36 research outputs found

    Field Measurements in Determining Incumbent Spectrum Utilization and Protection Criteria in Wireless Co-existence Studies

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    Studies of spectrum sharing and co-existence between different wireless communication systems are important, as the current aim is to optimize their spectrum utilization and shift from static exclusive spectrum allocation to more dynamic co-existence of different systems within same frequency bands. The main goal of this thesis is to provide measurement methodologies for obtaining realistic results in modeling incumbent spectrum utilization and in determining incumbent protection criteria. The following research questions are considered in this thesis: Q1) How should field measurements be conducted and used to model incumbent spectrum utilization? Q2) How should field measurements be conducted and used to determine protection criteria for incumbents in a co-existence scenario with mobile broadband? and Q3) Which licensing methods and technological solutions are feasible to enable spectrum sharing in frequency bands with incumbents? To answer to Q1, this thesis describes the development of a spectrum observatory network concept created through international collaboration and presents measurement methodologies, which allow to obtain realistic spectrum occupancy data over geographical areas using interference map concept. A cautious approach should be taken in making strong conclusions from previous single fixed location spectrum occupancy studies, and measurements covering larger geographical areas might be needed if the measurement results are to be used in making spectrum management decisions. The field interference measurements considered in Q2 are not covered well in the current research literature. The measurements are expensive to conduct as they require substantial human resources, test network infrastructure, professional level measurement devices and radio licenses. However, field measurements are needed to study and verify hypotheses from computer simulations or theoretical analyses in realistic operating conditions, as field measurement conditions can not or are not practical to be adequately modeled in simulations. This thesis proposes measurement methodologies to obtain realistic results from field interference measurements, taking into account the propagation environments and external sources of interference. Less expensive simulations and laboratory measurements should be used both to aid in the planning of field measurements and to complement the results obtained from field measurements. Q3 is investigated through several field interference measurement campaigns to determine incumbent protection criteria and by analyzing the spectrum observatory data to determine the occupancy and trends in incumbent spectrum utilization. The field interference measurement campaigns have been conducted in real TV White Space, LTE Supplemental Downlink and Licensed Shared Access test network environments, and the obtained measurement results have been contributed to the development of the European spectrum regulation. In addition, field measurements have been conducted to contribute to the development and technical validation of the spectrum sharing frameworks. This thesis also presents an overview of the current status and possible directions in spectrum sharing. In conclusion, no single spectrum sharing method can provide universally optimal efficiency in spectrum utilization. Thus, an appropriate spectrum sharing framework should be chosen taking into account both the spectrum utilization of the current incumbents and the future needs in wireless communications.Siirretty Doriast

    Survey of Spectrum Sharing for Inter-Technology Coexistence

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    Increasing capacity demands in emerging wireless technologies are expected to be met by network densification and spectrum bands open to multiple technologies. These will, in turn, increase the level of interference and also result in more complex inter-technology interactions, which will need to be managed through spectrum sharing mechanisms. Consequently, novel spectrum sharing mechanisms should be designed to allow spectrum access for multiple technologies, while efficiently utilizing the spectrum resources overall. Importantly, it is not trivial to design such efficient mechanisms, not only due to technical aspects, but also due to regulatory and business model constraints. In this survey we address spectrum sharing mechanisms for wireless inter-technology coexistence by means of a technology circle that incorporates in a unified, system-level view the technical and non-technical aspects. We thus systematically explore the spectrum sharing design space consisting of parameters at different layers. Using this framework, we present a literature review on inter-technology coexistence with a focus on wireless technologies with equal spectrum access rights, i.e. (i) primary/primary, (ii) secondary/secondary, and (iii) technologies operating in a spectrum commons. Moreover, we reflect on our literature review to identify possible spectrum sharing design solutions and performance evaluation approaches useful for future coexistence cases. Finally, we discuss spectrum sharing design challenges and suggest future research directions

    Uplink Transmission Control Methods in LSA-Enabled Cellular Networks

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    As of now, multiple approaches to increasing network throughput are being studied. For instance, mmWave communications are expected to deliver increase in network throughput to 7 Gbps over 60 and 28 GHz. As a consequence of increasing frequency, the range of communication decreases, but new possibilities arise, such as directional transmissions. Another approach is offloading traffic onto neighbors in case they are connected to a faster link. In case of mobile devices it leads to decreased battery lifetime and increase of power consumption. Another approach is reusing stale bands that were reserved for services that are obsolete and/or defunct. However, there are cases when stale bands are allocated to services that are not defunct, but their activity is low. In this case, it is impossible to reallocate the bands. Despite that, it is still possible to use these bands by using LSA approach by sharing bands between the original owner (incumbent) and licensee. Licensee will need to satisfy the terms of the licensed sharing by keeping the interference power below the threshold and vacating the bands when latter are requested by incumbent. Hence, we must not use shared bands for delay-sensitive traffic or mission-critical services. One possible application of LTE LSA is non-critical IoT devices that are linked to the power grid (weather stations). Therefore, we should balance between satisfying license agreement terms and keeping the network operational. We also need to realize that LSA approach can be applied in cases when location of the incumbent changes rapidly. In this work, power control methods developed for LSA-enabled cellular networks are given. These methods were built for dynamic LSA scenarios, when position of the incumbent changes rapidly and licensee has to readjust power limits on the infrastructure. Aside from that, some minor improvements that were done to the algorithms are described, as well as practical operation example is shown

