What Is The Meaning Of Signal

Published Date: 02 Nov 2017

Introduction

Global positioning system is based on space satellite navigation. This satellite navigation system gives us accurate, worldwide and 3D location details and real time weather conditions to all over the world with help of a receiving kit. There will be four or more Global positioning system satellites near or anywhere in the world gives useful information to different type of users such as military, commercial, transport etc. All these satellites are monitors and controlled by US government and it can be uses free to everyone help of GPS Receiver.

This global positioning system project were established in 1973s and defeat the drawbacks of the Navigation systems. Global positioning system was developed and released by United states defence departments and it was runs with aid of 24 satellites.

In 1994 this whole system becomes to fully operational and Roger L.Easton was accredited as its discoverer.

Designing of the GPS is Partially or likewise on ground based Radio navigation systems, established in 1940s and also in the world war 2 and uses Decca navigator, Loran.

How GPS works

Now let see how the GPS working, satellites are surrounding the world two times a day in a fixed orbits. Global positioning system receivers are collect this details and use to measure the users location. importantly Global positioning system receiver measure up the time a signal is transit by another satellite with exact time was received. The time deviation will tell to the Global positioning system receiver how far the satellite stays. with the other satellites helps the receiver calculate the users positioning and display to the map.

In order to calculate the two dimension position and a tracking movement a global positioning system receiver have to be in contact with at least three satellites. with the help of four satellites or more receiver could be determined the user three dimensions position. once it has been determine the unit could be measure the other details such as track, destination, speed and more.

How far GPS is accurate

http://www8.garmin.com/aboutGPS/

Now a days global positioning system receivers are doing an extra ordinary job, with the aid of parallel multi-channel design. when satellites initially turned on Gamin's 12 parallel channel receivers are lock them quickly and maintains strongly. even in dense with taller buildings. some of the atmosphere factors could effect the receivers accuracy.

newer versions of gamins wide area augmentation system technology receivers could develop the accuracy in less than a three meters . there is no need of extra fees or additional tools WAAS. Additionally to their GPS to receive a correct signal should use the different beacon receiver and antenna.

Basics of the GPS Satellite system

In the earth more than 12,000 miles high, 24 satellites are making a GPS segment and continually circle two orbits less than a day. their speed nearly 7000m/h.

These satellites are powered by solar energy system. If the solar hide from view they have a backup using batteries. and also small rockets helps to keep them in correct track in the event of solar power failure.

what is the meaning of signal

Satellites transfer two type of low power radio signals, Intended 1.57542 Ghz (L1) and 1.2276Ghz(L2). Civilian global position system uses the L1 frequency in the UHF band. The signals can pass through glasses and plastics but not through like solid objects like buildings.

A signal includes three types of information such as a pseudorandom code, and ephemeris data and almanac data. the first one is an ID code which is find out which satellites are transmitting the information. we can able to see this number on a garmins GPS satellites page.

The second one ephemeris data is frequently transmits by satellites, which is keep the information about satellites status, date and time. these parts of the signal is important to decide the location.

The last one almanac data informs the receiver where satellite belongs to be in certain time. every satellites are transmitting almanac data which is showing the orbit details for each and every satellites in the system.

Vulnerabilities of Global positioning system

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA440372

Global positioning system could be demoralized in different three ways such as

Intentional interference

Unintentional Interference

human factors problems

First one intentional interference is related to GPS jamming and GPS spoofing, And the broadcast of forge signals.

Take second one unintentional interface threads it is consist of common problems of radio frequency interferences and ionospheric interference, these related to Spectrum congestion.

The third one is human factors difficulties, such as limited of user equipments , GPS space restriction. lack of user training in related technology.

GPS spoofing

http://en.wikipedia.org/wiki/Spoofing_attack

When we have look for what is GPS spoofing attack is try to mislead a GPS receiver by broadcast a powerful signal than normally its received from a GPS satellite, prepared to resemble a set of GPS signals. these modified spoofed signals uses to cause the receiver to decide to taken away from its actual position. specially attacker will decide where it should be. But GPS works by measures the time and how long it takes to reach the receiver from satellite. A spoofing requires know exactly where the target and so spoofed signal could prepared with proper signal delays.

Spoofing attack can starts by broadcast a powerful signal that create the correct position. after that diverge towards the position selected by the attacker. at this point this attacker working as a jammer.

GPS jamming

Now a days GPS become gradually more incorporated in civilian life. It is now uses in Shipping and Trucking flight control, personal uses and tracking devices, and other many applications. These increased uses in GPS integrated devices brought more vulnerability of this systems Interference and jamming. these type over uses could cause to break the law and interferes the operations of the GPS systems. past recent years many of jamming equipments become available and they are cheap. There are plenty of RF interference, includes pulse, broadband noise, tones, waveforms, and other frequency.

Accessible through the Internet and cheap jammers are contains single antenna devices which can be interrupt GPS frequency L1. this frequency is used by most people.

Most costly jammers could contains more than two antennas which can be interrupt GPS frequencies(L1 and L2 and L5) and mobile phones.

But it is not a criminal offence to carry such device.

The threads of the GPS jamming is happens more frequently.

Cause to mislead the GPS Positions, civil transport, flight navigation. car hijacks and etc..

How to mitigate the vulnerabilities of GPS systems

Mitigation of the military based vulnerability

Some of the military based threads are Signal blocks, satellite view in positions and number, environmental conditions and motions, software design architecture and signal process. velocity and time position and receiver noise level.

The military advanced bunch of techniques which are considerably reduce the jamming sensitivity. at the time most of them are expensive for civil uses. but some of the other vulnerabilities are linked some military security problems. The latest technology called Selective availability anti spoof module, this is solves three vulnerabilities. the first one is offer receiver software and hardware security. just in case if the receiver could captured by enemies the receiver remains unclassified.

second is military developed a technique is automatically re key the receiver then it can be P(Y) code. This can be complete with unclassified key. but the original mechanism remains classified. at last modern military receivers allows P(Y) code without obtaining the C/A code.

Recommends military based anti- jam solutions, such as encrypted GPS signal that provides ant jam protection. use special antenna and hardware to reduce the impacts of jammers.

Mitigation of the commercial vulnerability

To reduce the threads of the signal loss can be use jam resistant antennas and receiver. when compared with military equipments these are lower cost, weight and less power use. while these couldn't provide a complete protection at least they try to maintain the origin of the signals as long as it could.

Using alternatives to GPS

The last way to reduce the vulnerabilities is not to use GPS often. other methods are still in consideration are challenging global satellite systems like GLONASS and GALILEO. Galileo system is developed in cooperative way, so receivers able to navigate with GPS or Galileo some times if one failure.

last LORAN-C(Long range Navigation radio system) is consider and recommended as a back up to Global positioning system in volpe report.

Micro electromechanical systems

Attached a small inertial sensors inside of the antena it will improves anti jam perfomance

Conclusion