Difference between revisions of "Aufgaben:Exercise 5.1: FDMA, TDMA and CDMA"

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{{quiz-Header|Buchseite=Modulationsverfahren/Aufgaben_und_Klassifizierung
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{{quiz-Header|Buchseite=Modulation_Methods/Tasks_and_Classification
 
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[[File:P_ID1862__Mod_A_5_1.png|right|frame|FDMA, TDMA und CDMA]]
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[[File:EN_Mod_A_5_1.png|right|frame|FDMA, TDMA and CDMA]]
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Das Schaubild verdeutlicht das Prinzip von
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The diagram illustrates the principle of
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* ''Frequency Division Multiple Access''  $\rm (FDMA)$,
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# Frequency Division Multiple Access  $\rm (FDMA)$,
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* ''Time Division Multiple Access''  $\rm (TDMA)$, und
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# Time Division Multiple Access  $\rm (TDMA)$,
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* ''Code Division Multiple Access''  $\rm (CDMA)$.
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# Code Division Multiple Access  $\rm (CDMA)$.
  
  
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Bei den hier aufgeführten  ''Vielfachzugriffsverfahren''  geht man davon aus, dass es mehrere Sender–Empfänger–Paare gibt, die sich ein Übertragungsmedium selbständig aufteilen.  Dagegen spricht man von  ''Multiplexing'', wenn am Anfang eines Übertragungsweges ein Multiplexer  $\rm (MUX)$  mehrere Signale bündelt und am Ende ein Demultiplexer  $\rm (DEMUX)$  das gemeinsame Signal wieder auftrennt.  Hierfür verwendet man abkürzend  $\rm FDM$, $\rm TDM$  und  $\rm CDM$ – also  ''Frequency (Time, Code) Division Multiplexing.''
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In the  "multiple access methods"  listed here,  it is assumed that there are several transmitter-receiver pairs that independently divide up a transmission medium.   
  
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In der vorliegenden Aufgabe ist gefragt, welche dieser Verfahren (FDMA/FDM, TDMA/TDM, CDMA/CDM) einige der auch heute noch wichtigen Kommunikationssysteme (DSL,GSM, UMTS) nutzen.
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"Multiplexing",   on the other hand,  is when a multiplexer  $\rm (MUX)$  bundles several signals at the beginning of a transmission path and a demultiplexer  $\rm (DEMUX)$  splits the common signal again at the end. 
  
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The following abbreviations are used for this purpose:
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# Frequency Division Multiplexing  $\rm (FDM)$,
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# Time Division Multiplexing  $\rm (TDM)$,
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# Code Division Multiplexing  $\rm (CDM)$.
  
  
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This exercise asks which of these methods (FDMA/FDM, TDMA/TDM, CDMA/CDM) are used by some of the communication systems (DSL,GSM, UMTS) that are still important today.
  
  
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''Hinweise:''
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Notes:  
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*Die Aufgabe gehört zum  Kapitel  [[Modulation_Methods/Aufgaben_und_Klassifizierung|Aufgaben und Klassifizierung]].
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*The exercise belongs to the chapter  [[Modulation_Methods/Aufgaben_und_Klassifizierung|Tasks and Classification]].
 
   
 
   
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*Informationen zu den betrachteten Kommunikationssystemen finden Sie unter folgenden Links:
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*Information on the communications systems under consideration can be found under the following links:
 
:[[Examples_of_Communication_Systems/Allgemeine_Beschreibung_von_DSL|(1) Digital Subscriber Line]]  $\rm (DSL)$,
 
:[[Examples_of_Communication_Systems/Allgemeine_Beschreibung_von_DSL|(1) Digital Subscriber Line]]  $\rm (DSL)$,
 
:[[Examples_of_Communication_Systems/Allgemeine_Beschreibung_von_GSM|(2) Global System for Mobile Communications]]  $\rm (GSM)$,
 
:[[Examples_of_Communication_Systems/Allgemeine_Beschreibung_von_GSM|(2) Global System for Mobile Communications]]  $\rm (GSM)$,
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===Fragebogen===
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===Questions===
  
 
<quiz display=simple>
 
<quiz display=simple>
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{Was bezeichnen FDMA, TDMA und CDMA?
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{What do FDMA, TDMA and CDMA refer to?
 
|type="[]"}
 
|type="[]"}
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- Modulationsverfahren,
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- Modulation methods,
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+ Vielfachzugriffsverfahren,
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+ Multiple access methods,
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- Entzerrungsverfahren.
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- Equalization methods.
  
