PhD Supervision & Postdocs

Postdocs

  • Arifur Rahman- (CentraleSupélec), on research topic: “Enhanced PHY for Cellular Low power communication IoT“. Under the French National Research Agency project EHYL: ANR-16-CE25-0002-03. Period: Jan. 2019 end Sep: 2019;
  • Julio César Manco Vásquez (CentraleSupélec), on research topic: “Enhanced PHY for Cellular Low power communication IoT“. Under the French National Research Agency project EHYL: ANR-16-CE25-0002-03. Period: March 2018 end Sept. 2019.
  • Marwa CHAFII (CentraleSupélec), on research topic: “Enhanced PHY for Cellular Low power communication IoT“. Under the French National Research Agency project EHYL: ANR-16-CE25-0002-03. Period: Jan.2017-Feb. 2018.
  • Vincent SAVAUX (CentraleSupélec), on research topic: “Blind detection strategies for OQAM-OFDM Systems“. Under the French National Research Agency project PROFIL: ANR-13-INFR-0007-03. Period: 2013-2015. Related publications: [J24, J23, J20, J18], and [C104, C101, C99, C94, C92, C91, C87].
  • Malek NAOUS (CentraleSupélec), on research topic: “FBMC Equalization- HW Implementation“. Under the French National Research Agency project PROFIL: ANR-13-INFR-0007-03. Period: 2014-June 2016. Related publications: [C104, C92], and [O1].

PhD Supervisions

In progress

  • Majed SAAD, PhD. title: “Terabits Wireless Communication Receiver Using SC Modulation“, Joint doctoral supervision with Lebanese International University (LIU) (Lebanon), and CentraleSupélec (France). Advisors: Jacques Palicot and Faouzi Bader (France), and Ali Al Gouwhayel with Hussein Hijazi (Lebanon). Period: Jan. 2018 end 2020.

Finished

  • Hussein CHOUR, PhD. title: “Full-Duplex Device-to-Device Communication for 5G Network“. Joint doctoral supervision with the Lebanese University in Beirut (Lebanon), and CentraleSupélec ( campus of Rennes, France).
    Advisors: Dr. Faouzi Bader (France), Prof. Oussama Bazzi and Dr. Youssef Nasser (Lebanon). Period: Oct. 2016 end Oct. 2019.

Short description:  With the rapidly growing of the customers’ data traffic demand, improving the system capacity and increasing the user throughput have become essential concerns for the future fifth-generation (5G) wireless communication network. In this context, device-to-device (D2D) communication and in-band full-duplex (FD) are proposed as potential solutions to increase the spatial spectrum utilization and the user rate in a cellular network. D2D allows two nearby devices to communicate without base station (BS) participation or with limited participation. On the other hand, FD communication enables simultaneous transmission and reception in the same frequency band. Due to the short distance property of D2D links, exploiting the FD technology in D2D communication is an excellent choice to further improve the cellular spectrum efficiency and the users’ throughput. However, practical FD transceivers add new challenges for D2D communication. For instance, the existing FD devices cannot perfectly eliminate the self-interference (SI) imposed on the receiver by the node’s own transmitter. Thus, the residual self-interference (RSI) which is tightly related to the transmitter power value highly affects the performance of FD transmission. Moreover, the FD technique creates additional interference in the network which may degrade its performance when compared with the half-duplex transmission. Thus, proper radio resource management is needed to exploit the benefits of FD and guarantee the quality of service (QoS) of the users. The works in this dissertation focus on the power allocation (PA) and channel assignment (CA) of a full-duplex device-to-device (FD-D2D) network. In particular, this thesis first addresses the PA problem and proposes a simple yet efficient centralized optimal PA framework, and next, it derives the optimal joint PA and CA scheme for an FD-D2D network. A simple sub-optimal algorithm for resource allocation named CATPA, based on CA followed by PA, is also derived and proposed.
This dissertation also develops, in the end, an efficient decentralized PA using game theory tools that will be an essential part of future works in the context of distributed radio resource management.

Keywords: 5g, Channel assignment, device-to-device (D2D), energy efciency, full-duplex (FD), power allocation, resource allocation, weighted sum-rate, Optimisation algorithms.

Short description: Future wireless networks are envisioned to accommodate the heterogeneous needs of entirely different systems. New services obeying various constraints will coexist with legacy cellular users in the same frequency band. This coexistence is hardly achievable with OFDM, the physical layer used by current systems, because of its poor spectral containment. Thus, a myriad of multi-carrier waveforms with enhanced spectral localization have been proposed for future wireless devices. In this thesis, we investigate the coexistence of new systems based on these waveforms with legacy OFDM users. We provide the first theoretical and experimental analysis of the inter-system interference that arises in those scenarii. Then, we apply this analysis to evaluate the merits of different enhanced waveforms and we finally investigate the performance achievable by a network composed of legacy OFDM cellular users and D2D pairs using one of the studied enhanced waveforms.

Keywords: Enhanced waveforms for 5G, D2D systems, Interference modeling, Coexistence, PSD model, and EVM-based model

  • Marwa CHAFII, PhD. title: “Study of a New Multi-Carrier Waveform with Reduced PAPR” (original in French), at SCEE Research group, SUPELEC-Rennes-France. Advisors: Prof. Jacques Palicot (Supélec, France), Prof. Rémi Gribonval (INRIA-Rennes, France), and Dr. Faouzi Bader (Supélec, France).
    Duration: Sept. 2013- end Oct. 2016.

