146 research outputs found

    Assessing the transmission performance of iGMAS real-time data streams

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    Methods for Improving Performance in Consumer Grade GNSS Receivers

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    Viimeisten kolmen vuosikymmenen aikana satelliittinavigointi on kehittynyt ammatti ja sotilaskäyttäjien tekniikasta kaikkien saatavilla olevaksi tekniikaksi. Varsinkin viimeisen 15 vuoden aikana, kun vastaanottimet alkoivat pienentyä ja halpenivat, on lisääntynyt määrä yrityksiä, jotka toimittavat GPS-laitteita satoihin erilaisiin sovelluksiin. Kaikille moderneille tekniikoille on myös tyypillistä, että tutkimukseen ja siihen liittyvään vastaanottimien kehittämiseen on käytetty valtavasti rahaa, mikä on johtanut huomattavaan parantumiseen vastaanottimen suorituskyvyssä. GPS-vastaanottimien kehitystyön lisäksi uusien maailmanlaajuisten satelliittinavigointijärjestelmien, kuten venäläisen GLONASS, kiinalaisen BeiDou- ja eurooppalaisen Galileo-järjestelmien käyttöönotto tarjoaa entistä enemmän mahdollisuuksia suorituskyvyn parantamiseen. Sekä GPS että nämä uudet järjestelmät ovat myös ottaneet käyttöön uudentyyppisiä signaalirakenteita, jotka voivat tarjota parempilaatuisia havaintoja ja siten parantaa kaikkien vastaanottimien suorituskykyä. Lopuksi menetelmät, kuten PPP ja RTK, jotka aiemmin olivat varattu ammattikäyttäjille, ovat tulleet kuluttajamarkkinoille mahdollistaen ennennäkemättömän suorituskyvyn jokaiselle satelliittinavigointivastaanottimien käyttäjälle. Tässä opinnäytetyössä arvioidaan tämän kehityksen vaikutusta sekä suorituskykyyn että vastaanottimen arkkitehtuuriin. Työssä esitellään yksityiskohtaisesti FGI:ssä kehitetyn ohjelmistopohjaisen vastaanottimen, FGI-GSRx:n. Tämän vastaanottimen avulla on työssä arvioitu miten sekä uudet konstellaatiot että uudet nykyaikaiset signaalit ja niitten seurantamenetelmät vaikuttavat suorituskykyyn ja vastaanotin arkkitehtuuriin. Tämän lisäksi on arvioitu PPP- ja RTK-tarkkuuspaikannusmenetelmien vaikutus FinnRefCORS-verkkoa käyttäen useiden erityyppisten vastaanottimien kanssa, mukaan lukien kuluttajalaatuiset vastaanottimet. Tulokset osoittavat, että enemmän konstellaatioita ja signaaleja käytettäessä paikannusratkaisun tarkkuus paranee 3 metristä 1,4 metriin hyvissä olosuhteissa ja yli 10-kertaiseksi tiheästi rakennetuissa kaupungeissa, jossa käytettävissä olevien signaalien määrä kasvaa kertoimella 2 käytettäessä kolmea konstellaatiota. Uusia moderneja modulaatiotekniikoita, kuten BOC-modulaatiota, käytettäessä tulokset osoittavat Galileo-ratkaisun tarkkuuden paranevan lähes 25%:lla ja esitelty uusi signaalinkäsittelymenetelmä lisää tällaisen tarkkuuden saatavuutta 50%:sta lähes 100%:iin. Lopuksi tarkkuuspaikannusmenetelmien tulokset osoittavat, että 15 cm:n tarkkuus on saavutettavissa, mikä on merkittävä parannus verrattuna 1,4 metrin tarkkuuteen. Näiden parannusten saavuttamiseksi on olennaista, että itse vastaanotin on mukautettu hyödyntämään näitä uusia signaaleja ja konstellaatioita. Tämä tarkoittaa, että nykyaikaisten kuluttajamarkkinoiden vastaanottimien suunnittelu on haastavaa ja monissa tapauksissa ohjelmistopohjainen vastaanotin olisi parempi ja halvempi valinta kuin uusien mikropiirien kehittäminen.For the last three decades, satellite navigation has evolved from being a technology for professional and military users to a technology available for everyone. Especially during the last 15 years, since the receivers started getting smaller and cheaper, there has been an increasing number of companies delivering Global Positioning System (GPS) enabled devices for hundreds of different kind of applications. Typical for any modern technology, there has also been an enormous amount of money spent on research and accompanied receiver development resulting in an immense increase in receiver performance. In addition to the development efforts on GPS receivers the introduction of new global navigation satellite systems such as the Russian Globalnaja Navigatsionnaja Sputnikovaja Sistema (GLONASS), the Chinese BeiDou, and the European Galileo systems offers even more opportunities for improved performance. Both GPS and these new systems have also introduced new types of signal structures that can provide better quality observations and even further improve the performance of all receivers. Finally, methods like Precise Point Positioning (PPP) and Real Time Kinematic (RTK) that earlier were reserved for professional users have entered into the consumer market enabling never before seen performance for every user of satellite navigation receivers. This thesis will assess the impact of this development on both performance as well as on receiver architecture. The design of the software defined receiver developed at FGI, the FGI-GSRx, is presented in detail in this thesis. This receiver has then been used to assess the impact of using multiple constellations as well as new novel signal processing methods for modern signals. To evaluate the impact of PPP and RTK methods the FinnRef Continuously Operating Reference Station (CORS) network has been used together with several different types of receivers including consumer grade off the shelf receivers. The results show that when using more constellations and signals the accuracy of the positioning solution improves from3 meters to 1.4 meters in open sky conditions and by more than a factor 10 in severe urban canyons. For severe urban canyons the available also increases by a factor 2 when using three constellations. When using new modern modulation techniques like high order BOC results show an accuracy improvement for a Galileo solution of almost 25 % and the presented new signal processing method increase the availability of such an accuracy from 50 % to almost 100 %. Finally, results from precise point positioning methods show that an accuracy of 15 cm is achievable, which is a significant improvement compared to an accuracy of 1.4 m for a standalone multi constellation solution. To achieve these improvements, it is essential that the receiver itself is adapted to make use of these new signals and constellations. This means that the design of modern consumer market receivers is challenging and in many cases a software define receiver would be a better and cheaper choice than developing new Application Specific Integrated Circuit (ASIC)’s

