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Cancellation technique doubles wireless throughput

Full duplex, one frequency, no trouble

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Researchers at Rice University have pulled a neat trick of noise cancellation which they say could double the throughput of wireless systems, by allowing full-duplex communications using a single frequency.

As El Reg readers surely know, wireless systems use either time- or frequency-domain multiplexing (or a mixture of the two) to support two-way communication. Either the transmit and receive channels use different frequencies; or only one direction transmits at any given time.

The idea that frequency multiplexing could be eliminated would be highly attractive to mobile carriers, since they would effectively double the capacity of their spectrum, without spending a cent.

The problem with using the same frequency to transmit and receive is that it’s hard to distinguish one signal from another.

The Rice researchers used a quite simple trick to get around the problem: with two antennas at a transmitter (call it the “A end”), it’s possible to identify what’s been sent from the A end and subtract it from the received signal; what’s left over should be the signal from the other station – the B end.

The researchers have published their paper http://arxiv.org/pdf/1107.1276v1 here.

Although the technique has been touted as a saviour for future cellular communication standards, it should be noted that the researchers’ experiments were conducted on indoor scenarios under favourable conditions. ®

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