Difference between revisions of "Aufgaben:Exercise 3.2Z: Components of the GSM System"

From LNTwww
m (Text replacement - "[File:" to "[File:")
 
(13 intermediate revisions by 3 users not shown)
Line 1: Line 1:
  
  
−
{{quiz-Header|Buchseite=Mobile Kommunikation/Gemeinsamkeiten von GSM und UMTS
+
{{quiz-Header|Buchseite=Mobile_Communications/Similarities_Between_GSM_and_UMTS
  
 
}}
 
}}
 +
[[File:EN_Bei_Z_3_7.png|right|frame|GSM system components]]
 +
The diagram shows the entire GSM transmission path,  with the transmitter on the left and the receiver on the right.
  
−
[[File:EN_Mob_A_3_2_Z.png|right|frame|GSM system components]]
+
The illustration refers only to speech transmission.  In GSM data transmission,  only the top block  $($speech encoder or decoder$)$  is replaced by another channel encoder or decoder  $($concatenation of two channel codes$)$.
−
Die Grafik zeigt die gesamte Übertragungsstrecke des GSM,
 
−
*im linken Teil den Sender,  
 
−
*im rechten den Empfänger.
 
  
 +
The two respective lowest system components were already treated in detail in the exercises for the chapter  [[Examples_of_Communication_Systems/Radio_Interface|"Radio Interface"]].
  
−
Die Darstellung bezieht sich allein auf die Sprachübertragung. Bei der GSM–Datenübertragung wird nur der jeweils oberste Block (Sprachcoder bzw. –decoder) durch einen weiteren Kanalcoder/–decoder ersetzt (Verkettung zweier Kanalcodes).
+
In this exercise,  on the other hand,  some basic properties are queried from
 +
*Speech encoders and speech decoders,
  
−
Behandelt werden In dieser Aufgabe einige grundlegende Eigenschaften von
+
*convolutional encoder and convolutional decoder,
−
*Sprachcoder und Sprachdecoder,
 
−
*Faltungscoder und Faltungsdecoder,
 
−
*Interleaver und De–Interleaver sowie
 
−
*Verschlüsselung und Entschlüsselung.
 
  
 +
*interleaver and de-interleaver,  and
  
 +
*encryption and decryption.
  
  
  
  
 +
<u>Hint:</u>
 +
*The exercise belongs to the chapter&nbsp; [[Mobile_Communications/Similarities_Between_GSM_and_UMTS|"Similarities between GSM and UMTS"]].
  
−
''Hinweise:''
+
*Reference is also made to the chapter&nbsp;  [[Mobile_Communications/Characteristics_of_GSM|"Characteristics of GSM"]].
  
−
*Die Aufgabe gehört zum Kapitel&nbsp; [[Mobile_Kommunikation/Gemeinsamkeiten_von_GSM_und_UMTS|Gemeinsamkeiten von GSM und
 
−
UMTS]].
 
−
*Bezug genommen wird auch auf das Kapitel&nbsp;  [[Mobile_Kommunikation/Die_Charakteristika_von_GSM|Die Charakteristika von GSM]].
 
−
 
−
 
−
 
−
 
−
===Fragebogen===
 
  
 
<quiz display=simple>
 
<quiz display=simple>
−
 
+
{Which statements are true for speech encoding/decoding?
−
{Welche Aussagen treffen für die Sprachcodierung bzw. –decodierung zu?
 
 
|type="[]"}
 
|type="[]"}
−
+ Es handelt sich um Komponenten der Quellencodierung.
+
+ These are source coding components.
−
- Es handelt sich um Komponenten der Kanalcodierung.
+
- They are components of channel coding.
−
- Durch den Sprachcoder wird Redundanz hinzugefügt.
+
- Redundancy is added by the speech encoder.
−
+ Durch den Sprachcoder wird Redundanz entfernt.
+
+ Redundancy is removed by the speech encoder.
  
−
{Welche Aussagen treffen für den Faltungscodierer bzw. –decodierer zu?
+
{Which statements are true for the convolutional encoder or decoder?
 
|type="[]"}
 
|type="[]"}
−
- Es handelt sich um Komponenten der Quellencodierung.
+
- They are components of source coding.
−
+ Es handelt sich um Komponenten der Kanalcodierung.
+
+ They are components of channel coding.
−
+ Durch den Faltungscodierer wird Redundanz hinzugefügt.
+
+ Redundancy is added by the convolutional encoder.
−
- Durch den Faltungscodierer wird Redundanz entfernt.
+
- Redundancy is removed by the convolutional encoder.
  
