Vincenzo Icolari

An interference estimation technique for Satellite cognitive radio systems

The increasing request of communication capacity for the introduction of modern multimedia services has collided with the problem of the spectrum shortage. One of the most known approach is represented by cognitive radios, which are supposed to exploit already deployed frequency bands in use by an incumbent system. Among other cognitive radio features, detection and estimation of the incumbent user are essential for implementing the cognitive radio system avoiding any interference. This is particularly important in SatCom cognitive scenarios due to transmission power impairments. In this paper, we focus on a joint interference and noise estimation algorithm aiming at detecting and estimating incumbent interference, for allowing the coexistence of the two systems. The behavior of the algorithm is analytically derived, and numerical results obtained through computer simulations confirm the effectiveness of the proposed approach.

An energy detector based radio environment mapping technique for cognitive satellite systems

The increasing request of bandwidth for multimedia advanced services is one of the major issues of modern wireless systems. The spectrum shortage has been faced in several ways; among others the cognitive radio approach, aiming to exploit the unused spectrum resources already assigned to incumbent users, is maybe the most known. However, even if its application has been extensively proposed for wireless terrestrial communications, it remains a still unexplored area concerning Satellite Communications. The aim of this paper is to propose an Energy Detector based Radio Environment Mapping for the spectrum awareness functionality of a hybrid terrestrial/satellite scenario where the satellite components aim at exploiting the resources unused by terrestrial communications. The proposed approach allows to take advantage of cooperation between multiple sensing nodes evaluating spatial detection and false alarm probabilities besides their relationship with device detection and false alarm probabilities.

Beam pattern allocation strategies for satellite cognitive radio systems

One of the major enabler for future wireless communication technologies is spectrum sharing, allowing to effectively share spectrum portions among different services. Even if much more considered in wireless terrestrial communications, spectrum sharing is increasing importance also in satellite communications where the spectrum scarcity issue is arising; cognitive techniques are a promising tool to cope with this problem. Taking into account the wide coverage and the flexibility that multibeam satellite systems can provide, in this paper we propose an optimization strategy that allows to efficiently assigns spectrum portions and polarizations to the beams. The proposed strategy is based on the definition of a Quality Index and aims at evaluating the beam pattern that maximizes the coverage. Assessments and evaluations of the potential gain in spectrum usage are performed with respect to the considered scenario.

On the Feasibility of Interference Estimation Techniques in Cognitive Satellite Environments with Impairments

The increasing demand of wider frequency bands in wireless communications has lead in the last years to the introduction of novel techniques allowing to exploit more efficiently the radio spectrum. In particular, spectrum sharing is considered one of the key technologies for future wireless systems. Cognitive radio is considered the most important technique for efficiently allowing the spectrum sharing among heterogeneous systems. If on one hand the cognitive radio techniques have been extensively assessed in terrestrial communications, they remain quite an unexplored area in Satellite Communications (SatComs). In this paper an Interference Estimation technique for SatComs aiming to reuse the spectrum resources primarily allocated to terrestrial communications is discussed. In particular, its assessment in a realistic scenario, where multiple impairments are considered, is discussed.

Flexible precoding for mobile satellite system hot spots

To face the challenges of the new era of heterogeneous networks, mobile satellite systems need to provide an increased level of flexibility. As a consequence, a more effective use of the available resources and the exploitation of interference mitigation techniques are considered necessary to tackle the issue. The limits of a traditional configuration are even more noticeable in specific areas of high traffic requests i.e., in hot spots. In this paper, focusing on the forward link of a typical mobile interactive satellite system operating in L-band, where a large imbalance in traffic demand between the multiple beams is common, new configurations that aim at improving the performance of the system are studied. The proposed approach, based on a higher frequency reuse factor and the application of precoding techniques, boosts the system in terms of total capacity and provides higher flexibility, without making any change whatsoever to the space segment. A general analytic formulation of the problem and a pragmatic solution are provided for hot spot scenarios. Simulations are carried out to validate the proposed solution.

Spectrum awareness techniques for 5G satellite communications

5G communications will enable new paradigms architectures and services, and the integration of satellite and terrestrial networks can play a key role. Cognitive radios are seen as the most promising solution to dynamically cooperate, in order to exploit advanced frequency sharing techniques. To this end, efficient sensing techniques for spectrum awareness are a must. In this paper, we provide preliminary results on energy detection (ED) and cyclostationary feature detection (CFD) algorithms applied to a downlink Ka-band scenario. These results show that coexistence between satellite and terrestrial networks is possible and cognitive radios can ease their integration in future 5G communications.

Extending the Usable Ka Band Spectrum for Satellite Communications: The CoRaSat Project

Broadband access by satellite in Ka band will become constrained by spectrum availability. In this context, the EU FP7 project CoRaSat is examining the possible spectrum extension opportunities that could be exploited by a database or sensing approach in Ka band via the use of cognitive mechanisms. The database/sensing approach utilises spectrum sharing scenarios between Fixed Satellite Services (FSS), Fixed Services (FS) and Broadcast Satellite Service (BSS) feeder links are considered. Data bases and spectrum sensing have been evaluated to determine white spaces across the shared spectrum for several EU countries. Resource allocation schemes are investigated to place the carriers in the white spaces so as to maximize the throughput of the system. A multibeam satellite system model has been used to demonstrate the capacity gains that can be achieved by using the cognitive schemes. The overall system is being demonstrated in a laboratory trial.

Precoding, Scheduling, and Link Adaptation in Mobile Interactive Multibeam Satellite Systems

This paper deals with the problem of precoding, scheduling, and link adaptation in next generation mobile interactive multibeam satellite systems. In contrast to the fixed satellite services, when the user terminals move across the coverage area, additional challenges appear. Due to the time varying channel, the gateway has only access to a delayed version of the channel state information (CSI), which can eventually limit the overall system performance. However, in contrast to general multiuser multiple-input multiple-output terrestrial systems, the CSI degradation in multibeam mobile applications has a very limited impact for typical fading channel and system assumptions. Under realistic conditions, the numerical results show that precoding can offer an attractive gain in the system throughput compared with the conservative frequency reuse allocations.

Genetic inspired scheduling algorithm for cognitive satellite systems

Wireless communication systems are predicted to appear massively in the future human life. In case of 5G communications, high expectations in terms of Quality of Service and reliability are foreseen. However, the development of future systems has to cope with a better exploitation of the available resources. As a matter of fact, system coexistence and frequency sharing are two of the most promising approaches to achieve spectrum efficiency. Cognitive Radio (CR) is a key enabler of these approaches, which are also arising in Satellite Communications (SatComs). In this paper, a carrier allocation based scheduling algorithm inspired by genetic algorithms (GA) is proposed by taking into account different environment conditions and service requirements of the users of the cognitive satellite system.