Cognitive-Based Solutions to Spectrum Issues in Future Satellite Communication Systems

With particular attention to Satellite Communications (SatComs), cognitive-based solutions are investigated. With cognitive-based solutions we refer to all those techniques that aim at improving spectrum utilization of the available spectrum and rely on the knowledge of the environment in which the systems operate. As a matter of fact, an improved spectrum utilization enables higher throughput capacities that will satisfy the future markets and demands of an increasingly connected world. Throughout the thesis, several techniques are proposed, developed, and assessed with respect to specific scenarios of interest. Particular focus has been put on spectrum awareness techniques for system coexistence, and on spectrum exploitation techniques for an improved efficiency in terms of resource utilization

Co-existence of the still used and upcoming digital terrestrial television and mobile communication services

Táto práca sa zaoberá skúmaním, meraním a vyhodnotením možných koexistenčných scenárov, ktoré sa môžu vyskytnúť medzi terestriálnou digitálnou televíziou (DVB-T/T2) a mobilnými bezdrôtovými službami, poskytovaný štandardom LTE. Štandardy DVB-T/T2 a LTE sú stručne popísané a sú definované rádiofrekvenčné pásma, kde sa ich služby vysielajú. Na základe jednotlivých frekvenčných pásiem sú definované možné koexistenčné scenáre. Pre meranie, monitorovanie a vyhodnotenie definovaných koexistenčných scenárov je navrhnuté a realizované vhodné laboratórne pracovisko. Výsledky z merania ukazujú rôzne ovplyvňovanie kvality a chybovosti DVB-T/T2 signálu v závislosti uvažovaného koexistenčného scenára.This work deals with exploring, measuring and evaluation of possible coexistence scenarios between terrestrial digital TV (DVB-T/HT2) and mobile wireless services (GSM, LTE), which can occur in a shared RF frequency bands The DVB-T, DVB-T2 and LTE standards are briefly described. RF band, where these systems are operated, are outlined too. . There are defined different coexistence scenarios. For the measuring, monitoring and evaluation of these scenarios, an appropriate laboratory workplace is proposed and realized. Results from the measurements show various influence of interfering mobile services on the interacted DVB-T/H system, depending on the considered coexistence scenario.

D13.1 Fundamental issues on energy- and bandwidth-efficient communications and networking

Deliverable D13.1 del projecte europeu NEWCOM#The report presents the current status in the research area of energy- and bandwidth-efficient communications and networking and highlights the fundamental issues still open for further investigation. Furthermore, the report presents the Joint Research Activities (JRAs) which will be performed within WP1.3. For each activity there is the description, the identification of the adherence with the identified fundamental open issues, a presentation of the initial results, and a roadmap for the planned joint research work in each topic.Preprin

Radio Communications

In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks

Potentzia domeinuko NOMA 5G sareetarako eta haratago

Tesis inglés 268 p. -- Tesis euskera 274 p.During the last decade, the amount of data carried over wireless networks has grown exponentially. Several reasons have led to this situation, but the most influential ones are the massive deployment of devices connected to the network and the constant evolution in the services offered. In this context, 5G targets the correct implementation of every application integrated into the use cases. Nevertheless, the biggest challenge to make ITU-R defined cases (eMBB, URLLC and mMTC) a reality is the improvement in spectral efficiency. Therefore, in this thesis, a combination of two mechanisms is proposed to improve spectral efficiency: Non-Orthogonal Multiple Access (NOMA) techniques and Radio Resource Management (RRM) schemes. Specifically, NOMA transmits simultaneously several layered data flows so that the whole bandwidth is used throughout the entire time to deliver more than one service simultaneously. Then, RRM schemes provide efficient management and distribution of radio resources among network users. Although NOMA techniques and RRM schemes can be very advantageous in all use cases, this thesis focuses on making contributions in eMBB and URLLC environments and proposing solutions to communications that are expected to be relevant in 6G

Physical Layer Challenges and Solutions in Seamless Positioning via GNSS, Cellular and WLAN Systems

