Time-Frequency Communications

Description of research

The radio-spectrum has been untouched for centuries, but in recent years wireless devices have been competing more and more for some scarce bandwidth. As bandwidth auctions are billion-dollar affaires, wireless devices pop-up literally everywhere and forecasts state a 50x increase of data usage in just a few years, an efficient usage of the radio-spectrum is of ever increasing importance.

To arrive at a more efficient usage of the radio-spectrum, spectral leakage associated with Orthogonal Frequency Division Multiplexing (OFDM) has been analyzed and solutions are aimed for. Conventional solutions target the consequences, reducing sidelobes, rather than targeting the problems, the signals themselves. Instead, this PhD research aims for a set of signals localized in time-frequency. The localization in time and frequency is lower-bounded by the uncertainty principle. The Hermite functions form a set of solutions to this lower-bound.

Although Hermite functions are optimally localized in time-frequency, that does not necessarily imply that the signals are also suitable for communication. Based on the discussion of ten signal attributes, criteria are formulated for a set of basis signals for communication. The Hermite functions have been assessed based on these criteria and subsequently modified in order to meet the criteria. The resulting set of time-frequency localized signals, referred to as S_TFL, meet these criteria.

In case the spectrum becomes more and more utilized, mutual interference caused by conventional OFDM sidelobes severely degrades the effective data-throughput. Unlike OFDM, the signals S_TFL have a near-optimal localization and allow multiple users to communicate efficiently over time and frequency. The performance of S_TFL in mobile radio channels, the transceiver power efficiency and hardware complexity have been investigated and compared to conventional OFDM.

Given the increasing competition for some scarce bandwidth and the attention paid to energy- and power-efficient transmission systems, there is good evidence to believe that the realization of transceivers employing Hermite functions, or their practical counterparts STFL, could be a major improvement in communication.

The research is of particular interest in the context of cognitive radio, dynamic spectrum access, localization & sensor systems and high-data rate/energy-efficient multi-user communication systems.

Advisor(s)

A.B.J. Kokkeler

G.J.M. Smit

Duration

2009-2013

Project

Tracking, Tracing, Sensoring Platform - TSP

Funding institution

Gelderland-Overijssel & Europa

Strategic Research Orientation

Wireless and Sensor Systems

Links to relevant web pages:

http://www.tsp-project.nl/

Pictures

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Home CTIT symposium 2013 About CTIT News NIRICT Research Meet the PhDs Working at CTIT Internal Information Conferences Open Calls (updated May 3, 2013) Library and Videos Knowledge Transfer Links Sitemap Search	Time-Frequency Communications Description of research The radio-spectrum has been untouched for centuries, but in recent years wireless devices have been competing more and more for some scarce bandwidth. As bandwidth auctions are billion-dollar affaires, wireless devices pop-up literally everywhere and forecasts state a 50x increase of data usage in just a few years, an efficient usage of the radio-spectrum is of ever increasing importance. To arrive at a more efficient usage of the radio-spectrum, spectral leakage associated with Orthogonal Frequency Division Multiplexing (OFDM) has been analyzed and solutions are aimed for. Conventional solutions target the consequences, reducing sidelobes, rather than targeting the problems, the signals themselves. Instead, this PhD research aims for a set of signals localized in time-frequency. The localization in time and frequency is lower-bounded by the uncertainty principle. The Hermite functions form a set of solutions to this lower-bound. Although Hermite functions are optimally localized in time-frequency, that does not necessarily imply that the signals are also suitable for communication. Based on the discussion of ten signal attributes, criteria are formulated for a set of basis signals for communication. The Hermite functions have been assessed based on these criteria and subsequently modified in order to meet the criteria. The resulting set of time-frequency localized signals, referred to as S_TFL, meet these criteria. In case the spectrum becomes more and more utilized, mutual interference caused by conventional OFDM sidelobes severely degrades the effective data-throughput. Unlike OFDM, the signals S_TFL have a near-optimal localization and allow multiple users to communicate efficiently over time and frequency. The performance of S_TFL in mobile radio channels, the transceiver power efficiency and hardware complexity have been investigated and compared to conventional OFDM. Given the increasing competition for some scarce bandwidth and the attention paid to energy- and power-efficient transmission systems, there is good evidence to believe that the realization of transceivers employing Hermite functions, or their practical counterparts STFL, could be a major improvement in communication. The research is of particular interest in the context of cognitive radio, dynamic spectrum access, localization & sensor systems and high-data rate/energy-efficient multi-user communication systems. Advisor(s) A.B.J. Kokkeler G.J.M. Smit Duration 2009-2013 Project Tracking, Tracing, Sensoring Platform - TSP Funding institution Gelderland-Overijssel & Europa Strategic Research Orientation Wireless and Sensor Systems Links to relevant web pages: http://www.tsp-project.nl/ Pictures