13 research outputs found

    Design, implementation and verification of CubeSat systems for Earth Observation

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    In recent years, Earth Observation (EO) technologies have surged in an attempt to better understand the world we live in, and exploit the vast amount of data that can be collected to improve our lives. The field of EO encompasses a broad array of technologies capable of extracting information remotely, in a process called Remote Sensing (RS). CubeSats are causing a revolution in the RS field, and are becoming a really important contribution to it. The lack of testing and preparation are common in CubeSat EO missions due to the low budgets they usually suffer from. A successful CubeSat EO mission must supply the lack of size or funding with properly tested components and environments. In this document, emphasis will be given to preemptive approaches such as studying the performance of Commercial Off-The-Shelf (COTS) Global Positioning System (GPS) receivers and the development of simulators for highly dynamic environments This topic will be expanded upon by introducing the problematic of simulating such signals for testing, and the possible countermeasures to Radio-Frequency Interference (RFI) that threatens the success of the mission. Finally, a new S-Band Ground Station will be built to provide access to this band for future CubeSat missions. All of the above will provide a holistic view on some of the hot challenges that EO faces, and multiple future research paths that open with the recent rise of New Space technologies

    Comparative study of tool-flows for rapid prototyping of software-defined radio digital signal processing

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    This dissertation is a comparative study of tool-flows for rapid prototyping of SDR DSP operations on programmable hardware platforms. The study is divided into two parts, focusing on high-level tool-flows for implementing SDR DSP operations on FPGA and GPU platforms respectively. In this dissertation, the term ‘tool-flow’ refers to a tool or a chain of tools that facilitate the mapping of an application description specified in a programming language into one or more programmable hardware platforms. High-level tool-flows use different techniques, such as high-level synthesis to allow the designer to specify the application from a high level of abstraction and achieve improved productivity without significant degradation in the design’s performance. SDR is an emerging communications technology that is driven by - among other factors – increasing demands for high-speed, interoperable and versatile communications systems. The key idea in SDR is the need to implement as many as possible of the radio functions that were traditionally defined in fixed hardware, in software on programmable hardware processors instead. The most commonly used processors are based on complex parallel computing architectures in order to support the high-speed processing demands of SDR applications, and they include FPGAs, GPUs and multicore general-purpose processors (GPPs) and DSPs. The architectural complexity of these processors results in a corresponding increase in programming methodologies which however impedes their wider adoption in suitable applications domains, including SDR DSP. In an effort to address this, a plethora of different high-level tool-flows have been developed. Several comparative studies of these tool-flows have been done to help – among other benefits – designers in choosing high-level tools to use. However, there are few studies that focus on SDR DSP operations, and most existing comparative studies are not based on well-defined comparison criteria. The approach implemented in this dissertation is to use a system engineering design process, firstly, to define the qualitative comparison criteria in the form of a specification for an ideal high-level SDR DSP tool-flow and, secondly, to implement a FIR filter case study in each of the tool-flows to enable a quantitative comparison in terms of programming effort and performance. The study considers Migen- and MyHDL-based open-source tool-flows for FPGA targets, and CUDA and Open Computing Language (OpenCL) for GPU targets. The ideal high-level SDR DSP tool-flow specification was defined and used to conduct a comparative study of the tools across three main design categories, which included high-level modelling, verification and implementation. For tool-flows targeting GPU platforms, the FIR case study was implemented using each of the tools; it was compiled, executed on a GPU server consisting of 2 GTX Titan-X GPUs and an Intel Core i7 GPP, and lastly profiled. The tools were moreover compared in terms of programming effort, memory transfers cost and overall operation time. With regard to tool-flows with FPGA targets, the FIR case study was developed by using each tool, and then implemented on a Xilinx 7 FPGA and compared in terms of programming effort, logic utilization and timing performance

    Localization technique based on dual-frequency doppler ranging estimation

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    Positioning awareness plays an important role in modern applications such as internet of thing (IoT) and intelligent transportation system (ITS). One of the commonly used positioning techniques is trilateration as it estimates the location of a blind device or node by using the distance from several other devices or anchor nodes. The ranging technique used to obtain distance information is a crucial step to provide high accuracy in location estimation. Dual-frequency Doppler radar (DFDR) ranging technique has been widely used in radars and radio frequency identification (RFID) applications. In radar application, this technique requires a closed-loop communication link to estimate distance and has not been exploited in single radio frequency transmission. In this thesis, a ranging technique not requiring a closedloop communication link named one-way forward communication link dual-frequency Doppler (DFD) ranging technique is introduced. The performances of the DFD distance estimation were analysed using simulations and experimental measurements. In the DFD experiment, the anchor node transmitted two different frequencies with a certain frequency separation. The blind node captured the received signal, and the phase difference was extracted and unwrapped using offline processing system. The phase difference between the two received signals was used for DFD ranging estimation before being applied to locate the position of the blind node through trilateration method. Software defined radio (SDR) platform using GNU radio and universal software radio peripheral (USRP) was used to develop the localization system. The experimental results showed that DFD ranging technique can deliver up to 84% distance estimation improvement in comparison to conventional receive signal strength (RSS) ranging technique. In conclusion, the proposed DFD ranging technique is a promising positioning solution for future applications such as IoT and ITS