  
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{Welche dieser Verfahren sind nur bei Digitalsystemen anwendbar?
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{Which of these methods can only be used with digital systems?
 
|type="[]"}
 
|type="[]"}
 
- FDMA/FDM,
 
- FDMA/FDM,
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+ CDMA/CDM.
 
+ CDMA/CDM.
  
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{Welche Technik(en) nutzt der europäische 2G–Mobilfunkstandard GSM?
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{Which method(s) does the European 2G mobile communications standard GSM use?
 
|type="[]"}
 
|type="[]"}
 
+ FDMA/FDM,
 
+ FDMA/FDM,
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-  CDMA/CDM.
 
-  CDMA/CDM.
  
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{Welche Technik(en) nutzt der 3G–Mobilfunkstandard UMTS?
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{Which method(s) does the 3G mobile communications standard UMTS use?
 
|type="[]"}
 
|type="[]"}
 
+ FDMA/FDM,
 
+ FDMA/FDM,
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+  CDMA/CDM.
 
+  CDMA/CDM.
  
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{Welche Technik(en) nutzt das „schnelle Internet” (DSL)?
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{Which method(s) does the "fast Internet" (DSL) use?
 
|type="[]"}
 
|type="[]"}
 
+ FDMA/FDM,
 
+ FDMA/FDM,
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</quiz>
 
</quiz>
  
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===Musterlösung===
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===Solution===
 
{{ML-Kopf}}
 
{{ML-Kopf}}
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'''(1)'''&nbsp;   Richtig ist die <u>Antwort 2</u>:
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'''(1)'''&nbsp; <u>Solution 2</u>&nbsp; is correct:
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*FDMA, TDMA und CDMA sind Vielfachzugriffsverfahren oder auch Multiplextechniken, die man dann allerdings mit FDM, TDM und CDM abkürzt: &nbsp; <br>''Frequency (Time, Code) Division Multiplexing''.
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*FDMA, TDMA and CDMA are multiple access methods or multiplexing techniques,&nbsp; which are then abbreviated to FDM, TDM and CDM: &nbsp; <br>"Frequency (Time, Code) Division Multiplexing".
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*Mit Modulation und Entzerrung haben diese Begriffe nichts zu tun.
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*These terms have nothing to do with modulation and equalization.
  
  
  
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'''(2)'''&nbsp; Richtig sind die <u>Antworten 2 und 3</u>:
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'''(2)'''&nbsp; <u>Solutions 2 and 3</u>&nbsp; are correct:
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*FDMA wird auch bei Analogsystemen eingesetzt, wofür die klassische Rundfunkübertragung (seit den 1930er Jahren) ein Beispiel ist.
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*FDMA is also used in analog systems,&nbsp; of which classical broadcasting&nbsp; (since the 1930s)&nbsp; is an example.
  
  
  