As different positioning applications have started to be a common part of our lives, positioning methods have to cope with increasing demands. Global Navigation Satellite System (GNSS) can offer accurate location estimate outdoors, but achieving seamless large-scale indoor localization remains still a challenging topic. The requirements for simple and cost-effective indoor positioning system have led to the utilization of wireless systems already available, such as cellular networks and Wireless Local Area Network (WLAN). One common approach with the advantage of a large-scale standard-independent implementation is based on the Received Signal Strength (RSS) measurements.This thesis addresses both GNSS and non-GNSS positioning algorithms and aims to offer a compact overview of the wireless localization issues, concentrating on some of the major challenges and solutions in GNSS and RSS-based positioning. The GNSS-related challenges addressed here refer to the channel modelling part for indoor GNSS and to the acquisition part in High Sensitivity (HS)-GNSS. The RSSrelated challenges addressed here refer to the data collection and calibration, channel effects such as path loss and shadowing, and three-dimensional indoor positioning estimation.This thesis presents a measurement-based analysis of indoor channel models for GNSS signals and of path loss and shadowing models for WLAN and cellular signals. Novel low-complexity acquisition algorithms are developed for HS-GNSS. In addition, a solution to transmitter topology evaluation and database reduction solutions for large-scale mobile-centric RSS-based positioning are proposed. This thesis also studies the effect of RSS offsets in the calibration phase and various floor estimators, and offers an extensive comparison of different RSS-based positioning algorithms

User-centric power-friendly quality-based network selection strategy for heterogeneous wireless environments

The ‘Always Best Connected’ vision is built around the scenario of a mobile user seamlessly roaming within a multi-operator multi-technology multi-terminal multi-application multi-user environment supported by the next generation of wireless networks. In this heterogeneous environment, users equipped with multi-mode wireless mobile devices will access rich media services via one or more access networks. All these access networks may differ in terms of technology, coverage range, available bandwidth, operator, monetary cost, energy usage etc. In this context, there is a need for a smart network selection decision to be made, to choose the best available network option to cater for the user’s current application and requirements. The decision is a difficult one, especially given the number and dynamics of the possible input parameters. What parameters are used and how those parameters model the application requirements and user needs is important. Also, game theory approaches can be used to model and analyze the cooperative or competitive interaction between the rational decision makers involved, which are users, seeking to get good service quality at good value prices, and/or the network operators, trying to increase their revenue. This thesis presents the roadmap towards an ‘Always Best Connected’ environment. The proposed solution includes an Adapt-or-Handover solution which makes use of a Signal Strength-based Adaptive Multimedia Delivery mechanism (SAMMy) and a Power-Friendly Access Network Selection Strategy (PoFANS) in order to help the user in taking decisions, and to improve the energy efficiency at the end-user mobile device. A Reputation-based System is proposed, which models the user-network interaction as a repeated cooperative game following the repeated Prisoner’s Dilemma game from Game Theory. It combines reputation-based systems, game theory and a network selection mechanism in order to create a reputation-based heterogeneous environment. In this environment, the users keep track of their individual history with the visited networks. Every time, a user connects to a network the user-network interaction game is played. The outcome of the game is a network reputation factor which reflects the network’s previous behavior in assuring service guarantees to the user. The network reputation factor will impact the decision taken by the user next time, when he/she will have to decide whether to connect or not to that specific network. The performance of the proposed solutions was evaluated through in-depth analysis and both simulation-based and experimental-oriented testing. The results clearly show improved performance of the proposed solutions in comparison with other similar state-of-the-art solutions. An energy consumption study for a Google Nexus One streaming adaptive multimedia was performed, and a comprehensive survey on related Game Theory research are provided as part of the work

