The interplay between mapping/demapping and non-binary LDPC coding in MIMO wireless communication systems

Recently, the need for innovative services available for the end users has led to an increasing demand of higher throughputs of wireless systems. On the other hand higher throughput means wider bandwidth, so that channel selectivity and fading might be a severe challenge to combat in order to ensure high level of Quality of Service (QoS). In this scenario one of the possible approach to increase the system throughput is the use of multiple antennas, both at the transmitter and the receiver side. Instead the typical manner to combat channel effects is to employ powerful channel coding schemes, which target the mitigation of these propagation effects. This work follows this approach combining the MIMO techniques jointly with the powerful channel coding scheme of non-binary LDPC. The expression "non-binary" refers to the fact that these codes are defined over high order Galois Field. These codes have been researched in the literature to achieve higher error protection than conventional binary codes for transmission over different noisy channels. The main novelty of this work is related to the mapping and demapping of the non-binary information. Typically the main contributions in the literature focus on the low complexity decoders, whilst the demapping complexity is neglected. However, the demapping complexity might become a real bottleneck in the global receiver complexity, so that we decide to investigate this topic. A strategy is devised to guarantee an efficient mapping at the transmitter, together with an algorithm for low complexity soft demapping at the receiver. The proposed solutions target the best trade-off between performance and complexity, for any combination of the Galois field order, QAM constellation order, and MIMO scheme

Rivelazione e Sincronizzazione di tempo per un segnale multiportante UMTS-LTE

Questo elaborato si occupa per prima cosa di illustrare brevemente le reti cellulari di terza generazione (UMTS), prima di introdurre gli obiettivi e lo standard downlink 3GPP – Long Term Evolution (LTE), che rappresenta il futuro delle comunicazioni mobili cellulari. In seguito viene presentata la catena di trasmissione downlink implementata, soffermandosi poi sul ricevitore LTE, in particolare sul filtro di ricezione e sull’equalizzatore. Successivamente l’attenzione di questo elaborato di tesi si concentra sulla procedura di sincronizzazione, che rappresenta la parte principale delle simulazioni effettuate; vengono illustrati nel dettaglio tutti i passi dell’algoritmo di sincronizzazione scelto, con una trattazione analitica là dove è stato ritenuto opportuno. Infine vengono presentate le curve di probabilità d’errore (BER), che consentono una valutazione delle prestazioni del ricevitore in analisi, ed eventuali possibili evoluzioni dello stesso

Low complexity soft demapping for non-binary LDPC codes

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Low complexity soft demapping for non-binary LDPC codes

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Rainfall Field Reconstruction by Opportunistic Use of the Rain-Induced Attenuation on Microwave Satellite Signals: The July 2021 Extreme Rain Event in Germany as a Case Study

This paper presents a practical application of an opportunistic technique for the estimation of rainfall intensity and accumulated precipitation. The proposed technique is based upon signal strength measurements made by commercial-grade interactive satellite terminals. By applying some processing, the rain-induced attenuation on the microwave downlink from the satellite is first evaluated; then the rain attenuation is eventually mapped into a rainfall rate estimate via a tropospheric model. This methodology has been applied to a test area of 30×30 km2 around the city of Dortmund (North Rhine-Westphalia, upper basin of Ermscher river), for the heavy rain event that devastated western Germany in July, 2021. A rainfall map on this area is obtained from the measurements collected by a set of satellite terminals deployed in the region, and successfully compared with a map obtained with a conventional weather radar

The electrical design of the thermal control systems of the all-aluminum ARIEL telescope

The Atmospheric Remote-sensing InfraRed Large-survey (ARIEL) is a medium-class mission of the European Space Agency whose launch is planned by late 2029 whose aim is to study the composition of exoplanet atmospheres, their formation and evolution. The ARIEL’s target will be a sample of about 1000 planets observed with one or more of the following methods: transit, eclipse and phase-curve spectroscopy, at both visible and infrared wavelengths simultaneously. The scientific payload is composed by a reflective telescope having a 1m-class primary mirror, built in solid aluminum, and two focal-plane instruments: 1. FGS (Fine Guidance System), performing photometry in visible light and low resolution spectrometry over three bands (from 0.8 to 1.95 µm) 2. AIRS (ARIEL InfraRed Spectrometer) that will perform infrared spectrometry in two wavelength ranges between 1.95 and 7.8 µm. This paper depicts the status of the TA (Telescope Assembly) electric section whose purpose is to deploy sensors, managed by the Telescope Control Unit, for the precise monitoring of the Telescope’s temperatures and the decontamination system, used to avoid the contamination of the optical surfaces (mirrors in primis)

