Besma Smida Besma Smida, postdoctoral fellow

Harvard University,
Harvard School of Engineering and Applied Sciences
33 Oxford Street MD-117
Cambridge, MA 02138, USA
Tel: (617) 496-7661
email: bsmida@deas.harvard.edu

Besma Smida received the Diplome d'Ingenieur degree in telecommunications from Ecole Superieure des Communications de Tunis, Tunisia, in 1995 and the M. Sc. and Ph. D. degrees in telecommunications from INRS-EMT, University of Quebec, Montreal, Canada, in 1998 and 2006.

From 1998 to 1999, she worked as a research assistant in the Personal Communications Group of INRS-EMT. >From 1999 to 2002, she was a research engineer in the Technology Evolution and Standards group of Microcell Solutions, Montreal, surveying and studying radio-communication technology evolution. She also took part in major wireless normalization committees (3GPP, T1P1).

She is currently a Post-doctorate Fellow at the Division of Engineering and Applied Sciences, Harvard University, Cambridge, USA. Her current research interests include multicarrier modulation, spread spectrum, and network-aware application.

- FQRNT Postdoctoral Fellowship, Harvard University from 2006 to 2008.
- Recipient of the Gold Medal at the student poster session of SYTACom Technology Forum 2005.

Ph.D. research topic: Nouveau récepteur CDMA à porteuses multiples pour les systèmes sans fil 3G+ (in french).

- Prof. Sofiène Affès, INRS-EMT.

Ph.D. research summary: The subject of my Ph.D. thesis is the design of an adaptive multicarrier CDMA receiver. The purpose of this receiver is twofold: (1) performs blind channel identification and equalization as well as fast and accurate joint synchronization in time and frequency, and (2) mitigates the full interference effect.

We introduced the different multicarrier-CDMA (MC-CDMA) schemes and classify them based on the spreading domain. It was shown that there are a number of tradeoffs associated with the design and employment of the various multicarrier CDMA schemes proposed in the literature.

After that, we derived a new post-correlation model for MC-CDMA that characterizes the structure of the channel in space, time and frequency. Based on this model, we introduced a new multicarrier array-receiver (MC-STAR) with rapid and accurate joint synchronization in time and frequency. There, we exploit jointly the spatial, temporal and frequency diversities as well as the intrinsic inter-carrier correlation (termed hereafter frequency gain) to improve the channel identification and the synchronization operations.

Then, we derived a complete model of the interference which takes into account the multiple access interference (MAI) and the inter-symbol interference (ISI), and the inter-carrier interference (ICI). Based on this model, we introduced a new multicarrier interference subspace rejection (MC-ISR) receiver. We also proposed a realistic implementation of this receiver which includes an efficient strategy for carrier offset recovery in a multicarrier and multiuser detection scheme.

We analyzed the performance of MC-STAR and MC-ISR in an unknown time-varying Rayleigh channel with multipath, carrier offset, a band-limited chip waveform assumption and cross-correlation between subcarrier channels. Based on this link/system-level performance analysis, we also provided a comparative performance study of MC-STAR and MC-ISR over two multicarrier CDMA air-interface configurations, namely MT-CDMA and MC-DS-CDMA. Simulation results confirmed the advantages of MT-CDMA in increasing throughput and bandwidth efficiency. The current trend is to design radio air-interfaces with flat fading subcarriers. In contrast, with MC-STAR we show that the positive effects of multipath diversity and frequency gain over large strongly-overlapping subcarriers is more significant than the negative effects of multipath and multicarrier interference. In addition, by applying MC-ISR the performance gap between MT-CDMA and MC-DS-CDMA increases.

Last update 01-08-2006

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