Manager: Iyad DAYOUBMCF-HDR - Tel: 03 27 51 13 74

This research theme concerns intelligent, multi-user, cooperative and opportunistic communication systems. We are interested in the development of transmission, multiple access and reception technologies for radio frequency communication systems as well as for mixed radio and optical networks. Intelligent Transportation Systems intelligent transport are one of the applications targeted. The work covered is mainly :

Radio frequency communications :

• Cognitive Radio: We have seen an explosion of new radio standards, with the terminal evolving in an increasingly heterogeneous and complex radio landscape. This raises problems of system cohabitation, interoperability between systems and frequency availability. These systems must guarantee availability, service continuity, traffic heterogeneity, robustness and quality of service for the applications concerned, sometimes in a context of high mobility and regardless of the environments crossed. These requirements of dynamic reconfigurability are common with the world of telecommunications and solutions are sought through the development of the "intelligent" radio allowing to realize, via software functions, the functions currently ensured by hardware components in the radio modems. In this context, we are interested in the following problems blind identification and classification of waveforms of 2nd, 3rd and 4th generation telecommunications systems as well as adaptive radio channel estimation in particular high mobility (i.e. rail, TGV).

  Related keywords: MIMO, OFDM, blind detection, spatial correlation, higher order statistics, adaptive channel estimation, intelligent mobile terminal

Multi-user communicating systems:

In the context of multi-cell networks, we are interested in the problem of low spectral efficiency at the edge of the cell, due to the high level of interference between the cells in this area.

Within this framework, three themes are addressed:

1. The search for cooperation strategies between the base stations of the network (downlink), with a distributed scheme constraint (decisions are made at the level of each base station, and not in a centralized manner). This corresponds to a virtual MIMO approach. We have proposed a cooperation scheme that takes advantage of the spatial diversity, but also of the frequency diversity of the network. This is implemented through an adaptation of the optimal space-time coding: the golden code.

2. The search for a statistical model of the power of inter-cell interference experienced by a network user. The interest of such a model is to facilitate the analysis and the simulation of the network, in particular in the search for solutions aiming at limiting these interferences. We have implemented a semi-analytical method that allows us to obtain a reliable model, including path-loss, shadowing and multipath propagation phenomena, for the downstream channel, and in a distributed environment where the resource allocation is opportunistic (optimal from a sum flow point of view). The proposed statistical model is derived from a Burr's law, and is parameterized by the importance parameter of the shadowing effect σdB

3. Resource allocation with ARQ feedback (Xlayer approach).

   Related keywords: Cooperative Networks, Virtual MIMO, Interference Modeling, Cross-Layer Design, Ad hoc Networks.

Mixed Radio-Optical Networks :

Due to their unbeatable throughput, single-mode (SMF) or multi-mode (MMF) fiber links represent an ever-growing infrastructure today. Thus, the need for a mixed radio-fiber technology is becoming apparent in order to satisfy requirements (i.e. high-speed services) and to take advantage of the complementarity of the two technologies.

In this context, two themes are developed: 

1. Optical CDMA and multiple access interference processing: the direct radio transmission model on fiber limits its use to radio applications only. In this context, we are interested in the optical CDMA multiple access technique (i.e. more specifically in the treatment of multiple access interference) on SMF fiber. Thus, we develop optical multi-user detectors (O-MUD) based on the parallel (SPIC) and serial (SIC) cancellation of multiple access interferences associated with optical codes in 1 and 2 Dimensions (i.e. OOC, PC).

2. Optical MIMO: With its enormous bandwidth, the MMF fibre appears to be the only media capable of delivering high-speed multi-service in enterprise and "in-door" networks. An MMF network can be the network backbone that feeds fixe-filaire services (such as GbE data services), as well as wireless services (e.g., IEEE 802.x) throughout the building using a multiplexing technique. In this context, we have performed a complete analytical development of an optical MIMO system using the principle of mode group diversity multiplexing (MGDM). We are also interested in the optimization of these systems, namely: optical power and frequency allocation per service, modeling and decomposition of the optical MIMO channel, cross-layer (PHY-MAC) for better capacity and/or quality.

   Related keywords: RoF, CDMA-Optique, MUD-Optique, SIC-Optique, PIC-Optique, MIMO-Optique, MGDM, Cross-Layer

This work is supported by several projects and contacts: programme CPER « CISIT », Europe/INTERREG « ROSETTE », Europe/INTERREG « EXTRACTT », ANR/CORRIDOR, IRT/RAILENIUM,…

Academic collaborations:

• National : IFSTTAR, UBO-LabSTICC, TELECOM Bretagne, Supelec, EURECOM, XLIM, INSA de Rouen (LITIS),
• International: Concordia University (Canada), Kent University (UK), Detroit University (USA), EPT and ENIT (Tunis), Damascus University, ENSAT (Tangiers).
• Industry: THALES, SNCF, RFF, Micromodule, Bombardier