    Cryptography Is Not Enough: Relay Attacks on Authenticated GNSS Signals

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    Civilian-GNSS is vulnerable to signal spoofing attacks, and countermeasures based on cryptographic authentication are being proposed to protect against these attacks. Both Galileo and GPS are currently testing broadcast authentication techniques based on the delayed key disclosure to validate the integrity of navigation messages. These authentication mechanisms have proven secure against record now and replay later attacks, as navigation messages become invalid after keys are released. This work analyzes the security guarantees of cryptographically protected GNSS signals and shows the possibility of spoofing a receiver to an arbitrary location without breaking any cryptographic operation. In contrast to prior work, we demonstrate the ability of an attacker to receive signals close to the victim receiver and generate spoofing signals for a different target location without modifying the navigation message contents. Our strategy exploits the essential common reception and transmission time method used to estimate pseudorange in GNSS receivers, thereby rendering any cryptographic authentication useless. We evaluate our attack on a commercial receiver (ublox M9N) and a software-defined GNSS receiver (GNSS-SDR) using a combination of open-source tools, commercial GNSS signal generators, and software-defined radio hardware platforms. Our results show that it is possible to spoof a victim receiver to locations around 4000 km away from the true location without requiring any high-speed communication networks or modifying the message contents. Through this work, we further highlight the fundamental limitations in securing a broadcast signaling-based localization system even if all communications are cryptographically protected

    Satellite-Based Communications Security: A Survey of Threats, Solutions, and Research Challenges