    Spectrum sensing algorithms and software-defined radio implementation for cognitive radio system

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    The scarcity of spectral resources in wireless communications, due to a fixed frequency allocation policy, is a strong limitation to the increasing demand for higher data rates. However, measurements showed that a large part of frequency channels are underutilized or almost unoccupied. The cognitive radio paradigm arises as a tempting solution to the spectral congestion problem. A cognitive radio must be able to identify transmission opportunities in unused channels and to avoid generating harmful interference with the licensed primary users. Its key enabling technology is the spectrum sensing unit, whose ultimate goal consists in providing an indication whether a primary transmission is taking place in the observed channel. Such indication is determined as the result of a binary hypothesis testing experiment wherein null hypothesis (alternate hypothesis) corresponds to the absence (presence) of the primary signal. The first parts of this thesis describes the spectrum sensing problem and presents some of the best performing detection techniques. Energy Detection and multi-antenna Eigenvalue-Based Detection algorithms are considered. Important aspects are taken into account, like the impact of noise estimation or the effect of primary user traffic. The performance of each detector is assessed in terms of false alarm probability and detection probability. In most experimental research, cognitive radio techniques are deployed in software-defined radio systems, radio transceivers that allow operating parameters (like modulation type, bandwidth, output power, etc.) to be set or altered by software.In the second part of the thesis, we introduce the software-defined radio concept. Then, we focus on the implementation of Energy Detection and Eigenvalue-Based Detection algorithms: first, the used software platform, GNU Radio, is described, secondly, the implementation of a parallel energy detector and a multi-antenna eigenbased detector is illustrated and details on the used methodologies are given. Finally, we present the deployed experimental cognitive testbeds and the used radio peripherals. The obtained algorithmic results along with the software-defined radio implementation may offer a set of tools able to create a realistic cognitive radio system with real-time spectrum sensing capabilities

    Development of a Nanosatellite Software Defined Radio Communications System

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    Communications systems designed with application-specific integrated circuit (ASIC) technology suffer from one very significant disadvantage - the integrated circuits do not possess the ability of programmability. However, Software Defined Radio’s (SDR’s) integrated with Field Programmable Gate Arrays (FPGA) provide an opportunity to update the communication system on nanosatellites (which are physically difficult to access) due to their capability of performing signal processing in software. SDR signal processing is performed in software on reprogrammable elements such as FPGA’s. Applying this technique to nanosatellite communications systems will optimize the operations of the hardware, and increase the flexibility of the system. In this research a transceiver algorithm for a nanosatellite software defined radio communications is designed. The developed design is capable of modulation of data to transmit information and demodulation of data to receive information. The transceiver algorithm also works at different baud rates. The design implementation was successfully tested with FPGA-based hardware to demonstrate feasibility of the transceiver design with a hardware platform suitable for SDR implementation

    Monitoring the radio frequency interference in radio astronomical measurements using software radio

