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Evènements et manifestations

22/12/2018

Doctorate thesis defense of Zeineb Hraiech




Doctorate thesis defense on December 22th 2018 at 10H00 ,in Sup’Com Amphitheater Ibn Khaldoun.


Entitled :Advanced OFDM Modulation Schemes for 5G Systems and Beyond

Presented by :

Zeineb Hraiech


Committee


President

Ridha Bouallegue

Professor at Sup'Com, Tunisia

 

 

 

Referees

Mohamed-Lassaad Ammari

Associate Professor at ENISo, Tunisia

 

Mohamed-Slim Alouini

Professor at KAUST, Saudi Arabia

 

 

 

Examiner:

Ines Kammoun Jmal

Professor at ENIS, Tunisia

 

 

 

 

Thesis Director :

Mohamed Siala

Professor at Sup'Com, Tunisia

 

 

 

 

Thesis Co-Director :

Fatma Abdelkefi

Professor at Sup'Com, Tunisia

 

 

 

 


Abstract


Future wireless networks are required to offer new applications and services, which will experience high dispersions in time and frequency, incurred mainly by coarse synchronization at the receiver. Coarse synchronization is induced by signaling overhead reduction and dictated by the tremendous optimization of the radio interface efficiency. It is expected to dramatically damage waveform orthogonality in conventional Orthogonal Frequency Division Multiplexing (OFDM) systems and to result in oppressive Inter-Carrier Interference (ICI). To alleviate the degradation in performance caused by ICI, the concept of non-orthogonal multiplexing has been promoted as a serious alternative to strict orthogonal multiplexing, for guaranteeing OFDM benefits without requiring high-level synchronization.


Within the framework of non-orthogonal multiplexing framework, Ping-pong Optimized Pulse Shaping (POPS) algorithm is introduced as a powerful tool to efficiently design waveforms which withstand future multicarrier systems dispersion impairments. In this regard, we first investigate the discrete time version of POPS approach, which is referred as POPS-OFDM. We study its sensitivity and robustness against estimation and synchronization errors. Based on numerical results, we show that POPS-OFDM provide an important gain in Signal to Interference Ratio (SIR), typically higher than 5 dB, with respect to conventional OFDM. We also demonstrate that, as a by-product, POPS-OFDM brings an increased robustness against synchronization errors and ensures a dramatic reduction in out-of-band (OOB) emissions, enabling flexible and improved spectrum utilization. In the sequel, we also propose a new design of PHYDYAS waveforms, nicknamed POPS-PHYDYAS. This design is based on a mix of the POPS algorithm and the PHYDYAS filter expansion. The results confirm the advantage behind the POPS-PHYDYAS design in enhancing the performance in terms of SIR, in comparison to multicarrier systems banking on PHYDYAS waveforms, as conceived by Mirabbasi and Martin. To complete the research work and get a whole picture on POPS approach, we consider a continuous-time version of the POPS algorithm, where the optimized Tx/Rx waveforms are considered as linear combinations of the most localized Hermite functions. Such choice is motivated by the fact that the Hermite functions are very localized in both time and frequency. We also derive the exact closed-form expressions of the SINR of the considered multicarrier system in terms of Hermite functions expansion coefficients.


Keywords :


POPS, FBMC, OFDM, Waveform Design, PHYDYAS, Hermite Functions, OOB Emissions, ICI, ISI, SINR