Performance of an Echo Canceller and Channel Estimator for On-Channel Repeaters in DVB-T/H Networks

This paper investigates the design and performance of an FIR echo canceller for on-channel repeaters in DVB-T/H network within the framework of the PLUTO project. The possible approaches for echo cancellation are briefly reviewed and the main guidelines for the design of such systems are presented. The main system parameters are discussed. The performance of an FIR echo canceller based on an open loop feedforward approach for channel estimation is tested for different radio channel conditions and for different number of taps of the FIR filter. It is shown that a minimum number of taps is recommended to achieve a certain mean rejection ratio or isolation depending on the type of channel. The expected degradation in performance due to the use of fixed point rather than floating point arithmetic in hardware implementation is presented for different number of bits. Channel estimation based on training sequences is investigated. The performance of Maximum Length Sequences and Constant Amplitude Zero Autocorrelation (CAZAC) Sequences is compared for different channels. Recommendations are given for training sequence type, length and level for DVB-T/H on-channel repeater deployment

A design strategy for phase synchronization in precoding-enabled DVB-S2X user terminals

This paper address the design of a phase tracking block for the DVB-S2X user terminals in a satellite precoding system. The spectral characteristics of the phase noise introduced by the oscillator, the channel, and the thermal noise at the receiver are taken into account. Using the expected phase noise mask, the optimal parameters for a second-order PLL intended to track channel variations from the pilots are calculated. To validate the results a Simulink model was implemented considering the characteristics of the hardware prototype. The performance of the design was evaluated in terms of the accuracy and stability for the frame structure of superframe Format 2, as described in Annex E of DVB-S2X.This work was supported by the Fond National de la Recherche Luxembourg, under the CORE project COHESAT: Cognitive Cohesive Networks of Distributed Units for Active and Passive Space Applications and the Bridges Program DISBuS: Dynamic Beam Forming and In-band Signalling for Next Generation Satellite Systems.Peer ReviewedPostprint (author's final draft

Semi-Analytic Techniques for Fast MATLAB Simulations

Semi-analytic techniques are a powerful tool for the analysis of complex systems. In the semi-analytic framework, the knowledge of the system under analysis is exploited to reduce the computational load and complexity that full Monte Carlo simulations would require. In this way, the strengths of both analytical and Monte Carlo methods are effectively combined. The main goal of this chapter is to provide a general overview of semi-analytic techniques for the simulation of communications systems. Specific emphasis is given to their implementation in Matlab and two examples from the communications and navigation context are analyzed in detail. More specifically, the impact of RF interference on acquisition and tracking, the two main stages of a Global Navigation Satellite System (GNSS) receiver, are considered. Although semi-analytic techniques have been considered in textbooks on simulations, limited attention has been provided to their analysis and implementation. This chapter mainly focuses on these two aspects with specific emphasis on the potential of the Matlab environment for their implementation.JRC.G.6-Security technology assessmen

DVB-S Signal Tracking Techniques for Mobile Phased Arrays

Abstract—A system that uses adaptive beamforming techniques for mobile Digital Video Broadcasting Satellite (DVB-S) reception is proposed in this paper. The purpose is to enable DVB-S reception in moving vehicles. Phased arrays are able to electronically track the desired signal during dynamic behaviour of the vehicle the array is mounted on.\ud The proposed system uses blind beamforming to adapt the array steering vector to changing signal (conditions and) directions. Movement of the vehicle, the phased array is mounted on, leads to modulus and phase deviations at the beamformer output. An extended version of the Constant Modulus Algorithm (CMA) algorithm is used to adapt the steering vector weights to compensate for those deviations.\ud For simulation of the proposed system a model of vehicle dynamics is used to generate realistic antenna data. Simulation of the proposed system based on this antenna data shows appropriate corrections for modulus and phase deviations

End-to-end Precoding Validation over a Live GEO Satellite Forward Link

In this paper we demonstrate end-to-end precoded multi-user multiple-input single-output (MU-MISO) communications over a live GEO satellite link. Precoded communications enable full frequency reuse (FFR) schemes in satellite communications (SATCOM) to achieve broader service availability and higher spectrum efficiency than with the conventional four-color (4CR) and two-color (2CR) reuse approaches. In this scope, we develop an over-the-air test-bed for end-to-end precoding validations. We use an actual multi-beam satellite to transmit and receive precoded signals using the DVB-S2X standard based gateway and user terminals. The developed system is capable of end-to-end real-time communications over the satellite link including channel measurements and precompensation. It is shown, that by successfully canceling inter-user interference in the actual satellite FFR link precoding brings gains in terms of enhanced SINR and increased system goodput.Comment: Submitted to IEEE Access Journa

Software Defined Radio for processing GNSS signals

GPS satellites are fitted with atomic clocks, in which it relapses the main objective of this project, to recover some of their accuracy and stability on a ground based receiver. This project describes the fundamentals of GPS signals, the assembly of the installation implemented to process them in software and the corresponding experiments. In order to achieve the software processing, a USB DVB-T dongle is connected to an active antenna and to the computer. As mentioned, one of the purposes is also to understand how a GPS can be implemented by software as a the substitution of a big part of the hardware that makes it impenetrable, as they are black boxes of integrated circuits, and expensive. It is known that a Global Navigation Satellite System (GNSS) software-defined open source receiver has already been created by people in Barcelona in “Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)”, a testbed for GNSS signal processing since it can be customized in every way. It has been used at some intermediate steps of the study while executing parallel experiments in the course of understanding how a GPS signal is digitally processed. In the meantime, some experiments have also been performed only employing hardware before implementing them in software, so that the concepts are visually reflected. When realizing software experiments, an interface called GNURadio has been used because of its enormous implementation of signal processing blocks. GNURadio can be used with external RF hardware to create software-defined radios, or without hardware in a simulation-like environment. Nevertheless, various simulations in the GNU (Octave software environment) have also been executed as processing in real time has not been considered a goal. However, to successfully accomplish the demodulation of the navigation data, which will contribute to restore the accuracy and stability of the satellites clocks that have sent it, the carrier frequency needs to be perfectly recovered, being this last point where the final aim of the project falls on.Outgoin

Hardware Precoding Demonstration in Multi-Beam UHTS Communications under Realistic Payload Characteristics

In this paper, we present a new hardware test-bed to demonstrate closed-loop precoded communications for interference mitigation in multi-beam ultra high throughput satellite systems under realistic payload and channel impairments. We build the test-bed to demonstrate a real-time channel aided precoded transmission under realistic conditions such as the power constraints and satellite-payload non-linearities. We develop a scalable architecture of an SDR platform with the DVB-S2X piloting. The SDR platform consists of two parts: analog-to-digital (ADC) and digital-to-analog (DAC) converters preceded by radio frequency (RF) front-end and Field-Programmable Gate Array (FPGA) backend. The former introduces realistic impairments in the transmission chain such as carrier frequency and phase misalignments, quantization noise of multichannel ADC and DAC and non-linearities of RF components. It allows evaluating the performance of the precoded transmission in a more realistic environment rather than using only numerical simulations. We benchmark the performance of the communication standard in realistic channel scenarios, evaluate received signal SNR, and measure the actual channel throughput using LDPC codes