Walking through a wireless wonderland

Wireless communication and mobile devices have become a staple of modern life over the past few decades. It’s tough to imagine the world without them but there are many corners of the planet where they’re still notoriously unreliable.

Needless to say, whether it’s remote Africa or the frosty expanses of northern Canada, there’s a good chance that your iPhone’s ‘Personal Hotspot’ feature isn’t going to work very well. Faculty of Electrical Engineering, Mathematics, and Computer Science (EWI) PhD graduate Dr. Seyran Khademi, who defended her thesis on November 22, 2016, spent the past several years analysing signal processing algorithms as part of an effort to improve the ability of various mobile devices to perform in harsh environments like these or those with highly reflective surroundings.

The project initially began as a collaboration between TU Delft and ASML, a Dutch company that served as an industrial partner. It initially focussed on the development of a short range gigabit wireless link installed within a lithography machine.

“This unique experiment opened up new research challenges to look back to popular design paradigms and reevaluate them with respect to the proposed channel model with a delay spread in the order of milliseconds,” Khademi explained.

This portion of the project involved inspecting field measurements and creating a reliable propagation model. A customised system was later developed to make use of what’s called orthogonal frequency division multiplexing (OFDM) transmissions. Khademi then studied its effectiveness in a series of simulations created in a MATLAB computing environment that used different types of channels.

The second part of the project was devoted to comparing and contrasting a single-input single-output (SISO) system studied in the first portion against different multiple-input multiple-output (MIMO) systems. This was done in order to look at many of the problems that high-speed and communication systems often encounter. The project also took into consideration factors including power-ratio reductions in certain systems and other scenarios as part of an effort to come up with an effective algorithm to tackle these issues in MIMO systems. Finally, Khademi looked at antennas used in these systems to see if their designs and selection could have an impact on common hardware constraints that can limit a wireless device’s range.

Khademi, Seyran, Gigabit Wireless Transmission in Dispersive Environments. Channel Characterisation and Signal Processing, Promoter: Van der Veen, A.J. Defence: November 22, 2016

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