    Database-assisted spectrum sharing in satellite communications:A survey

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    This survey paper discusses the feasibility of sharing the spectrum between satellite telecommunication networks and terrestrial and other satellite networks on the basis of a comprehensive study carried out as part of the European Space Agency's (ESA) Advanced Research in Telecommunications Systems (ARTES) programme. The main area of investigation is the use of spectrum databases to enable a controlled sharing environment. Future satellite systems can largely benefit from the ability to access spectrum bands other than the dedicated licensed spectrum band. Potential spectrum sharing scenarios are classified as: a) secondary use of the satellite spectrum by terrestrial systems, b) satellite system as a secondary user of spectrum, c) extension of a terrestrial network by using the satellite network, and d) two satellite systems sharing the same spectrum. We define practical use cases for each scenario and identify suitable techniques. The proposed scenarios and use cases cover several frequency bands and satellite orbits. Out of all the scenarios reviewed, owing to the announcement of many different mega-constellation satellite networks, we focus on analysing the feasibility of spectrum sharing between geostationary orbit (GSO) and non-geostationary orbit (NGSO) satellite systems. The performance is primarily analysed on the basis of widely accepted recommendations of the Radiocommunications Sector of the International Telecommunications Union (ITU-R). Finally, future research directions are identified

    Spectrum Sharing and SAS-CBSD Interface Simulation

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    Spectrum Sharing technologies enables more dynamic spectrum management regulation and framework to provide capacity for the ever-increasing demand of mobile data traffic. This thesis reviewed the background and current state of the development of Spectrum Sharing approaches. TVWS, LSA and CBRS were examined in detail as the most representative solutions. The thesis compared architectural similarities and differences between LSA and CBRS. The thesis reviewed SAS-CBSD interface protocol and continued with a practical validation of SAS-CBSD interface specification. By implementing the interface in Python, interface simulation was conducted via the assistance of automation scripts. The thesis concluded that the SAS-CBSD interface is functioning as designed, noting that ESC will further extend the spectrum access dynamism. The thesis also pointed out the need to specify SAS-relevant data models for database API standardization

    On the efficiency of dynamic licensed shared access for 5G/6G wireless communications

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    The licensed shared access (LSA) is a spectrum licensing scheme authorizing additional new users (the licensees) to dynamically share the same spectrum with the old users (the incumbents). Contained in the terms of the spectrum usage authorization is a set of strict protective measures for the incumbent system which introduce extra restrictions on the licensee operations. Such measures imply that the licensee’s access to the spectrum can be revoked or restricted at any time which may result in the degradation of critical performance metrics of the latter. Addressing this issue and the accompanying challenges as we enter the 5G zettabytes era motivates the research problems addressed in this thesis. A vertical LSA spectrum sharing involving a mobile network operator (MNO) as the licensee and two categories of incumbent including the aeronautical telemetry, and a group of terrestrial public and ancillary wireless services is adopted in this thesis. Firstly, an analytical examination of the uplink and downlink licensee’s transmit power, when its spectrum access right is revoked (i.e., the limited transmit power) is done. Then a power allocation scheme that maximizes the energy efficiency (EE) of the licensee when it is operating with limited transmit power is proposed. Simulation results reveal the impact of the LSA spectrum access revocation on the allowable transmit power of the licensee as a function of the effect of different interference propagation path and the transmission direction. A comparison of the proposed optimal power allocation method with the equal power allocation (EPA) method further shows considerable improvement in the achievable EE of the licensee. Furthermore, in the LSA, the achievable spectrum efficiency (SE) of the licensee is limited by the interference threshold constraint set by the incumbent’s protective measures. Consequent on this, we propose an SE maximization of the licensee’s system subject to the incumbent interference threshold constraint. Furthermore, the LSA band spectral utilization was characterised as a function of the licensee’s achievable SE and the statistics of the LSA spectrum availability. The obtained results provide quantitative insights for practical system design and deployment of the LSA system, especially when compared to the results obtained in the maximization of the EE. In particular, the effect of variations in critical operational parameters throws up interesting network design trade-off challenge, worthy of consideration. This informs the subsequent multi objective optimization of the EE-SE trade-off investigated next. Interestingly, the obtained results indicate that with careful selection of the licensee eNodeB coverage radius, transmit power, and number of user equipment per eNodeB coverage area, one can engineer the best possible trade-off between the spectrum and energy efficiency in practical LSA deployment. A major LSA feature is guaranteeing predictable quality of service (QoS) for both the incumbent and the licensee systems. In terrestrial implementation, the reduction in the achievable data rate caused by the incumbents’ protective measures, may violate guaranteed QoS in the licensee system. To address this issue, we propose a LSA - based hybrid aerialterrestrial system with drone base station (D-BS). Simulation results show that using the proposed scheme, the licensee, when operating under the incumbents’ imposed restrictions, is able to achieve the QoS data rate requirements of the users on its network. In conclusion, the findings in this research indicates that the dynamic LSA is a practically viable solution to the spectrum management requirements of the emerging vertical wireless technologies in 5G and beyond

