Introduction

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來自 Institut Mines-Télécom 的課程

Introduction to Satellite Communications

180 個評分

Institut Mines-Télécom

Introduction to Satellite Communications

180 個評分

How is a satellite built? How do they fly? How do they communicate and how does the network operate? You will get all the answers in this course from teachers and researchers from three schools associated with Institut Mines-Télécom. The course is made of : teaching videos, equipment demonstrations and simulation programs. They will guide you through the discovery of satellite communications. Professionals in the space field will share there vocation for this scientific and technical sector. Have you ever wanted to know more about transponders, the geostationary orbit, QPSK modulation, channel coding, link budget, TCP over large bandwdith x delay product links ? This course is for you! This course is available in English: French-speaking lecturers with English subtitles and fully translated contents (slides, practices). This MOOC is supported by the Patrick and Lina Drahi Foundation.

從本節課中

Digital communications

This module discusses the basics of information transmission

Introduction3:43

Bit rate / symbol rate2:15

Concept of frequency1:48

Bandwidth occupied by the signal3:45

Bandwidth / rate relation3:32

Carrier transmission2:56

與講師見面

Laurent Franck
Professor
IMT Atlantique, on leave to Airbus Defence & Space as of September 1st, 2017
Tarik Benaddi
Assistant Professor
IMT Atlantique
Julien Fasson
Associate Professor
INPT/ENSEEIHT
Nathalie Thomas
Associate professor
INPT/ENSEEIHT
Marie-Laure Boucheret
Professor
INPT/ENSEEIHT

-In the previous sequence, we saw that the role of the modulator

found within the transmitter was to build a signal

from the original binary information to be transmitted.

This sequence aims at having a closer look at how this signal can be built

and looking at the impact of the signal formation

on the transmission chain.

No matter how the signal is built, the principle is identical.

We associate a different physics symbol to each bit

or group of bits to be transmitted.

We will start this sequence by introducing a few signals.

Here, two different signals

for a same binary sequence to be transmitted.

In the first case, 0s are coded with a low level

and 1s are coded with a high level. This is level coding.

It is a NRZ-type signal meaning Non Return to Zero.

This signal can be found in GPS systems.

The two levels can be two voltage levels.

In the second signal example, coding is done via an edge.

0s are coded with a rising edge and 1s are coded with a falling edge.

This signal is called Manchester type.

It can be found in the Ethernet for example.

You see that, for a same binary sequence,

we have formed two different signals with different appearances.

In both cases, a physics symbol codes one bit.

But we could imagine a physics symbol coding several bits.

Like here, where a physics symbol codes a group of two bits.

So there are four possible physics symbols

to code the four possible groups that can be formed with two bits,

that is to say 00, 01, 11 and 10.

The duration of this physics symbol is the symbol duration.

You see here that it increased since we coded two bits in one symbol.

We can go further

and code three bits in a symbol like here.

So we will need eight different levels, here we have a level coding,

to code the eight possible groups of three bits to form eight symbols.

We note that the symbol duration increased again

since we code three bits with one symbol.

The signal dynamics also increased. The signal dynamics is the difference

between the minimal and maximal amplitude of the signal.

If we want to keep the same distance between each levels,

and we increase the number of levels, the signal dynamics increases.

The minimal distance between symbols

will impose the bit error rate we get,

which measures the quality of the transmission.

The bit error rate

is linked to the minimal distance between the symbols.

The energy dedicated to transmission is linked to the signal dynamics.

Later on, we will see that the number of bits put in a symbol

is linked to the band used by the signal.

This is something you do not know yet, but we will talk about it later on.

The band used by the signal

will depend on the number of bits put in a symbol.

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