Events Calendar

Low-Complexity Equalization for Multi-scale Multi-lag OFDM Channels

Speaker: Zijian Tang, Research Scientist of TNO the Hague, the Netherlands

Talk Title: Low-Complexity Equalization for Multi-scale Multi-lag OFDM Channels

Abstract: We consider an orthogonal frequency-division multiplexing (OFDM) transmission scheme over wideband underwater acoustic channels, where the propagation paths can experience distinct Doppler effects (manifested in signal scales) and time of arrivals (manifested in delays). We capture such an effect in this paper with a multi-scale multi-lag (MSML) model, and show that the resulting frequency-domain MSML-OFDM channel is subject to inter-carrier interference (ICI), whose amount differs per subcarrier. The corresponding channel matrix can still be approximated as highly sparse, but lacks a specific structure that can optimally be exploited by those low-complexity equalizers proposed for narrowband channels. In this paper, we propose to use the conjugate gradient (CG) algorithm to equalize the channel iteratively. The suitability of the preconditioning technique, that often accompanies the CG to accelerate the convergence, is discussed for the MSML-OFDM channel. We show that in order for the preconditioner to function properly, optimal resampling is indispensable.

Biography: Zijian Tang received the MSc in electrical engineering and the PhD degree from the Delft University of Technology (TU Delft) in 2003 and 2007, respectively. After working with Mathworks for one year, he joined the Sonar Group at Netherlands Organisation for Applied Scientific Research (TNO) in 2008 as a research scientist, where the research area covers underwater acoustic communications, anti-submarine warfare, marine mammal detection etc. Since 2010, he has also been holding a (part-time) research fellow position at the Network & Circuits Group of TU Delft. Zijian Tang is the recipient of the best student paper award (honourable mention) at ICASSP 2007, and was nominated to the Simon Stevin Gezel prize in 2008.

Host: Prof. Urbashi Mitra, ubli@usc.edu, x04667

Location: Hughes Aircraft Electrical Engineering Center (EEB) - 539

Audiences: Everyone Is Invited

Contact: Gerrielyn Ramos