer.

Internet via radio is now available in almost every German apartment: The WLAN technology (Wireless Local Area Network) in laptops, PCs, tablets or smartphones together with cost-effective routers on the broadband connection makes it possible. The problem: Especially in cities, the crowding in the case of the main frequency range used by 2.4 GHz is now large.

In addition, in the same segment, the so-called ISM band (Industrial, Scientific, Medical), also spark numerous other devices: It is license-free and can be used for any application, be it commercial or scientific. These include, for example, Bluetooth headsets, some cordless phones, garage door openers, wireless video cameras, and even some on-kitchen kitchens.

The intelligence to deal with such signal interference, however, is limited in the currently widespread WLAN standard 802.11b / g. Algorithms designed to increase noise immunity decimate the potential data rate and by no means function perfectly. It is also often not possible to switch occupied areas ad hoc: Many devices are set to fixed channels. The best alternative is therefore to use a different frequency. In the newer WLAN variant 802.11n, this is the much less crowded 5 GHz band. However, 802.11n is by no means in every computer, smartphone or router. The older 802.11b / g should therefore be preserved for a long time – it is considered a universal “fallback” if newer standards do not work.

Researchers at the University of Wisconsin in Madison to the computer scientist Shravan Rayanch therefore try to use the frequency band around 2.4 GHz better and more efficiently. For this to happen, it must first be known what is working here at all. Wi-Fi modules in routers and computers do not know the signatures of other radio-frequency devices – they only handle Wi-Fi, but not around the spectrum competing procedures such as Bluetooth, Zigbee or the popular in America wireless telephone standard FHSS.

Rayanch and his colleagues have therefore written a novel software that extends standard WLAN modules with detection routines. She listens to the name “Airshark” (“Lufthai”) and constantly scans her surroundings. Airshark should be smart enough to at least rudimentary detect even previously unknown radio methods.

Currently, the software, which is supposed to have an accuracy of up to 90 percent with a search resolution of 1 MHz, is in the prototype stage. But the University of Wisconsin researchers have a lot in mind. You can imagine that the technology is placed in the firmware of routers, so that they can better adapt the radio frequencies used. After the detection of a disturbance signal, the WLAN module would then change the channel – and as accurately as possible, so as not to consume unnecessarily much spectrum.