Tri-Orthogonal Polarisation Diverse Communications

This thesis investigates improving communication link coverage through triorthogonal polarisation diversity. Tri-orthogonal polarisation diversity exploits radiated electromagnetic energy transmission and reception in three orthogonal spatial directions with an aim to provide enhanced communication link performance. Original contributions to this branch of diversity are presented in areas of both software and hardware design. First, simulations are presented highlighting the benefit of tri-orthogonal polarisation diversity at both the transmitter and receiver over a range of terrestrial channel conditions. The results are presented in an easily understandable graphical format that results from a novel model design considering all antenna orientations. Orientation robustness at the antenna is demonstrated as a consequence of a tri-orthgonal polarisation diverse approach. Second, additional research is performed in order to extend the model into the field of satellite systems. The ionosphere is required to be modelled, and this is performed according to a novel vectorised approach using realtime ionospheric data and terrestrial magnetic field appreciation. Third, ionospheric modelling is incorporated into a non-geosynchronous satellite orbit channel model that provides an insight into the benefit of applying a tri-orthogonal polarisation diverse approach uniquely at the receiver. Novelty is provided in the form of a vectorised approach to simulation covering all antenna orientations in a field-ofview as observed from a satellite transmitter. This is extended over the orbits of three distinct satellite systems. Output is provided in graphical format and conclusions are drawn form the data which suggest that a tri-orthogonal polarisation diverse approach applied at the receiver provides an increase in reception performance. Fourth, an antenna is designed, simulated, constructed and tested that provides three orthogonal polarisations in a phase-centred differentially-fed package. Novelty is provided in the design being planar in nature, with three orthogonal modes being able to be transmitted from a single slot. Results emanating from the testing procedure demonstrate the benefits of the design in terms of diversity and extension to beamforming applications. Fifth, as an extension to the antenna design, a circularly polarised feeding arrangement is used together with an omnidirectional vertically polarised mode feed in an antenna and feed combination. This provides the possibility of a direct comparison with conventional circularly polarised techniques, such as those used in both terrestrial and satellite receive antennas. Sixth, the operational bandwidth of the omnidirectional vertically polarised mode is extended by adapting the design of the cavity wall resonating slots in a substrateintegrated monopole antenna while maintaining a planar structure. The electric monopole design demonstrates an increase in operating bandwidth from 2.5% to 56%. In the thesis, a tri-orthogonal polarisation diverse approach is shown to be beneficial to signal reception over a range of channels, both in the areas of terrestrial and satellite communications. The concept is demonstrated to be feasible in a planar structure. Triorthogonal polarisation diversity is likely to play an increasing role in the future as systems look to cope with an ever increasing data flow. The demand for content on mobile devices has forced massive growth in mobile data over the past two decades. This growth has recently reached saturation point, and so new avenues for extending growth have to be considered. A search for available bandwidth has lead research to focus on the mmWave section of the electromagnetic spectrum. The advent of the next generation of wireless connectivity, dubbed fifth generation or 5G, is now upon us (Rappaport et al. 2013b). With data traffic set to multiply by up to one thousand fold by 2020 (Qualcomm Inc. Accessed: 2014b, Qualcomm Inc. Accessed: 2014a, Li et al. 2014, Chin et al. 2014), as The Internet of Things (Ashton 2009, Cisco Inc. Accessed: 2014, Gubbi et al. 2013) enters into the fray, an overhaul of wireless design is somewhat overdue. For static point-to-point, or LoS systems, challenges exist according to the channel environment and temporal changes that may occur within. For any network that has a mobile component built in, where spatial position and alignment of transmitter and receiver change over time, signal propagation is additionally influenced by link geometry. In an increasingly mobile world, this presents challenges as increased coverage, one of the main focus points of the 5G system, will require efficient use of radiated electromagnetic energy. Conventional techniques for improving data rate have typically aimed at increasing performance at the transmitter. For terrestrial networks, a transmitter is typically stationary. Performance outweighs size constraints and so power amplification and combination may be used to excite antennas that flood a network cell with a strong linearly polarised transmitted signal. For commercial providers, this has proved a very successful technique, mainly as a result of the majority of wireless subscribers living in dense urban environments. For a linearly polarised wave, operating at conventional operating frequencies around 2 GHz, and transmitted with relatively high power, the urban environment typically provides assistance for signal reception at the receiver through diversity brought about by reflection, refraction and scattering or multipath due to the presence of buildings. Small misalignments in transmit and receive antennas are mitigated as the propagating signal wavelength is large and a relatively high transmit power establishes a relatively high signal-to-noise ratio, providing useful multipath effects over the channel. At certain receive positions, channel fading may occur when superposition of received multipath components effectively cancel each other. This may be mitigated through additional transmitters that are spaced appropriately; a concept known as spatial diversity that has been cited at mmWave frequencies (Smulders 2002, Park and Pan 2012). Diversity of signal is important in that it offers a greater possibility of a signal being received due to individuality of uncorrelated channel propagation for each diverse signal component. As more content is demanded by subscribers within an ever shrinking timeframe, a higher frequency of operation is typically required for a carrier wave capable of providing this service. Add in the context of mobility, and issues quickly appear. Beneficial effects on a linearly polarised signal operating at conventional low gigahertz frequencies arising from reflection, refraction, and scattering or multipath effects, assist