−
{Welche Aussagen treffen für den Interleaver und De–Interleaver zu?
+
{Which statements are true for the interleaver and de-interleaver?
 
|type="[]"}
 
|type="[]"}
−
- Der Interleaver fügt Redundanz hinzu.
+
- The interleaver adds redundancy.
−
+ Der De–Interleaver dient dazu, Bündelfehler zu verteilen.
+
+ The interleaver is used to distribute bundle errors.
−
- Der Interleaver hat beim AWGN–Kanal die größte Bedeutung.
+
- The interleaver has the most significance for the AWGN channel.
  
−
{Welche Aussagen treffen für die Verschlüsselung und die Entschlüsselung zu?
+
{Which statements are true for encryption and decryption?
 
|type="[]"}
 
|type="[]"}
−
+ Beide dienen der Datensicherheit im Sinne von Datenschutz.
+
+ Both serve data security in the sense of data protection.
−
- Diese Komponenten dienen der Fehlerkorrektur.
+
- These components are for error correction.
−
- Die Verschlüsselung fügt Redundanz hinzu.
+
- Encryption adds redundancy.
−
+ GSM verwendet meist eine symmetrische Verschlüsselung.
+
+ GSM mostly uses symmetric encryption.
 +
</quiz>
  
−
</quiz>
 
  
−
===Musterlösung===
+
===Solution===
 
{{ML-Kopf}}
 
{{ML-Kopf}}
 +
'''(1)'''&nbsp; Correct are the&nbsp; <u>answers 1 and 4</u>:
 +
*The goal of speech coding is data compression and thus redundancy reduction.
 +
 +
*This is a typical task of source coding.
 +
 +
  
−
'''(1)'''&nbsp; Richtig sind die <u>Antworten 1 und 4</u>:
+
'''(2)'''&nbsp; Correct are the&nbsp; <u>answers 2 and 3</u>:
−
*Ziel der Sprachcodierung ist die Datenkomprimierung und damit die Redundanzminderung.  
+
*Convolutional coding is a form of channel coding by which the receiver&nbsp; (convolutional decoder)&nbsp; is enabled to detect and possibly correct errors.
−
*Dies ist eine typische Aufgabe der Quellencodierung.  
+
   
 +
*The channel encoder adds (meaningful) redundancy for this purpose,&nbsp; while the speech encoder removes irrelevant redundancy.
 +
 +
*Often both components are implemented together or at least closely coordinated.&nbsp; This is then referred to as&nbsp; "joint source and channel coding".  
  
  
−
'''(2)'''&nbsp; Richtig sind die <u>Antworten 2 und 3</u>:
 
−
*Faltungscodierung ist eine Form der Kanalcodierung, durch die der Empfänger (Decoder) in die Lage versetzt wird, Fehler zu erkennen und eventuell zu korrigieren.
 
−
*Der Kanalcodierer fügt hierzu (sinnvolle) Redundanz hinzu, während der Sprachcodierer irrelevante Redundanz entfernt.
 
−
*Häufig werden beide Komponenten gemeinsam realisiert oder zumindest eng aufeinander abgestimmt.
 
−
*Man spricht dann von &bdquo;gemeinsamer Quellen&ndash; und Kanalcodierung&rdquo;.
 
  
 +
'''(3)'''&nbsp; Only&nbsp; <u>answer 2</u>&nbsp; is correct:
 +
*The convolutional decoder has major problems when the transmission errors are clustered rather than they are statistically independent.
 +
 +
*The task of interleaver and de-interleaver is to break up such bunching errors and spread them over a larger time period.
 +
 +
*The redundancy is not changed by this procedure.
 +
 +
*In the AWGN channel,&nbsp; bit errors occur statistically independently,&nbsp; so interleaver and de-interleaver can be omitted.
  
−
'''(3)'''&nbsp; Richtig ist allein die <u>Antwort 2</u>:
 
−
*Der Faltungsdecoder hat große Probleme, wenn die Übertragungsfehler nicht statistisch unabhängig auftreten, sondern gebündelt.
 
−
*Aufgabe von Interleaver und De&ndash;Interleaver ist es, solche Bündelfehler aufzubrechen und über einen größeren Zeitraum zu verteilen.
 
−
*Die Redundanz wird durch diese Prozedur nicht verändert.
 
