Core Research description

The technical content of the set of core research workpackages is described in the following list of abstracts.

WP R.1- Modeling, calibration, and validation of multi-dispersive, multi-link channels aims at extending existing channel models, like the Winner model, by including all effects in the radio channel that affect the performance of advanced wireless systems and networks. Due to the specific characteristics of theses systems and networks, the sought models will be multi-dispersive, i.e. they will incorporate all dispersion dimensions of the channel, and multi-link, i.e. they will reflect the real statistical dependence between radio links in a wireless network. Adaptive models matched to the adaptive structure of flexible radio will also be developed. The models will be calibrated by measurement data and data synthetically generated using accurate ray-tracing methods to be designed as well. To this purpose, robust, efficient estimators of the parameters entering the models will be derived and their performance will be assessed theoretically.

Reference person: Bernard Fleury

WP R.2- Feedback and Resolution of the Channel State aims to explore the role of feedback in wireless communication networks and its relation to the resolution of the time-varying channel state. Aside from pure broadcast services, a important element of modern radio systems is their two-way nature which allows for a sharing of the medium in both directions for both communication and lowlayer signalling of channel quality indicators and decoding capacity indicators. The focus of this study is the assessment of effects stemming from imperfect channel knowledge at the receiving end (and thus the transmitting end as well) and furthermore its impact on the construction of feedback information. proper exploitation of feedback for both point-to-point two-way channels and multiuser/broadcast channels are considered. Broadband systems exploiting multiple-antennas at both the transmission and receiving ends are assumed from the outset.

Reference person: Raymond Knopp

WP R.3- Adaptive Coding/Modulation for the Wireless Channel aims at the investigation and development of AMC algorithms for the evolving wireless standards. MIMO/OFDMA systems will be at the centre of investigation, while the results will be extended to include non-orthogonal multicarrier modulation techniques. A survey of the state of the art will provide the basis in which an appropriate framework for design AMC solutions will be developed. Based on that, new algorithms will be designed and their performance will be assessed under various optimization/system scenarios.

Reference person: Andreas Polydoros

WP R.4- Iterative Receivers for Wireless Communications targets advances in the theory and implementation of iterative "turbo" receiver algorithms. We will devise new methods for code design, new decoding algorithms, and develop a theoretical framework for tackling scenarios where the channel is not perfectly known, and for implementing iterative algorithms efficiently in fixed point arithmetic. Furthermore, we will investigate the interplay between iterative decoding and the remaining receiver components, and apply the turbo principle to other parts of the receiver, such as synchronization.

Reference person: Erdal Arikan

WP R.5- Coding for Multi-Hop Wireless Networks is concerned with coding for wireless multihop channels. While for single-hop channels, the coding problem has already been almost completely solved (e.g., by Turbo codes or Low Density Parity Check codes), coding for multi-hop network is still an unsolved problem showing essentially different problems. Recent results promise that network coding is an appropriate template for an efficient multi-hop coding and this workpackage aims to provide further insights on this prediction.

Reference person: Michael Heindlmaier

WP R.6- Relaying and cooperation in networks. MIMO techniques can also be imitated by means of cooperative techniques, coined distributed MIMO, coalition techniques or relaying. In this WPR6, cooperative techniques will be investigated both for the physical layer and the network layer. At the physical layer, space-time or space-frequency codes will be designed for various optimization criterions and various trade-offs between diversity and multiplexing gains. The design will be based
on the amount and the type of channel state information available at the different nodes, or will be scalable with respect to the number of cooperative nodes, or even robust against uncertainties about the environment. Various practical relaying mechanisms will also be considered. The results will be compared to bounds obtained from information theory. At the network layer, protocols will be designed which account for not only for transmission, but also for the battery life of the cooperating nodes.