signal reception. Relatively long wavelengths are subjected to many scatterers, and due to the relatively high transmit power involved, scattering effects provide diversity at the receiver in the form of many smaller receivable diverse signal components. These signal components are superpositioned either constructively or destructively, after diverse individual propagation through the channel, at the receiver to provide signal reception. At mmWave frequencies, due to a shrinking wavelength, the following issues arise: • increased path loss over a defined range due to spreading loss (Pozar 2011), and increased atmospheric absorption (Liebe et al. 1989). An obvious solution is to provide more transmit power at the transmitter. At higher frequencies, miniaturisation of devices limits this possibility as heat sinking becomes problematic. Amplifier non-linearity and unwanted third order intermodulation impact on system performance (Niknejad and Hashemi 2008, Hashemi and Raman 2016) • the beneficial effect of multipath fading may not exist in a mmWave terrestrial channel (Pi and Khan 2011), as a smaller wavelength typically implies a reduced beamwidth and less scatterers available for the LoS signal to scatter into useful smaller diverse signal components. Due to a relatively low transmit power involved, any scattering of a LoS signal into smaller, weaker diverse signal components may result in no received signal. As a result, cell range is reduced and more transmitters are required to provide coverage over a network • with a shrinking wavelength, relatively lower transmit power, and increased mobility, antenna misalignment becomes problematic. A drive for radiated power efficiency is paramount in providing the next generation of wireless networks. An ability to transmit signals into and receive signals from all angles is necessary (Rappaport et al. 2013b). The terahertz range, for example, offers extremely high transfer rates, although any small misalignment greatly affects rate. The use of dielectric mirrors is required to effectively steer the transmitted signal to its destination. Mitigation of misalignment becomes important in maintaining system performance. For the next generation of mobile wireless systems to operate within the mmWave section of the electromagnetic spectrum, a solution to extend range is to increase radiated energy in a direction of propagation, through beam steering techniques. Within a mobile context, this poses challenges, not least as the link geometry is variable. For terrestrial networks, conventional transmitted waveforms are mainly vertically polarised, or circularly polarised, and as such are mainly one dimensional, or two dimensional at best, in performance. To provide the next generation of wireless networks, a third dimension needs to be considered to provide efficient use of radiated electromagnetic energy. Frequency bands of interest for 5G systems differ from country to country. According to the US Federal Communications Commission (FCC), the mmWave region that will be studied ranges from 24–80 GHz (Rappaport et al. 2013b, Rappaport Accessed: 2014, Above Ground Level Media Group Accessed: 2015). One of the aims of 5G is to improve coverage (Rappaport et al. 2013b). One method that is being considered is the joining of terrestrial and satellite services into one seamless network that may be readily accessed by the subscriber at the receiver (Evans et al. 2005, Evans et al. 2015, Federal Communications Commission Accessed: 2016). Satellite networks provide their own specific challenges, as transmit power is limited to payload specifications, and coverage typically requires a satellite that is moving relative to the Earth’s surface. Once again we find ourselves facing the same three issues that we encountered within the terrestrial context of a mmWave channel. If we are to increase link performance in a satellite channel to complement any improvement in terrestrial channels then the following points need to be considered: • propagation using higher operating frequencies typically suffers from higher path losses (Liebe et al. 1989, Pozar 2011). In some circumstances this can be mitigated by higher transmit power, but not all. A satellite payload is subject to a strict payload capacity and this restricts the size of transmit power devices and hence available transmit power that can be launched into orbit • a lack of beneficial reflectors, refractors, and scatterers is observed during channel propagation as the signal is typically LoS, narrow in beamwidth, and weak due to higher path loss and lower transmit power (Pi and Khan 2011). Multipath effects may degrade system performance as signals are weak • an evolving link geometry that affects antenna alignment. Linear and circular polarised signals are only two dimensional in nature. Three dimensions need to be considered, and beam steering of radiated power to provide the required range is a requirement (Evans et al. 2005, Hong et al. 2014b). To ensure that the next generation of mobile systems are fully mobile, while providing increased data rate, we need to consider diversity in three dimensions. Beam steering of a transmitted signal with high gain in the direction of a receiver is one viable option, and in the context of full mobility, three dimensional signal transmission and reception appears a logical step to achieving this (Hong et al. 2014a). While at a terrestrial transmitter, it is suggested that size is not a constraint, it remains so for a satellite transmitter, as it is at a mobile receiver. This rules out spatial diversity as an approach to increasing system performance. One approach of increasing diversity within a confined volume is through polarisation techniques (Vaughan 1990). In this thesis, we investigate the benefit of a subset of this approach—tri-orthogonal polarisation diversity (Andrews et al. 2001). In effect, the concept provides at least one additional degree of freedom or layer of diversity over conventional techniques such as circular polarisation. Due to orthogonality in three directions, this approach has a wide field of view, and potentially offers diversity and improved system performance through beam steering in any unit direction. Tri-orthogonal polarisation diversity may be applied either at the transmitter, at the receiver, or at both. In Chapter 1 of the thesis, both novel software and hardware aspects of the research are highlighted. Overall, the research outcomes of this thesis from both simulation and measured results suggest that the concept of tri-orthogonal polarisation diversity is: • beneficial to wireless performance over a majority of antenna orientations • plausible for implementation within typical antenna volume constraints.Thesis (Ph.D.) -- University of Adelaide, School of School of Electrical and Electronic Engineering, 201