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    Satellite-based Communication systems are gaining renewed momentum in Industry and Academia, thanks to innovative services introduced by leading tech companies and the promising impact they can deliver towards the global connectivity objective tackled by early 6G initiatives. On the one hand, the emergence of new manufacturing processes and radio technologies promises to reduce service costs while guaranteeing outstanding communication latency, available bandwidth, flexibility, and coverage range. On the other hand, cybersecurity techniques and solutions applied in SATCOM links should be updated to reflect the substantial advancements in attacker capabilities characterizing the last two decades. However, business urgency and opportunities are leading operators towards challenging system trade-offs, resulting in an increased attack surface and a general relaxation of the available security services. In this paper, we tackle the cited problems and present a comprehensive survey on the link-layer security threats, solutions, and challenges faced when deploying and operating SATCOM systems.Specifically, we classify the literature on security for SATCOM systems into two main branches, i.e., physical-layer security and cryptography schemes.Then, we further identify specific research domains for each of the identified branches, focusing on dedicated security issues, including, e.g., physical-layer confidentiality, anti-jamming schemes, anti-spoofing strategies, and quantum-based key distribution schemes. For each of the above domains, we highlight the most essential techniques, peculiarities, advantages, disadvantages, lessons learned, and future directions.Finally, we also identify emerging research topics whose additional investigation by Academia and Industry could further attract researchers and investors, ultimately unleashing the full potential behind ubiquitous satellite communications.Comment: 72 page

    Next Generation Multi-System Multi-Frequency GNSS Receivers

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    Nowadays we have satellites available from GPS, GLONASS, Galileo and BeiDou systems. This will lead to an increased demand for solutions, which utilize multiple Global Navigation Satellite Systems (GNSS). Such solutions can have great market potential since they can be applied in numerous applications involving GNSS navigation, e.g. smartphones and car navigators. The aim of this thesis is to present the issues that arise in modern high sensitivity receivers, and to present research results of navigation algorithms suitable for the next generation multi-system multi-frequency GNSS receivers.With the availability of multiple satellites systems, the user benefits mostly from the improved visibility of the satellites. The increased availability of satellites naturally increases the computational requirements in the receiver. The main focus of the presented algorithms is on critical factors like provided accuracy versus low cost, low power consumption. In addition, the presented algorithms have been collected into a comprehensive navigation algorithm library where they have additional value for educational purposes.The presented navigation algorithms focus mainly in the GPS and Galileo systems, with the combination of L1/E1 & L5/E5a frequencies. A novel GPS + Galileo dual frequency receiver was developed by the team over the years. Where applicable, the thesis collects important facts from modern GLONASS and BeiDou systems.The first part of the thesis introduces all available open service signals from the GNSS systems, revealing how vast the scope of multi-system, multi-frequency receiver design is. The chapter continues with introduction to the basics of GNSS systems, and description of the problems that the receiver designer must overcome. The chapter further continues by describing a basic receiver architecture suitable for multi-system multi-frequency reception. The introductory part also has a short section is dedicated for underlining the importance of testing mechanisms for a novel receiver under development.The second part of the thesis concentrates on the baseband processing of the GNSS receiver. Topics cover acquisition and tracking, with multi-system multi-frequency implementation Abstract details kept in mind. The chapter also contains sections for issues that must be handled in high sensitivity receivers, e.g. cross-correlation and cycle slip detection. The second part of the thesis is concluded with a description how Assisted-GNSS capability would alter many of the design considerations.The third part of the thesis describes algorithms related to the data bit decoding issues. All the different satellite systems have their own low-level navigation data structure with additional layers of error detection / correction mechanisms. This part of the thesis provides the algorithms for successful decoding of the data.The final part of the thesis describes the basic navigation solution algorithms suitable for the mass-market receivers. In this part, the method of combining the measurements from the different satellite systems is discussed. Additionally, all the issues of processing multisystem signals are collected here, and in the end the Position, Velocity, and Time (PVT) solution is obtained

    GLONASS-satelliittipaikannussignaalin toteutus monijärjestelmä-ohjelmistosatelliittipaikannusvastaanottimessa

