Rosalba Suffritti

A power allocation strategy using Game Theory in Cognitive Radio networks

The Cognitive Radio approach can be considered as a promising and suitable solution to solve in an efficient and flexible way the increasing and continuous demand of services and radio resources. This paper investigates how the adoption of a cognitive radio strategy can help in the coexistence problem of two wireless networks operating on the same spectrum of frequencies. A DVB-SH based satellite network will be considered as primary system, while an infrastructured wireless terrestrial network will constitute the cognitive radio based secondary system. In this work it will be presented a power resource allocation technique based on Game Theory, considering mainly Potential Games. We will show the proposed approach is suitable for distributed implementation, furthermore it provides performances comparable to an heuristic allocation method representing the optimum allocation. The comparison between these two resource allocation methods will be provided as result of this work.

Resource Allocation in Cognitive Radio Networks: A Comparison Between Game Theory Based and Heuristic Approaches

Cognitive Radio (CR) approach can be considered as a promising and suitable solution to solve in an efficient and flexible way the increasing and continuous demand of services and radio resources. This paper shows the potential benefits of the adoption of a cognitive radio strategy to the coexistence problem. Two different approaches have been considered: the first one is based on the Game Theory while the second one is formalized as a constrained maximum search and represent the optimum solution. The Game theory approach, suitable for a distributed implementation, provides performances comparable to the heuristic one which is a centralized optimization problem. The paper analyzes the performances of both approaches in terms of secondary rates and spectral efficiency provided by the secondary system.

Power allocation strategy for Cognitive Radio terminals

Traditional communications systems imply an a priori association of the frequency band, the service assigned to it and the used technology. Breaking this static association can provide much more flexible, efficient and easy-to-use dynamic systems able to cope with the requirements and constraints of the environment and the users. Cognitive radio and software defined radio modify this current communication paradigm. They provide the enabling technologies to perceive, learn, reason and interact accordingly in open-ended changing environments for the coexistence of different services and systems technologies on the same radio bands. They benefit from the recent advances in digital signal processing, fast computing and advanced reception techniques. This paper evaluates the performances of a cognitive radio approach to the coexistence problem for two application scenarios: a meshed OFDM-based secondary wireless service in coexistence with a primary terrestrial and satellite DVB-SH system.

Hybrid satellite/terrestrial cooperative relaying strategies for DVB-SH based communication systems

The integration of satellite and terrestrial systems in a hybrid network permits to benefit from both systems, overcoming the drawbacks of a Non-Line-Of-Sight (NLOS) propagation. The purpose of this paper is to study simple cooperative relaying strategies which rely on the introduction of the Delay Diversity (DD) technique in a DVB-SH compliant hybrid satellite/terrestrial network with the aim of improving the performance of the network. The application of this strategy represents a promising solution to guarantee communication also in public emergency situations, such as the ones caused by fire, earthquake, flood or explosion. We investigated the pros and cons of the proposed scheme, comparing the assumptions which are required and the simulation results with respect to the satellite-only and the terrestrial-only systems.

Multiple Alert Message Encapsulation over Satellite

Alert systems are key elements for effective management of a disaster. They are used to alert citizens and professional responders. Alert systems should be robust, multi-modal and simple. Satellites are resilient to Earth damages and display an inherent broadcast capability. For these reasons, satellite systems are suited for alert systems either as primary or backup technology. This contribution proposes a flexible encapsulation scheme called MAMES (Multiple Alert Message Encapsulation over Satellite) for transporting alert messages over satellite links. This encapsulation scheme features an optimised byte footprint and is agnostic with respect to the type of alert messages and satellite transmission technology. It can support all the necessary mechanisms to comply with the needs of alert transmission: reliability, prioritisation, geocasting. MAMES specification is currently handled by the SES/SatEC (Satellite Emergency Communications) working group within ETSI.