    5G and beyond networks

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    This chapter investigates the Network Layer aspects that will characterize the merger of the cellular paradigm and the IoT architectures, in the context of the evolution towards 5G-and-beyond, including some promising emerging services as Unmanned Aerial Vehicles or Base Stations, and V2X communications

    Spectrum sharing and management techniques in mobile networks

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    Το φάσμα συχνοτήτων αποδεικνύεται σπάνιο κομμάτι για τους πόρους ενός κινητού δικτύου το οποίο πρέπει να ληφθεί υπόψιν στη σχεδίαση τηλεπικοινωνιακών συστημάτων 5ης γενιάς. Επιπλέον οι πάροχοι κινητών δικτύων θα πρέπει να επαναπροσδιορίσουν επιχειρησιακά μοντέλα τα οποία μέχρι τώρα δεν θεωρούνταν αναγκαία (π.χ., γνωσιακά ραδιοδίκτυα), ή να εξετάσουν την υιοθέτηση νέων μοντέλων που αναδεικνύονται (π.χ., αδειοδοτούμενη από κοινού πρόσβαση) ώστε να καλύψουν τις ολοένα αυξανόμενες ανάγκες για εύρος ζώνης. Ο μερισμός φάσματος θεωρείται αναπόφευκτος για συστήματα 5G και η διατριβή παρέχει λύση για προσαρμοστικό μερισμό φάσματος με πολλαπλά καθεστώτα εξουσιοδότησης, βάσει ενός καινοτόμου αρχιτεκτονικού πλαισίου το οποίο επιτρέπει στα δικτυακά στοιχεία να λαμβάνουν αποφάσεις για απόκτηση φάσματος. Η προτεινόμενη διαδικασία λήψης αποφάσεων είναι μία καινοτόμα τεχνική προσαρμοστικού μερισμού φάσματος βασιζόμενη σε ελεγκτές ασαφούς λογικής που καθορίζονν το καταλληλότερο σχήμα μερισμού φάσματος και σε ενισχυμένη μάθηση που ρυθμίζει τους κανόνες ασαφούς λογικής, στοχεύοντας να βρει τη βέλτιστη πολιτική που πρέπει να ακολουθεί ο πάροχος ώστε να προσφέρει την επιθυμητή ποιότητα υπηρεσιών στους χρήστες, διατηρώντας πόρους (οικονομικούς ή ραδιοπόρους) όπου είναι εφικτό. Η τελευταία συνεισφορά της διατριβής είναι ένας μηχανισμός που εξασφαλίζει δίκαιη πρόσβαση σε φάσμα ανάμεσα σε χρήστες σε σενάρια στα οποία η εκχώρηση άδειας χρήσης φάσματος δεν είναι προαπαιτούμενη.Radio spectrum has loomed out to be a scarce resource that needs to be carefully considered when designing 5G communication systems and Mobile Network Operators (MNOs) will need to revisit business models that were not of their prior interest (e.g. Cognitive Radio) or consider adopting new business models that emerge (e.g. Licensed Shared Access) so as to cover the extended capacity needs. Spectrum sharing is considered unavoidable for 5G systems and this thesis provides a solution for adaptive spectrum sharing under multiple authorization regimes based on a novel architecture framework that enables network elements to proceed in decisions for spectrum acquisition. The decision making process for spectrum acquisition proposed is a novel Adaptive Spectrum Sharing technique that uses Fuzzy Logic controllers to determine the most suitable spectrum sharing option and reinforcement learning to tune the fuzzy logic rules, aiming to find an optimal policy that MNO should follow in order to offer the desirable Quality of Service to its users, while preserving resources (either economical, or radio) when possible. The final contribution of this thesis is a mechanism that ensures fair access to spectrum among the users in scenarios in which conveying spectrum license is not prerequisite
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