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Equipe de recherche SWING

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Overall Objectives

SWING is a joint team between INRIA Rhône Alpes and INSA Lyon that follows the end of the ARES project.

Pervasive communications and ambient networking are becoming part of more and more facets of our daily life. Probably the most popular usage is the mobile Internet access made possible by numerous access technologies, e.g. cellular mobile networks, WiFi, Bluetooth,... The access technology is becoming transparent for the end user, who does not care about how to access the network but is only interested in the services available and in the quality of service (QoS). A first aspect on the QoS can be made in terms of capacity, which impacts on the delay or the latency in the network. The second aspect of QoS includes robustness in a general meaning, e.g.lifetime, reliability and security. This complete view of QoS is ultimately constrained by system parameters and is related to energy efficiency and radio resource availability.

Beyond a simple Internet access, many other applications and services are built on the basis of pervasive communications, for which the communication is just a mean, and not a finality. Thus, the wireless link is expected to be invisible to the end userand constitutes the first element of the future Internet of things; to develop a complete twin virtual world fully connected to the real one.

Then, the tremendously growing needs of radio resources led the standardization industry to propose a large number of standards driven by different groups from the IEEE (802 family), ETSI (GSM), 3GPP (3G, 4G) or the Internet Society (IETF standards). Roughly speaking, the upper layers of the OSI model, from layer 3 (network) up to layer 7 (application) are nowadays mostly driven by the proposals of the IETF, while the IEEE802 standards' family offers the major contributions at layers 1 and 2 (except for cellular networks) and represents the basis of numerous famous commercially available technologies such as WiFi (802.11), Wimax (802.16), Bluetooth or Zigbee (802.15.4),...

The bottom-up approach used for designing new radio technologies is far from offering a real wireless convergence. The current development of the wireless industry is surely slowed down by the lack of radio resources and the lack of systems flexibility.

This technological bottleneck will be only overtaken if three complementary problems are solved : terminal flexibility, agile radio resource managementand autonomous networking.

Terminal flexibility is advocated to obtain full-band and all-standards compliant systems by exploiting the concept of Software Radiointroduced in a seminal paper by J. Mitola in 1991. A full software radio node is still an utopia, but many architectures based on software defined radio have now hit the market.

In parallel, the development of new standards is threatened by the radio spectrum scarcity.The increasing number of standards has led to the partial saturation of the UHF band. It will probably lead to its full saturation on the long run. However, this saturation is only 'virtual' because all equipments are fortunately not emitting all the time. This is why a solution for increasing the real capacity of the UHF band originates from self-adaptive behavior. In this case, flexible terminals will have to implement agile algorithms to share the radio spectrum and to avoid interference. In this context, cooperative approaches are even more promising than simple resource sharing algorithms.

Last but not least, as radio systems are going to expend into very large scale networks, multi-hop networking is becoming an important issue as widely studied in ad hoc networks, wireless sensor networks or mesh networks. In these networks, the most challenging issues concern the design of localized and/or distributed networking protocols that can cope with the topology changes, the neighborhood dynamics and the large-scale dimension of the network. Beyond classical routing problems, self-organization, self-configuration, flooding strategies or data-gathering represent the most important issues to improve the system efficiency and to provide the required framework for the Internet of Things.

These three fundamental and complementary research axes are most often evaluated independently, in different research community. From an optimization point of view, the proof of separability of these three axes is not yet stated, and we even guess it is not possible to exhibit the best solutions with such an approach. The interactions between these three axes constitute the core of the SWING proposal that will be structured around them but with strong connexions and specific identified cross-problems at the intersections.

A first common objective concerns the end-to-end QoS. For instance end-to-end delay and reliabilityare important issues. They are related to the network capacity, which is not clearly defined for real environments. Depending on the nodes capability, this capacity can strongly change. For instance, introducing network coding or relaying nodes may change drastically the global capacity. We can claim that the end-to-end capacity is truly not the direct extension of a single hop capacity.

A second up-to-date objective is related to the energy consumption of wireless systems. There is a clear tendency in the wireless community to address the energy consumption minimization as a primary objective. Green radio and green networking are becoming strategic issues as for instance promoted by the green touch consortium http:// www. greentouch. org/ in which INRIA is involved. It is expected that the energy reduction will be possible from a global approach only.

Lastly, security represents the third cross-problem we want to point out. Indeed, all the degrees of freedom that are introduced into embedded system with flexible radio, radio resource sharing, or autonomous networking, could lead to as many security holes. Security must be completely re-engineered in this context.

These three objectives can be alternatively considered as constraints or purposes, depending on the point of view. In our work, we pay a strong attention to always consider these complementary objectives. Instead of defining constrained problems, e.g.capacity maximization under power constraints, we will rather focus on studying Pareto optimal fronts and on proving the optimality of some algorithms with respect to these fronts.

As a conclusion, including radio node flexibility features and agile radio resource sharing capabilities together with routing and aggregation aspects within a global formulation offers a very complete framework for addressing the challenges of future wireless networks.

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