% !TEX root = ../toptesi-scudo-example.tex
% !TEX encoding = UTF-8 Unicode
%*****************************************************************
%*********************** Final chapter ***************************
%*****************************************************************

%%%%% CHAPTER 6. Conclusions %%%%%
\chapter{Conclusions}\label{Conclusions}

% ********************** Define Graphics Path ********************
    \graphicspath{{Chapter8/}}

\par The thesis deals with analysis of COTS GNSS chipsets and developing algorithms to implement in service robotics, specifically unmanned arial and ground vehicle scenarios. Focus has also been made into defense mechanisms to RF interference threats in such chipsets. 

\par Chapter \ref{GlobalNavigationSatelliteSystems} gives an overview of the fundamentals of GNSS technology and defines the design of GNSS signals, receivers and raw measurements which enable positioning solutions. A discussion on the performances of different grade GNSS receivers follows and the positioning performances of high-end GNSS receivers is seen to set the benchmark for COTS GNSS chipsets.

\par Chapter \ref{Navigation_in_Service_Robotics} introduces service robotics and outlines its importance to the modern world. With focus on outdoor unmanned  vehicles, the navigational technologies widely used are explained. The current challenges to robust and low cost GNSS based navigation in UAVs and UGVs are explained thereafter. The approach taken in the thesis towards collaborative positioning solutions and the use of Android smartphones to represent COTS GNSS receivers is justified.

\par The analysis of Android GNSS raw measurements under a completely controlled environment has been documented in Chapter \ref{AndroidSmartpohnes_Based_GNSS}. Based on its comparison to real environment-based peer research, the high stability of the $C/N_0$ in Android devices and significantly reduced pseudorange noises display the vital need for solving the propagation nuisances troubling Android measurements. Comparisons of position measurements between anechoic chamber and a real environment reveal the nuances behind the large errors seen in GNSS only Android positioning solutions, such as the duty cycle occurrence. It is noted that understanding and mitigating them is vital towards the push to achieve higher performance through such devices. The low quality of the GNSS hardware on commercial Android devices also factor in these errors. The limitation of the record and replay paradigm with one transmitting antenna is seen along with the unsuitability of the Google Toolbox PVT algorithm in such a scenario.

\par Chapter \ref{Collaborative_GNSS_Methodology_and_Application} details the different collaborative GNSS approaches applicable to a service robotics scenario with low cost GNSS receivers and the results are seen. In Section \ref{Fast_Deformation_Monitoring}, analysis of displacements and deformation phenomena through the single difference, time differenced approach shows promise through observation of the relative velocities of the two low cost master-rover GNSS receivers. 100\% of induced deflections were identified and the false alarm rates were brought down to close to a basic Geodetic GNSS master-rover receiver setup. Section \ref{GNSS_Collaborative_Ranging} demonstrated the successful data exchange of raw GNSS measurements through the IEEE802.11b Wi-Fi connection in Android smartphones. The superior performance of such raw GNSS measurements for relative ranging when compared to stand alone positioning based solutions has been validated. This not only provides a platform for localised exchange of data between Android smartphones, but also a useful computationally efficient ranging methodology in a network of smartphones. The methodology can be transferrable to connected unmanned vehicles with GNSS based autopilots. Section \ref{Proof_of_Concept} confirmed that the paradigm can be exploited to collaboratively improve the accuracy in the position estimation of the UGV but the DGNSS solution requires further optimization to be properly effective in open-sky context. The findings motivate the use of low-cost hardware and software implemented in smartphones, thus reducing the overall cost of the next generation of service robots.

\par Chapter \ref{InterferenceThreats} looks at the interference threats to GNSS in service robotics. The effects of anthropogenic disturbances on the GNSS units integrated in a high end commercial and a low cost customized drone is seen in Section \ref{Overview_and_Assessment_of_Vulnerability}. The resistance of the drones towards jamming disturbance is found to be is different, where the commercial drone show much better positioning performance compared to the low cost one due to the presence of higher quality IMU unit. However, although the two drones have different resistance to simplistic spoofing, they are successfully spoofed by the HackRF One platform. Analysis on the performance of modern commercial smartphones under simplistic spoofing is done in Section \ref{Spoofing_Raw_GNSS_Measurements} and it is seen that the spoofing attack is not fully successful in open-sky conditions. Spoofer transmitted satellites though acquired, are not used by the smartphone GNSS receivers except in the case of overlapping satellites where they are not present in the set of already acquired signals. The spoofer acted more as an interference agent to the smartphones in the L1 band and their GNSS receiver clocks are not affected by it. In Section \ref{Cooperative_Positioning_Anti_Spoofing}, possible approaches of an attack to the proposed cooperative framework presented in this thesis are laid down and the anomalies to be considered to detect an attack in a network of cooperating devices are presented.


%%%%% SECTION 6.2 Future Activities %%%%%%
\section{Scope of Future Activities}
Future activities should include implementing the GNSS collaborative algorithms proposed in the thesis in the autopilot of UAVs and UGVs. Building effective defense and mitigation algorithms based on the findings of the thesis also carry importance.

\vspace{\baselineskip}