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'''(3)'''&nbsp; Richtig sind die <u>Antworten 1 und 2</u>:
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'''(3)'''&nbsp; <u>Solutions 1 and 2</u>&nbsp; are correct:
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*Bei GSM werden FDMA und TDMA genutzt.  
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*GSM uses FDMA and TDMA.  
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*Im so genannten D–Band (Uplink: 890 – 915 MHz, Downlink: 935 – 960 MHz) gibt es unter Berücksichtigung der Guard–Bänder von je 100 kHz am oberen und unteren Bereichsende in jeder Richtung 124 FDMA–Kanäle zu je 200 kHz.  
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*In the so-called&nbsp; "D&ndash;band"&nbsp; (uplink: 890 – 915 MHz,&nbsp; downlink: 935 – 960 MHz),&nbsp; there are 124 FDMA channels of 200 kHz each at the upper and lower ends of the range in each direction,&nbsp; taking into account the guard bands of 100 kHz each.  
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*Im E–Band (Uplink: 1710 – 1785 MHz, Downlink: 1805 – 1880 MHz) sind 374 FDMA–Kanäle nutzbar.
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*In the&nbsp; "E&ndash;band"&nbsp; (uplink: 1710 – 1785 MHz, downlink: 1805 – 1880 MHz),&nbsp; 374 FDMA channels can be used.
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*Mit Zeitmultiplex (TDMA) können in jedem Frequenzband zusätzlich acht Teilnehmer versorgt werden.&nbsp;  
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*With time division multiplexing&nbsp; (TDMA)&nbsp; an additional eight subscribers can be supplied in each frequency band.
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*Ein TDMA–Rahmen hat die Länge 4.62 ms, so dass für jeden Teilnehmer in diesem zeitlichen Abstand Zeitschlitze von 0.577 ms Dauer zur Verfügung stehen.
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*A TDMA frame has a length of 4.62 ms,&nbsp; so that time slots of 0.577 ms duration are available for each subscriber in this time interval.
  
  
  
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'''(4)'''&nbsp; Richtig sind die <u>Antworten 1 und 3</u>:
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'''(4)'''&nbsp; <u>Solutions 1 and 3</u>&nbsp; are correct:
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*Die in Deutschland eingesetzte&nbsp; UMTS–Variante&nbsp; "UMTS Terrestrial Radio Access–Frequency Division Duplex"&nbsp; (UTRA–FDD) besteht aus je zwölf gepaarten Uplink– und Downlink–Frequenzbändern zu je 5 MHz Bandbreite zwischen 1920 MHz und 1980 MHz&nbsp; (Uplink)&nbsp; bzw. zwischen 2110 MHz und 2170 MHz&nbsp; (Downlink).  
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*The&nbsp; UMTS variant&nbsp; "UMTS Terrestrial Radio Access–Frequency Division Duplex"&nbsp; (UTRA–FDD)&nbsp; used in Germany consists of twelve paired uplink and downlink frequency bands,&nbsp; each with a bandwidth of 5 MHz,&nbsp; between 1920 MHz and 1980 MHz&nbsp; (uplink)&nbsp; and between 2110 MHz and 2170 MHz&nbsp; (downlink).  
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*Es liegt somit stets auch eine FDMA–Komponente vor.&nbsp; In jedem der 5 MHz–Bänder wird zudem CDMA eingesetzt, so dass in jedem Frequenzband gleichzeitig bis zu 512 Teilnehmer aktiv sein können.
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*Thus,&nbsp; there is always an FDMA component.&nbsp; CDMA is also used in each of the 5 MHz bands,&nbsp; so that up to 512 subscribers can be active simultaneously in each frequency band.
  
  
  
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'''(5)'''&nbsp; Richtig ist nur die <u>Antwort 1</u>:
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'''(5)'''&nbsp; <u>Solution 1</u> is&nbsp; correct:
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*Für schnelle Internetanbindungen wird heutzutage üblicherweise DSL&nbsp; (''Digital Subscriber Line'')&nbsp; eingesetzt.  
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*Nowadays,&nbsp; DSL&nbsp; ("Digital Subscriber Line")&nbsp; is usually used for fast Internet connections.  
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*Dieses basiert auf OFDM&nbsp; (''Orthogonal Frequency Division Multiplexing''), was eine FDM–Variante ist.  
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*This is based on OFDM&nbsp; ("Orthogonal Frequency Division Multiplexing"),&nbsp; which is an FDM variant.
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*Die einzelnen Spektren sind dabei allerdings nicht getrennt, sondern überlappen sich.  
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*However,&nbsp; the individual spectra are not separated,&nbsp; but rather overlap.  
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*Aufgrund der Orthogonalität kommt es trotzdem nicht zu gegenseitiger Beeinflussung.
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*Due to the orthogonality,&nbsp; however,&nbsp; there is no mutual interference.
  
 
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[[Category:Modulation Methods: Exercises|^5.1 Vielfachzugriffsverfahren^]]
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[[Category:Modulation Methods: Exercises|^5.1 Multiple Access Methods^]]

Latest revision as of 18:37, 27 November 2021

FDMA, TDMA and CDMA

The diagram illustrates the principle of

  1. Frequency Division Multiple Access  $\rm (FDMA)$,
  2. Time Division Multiple Access  $\rm (TDMA)$,
  3. Code Division Multiple Access  $\rm (CDMA)$.


