In a GNSS receiver the measure of C/N0 is not only supplementary information provided to the user together with the PVT (position, velocity, time), but it is also fundamental information to determine the status of the tracking subsystems and to control the receiver in critical environments. A classic approach to estimate the C/N0 in a navigation receiver is known as the narrowband-wideband power ratio method (NWPR). We investigate the suitability of different estimation methods, properly adapted from the digital communications world where a wide range of literature is available on the problem of estimating the signal-to-noise power ratio (SNR) of M-PSK modulations in additive white Gaussian noise (AWGN). The objective here is to identify a subset of candidate algorithms for SNR estimation, previously proposed for communications receivers. These methods are compared in specific situations of interest, such as weak signals or high signal-to-noise conditions obtained with high-gain antennas, and considering software defined radio receiver implementations. Simulation campaigns and a set of real GPS-L1 signals are used to test and compare the performance of the selected algorithms in a broad range of C/N0 values (from 20 to 70 dBHz), where the classic NWPR method is used as an authoritative benchmark. We conclude that a number of low-complexity algorithms for SNR estimation, based on a simple communication signal model, can be tailored to digital GNSS receivers. The performance is comparable with respect to the NWPR approach, but the complexity is reduced and possible improvements can be foreseen using the tested algorithms.

Low Complexity Carrier-to-Noise Ratio Estimators for GNSS Digital Receivers

Receiver design challenges arising from new GNSS signals include required intermediate frequency, sampling rate, modulation type, spreading code, and secondary code. Several architectures are examined here aiming at a best model for multi-GNSS implementation, especially the underlying baseband and software realization platform. In this pursuit, it is found that the multi-core and multiple processor architectures are promising candidates. General purpose processors or digital signal processors demand excessive resources and power consumption. Alternative architectures are presented along with the general cost function, used to evaluate architecture efficiency. Taking into account (1) the superiority of a hardware time-interleaving technique, (2) RAM-based design versus register-based design, and (3) careful consideration of modern GNSS signal attributes, the proposed programmable custom pipeline correlator core provides flexibility and significantly reduces resources and power.

Feasibility analysis of baseband architectures for multi-GNSS receivers

This thesis explores the barriers to accessing primary care health service provision for \nGypsies and Travellers in England. Research took place 'in two phases. The first was a \nqualitative study of Gypsies' and Travellers' cultural beliefs, attitudes, perceptions of \nand access to health care. Findings included low expectations and poor experience of \nservices, as well as many examples of communication barriers between Gypsies and \nTravellers and health staff. The second phase built on these findings, by adopting \nparticipatory action research (PAR) methods, to explore communication processes \nfrom both staff and Gypsy and Traveller perspectives. The aim was to elicit \nunderstanding with a view to exploring how barriers might be overcome. \nBoth phases ofresearch show how Gypsy and Traveller experiences of discrimination \nand racism contribute to a sense ofdevalued identity, characterised by feelings of \nshame and humiliation. Shame and attempts to ward off shame are central features of \nrelationships and encounters with health staff as personal reactions to these \nexperiences can produce mutual mistrust and poor relations between staff and the \nGypsy and Traveller patients. At the same time, health staff reactions are shaped by \npressures related to role, status and setting. By focusing on processes of coconstructed \ncommunication, I identify specific patterns of tension and mistrust. \nIn conclusion, I argue that a reflective and collaborative staff approach in primary \ncare, based on effective leadership and a shared team ethos, can provide the empathic \nfocus needed as a starting-point for trust and effective communication. I also argue \nthat acquisition of good communication skills and development of experiential \ncultural awareness, whilst essential, are insufficient to guarantee cultural competence. \nA reflexive approach, focussing on personal qualities, values, beliefs and attitudes, is \nalso essential for cultural safety. I outline the specific staff training implications of \nthese findings, in terms of ensuring culturally safe health care for Gypsies and \nTravellers.

Abstract of thesis: Gypsies and Travellers accessing primary health care: interactions with health staff and requirements for ‘culturally safe’ services

Arena: A 64-antenna SDR-based ceiling grid testing platform for sub-6 GHz 5G-and-Beyond radio spectrum research

Some wireless communication systems must be able to receive and process signals from multiple source stations simultaneously. A common practice is to use multiple duplicated hardware resources; a different set of resources for each received station. A new coherent amplitude modulated (AM), time-division multiplexed (TDM), receiver system architecture and design, based on the software-defined radio (SDR) standard, is proposed, developed and validated via simulation and experimental hardware prototype testing. The new receiver system architecture and approach enables reception and processing of signals from multiple stations using the hardware resources normally needed for reception and processing of only one station. Production models of the proposed receiver/processing system architecture and design would be implemented in programmable-logic-device (PLD) technology [field-programmable-gate-array (FPGA) in our case] to accommodate rapidly changing communication protocols and standards and to enhance processing performance.