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    Global navigation satellite systems (GNSS) provide accurate positioning, navigation and timing anywhere on Earth. Several nations have developed their own systems. The most commonly used navigation satellite system is the Global Positioning System (GPS) provided for global use by the United States. The GLONASS system is the Russian counterpart of GPS. Other systems in development are the European Galileo and the Chinese BeiDou systems. The combined use of multiple GNSS offers many potential benefits, including improved availability, accuracy, reliability, and integrity. The use of software-defined GNSS receivers has been the focus of growing interest due to the ease of development of signal processing algorithms in software as compared to hardware. The software-defined GNSS receiver FGI-GSRx, which is used in this work, is a multi-constellation, multi-frequency software-defined receiver developed by the Finnish Geospatial Research Institute. It is a post-processing receiver developed in Matlab, currently capable of utilizing GPS, Galileo and BeiDou. This thesis presents implementation of a receiver software for the GLONASS satellite navigation system signal as part of the FGI-GSRx multi-constellation software-defined receiver. The implementation is limited to the GLONASS Standard Positioning Service signal on the L1 frequency. The implemented receiver is able to process digitized GLONASS signal samples and calculate a positioning solution. The work includes design, development, implementation, and verification of the receiver software. Verification results show that the receiver is able to acquire and track GLONASS signals and to use them to produce a combined GPS/GLONASS positioning solution. In addition, the receiver is used to test the impact of a GPS jammer on multi-GNSS positioning, showing results of the robustness benefits of adding multiple GNSS systems to into the positioning process.Satelliittinavigointijärjestelmät (GNSS) mahdollistavat tarkkoja paikannus-, navigointi- ja ajoituspalveluita kaikkialla maapallolla. Yleisimmin käytetty satelliittinavigointijärjestelmä on Yhdysvaltojen Global Positioning System (GPS). GLONASS-järjestelmä on Venäjän vastine GPS:lle. Muita järjestelmiä ovat EU:n Galileo ja Kiinan BeiDou. Useiden satelliittijärjestelmien yhteiskäyttö tarjoaa monia mahdollisia etuja, kuten parempi saatavuus, tarkkuus ja luotettavuus. Ohjelmistomääriteltyihin GNSS-vastaanottimiin on kohdistunut kasvavaa kiinnostusta johtuen signaalinkäsittelyalgoritmien kehityksen helppoudesta ohjelmistoissa verrattuna laitteistoon. Tässä työssä käytettävä GNSS-vastaanotin, FGI-GSRx, on ohjelmistomääritelty monijärjestelmä-monitaajuussatelliittinavigointivastaanotin, joka on kehitetty Maanmittauslaitoksen Paikkatietokeskuksessa. Se on jälkikäsittelyvastaanotin, joka tällä hetkellä pystyy hyödyntämään GPS:n, Galileon ja BeiDoun signaaleja. Työssä esitellään GLONASS -satelliittinavigointijärjestelmän signaalin vastaanoton toteutus FGI-GSRx -ohjelmistovastaanottimeen. Toteutus rajoittuu GLONASS Standard Positioning Service -signaaliin L1-taajuudella. Lopullinen vastaanotin pystyy käsittelemään digitoituja GLONASS-signaalinäytteitä ja laskemaan paikannusratkaisun niiden avulla. Työhön kuuluu vastaanottimen ohjelmiston suunnittelu, kehittäminen, toteuttaminen ja toiminnan testaaminen. Kokeelliset tulokset osoittavat, että vastaanotin pystyy vastaanottamaan GLONASS-signaaleja ja käyttämään niitä tuottamaan yhdistetyn GPS / GLONASS paikannusratkaisun. Lisäksi testataan häirintäsignaalin vaikutus useaa satelliittijärjestelmää hyödyntävän GNSS-vastaanottimen paikannukseen ja todetaan usean järjestelmän lisäämisen hyödyt paikannuksen häirinnänkestävyyteen