Short description: OFDM is a multi-carrier modulation system widely used in wireline and wireless applicationstions such as DVB-T/T2,Wifi, and 4G, due to its resilience against frequency selective channels compared with the single carrier modulation systems. However, the OFDM signal suffers from large amplitude variations. The fluctuations of the OFDM envelope generate non-linear distortions when we introduce the signal into a non-linear device like the power amplifier. Reducing the variations of the signal improves the power amplifier efficiency, reduces the energy consumption and decreases CO2 emissions. The peak-to-average power ratio (PAPR) has been introduced as a random variable that measures the power variations of the signal. There exist several multi-carrier modulation systems based on different modulation basis and shaping filters. We first prove in this work that the PAPR depends on this modulation structure. Moreover, the behavior of the PAPR regarding to the modulation waveforms is analyzed and the PAPR reduction problem is formulated as an optimization problem. Furthermore, a necessary condition for designing waveforms with better PAPR than OFDM is developed. This necessary condition is particularly satisfied by wavelet basis. Finally, a new adaptive wavelet packet waveform is proposed, allowing significant gain in terms of PAPR, while keeping the advantages of multi-carrier modulations.
Keywords: PAPR, OFDM, wavelet modulation, adaptive modulation.

Short description: The Orthogonal Frequency Division Multiplexing (OFDM) is the most commonly used multi-carriers modulation scheme in the telecommunication systems. It is used in most communication standards such as DVB-T2, Wireless Local Area Networks (WLAN), WiMAX and the LTE (Long Term Evolution) standard. The success of the OFDM comes from its robustness in presence of multi-paths and frequency selective fading channels, and the simplicity of the implementation of its transmitter and receiver. One of the main drawbacks of the OFDM modulation scheme is its high Peak-To-Average Power variation (PAPR) which can induce poor power efficiency at the transmitter amplifier. The digital base band pre-distortion for the linearization of the power amplifier (PA) and the PAPR mitigation are the most commonly used solutions in order to deal with efficiency and the linearisation at the high power amplifier. This thesis is focused on this last solution, and particularly on the addition of signal based techniques to mitigate the PA effects. Developed solutions in this thesis are about improving the Tone Reservation method which is the most popular adding signal based technique for PAPR mitigation, and also the classical clipping method which is nowadays the most simple method (in terms of computational complexity).

Keywords: OFDM, PAPR, high power amplifier, tone reservation, clipping;

Short description: In this dissertation, the resource management problem in multi-carrier based CR systems is considered. The dissertation focuses on three main issues: 1) design of efficient resource allocation algorithms to allocate subcarriers and powers between SUs such that no harmful interference is introduced to PUs, 2) compare the spectral efficiency of using different multi-carrier schemes in the CR physical layer, specifically, orthogonal frequency division multiplexing (OFDM) and filter bank multi-carrier (FBMC) schemes, 3) investigate the impact of the different constraints values on the overall performance of the CR system. Three different scenarios are considered in this dissertation, namely downlink transmission, uplink transmission, and relayed transmission. For every scenario, the optimal solution is examined and efficient sub-optimal algorithms are proposed to reduce the computational burden of obtaining the optimal solution. The suboptimal algorithms are developed by separate the subcarrier and power allocation into two steps in downlink and uplink scenarios. In the relayed scenario, dual decomposition technique is used to obtain an asymptotically optimal solution, and a joint heuristic algorithm is proposed to find the suboptimal solution. Numerical simulations show that the proposed suboptimal algorithms achieve a near optimal performance and perform better than the existing algorithms designed for cognitive and non-cognitive systems. Eventually, the ability of FBMC to overcome the OFDM drawbacks and achieve more spectral efficiency is verified which recommends the consideration of FBMC in the future CR systems.
Keywords: Power allocation, relay, multi-relays, cognitive radio, multi-carrier.

Short description: In this Ph.D. thesis, different adaptive techniques for B3G multi-carrier wireless systems are developed and proposed focusing on the SS-MC-MA and the OFDM(A) (IEEE 802.16a/e/m standards) communication schemes. The research lines emphasize into the adaptation of the transmission having (Partial) knowledge of the Channel State Information for both; single antenna and multiple antenna links. For single antenna links, the implementation of a joint resource allocation and scheduling strategies by including adaptive modulation and coding is investigated. A low complexity resource allocation and scheduling algorithm is proposed with the objective to cope with real- and/or non-real- time requirements and constraints. A special attention is also devoted in reducing the required signaling both in the downlink and the uplink. Moreover, for multiple antenna links, the performance of a proposed adaptive transmit antenna selection scheme jointly with space-time block coding selection is investigated and compared with conventional structures. In this
research line, mainly two optimizations criteria are proposed for spatial link adaptation, one based on the minimum error rate for fixed throughput, and the second focused on the maximization of the rate for fixed error rate. Finally, some indications are given on how to include the spatial adaptation into the investigated and proposed resource allocation and scheduling process developed for single antenna transmission.
Keywords: RRM, adaptive modulation, WiMAX, multi-carrier, spatial link adaptation.