A New Multichannel, Coherent Amplitude Modulated, Time-Division Multiplexed, Software-Defined Radio Receiver Architecture, and Field-Programmable-Gate-Array Technology Implementation

The advent of the Galileo system in Europe and the modernization plans for global positioning system (GPS) are giving a strong impulse to development of global navigation satellite systems (GNSS). The availability of a variety of new signals is boosting the growth of new services and applications. The next generation of receivers will have to deal with signals in different bandwidths with different modulation schemes. In such a context the reconfigurability offered by software defined radio (SDR) technologies, employing programmable hardware like field programmable gate arrays (FPGAs) and digital signal processors (DSPs), can play an important role. The paper presents a case-study of an efficient hardware/software partitioning for the baseband processor and discusses in detail how to meet the real-time constraints. Finally some results concerning the implementation of the proposed architecture on a prototyping board are given.

Efficient Software Defined Radio Implementations of GNSS Receivers

The first step of the digital processing within a Global Navigation Satellite System (GNSS) receiver is the signal acquisition. The receiver has to detect the satellites in view, and for each of them, has to estimate the Doppler shift and the code phase of the received signal. In order to speed up the acquisition process, modern receivers use fast acquisition technique based on the Fast Fourier Transform (FFT). This paper presents the complexity evaluation of a FFT-based acquisition technique, suitable for new GNSS signals and for both software and hardware implementations. After the description of the algorithm, the focus will be on the comparison of the results obtained with a Xilinx FPGA board and a software receiver implemented on a general-purpose processor.

https://www.researchgate.net/profile/Maurizio_Fantino/publication/4372964_Evaluation_of_a_FFT-Based_Acquisition_in_Real_Time_Hardware_and_Software_GNSS_Receivers/links/0912f5140a83c6ce7d000000.pdf

Evaluation of a FFT-Based Acquisition in Real Time Hardware and Software GNSS Receivers

With the recent launch of the first Galileo test satellite GIOVE-A, Europe made the first really important step towards the so-called Global Navigation Satellite System, which is already represented by the GPS and the GLONASS systems. In this context, the co-operation of these systems from the receiver point of view is going to ask the market for providing a user terminal able to deal with different signals. To achieve this target, a possible way forward goes through the study of dedicated signal processing algorithms based on Software Radio Defined principles. The paper will introduce the FPGA+DSP platform developed at the Politecnico di Torino, pointing out the advancements on the architecture design. Some results in terms of signal tracking performance will be also presented and discussed.

A Flexible FPGA/DSP Board for GNSS Receivers Design

During the past years, software platforms have proved a superior scalability with respect to hardware solutions. However, wireless communication rates can not be faced resorting only to software. Software defined radio paradigm will try to push reconfigurable blocks as near as possible to the antenna. The first block suitable in this implementation is the digital down converter, needed to adapt higher antenna's data rate to intermediate frequency ones. In this paper a fully reconfigurable IP of a cascaded integrator comb (CIC) filter, an economical class of multiplier-less filters, is proposed. FPGA implementation has lead to very satisfactory results: 135 MHz on a XCV100E.

FPGA digital down converter IP for SDR terminals

In a Global Navigation Satellite System (GNSS) receiver
the acquisition algorithm plays an important role since it
searches for the satellites in the line of sight which can be
used for navigation. Its speed and flexibility affect the
performance of the entire receiver.
This paper proposes a variant of the classical “fast
acquisition algorithm” where the signal correlation is
obtained in time domain by means of two FFTs and a
single IFFT.
The main idea is to apply a simple transformation to the
received signal allowing a reduction of the number of
samples to process and, at the same time, preserving the
signal characteristics. This transformation is here called
“compression” and involves accumulations and
decimations.
The proposed acquisition algorithm is analyzed and
compared, in terms of computational complexity and by
using the Receiver Operative Characteristic (ROC)
curves.

Gianmarco Girau

Papers

Efficient Software Defined Radio Implementations of GNSS Receivers

Evaluation of a FFT-Based Acquisition in Real Time Hardware and Software GNSS Receivers

A Flexible FPGA/DSP Board for GNSS Receivers Design

FPGA digital down converter IP for SDR terminals

Signal Compression for an Efficient and Simplified GNSS Signal Parallel Acquisition