Aerospace and Electronic Systems Magazine August 2017 - 2

In This Issue - Technically
ENHANCEMENT OF SAFETY MEASURES TO PREVENT AIR ACCIDENTS
Air Travel is becoming the favorite means of transportation in present times. Chances of accidents and various types of incidents including hijacking of aircraft
are also on the increase. Due to these accidents lot of precious lives are lost. With few modifications in avionics and structure of aircraft these accidents and
incidents may be made less fatal. It is endeavored to carryout study to prevent fatal accidents of passenger aircraft whilst it is on passage en route. Recommendations have been made to reduce handshake times and track an aircraft in real time as soon as it deviates from its planned Flight Path/Plan; carryout
modification to fuselage/wings/tail etc. by providing adjustable thin metallic sheets/ parachutes so that aircraft may be safely glided down for landing and
reduce damage that could otherwise take place due to strong impact with ground; and to control the aircraft remotely on the principles of UAV operations for
safe landing/touch down. In this way the loss of precious human lives can be prevented and air travel may be made safer.

FLIGHT DATA ASSESSMENT OF TIGHTLY-COUPLED PPP/INS USING REAL-TIME PRODUCTS
We present an analysis of the positioning performance of tightly-coupled Precise Point Positioning inertial navigation using two long-baseline flight data sets that
include data from a navigation-grade Inertial Measurement Unit. The benefits of integrating inertial navigation with Precise Point Positioning are evaluated when
using various GPS orbit and clock products (i.e., broadcast, real-time, and final), and whenever different troposphere models are adopted. We show that the positioning performance of PPP/INS, when using orbit and clock products generated in real-time is at the same level of accuracy as PPP when using post-processed
orbit and clock products. In addition, we show that significant benefits with respect to solution convergence are available with tight-INS, leading to a greater than
30% reduction in three-dimensional (3D) Root Mean Squared (RMS) positioning errors. For example, when using real-time orbit and clock products with tightlycoupled inertial navigation, the mean and standard deviation of the position errors with respect to ambiguity-fixed post-processed reference solutions are reduced
from 19 cm and 28 cm, to 15 and 18 cm, respectively. Furthermore, when using inertial data, a 10 cm or greater reduction in the 3D RMS position error is shown
to be independent of the quality of the a priori nominal troposphere and troposphere modeling approach adopted.

COMPRESSED FUSION OF GNSS AND INERTIAL NAVIGATION WITH SIMULTANEOUS LOCALIZATION AND MAPPING
Advances in low-cost inertial sensor technology and the global navigation satellite system (GNSS), the six degrees-of-freedom (6DOF) vehicle state can be estimated accurately by fusing information from both. This has been a crucial step towards real-time guidance and flight control. In this article, we present a computationally efficient and tightly coupled integration of GNSS and inertial navigation with simultaneous localization and mapping (SLAM), aiming for continuous 6DOF
navigation solutions in cluttered environments. The unscented SLAM filter was developed to be suitable for inertial measurement unit-based (IMU) navigation and
then extended to a compressed form by dividing the map into small manageable local maps and a global map. The locally collected information is compressed and
only propagated to the global map whenever the vehicle crosses the local boundary. The results from a high-fidelity simulator demonstrated the benefits of the tightly
coupled integration of raw sensor data, providing accurate GNSS receiver and IMU calibrations even under a single GNSS satellite vehicle.

CONTROL THEORETIC APPROACH TO GYRO-FREE INERTIAL NAVIGATION SYSTEMS
The research on Gyro-Free (GF) Inertial Navigation System (INS) is growing rapidly. In this work a state of the art literature review on GF-INS is presented
and a comparison to the classical INS architecture is made. Additionally, the GF-INS architecture is analyzed from a control theory point of view using concepts from systems theory such as stability and observability. Particularly, stationary GF-INS analysis will include stability computation and derivation of the
observable and unobservable subspaces during fine alignment process.

HIGH SENSITIVITY ACQUISITION OF GNSS SIGNALS WITH SECONDARY CODE ON FPGAS
The presence of a secondary code in modern global navigation satellite system signals complicates the acquisition of these signals, because there is a potential sign
transition between each period of the primary code. Some previous works proposed to use the parallel code search by performing the correlation over the primary
code several times and then combining the results according to the secondary code chips. In this article, we will focus on this method and compare different hardware
implementations, to determine if it is better to do the combinations before or after the correlations, and to compare serial and parallel architectures. In a second part,
we will show a simple method that manipulates the local secondary code to rearrange the equations, which approximately halves the theoretical number of operations related to the secondary code correlation and the processing time for hardware implementations, without any impact on the sensitivity.

AN APPROACH TO DETECT GNSS SPOOFING
GNSS signals are vulnerable to various types of interference sources, including jamming and spoofing attacks. The spoofing detection approaches proposed in the
literature mainly focus on detecting spoofing signals and detection thresholds are adjusted based on a clean data set. However, most of these metrics are also affected in
the presence of other interference sources such as jammers and multipath, which cause false alarms. This paper focuses on improving the correct detection of a spoofing
attack by distinguishing it from other interference sources including jamming and multipath signals. This paper proposes a spoofing detection architecture utilizing the
combination of different metrics to correctly detect spoofing signals and classify interference types. The interference signals considered include Continues Wave (CW),
chirp and wideband noise, multipath and spoofing signals. Several test scenarios based on different interference cases are considered to demonstrate the effectiveness of
the proposed architecture to correctly detect spoofing attacks. The detection and classification metrics are based on the use of different spoofing detection metrics, namely
time/frequency power analyses, Structural Power Content Analysis (SPCA), carrier-to-noise density ratio (C/N0) and the Signal Quality Monitoring (SQM) method.

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IEEE	A&E	SYSTEMS	MAGAZINE	

AUGUST	2017



Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine August 2017

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