Hybrid satellite/terrestrial telemedicine services: Network requirements and architecture

This paper proposes a novel, interactive telemedicine platform, providing real-time audio and video interactions among patients, physicians and health service provider. Such a system has been developed within the framework of the European Space Agency (ESA) project TElemedicine Services for HEALTH (TESHEALTH) in collaboration among industry, academia, and hospitals. In particular, in the framework of the project, all citizens from many different sites have the same opportunity to access services promoting disease prevention and healthy life style, and professional users (specialists, physicians, operators) can exploit the platform to accomplish clinical studies and medical research. In such a context, an IP-based heterogeneous network architecture, composed of both satellite and terrestrial components, is considered in order to provide properly the TESHEALTH services. The paper presents the network parameters, the user requirements, and the hybrid satellite/terrestrial network architecture of the TESHEALTH platform. In addition, the platform offers Quality-of-Service, tailored to the individual user profiles and services, as well.

Cooperative Strategies for Satellite Access

Satellite communications have become an important node of the global telecommunication infrastructure. Satellite capacity request is growing quickly, driven not only by broadcast applications but, mainly, by broadband services, in particular by the expectation of “always-on” broadband services available everywhere. Thus, new “killer” applications such as HDTV (High Definition Digital Television) and broadband Internet access, provided through satellites, can help to face the growth of capacity demand foreseen in the near future. Moreover, in addition to the provision of satellite multimedia services to fixed terminals, there is an increasing demand for broadband communications on the move (i.e. on ships, trains, aircrafts, vans, cars). Analysing such an increasing demand of satellite communications, the work reported in this chapter is focused on the study of different techniques which allow the improvement of the performance of satellite users displaced in severe environments. The analysis of this context, in fact, has revealed the need to adopt adequate advanced techniques to achieve a sufficient quality in satellite links, especially in those scenarios where the link budget is tighter, such as, for example, the mobile satellite one. These considerations havemotivated the study of cooperative strategies which allow the mitigation of the deleterious effects of fading. This is obtained thanks to a new form of spatial diversity in which the diversity gain can be achieved through the cooperation of different users which generate a virtual MIMO (Multiple-Input MultipleOutput) system. The adoption of these methodologies can be very helpful in those scenarios characterised by continuous occurrences of NLOS (Non-line-of-sight) and LOS (Line-of-sight) channel conditions and, therefore, it is interesting to assess their implementation in critical satellite contexts. Considering such a context, the chapter will investigate the adoption of different cooperative techniques in some satellite access scenarios, pointing out its advantages and drawbacks. The chapter is organised as follows. Starting from the identification of critical issues in different satellite access scenarios, reported in Section 2, a general overview on cooperative strategies and, in particular, on the selected cooperative approaches, is provided in Section 3. Then, Section 4 and Section 5 report some different satellite case studies in order to show the advantages of using this kind of approach in uplink and in downlink satellite access, respectively. Finally, Section 6 provides some concluding remarks. 3

Iterative Demapping and Decoding for DVB-S2 Communications

In this paper an original detection strategy for Satellite Digital Broadcasting communications is definited: particularly, we consider the DVB-S2 system, which is proposed as a development of the DVB systems and exploits iterative decoding and higher order modulation; these features allow the derivation of advanced detectors which are based on an iterative demapping and decoding approach. The adoption of this strategy approaches permits a remarkable performance gain and an improvement of the system throughput.

Soft Demapping and Iterative Decoding for Satellite Communications

In this paper an original detection strategy for satellite digital broadcasting communications is defined; particularly, we consider the DVB-S2 system, which is proposed as a development of the DVB systems and exploits iterative decoding and higher order modulation. The proposed approach relies on the use of the information which can be obtained by proper soft demapping schemes. Moreover, we introduce an original receiver which is based on iterative demapping and decoding. The adoption of these strategies permits a remarkable performance gain and an improvement of the system throughput.

Flexible and Dynamic Use of Spectrum: The Cognitive Radio Approach

In the future, the increasing and continuous demand of services anytime and anywhere and, therefore, the mandatory globalization of mobile and wireless communications for next generation networks services will require a more and more efficient use of the scarce radio spectrum resources. The traditional communication systems which imply an a priori association of the frequency band, the service assigned to it and the technology used, need to become much more flexible, efficient and easy-to-use dynamic systems able to cope with the requirements and constraints of the environment and the users. A Cognitive Radio (CR) approach can be considered as a promising and suitable solution to solve this problem. The CR technologies are able to modify this current communication paradigm because they define a system able to sense the electromagnetic environment (spectrum sensing), detect the spectral resources actually occupied in a given temporal interval and in a given location, and use the free bands (holes) for its own communication.