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    Langattomia yhteyksiä hyödyntävien laitteiden ja sovellusten määrä kasvaa jatkuvasti, mikä lisää myös radioympäristön sisältämien häiriöiden määrää. Laitteiden hyödyntämät yhteydet myös kehittyvät entistä dynaamisempaan suuntaan, mikä monimutkaistaa niistä aiheutuvia häiriöitä. Samalla radioastronomiassa käytetyt entistä herkemmät radiovastaanottimet tekevät mittauksista herkempiä tehotasoltaan yhä pienemmille häiriöille, korostaen häiriöiden monitoroinnin ja suodatuksen tärkeyttä radioastronomian tieteenalalla. Tämän diplomityön tavoitteena oli toteuttaa ohjaus- ja tiedonkeräysohjelmisto Ettus Research USRP N210 ohjelmistoradiolle radioastronomisten mittausten häiriötekijöiden monitorointiin. Järjestelmällä pyrittiin vastaamaan radioastronomisten mittausten kasvavan häiriöherkkyyden sekä häiriöympäristön kehityksen asettamiin haasteisiin. Ohjelmiston toteuttamisen lisäksi työssä tutkittiin ja karakterisoitiin USRP N210 -ohjelmistoradiojärjestelmän radioteknisiä ominaisuuksia, kuten laitteen herkkyyttä, pyyhkäisynopeutta, taajuusvastetta sekä laitteen kaistanleveyden selektiivisyyttä. Työssä myös selvitettiin järjestelmän suorituskykyä rajoittavia tekijöitä, millä pyrittiin tehostamaan ja edesauttamaan järjestelmän jatkokehittämistä. Työssä toteutetulla ohjelmistolla voidaan tukea Metsähovin nykyisen häiriömonitorointijärjestelmän toimintaa. Työssä hyödynnetyn ohjelmistoradiolaitteiston avulla voidaan esimerkiksi saavuttaa Metsähovin nykyistä häiriömonitorointijärjestelmää huomattavasti parempi aikatason resoluutio. Lisäksi toteutetulla järjestelmällä saavutetaan suurempi herkkyys nykyistä häiriömonitorointijärjestelmää pienemmillä pyyhkäisyajoilla. Järjestelmä mahdollistaa siis entistä lyhyempien ja tehotasoltaan pienempien radiohäiriöiden havaitsemisen. Luotettavien absoluuttisten mittausten suorittaminen USRP N210 -ohjelmistoradiojärjestelmällä vaatii kuitenkin laitteen kalibrointia sekä laitteen ulkoisten- ja sisäisten virhelähteiden huomiointia. Laitteen kalibrointiin ja mittaustulosten suodattamiseen kiinnitettiinkin erityistä huomiota laitteistoa ohjaavaa ohjelmistoa kehitettäessä. Järjestelmän mittaustulosten luotettavuuden varmistaminen vaatii kuitenkin vielä jatkotutkimuksia.The amount of Radio Frequency Interference (RFI) continues to increase as the number of wireless devices and applications continues to grow. Meanwhile, the spectrum usage continues evolving towards more dynamic operating models, which means that the RFI environment is also evolving. This evolution together with the increasing sensitivity of the receivers used in radio astronomical measurements continues to raise the importance of RFI mitigation and RFI monitoring in radio astronomy. The objective of this thesis was to implement a control- and data acquisition software for the Ettus Research USRP N210 software defined radio (SDR) for the use of monitoring the RFI in radio astronomical measurements. The goal was to use the SDR to improve the time-domain resolution, sensitivity and flexibility of the RFI monitoring system currently used in the Metsähovi Radio Observatory. Furthermore, the goal was to characterize the technical performance of the USRP N210. The characterization consisted of measuring the sensitivity, sweep speed, frequency response and bandwidth selectivity of the USRP N210. The performance limiting factors of the system were also examined and documented. Furthermore, the internal error sources and calibration of the USRP were also taken into account while implementing the software. The software implemented in this thesis can be used to improve the sweep speed and sensitivity of the current RFI monitoring system used in Metsähovi Radio Observatory. However, the reliability of the measurements made with the implemented software needs to be investigated further. Further investigations should also be carried out on the internal error sources and shielding of the USRP N210

    REAL-TIME ADAPTIVE PULSE COMPRESSION ON RECONFIGURABLE, SYSTEM-ON-CHIP (SOC) PLATFORMS

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    New radar applications need to perform complex algorithms and process a large quantity of data to generate useful information for the users. This situation has motivated the search for better processing solutions that include low-power high-performance processors, efficient algorithms, and high-speed interfaces. In this work, hardware implementation of adaptive pulse compression algorithms for real-time transceiver optimization is presented, and is based on a System-on-Chip architecture for reconfigurable hardware devices. This study also evaluates the performance of dedicated coprocessors as hardware accelerator units to speed up and improve the computation of computing-intensive tasks such matrix multiplication and matrix inversion, which are essential units to solve the covariance matrix. The tradeoffs between latency and hardware utilization are also presented. Moreover, the system architecture takes advantage of the embedded processor, which is interconnected with the logic resources through high-performance buses, to perform floating-point operations, control the processing blocks, and communicate with an external PC through a customized software interface. The overall system functionality is demonstrated and tested for real-time operations using a Ku-band testbed together with a low-cost channel emulator for different types of waveforms

    Implementación de un sistema de comunicaciones basado en Software Radio

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    En este trabajo, se propone la implementación de un sistema de comunicaciones basado en la emergente tecnología conocida como Software Radio haciendo uso de los periféricos disponibles en el laboratorio. En primer lugar, se realiza un estudio de la tecnología para conocer cuál es el fundamento y sus posibles alcances en el ámbito de las telecomunicaciones. Conocer los fundamentos de la tecnología reside en indagar los principios de ésta, así como los componentes físicos que la conforman. Una vez comprendido el objetivo de la tecnología e identificados los componentes físicos que la ponen en práctica, se realizará un estudio con la intención de mostrar las características que estos presentan. Posteriormente, se realiza un estudio acerca de la herramienta software a utilizar; la cuál se utilizará a la hora de diseñar el sistema de comunicaciones. Finalmente, con los conocimientos adquiridos en los pasos previos se dispondrá a realizar un sistema de comunicaciones basado en esta tecnología.The proposal of this project is the implementation of a communication system based on the Software Radio technology using the available peripherals in the laboratory. First of all, a research of the technology is carried out in order to provide an overview of its fundamentals and its scope relating the communications environment. The research of technology fundamentals includes not only exploring its principles, but also the components used. Once the aim of the technology and components has been understood, these will be deeply studied in order to show their characteristics. Afterwards, a research of the software tool is carried out. This tool will be used in order to design a complete communication system. Finally, with all the knowledge acquired, a full communication system based on Software Defined Radio will be deployed
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