In the  "multiple access methods"  listed here,  it is assumed that there are several transmitter-receiver pairs that independently divide up a transmission medium.   

"Multiplexing",  on the other hand,  is when a multiplexer  $\rm (MUX)$  bundles several signals at the beginning of a transmission path and a demultiplexer  $\rm (DEMUX)$  splits the common signal again at the end. 

The following abbreviations are used for this purpose:

  1. Frequency Division Multiplexing  $\rm (FDM)$,
  2. Time Division Multiplexing  $\rm (TDM)$,
  3. Code Division Multiplexing  $\rm (CDM)$.


This exercise asks which of these methods (FDMA/FDM, TDMA/TDM, CDMA/CDM) are used by some of the communication systems (DSL,GSM, UMTS) that are still important today.



Notes:

  • Information on the communications systems under consideration can be found under the following links:
(1) Digital Subscriber Line  $\rm (DSL)$,
(2) Global System for Mobile Communications  $\rm (GSM)$,
(3) Universal Mobile Communications Systems  $\rm (UMTS)$.


Questions

1

What do FDMA, TDMA and CDMA refer to?

Modulation methods,
Multiple access methods,
Equalization methods.

2

Which of these methods can only be used with digital systems?

FDMA/FDM,
TDMA/TDM,
CDMA/CDM.

3

Which method(s) does the European 2G mobile communications standard GSM use?

FDMA/FDM,
TDMA/TDM,
CDMA/CDM.

4

Which method(s) does the 3G mobile communications standard UMTS use?

FDMA/FDM,
TDMA/TDM,
CDMA/CDM.

5

Which method(s) does the "fast Internet" (DSL) use?

FDMA/FDM,
TDMA/TDM,
CDMA/CDM.


Solution

Solution

(1)  Solution 2  is correct:

  • FDMA, TDMA and CDMA are multiple access methods or multiplexing techniques,  which are then abbreviated to FDM, TDM and CDM:  
    "Frequency (Time, Code) Division Multiplexing".
  • These terms have nothing to do with modulation and equalization.


(2)  Solutions 2 and 3  are correct:

  • FDMA is also used in analog systems,  of which classical broadcasting  (since the 1930s)  is an example.


(3)  Solutions 1 and 2  are correct:

  • GSM uses FDMA and TDMA.
  • In the so-called  "D–band"  (uplink: 890 – 915 MHz,  downlink: 935 – 960 MHz),  there are 124 FDMA channels of 200 kHz each at the upper and lower ends of the range in each direction,  taking into account the guard bands of 100 kHz each.
  • In the  "E–band"  (uplink: 1710 – 1785 MHz, downlink: 1805 – 1880 MHz),  374 FDMA channels can be used.
  • With time division multiplexing  (TDMA)  an additional eight subscribers can be supplied in each frequency band.
  • A TDMA frame has a length of 4.62 ms,  so that time slots of 0.577 ms duration are available for each subscriber in this time interval.


(4)  Solutions 1 and 3  are correct:

  • The  UMTS variant  "UMTS Terrestrial Radio Access–Frequency Division Duplex"  (UTRA–FDD)  used in Germany consists of twelve paired uplink and downlink frequency bands,  each with a bandwidth of 5 MHz,  between 1920 MHz and 1980 MHz  (uplink)  and between 2110 MHz and 2170 MHz  (downlink).
  • Thus,  there is always an FDMA component.  CDMA is also used in each of the 5 MHz bands,  so that up to 512 subscribers can be active simultaneously in each frequency band.


(5)  Solution 1 is  correct:

  • Nowadays,  DSL  ("Digital Subscriber Line")  is usually used for fast Internet connections.
  • This is based on OFDM  ("Orthogonal Frequency Division Multiplexing"),  which is an FDM variant.
  • However,  the individual spectra are not separated,  but rather overlap.
  • Due to the orthogonality,  however,  there is no mutual interference.

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