    A Survey on Low-Power GNSS

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    With the miniaturization of electronics, Global Navigation Satellite Systems (GNSS) receivers are getting more and more embedded into devices with harsh energy constraints. This process has led to new signal processing challenges due to the limited processing power on battery-operated devices and to challenging wireless environments, such as deep urban canyons, tunnels and bridges, forest canopies, increased jamming and spoofing. The latter is typically tackled via new GNSS constellations and modernization of the GNSS signals. However, the increase in signal complexity leads to higher computation requirements to recover the signals; thus, the trade-off between precision and energy should be evaluated for each application. This paper dives into low-power GNSS, focusing on the energy consumption of satellite-based positioning receivers used in battery-operated consumer devices and Internet of Things (IoT) sensors. We briefly overview the GNSS basics and the differences between legacy and modernized signals. Factors dominating the energy consumption of GNSS receivers are then reviewed, with special attention given to the complexity of the processing algorithms. Onboard and offloaded (Cloud/Edge) processing strategies are explored and compared. Finally, we highlight the current challenges of today’s research in low-power GNSS.Peer reviewe

    GNSS Related Threats to Power Grid Applications

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    As power grid environments are moving towards the smart grid vision of the future, the traditional schemes for power grid protection and control are making way for new applications. The advancements in this field have made the requirements for power grid’s time synchronization accuracy and precision considerably more demanding. So far, the signals provided by Global Navigation Satellite Systems have generally addressed the need for highly accurate and stable reference time in power grid applications. These signals however are highly susceptible to tampering as they are being transmitted. Since electrical power transmission and distribution are critical functions for any modern society, the risks and impacts affiliated with satellite-based time synchronization in power grids ought to be examined. This thesis aims to address the matter. The objective is to examine how Global Navigation Satellite Systems are utilized in the power grids, how different attacks would potentially be carried out by employing interference and disturbance to GNSS signals and receivers and how the potential threats can be mitigated. A major part of the research is done through literature review, and the core concepts and different implementations of Global Navigation Satellite Systems are firstly introduced. The literature review also involves the introduction of different power grid components and subsystems, that utilize Global Positioning System for time synchronization. Threat modeling techniques traditionally practiced in software development are applied to power grid components and subsystems to gain insight about the possible threats and their impacts. The threats recognized through this process are evaluated and potential techniques for mitigating the most notable threats are presented.Sähköverkot ovat siirtymässä kohti tulevaisuuden älykkäitä sähköverkkoja ja perinteiset sähköverkon suojaus- ja ohjausmenetelmät tekevät tilaa uusille sovelluksille. Alan kehitys on tehnyt aikasynkronoinnin tarkkuusvaatimuksista huomattavasti aikaisempaa vaativampia. Tarkka aikareferenssi sähköverkoissa on tähän saakka saavutettu satelliittinavigointijärjestelmien tarjoamien signaalien avulla. Nämä signaalit ovat kuitenkin erittäin alttiita erilaisille hyökkäyksille. Sähkönjakelujärjestelmät ovat kriittinen osa nykyaikaista yhteiskuntaa ja riskejä sekä seuraamuksia, jotka liittyvät satelliittipohjaisten aikasynkronointimenetelmien hyödyntämiseen sähköverkoissa, tulisi tarkastella. Tämä tutkielma pyrkii vastaamaan tähän tarpeeseen. Päämääränä on selvittää, miten satelliittinavigointijärjestelmiä hyödynnetään sähköverkoissa, kuinka erilaisia hyökkäyksiä voidaan toteuttaa satelliittisignaaleja häiritsemällä ja satelliittisignaalivastaanottimia harhauttamalla ja kuinka näiden muodostamia uhkia voidaan lieventää. Valtaosa tästä tutkimuksesta on toteutettu kirjallisuuskatselmoinnin pohjalta. Työ kattaa satelliittinavigointijärjestelmien perusteet ja esittelee erilaisia tapoja, kuinka satelliittisignaaleja hyödynnetään sähköverkoissa erityisesti aikasynkronoinnin näkökulmasta. Työssä hyödynnettiin perinteisesti ohjelmistokehityksessä käytettyjä uhkamallinnusmenetelmiä mahdollisten uhkien ja seurausten analysointiin. Lopputuloksena esitellään riskiarviot uhkamallinnuksen pohjalta tunnistetuista uhkista, sekä esitellään erilaisia menettelytapoja uhkien lieventämiseksi
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