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University of Oxford claims to have invented a signal-processing scheme that improves the quality of digital radio based on OFDM (orthogonal frequency division multiplexing) with no additional hardware or system complexity.
“You play with the real data in such a way that you can optimise the spread at the front end so you can transfer data more effectively,” Dr Rakesh Roshan, project manager at Oxford University intellectual property licensing firm Isis Innovation told
EW.
“The proposed scheme can be applied to any OFDM systems used in commercial applications such as digital radios, television broadcasts and wireless local area networks,” said Roshan.
According to the University,
OFDM uses symbol spreading and overlap-add processing to increase desired signal power capture and suppress inter-carrier and inter-symbol interference (ICI and ISI).
“OFDM efficiently mitigates multi-path by using a zero pad (ZP) sequence that that is longer than the channel length,” said the University. “In the receiver, overlap-add (OLA) processing is used to recover transmitted signals without ICI or ISI. “
Most conventional ZP-OFDM systems implement x2 symbol spreading - a symbol is transmitted twice with a zero pad sequence inserted after each symbol.
The Oxford scheme transmits the symbol once rather than twice, with zeros being transmitted the remaining time. The receiver uses modified OLA to pull out the desired signal.
“It has been shown mathematically and by simulation that our scheme leads to a system with better signal reception and reduced ICI and ISI,” claimed the University.
The increase in the capture of the desired signal and the reduction in the ICI is a result if modified OLA processing which results in performance gain.
The reduction in ISI is due to the elimination of the second symbol which results in less interference for the following symbol.