NAVIGATION MESSAGE AUTHENTICATION FOR NEXT GENERATION GNSS

Since the early days of GNSS, one of the main issues has been the need to protect the final user from attackers trying to emulate the data sent by the real system, the so-called spoofers. This can be done in particular adding the system the function of navigation message authentication, that represents the subject of this paper. The paper introduces a general approach to the problem, to come to a detailed real-world in-orbit case, that is the Galileo Navigation System. This kind of authentication feature is in fact foreseen for the evolution of the system towards its own second generation, evolution that is currently ongoing. Recent research (performed by Wiser and TASI in the frame of internal R&D activities) within the GNSS evolution study for Galileo Second Generation as well as GPS evolution, are investigating the possibility to have a more robust and reliable signal through the broadcasting of navigation message authentication bits. The paper describes a possible solution to the problems wherein the authentication bits are included in a dedicated channel that is added on top of the current signal-in-space format using IBOC multiplexing. This represents an alternative solution to the standard idea of reserving some bits of the current navigation message for authentication. The advantage of the dedicated channel is relatively clear: the bit-rate dedicated to authentication is considerably larger than that resulting from the reserved bits in the current message, thus providing a higher security level, and lower time to first authenticated fix (TTFA)/time between authentication (TBA). This allows in particular to easily meet the latest recommendations stating that (at least) a security equivalent to a symmetric algorithm with 128-bit key is needed. Concerning the authentication algorithm, the present study proposes a combination of the TESLA protocol with a public-key protocol (such as ECDSA). This allows to improve on a weakness of TESLA that requires time synchronization: albeit loos, it cannot guaranteed at receiver start-up, and in addition the TESLA root key shall be authenticated anyway. The optimal combination is found based on a trade-off between security strength, bandwidth overhead, authentication error rate, and time between authentication. Our proposal may pave the way towards an Open Service Navigation Message Authentication (NMA) solution to be broadcast on future GNSS signal channel using IBOC multiplexing solution. The proposed NMA criteria are based on the mutual combination of Elliptic Curve Digital Signature Algorithm (ECDSA) and TESLA authentication protocol. NAVITEC 2018 The solution foresee the use of ECDSA in a first phase when time synchronization between the sender and the recipient is not available, to switch afterwards TESLA when time synchronization is achieved. The paper concentrates on a specific solution wherein iBOC multiplexing on the E1 channels is supplemented with NMEA. This feasibility assessment is just a case study to show the generality of the approach and does not preclude any other implementation for future GNSS signals. The paper is organized as follows: first a summary of the authentication protocols are provided, focusing on the TESLA one, and the IBOC multiplexing scheme for GNSS evolution signals. Then a proposed solution is detailed, together with associated performance, and finally the conclusions are draw

The EULER project: application of software defined radio in joint security operations

The task of improving the effectiveness of public safety communications has become a main priority for governments. This is partly motivated by the increased risk of natural disasters such as flooding, earthquakes and fires, and partly, due to the risks and consequent impact of terrorist attacks. This paper focuses on the experience from the European Commission (EC) Seventh Framework Programme (FP7) project known as EULER, which seeks to demonstrate the benefits of Software Defined Radio (SDR) technology to support the resolution of natural disasters of significant stature, which require the participation of different public safety and military organizations, potentially of different nations. In such scenarios, the presence of interoperability barriers in the disaster area is a major challenge because different organizations may use different wireless communication systems. In this context, the main aspect investigated in EULER is the definition of a common waveform that respects the Software Communications Architecture (SCA) constraints, and guarantees maximum portability across SDR platforms. This paper discusses a range of issues which have been identified thus far within the EULER project; in particular the perceived pan-European interoperability needs of Public Safety and the coordination with military devices and networks. Aspects of interoperability are also extended to the three dimensions of platform, waveform and information assurance.JRC.G.6-Security technology assessmen