−
*Beim AWGN&ndash;Kanal treten Bitfehler statistisch unabhängig auf, so dass auf Interleaver und De&ndash;Interleaver verzichtet werden kann.
 
  
  
−
'''(4)'''&nbsp; Richtig sind die <u>Antworten 1 und 4</u>:
+
'''(4)'''&nbsp; Correct are the&nbsp; <u>answers 1 and 4</u>:
−
*Verschlüsselung und Entschlüsselung &ndash; das Gegenstück empfangsseitig &ndash; dienen nur dazu, die Nutzerdaten gegenüber unbefugtem Zugriff zu schützen.  
+
*Encryption and decryption&nbsp; (the counterpart on the receiving side)&nbsp; are used solely to protect user data from unauthorized access.
−
*Sie dienen aber nicht der Fehlerkorrektur und fügen auch keine Redundanz hinzu.  
+
−
*Man unterscheidet zwischen symmetrischer und asymmetrischer Verschlüsselung. GSM nutzt vorwiegend die erste Variante.  
+
*They are not used for error correction,&nbsp; nor do they add redundancy.
 +
 +
*A distinction is made between symmetric and asymmetric encryption.&nbsp; GSM predominantly uses the first variant.
  
  
Line 99: Line 100:
  
  
−
[[Category:Exercises for Mobile Communications|^3.2 Similarities between GSM and UMTS
+
[[Category:Mobile Communications: Exercises|^3.2 Similarities between GSM and UMTS
 
^]]
 
^]]

Latest revision as of 17:26, 30 January 2023


GSM system components

The diagram shows the entire GSM transmission path,  with the transmitter on the left and the receiver on the right.

The illustration refers only to speech transmission.  In GSM data transmission,  only the top block  $($speech encoder or decoder$)$  is replaced by another channel encoder or decoder  $($concatenation of two channel codes$)$.

The two respective lowest system components were already treated in detail in the exercises for the chapter  "Radio Interface".

In this exercise,  on the other hand,  some basic properties are queried from

  • Speech encoders and speech decoders,
  • convolutional encoder and convolutional decoder,
  • interleaver and de-interleaver,  and
  • encryption and decryption.



Hint:


1

Which statements are true for speech encoding/decoding?

These are source coding components.
They are components of channel coding.
Redundancy is added by the speech encoder.
Redundancy is removed by the speech encoder.

2

Which statements are true for the convolutional encoder or decoder?

They are components of source coding.
They are components of channel coding.
Redundancy is added by the convolutional encoder.
Redundancy is removed by the convolutional encoder.

3

Which statements are true for the interleaver and de-interleaver?

The interleaver adds redundancy.
The interleaver is used to distribute bundle errors.
The interleaver has the most significance for the AWGN channel.

4

Which statements are true for encryption and decryption?

Both serve data security in the sense of data protection.
These components are for error correction.
Encryption adds redundancy.
GSM mostly uses symmetric encryption.


Solution

Solution

(1)  Correct are the  answers 1 and 4:

  • The goal of speech coding is data compression and thus redundancy reduction.
  • This is a typical task of source coding.


(2)  Correct are the  answers 2 and 3:

  • Convolutional coding is a form of channel coding by which the receiver  (convolutional decoder)  is enabled to detect and possibly correct errors.
  • The channel encoder adds (meaningful) redundancy for this purpose,  while the speech encoder removes irrelevant redundancy.
  • Often both components are implemented together or at least closely coordinated.  This is then referred to as  "joint source and channel coding".


(3)  Only  answer 2  is correct:

  • The convolutional decoder has major problems when the transmission errors are clustered rather than they are statistically independent.
  • The task of interleaver and de-interleaver is to break up such bunching errors and spread them over a larger time period.
  • The redundancy is not changed by this procedure.
  • In the AWGN channel,  bit errors occur statistically independently,  so interleaver and de-interleaver can be omitted.


(4)  Correct are the  answers 1 and 4:

  • Encryption and decryption  (the counterpart on the receiving side)  are used solely to protect user data from unauthorized access.
  • They are not used for error correction,  nor do they add redundancy.
  • A distinction is made between symmetric and asymmetric encryption.  GSM predominantly uses the first variant.


Retrieved from "http://en.lntwww.de/index.php?title=Aufgaben:Exercise_3.2Z:_Components_of_the_GSM_System&oldid=52340"
  • Powered by MediaWiki