Signal and Image Processing

The research focuses on estimation and detection techniques for wired and wireless environments. Transmitters and receivers are designed and optimized for OFDM (multicarrier) transmission schemes, filter-bank based multicarrier modulation schemes, OFDMA systems, multiuser multiantenna systems (MIMO) and multicell/interference limited systems.
Particular attention is paid to iterative/soft information/turbo receivers both for detection and estimation (carrier phase, carrier frequency, channel state information) or synchronization. Optimization of modulation, coding and resource allocation are also investigated.

This research focuses on security achieved at the PHY layer. Particular attention is paid to scenarios where a transmitter wants to communicate to a legitimate receiver over parallel channels (for instance OFDM over frequency selective channels). An eavesdropper is able to capture information from some of the links. Along the work of cooperative techniques (relays) emphasis is put on transmission schemes helped by a relay. The objectives are to obtain bounds on secure transmission rates, investigate situations where non perfect CSI is available, and to design coding schemes to exploit the potential for secure communications.

This researches focuses on ultra wide band (UWB) based localisation or positioning. Methods considered are time of arrival (TOA), time difference of arrival (TDOA) and angle of arrival (AOA). Bounds have been derived to assess the potential of UWB, understand the impact of multipath propagation and investigate the ambiguities. Practical estimators are proposed and their performance is investigated. A practical testbed has been developed and is being upgraded. An accuracy of a few millimeters has been achieved for indoor positioning over distances of about ten meters and with obstacles.

Source coding and channel coding (or decoding) and transmission are often designed independently. This research track investigates scenarios where there is advantage or potential in jointly designing the encoders or decoders. The research focuses on bounds for some techniques, and practical schemes applying this philosophy, in particular for sensor networks.

Compression & streaming

Image and video compression algorithms are investigated, including for stereo and multi-view contents. Visually pleasant and fluent video streaming or image browsing are implemented by adapting compression and forwarding mechanisms to network and terminal resources. This implies the rate-distortion optimization of image/video packet schedules, but also adaptive switching between multiple versions of the content. For low bandwidth wireless accesses, interactive streaming architectures are investigated to allow the end-user to control the trade-offs involved when reducing the spatial and temporal resolution of the streamed content.

Content-based retrieval

Coarse-to-fine JPEG2000 image classification, active learning for surveillance scene retrieval.

Watermarking

Fingerprinting of mono and stereo images for Digital Cinema; 3D meshes watermarking.

Object & people detection and tracking algorithms are developed to understand behaviors in natural scenes. Application domains include autonomous production of visual reports (e.g. for team sport events), but also video-surveillance. Resource constrained allocation solutions are also proposed to build automatically personalized summaries of edited video feeds.

Another field of research is the solving of inverse problems from generalized sparsity prior (with applications in optics and X-ray CT), Compressed Sensing (theory and application), theoretical questions linked to the design of new sensors (for computer vision), applied mathematics for astronomical and biomedical signal processing questions, and representation of data on strange spaces (e.g., sphere, manifolds, or graphs).

This project aims at detecting segments or contours of objects in a given picture by means of graph-based techniques that unfold the community structures in a large graph. The communities found are also hierarchical, allowing to find subregions inside an object.

The research develops image & signal processing tools for the use in various biomedical contexts, including protein docking, radiotherapy, proton therapy, brachytherapy, surgery, EEG analysis, kinematic assessment through accelerometers, etc. 

• Shape analysis for protein docking including 3D mesh processing and the analysis of protein surface properties; 
• Radio/proton therapy: rigid and non-rigid image registrations methods for 2D-3D and 3D-3D images both for single and multiple modalities as well as for surfaces; 
• Segmentation techniques either using prior knowledge (atlas-based) or allowing user interaction (graph cuts); 
• EEG reconstruction, transcranial magnetic stimulation, as well as on the use of functional imaging for measuring motion disorders;
• Accelerometers are used for kinematic analysis, e.g.  to quantify the motor disturbances due to Parkinson's disease or to measure objectively the effects of the rehabilitation process following a stroke;
• Human-computer interactions to create intuitive user interfaces for the clinical world.