An algorithm that estimates extraneous noise in radio-frequency communication signals can help to eliminate annoying interruptions in WiFi or digital television transmissions.
The background hiss of a poor-quality radio broadcast is often caused by random fluctuations in the receiver’s electronic circuits. In contrast, impulse noise is a relatively rare form of interference that can be caused by nearby electrical devices being switched on.
Impulse noise, according to Tareq Al-Naffouri of the King Abdullah University of Science and Technology (KAUST), brings such high power that it obliterates the signal. Turning on a light may cause clicks in a radio signal, for example, or momentarily cause a television screen to blank. “Impulse noise is also among the most severe limiting factors in ADSL (Asymmetric Digital Subscriber Line) communications,” Al-Naffouri adds.
Al-Naffouri and his colleagues from the Division of Computer, Electrical and Mathematical Science and Engineering aimed to remedy this problem by taking advantage of a widely-used technology in wireless communication systems called orthogonal frequency division multiplexing (OFDM). This carves up a band of radio frequencies into many narrower bands, each of which carries a separate data stream.
To ensure that these subcarriers do not interfere with each other, each is separated by very narrow ‘guard bands' which are a tight range of frequencies that carry no data. “It’s like a group of people talking in a hall — they have to spread out so that conversations don't get mixed up,” says Al-Naffouri.
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