The EULER project: application of software defined radio in joint security operations

International audienceRecently, the task of improving the effectiveness of public safety communications has become a main priority for governments. This is partly motivated by the increased risk of natural disasters such as flooding, earthquakes and fires, and partly, due to the risks and consequent impact of terrorist attacks. This paper focuses on the experience from the European Commission (EC) Seventh Framework Programme (FP7) project known as EULER, which seeks to demonstrate the benefits of Software Defined Radio (SDR) technology to support the resolution of natural disasters of significant stature, which require the participation of different public safety and military organizations, potentially of different nations. In such scenarios, the presence of interoperability barriers in the disaster area is a major challenge because different organizations may use different wireless communication systems. In this context, the main aspect investigated in EULER is the definition of a common waveform that respects the Software Communications Architecture (SCA) constraints, and guarantees maximum portability across SDR platforms. This paper discusses a range of issues which have been identified thus far within the EULER project; in particular the perceived pan-European interoperability needs of Public Safety and the coordination with military devices and networks. Aspects of interoperability are also extended to the three dimensions of platform, waveform and information assurance

WIDEBAND MATCHED VOLTERRA MODELING OF HIGH-POWER AMPLIFIERS FOR SATELLITE NAVIGATION AND COMMUNICATION PAYLOADS

The increasing demand in the communication and navigation satellite industry for i) greater throughput, ii) flexibility in terms of signal generation, iii) higher efficiency, iv) improved payload reconfigurability, has generated the need to develop more accurate simulation/emulation payload models. Inaccurate modelling of payload elements induces a non-negligible risk of over- or underdesigned elements as well as an incorrect prediction of the main KPIs derived from emulation/simulation tools. Therefore, assessing the accuracy of currently used models and possibly developing new, more accurate ones turns out to be an essential feature of new-generation system design tools to derive accurate performance metrics, to enable correct dimensioning of all system features, to better specify budget parameters (in particular equipment specifications), and to efficiently support engineers in payload design. In this respect, High-Power Amplifiers (HPAs) are very sensitive components within the overall payload architecture, because they are non-linear devices that behave differently depending on the input signal features such as occupied bandwidth, average power, Peak-to-Average Power Ratio (PAPR), etc.. Extensive measurement and characterization activities on such devices performed in Thales-Alenia Spacelaboratories on GNSS payloads suggested that the standard narrowband/memoryless model of an HPA (i.e., AM/AM and AM/PM characteristics) is not sufficiently representative to derive accurate results concerning (next generation) GNSS signals featuring bandwidth up to 100 MHz or more, especially in terms of the in-band and out-of-band distortions actually introduced by this element. Such inaccuracy, initially considered insignificant, turned out to be not negligible when the payload simulation model is used to define and optimize the specifications as well the on-board Navigation Signal Generation Unit (NSGU) design. These conclusions led us to carry out an extensive review of the state of art of wideband HPA models, in particular Wiener, Hammerstein and Volterra one, comparing their accuracy, efficiency and easiness of application to real-world devices. This analysis focuses on the Volterra model, which is usually considered too complicated and hard to be actually tailored to a specific device. In this study, both the issues were tackled: first, how to match the numerous parameters of the nonlinear model to the wideband Device Under Test (DUT) has been considered. Then, a way to reduce the number of significant parameters to be derived from the measurements activity has been defined, in order to guarantee a computationally manageable effort without sacrificing modelling accuracy. Starting from the lab characterization of a specific DUT operating in the L band, this paper reports a thorough comparison between the performance of a simplified matched Volterra model and the corresponding (memoryless) narrowband equivalent (with measured AM/AM and AM/PM curves). The following metrics were considered to perform the comparison: * Normalized Mean Square Error (NMSE), both in time and frequency domain, between the simulated HPA output and the result of the measurements after digitization of the corresponding signal at DUT output. * Power Spectral Density (PSD) deviation, in particular the spectral regrowth, between the simulated signal and the DUT output. The results obtained exhibit a remarkable agreement between the wideband model and the results measured on the DUT, as well as a remarkable improvement of the performance metrics of the matched Volterra wideband model as compared to those of the standard narrowband algorithm, with a manageable additional complexity