Reference person: Luc Vandendorpe

WP R.7- Joint Source and Channel Coding/Decoding deals with joint source and channel coding/decoding, which has been a subject of interest for many years now, and had difficulties to be really considered in practical situations, mainly because it was questioning the Shannon separation theorem that had guided the traditional way of designing communication systems, in which various teams were designing separately the different communication layers. The topics of interest here deal with the tools required for using JSCC/D in practical situations (compatibility with the work at various layers) and the improvement of the efficiency of the JSCC tools, in conjunction with the multiterminal situation which is likely to be met in the future. The emergence of new tools is also likely to rejuvenate the topic. For example, combination of specific channel codes such as fountain codes and JSCC should be a promising situation. Other new tools (such as distributed source coding) well suited to a multiterminal situation will also be considered.

Reference person: Christine Guillemot

WP R.8- Scheduling and adaptive radio resource assignment will address issues related to the design of fast radio resource assignment and scheduling techniques, under a cross-layer approach and considering both centralized and distributed paradigms, complex air interfaces exploiting time, frequency and space diversity, and new design methods.

Reference person: Roberto Verdone

WP R.9- Joint RRM and Flexible use of radio spectrum will develop and evaluate advanced Radio Resource Management (RRM) and spectrum management techniques for wireless communications systems in heterogeneous scenarios, where different access technologies co-exist so that by means of a joint use of the pool of resources significant capacity gains and a more efficient use of the spectrum can be achieved. The introduction of cognitive network functionalities in the developed strategies will be explored in order to provide the different systems with the ability to adapt to the changing conditions.

Reference person: Jordi Perez Romero

WP R.10- Network Theory will investigate theoretical foundations towards exploration of performance limits of wireless networks. We will pursue characterization of the theoretical limits in end-to-end traffic transport capacity of wireless networks, relationships with Shannon capacity and multiterminal information theory, scaling laws characterization as well as the potential impact of autonomic behaviour.

Reference person: Leandros Tassiulas

WP R.11- Opportunistic networks. In the pervasive communication scenarios delay-tolerant applications are expected to be frequently used whilst on the move, with the result that devices may often (but temporarily) be out of range and unable to access Internet services. This makes that a new paradigms, called opportunistic networking, is emerging as one of the most interesting evolution of MANETs (mobile ad hoc networks). Opportunistic networks exploit human mobility and local forwarding in order to distribute data. Information can be stored and passed, taking advantage of users mobility, or forwarded over a wireless link when an appropriate contact is met. New challenging cross-layer techniques are anticipated for this type of networks, including dissemination schemes, context-aware routing, and coding-based forwarding.

Reference person: Sergio Palazzo

WPR.A Security in Wireless Networks is one of the most challenging research topics as usual cryptographic schemes are not adapted to the mobility and changing condition patterns of the users. Similar to recent works based on opportunistic scheduling (where the channel is seen as an opportunity rather than a drawback), the objective of this WP is to exploit the random nature of the channel and the network topology to derive efficient cryptographic schemes. In particular, new definitions of capacity (where secrecy is incorporated) will be derived and analyzed from a theoretical and practical point of view.

Reference person: Merouane Debbah

WPR.B- Localization and Positioning Techniques. Starting from a review of the current state of the art, WPR.B will develop through a number of activities ranging from signal design for enhanced positioning accuracy, to the related estimation techniques to be used into positioning receivers, and the most modern cooperative/MIMO technologies. Special attention will be devoted to satellite positioning and to the related issue of integration of such techniques with indoor localization to
attain to truly seamless user positioning.

Reference person: Davide Dardari

WPR.C- Flexible Radio Platforms. Current and forthcoming radio standards are more and more complex and numerous due to the variety of user demand, application requirements and operation conditions. This has a stringent impact on hardware architecture that has to be more and more flexible and computation efficient. WPR.C addresses HW flexibility from the architectural point of view through the analysis of MP-SoC and from the algorithmic requirement point of view. Specific
highly intensive functions, such as bit level computation are also considered.

Reference person: Dominique Noguet