Difference between revisions of "Exercise 2.2: xDSL Variants"

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{{quiz-Header|Buchseite=Beispiele von Nachrichtensystemen/xDSL–Systeme
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{{quiz-Header|Buchseite=Examples_of_Communication_Systems/xDSL_Systems
 
}}
 
}}
  
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[[File:P_ID1929__Bei_A_2_2.png|right|frame|Vorgegebene xDSL–Konfiguration]]
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[[File:EN_Bei_T_2_2_S4.png|right|frame|ADSL connection from the end customer to the local exchange]]
  
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„xDSL” ist ein sehr weit gefasster Oberbegriff, der eine ganze Reihe verschiedener Systemvarianten für schnellen Internetzugang beinhaltet:
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$\rm xDSL$  is a very broad generic term that includes a whole range of different system variants for fast Internet access:
  
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*$\color{red}{\boldsymbol{\rm ADSL}}$: ''Asymmetric Digital Subscriber Line'',
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*$\rm ADSL$:  ''Asymmetric Digital Subscriber Line'',
  
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*die Erweiterungen $\color{red}{\boldsymbol{\rm ADSL2}}$ und $\color{red}{\boldsymbol{\rm ADSL2+}}$,
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*the extensions  $\rm ADSL2$  and  $\rm ADSL2+$,
  
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*$\color{red}{\boldsymbol{\rm VDSL}}$: ''Very high–speed Digital Subscriber Line'', in Deutschland das System VDSL(2).
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*$\rm VDSL$:  ''Very high-speed Digital Subscriber Line'', in Germany the system  $\rm VDSL(2)$.
  
  
 +
The exercise includes some general questions about the three system variants mentioned above.
  
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Die Aufgabe beinhaltet einige Fragestellungen zu den drei oben genannten Systemvarianten. Die Grafik zeigt die Ortsvermittlungsstelle sowie den Kabelverzweiger einer der oben genannten Varianten.
 
  
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''Hinweis:''
 
  
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Die Aufgabe gehört zum Themengebiet von Kapitel [[Beispiele_von_Nachrichtensystemen/xDSL–Systeme|xDSL–Systeme]].
 
  
  
 +
Hints:
  
 +
*This exercise belongs to the chapter  [[Examples_of_Communication_Systems/xDSL_Systems|"xDSL Systems"]].
 +
*The graphic shows the local exchange as well as the cable branch of one of the above mentioned variants.
  
  
  
  
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===Fragebogen===
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 +
 
 +
 
 +
===Questions===
 
<quiz display=simple>
 
<quiz display=simple>
  
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{ Welche xDSL–Variante ist in der Grafik dargestellt?
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{ Which xDSL variant is shown in the graphic?
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|type="[]"}
+
|type="()"}
 
+ ADSL,
 
+ ADSL,
 
- VDSL.
 
- VDSL.
  
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{ Welche Aussagen stimmen: Bei xDSL liegt der Glasfaser–Abschlusspunkt
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{ Which statements are true: &nbsp;With xDSL, the optical fiber termination point is located
 
|type="[]"}
 
|type="[]"}
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- immer in der Ortsvermittlungsstelle,
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- always in the local exchange,
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+ im so genannten DSLAM,
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+ in the so-called DSLAM,
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- beim Endkunden.
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- at the end customer.
  
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{
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{ the telephone signal (analog or ISDN) and the xDSL signal are separated
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Telefonsignal (analog oder ISDN) und das xDSL–Signal werden getrennt
 
 
|type="[]"}
 
|type="[]"}
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- mit Hilfe eines Routers,
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- with the help of a router,
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- des DSLAM,
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- the DSLAM,
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- des DSL–Modems,
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- the DSL modem,
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+ des Splitters.
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+ the splitter.
  
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{ Welche der folgenden Aussagen sind richtig?
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{ Which of the following statements are correct?
 
|type="[]"}
 
|type="[]"}
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+ Bei ADSL sind stets $32 \ \rm kbit/s$ für Verwaltungsdaten reserviert.
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+ With ADSL, 32 kbit/s are always reserved for management data.
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- Bei ADSL2 sind stets  $32 \ \rm kbit/s$ für Verwaltungsdaten reserviert.
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- With ADSL2, 32 kbit/s are always reserved for management data.
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+ Eine Neuerung bei ADSL2 ist ''Seamless Rate Adaption''.
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+ An innovation in ADSL2 is&nbsp; ''Seamless Rate Adaption''.
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- VDSL(2) bietet stets eine höhere Datenrate als ADSL2+.
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- VDSL(2) always offers a higher data rate than ADSL2+.
  
  
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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; Die Grafik zeigt ADSL $\Rightarrow$  <u>Lösungsvorschlag 1</u>. Bei VDSL ist der DSLAM (''Digital Subscriber Line Access Multiplexer'') in den Kabelverzweiger verlegt.
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'''(1)'''&nbsp; Correct is the <u>proposed solution 1</u>: The graphic shows ADSL.  
 +
*In VDSL, the DSLAM (''Digital Subscriber Line Access Multiplexer'') is located in the cable branch.
 +
 
 +
 
 +
 
 +
'''(2)'''&nbsp; Only <u>the proposed solution 2</u> is correct:
 +
*The fiber termination point is usually in the DSLAM in DSL. Only in the ADSL variant is the DSLAM located in the local exchange.
 +
*In contrast, the DSLAM in the VDSL variant is located in the cable distribution frame (or for the VDSL(2) variant in the ''Outdoor DSLAM'' next to the cable distribution frame) in order to reduce the "last mile" (length of the copper line) and thus achieve higher data rates.
 +
*The fiber optic termination is located at the end customer only if FttH or FttB technologies are used.
 +
*However, it is then no longer DSL.
 +
 
 +
 
 +
 
 +
'''(3)'''&nbsp; Only <u>the proposed solution 4</u> is correct:
 +
*The ''splitter'' contains one low-pass and one high-pass filter.
 +
*It can thus separate the low frequencies (telephone signal) from the higher frequencies (xDSL signal).
  
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'''(2)'''&nbsp; Der Glasfaser–Abschlusspunkt liegt bei DSL stets im DSLAM. Nur in der ADSL–Variante befindet sich der DSLAM in der Ortsvermittlungsstelle.
 
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Dagegen ist der DSLAM in der VDSL–Variante im Kabelverzweiger (oder für die VDSL(2)– Variante im Outdoor DSLAM neben dem Kabelverzweiger) untergebracht, um die „Last Mile” (Länge der Kupferleitung) zu reduzieren und somit höhere Datenraten zu erreichen. Der Glasfaserabschluss befindet sich beim Endkunden nur dann, wenn FttH– oder FttB–Technologien eingesetzt werden. Es handelt sich dann allerdings nicht mehr um DSL. Richtig ist somit allein <u>der Lösungsvorschlag 2</u>.
 
  
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'''(3)'''&nbsp; Der <u>Splitter</u> beinhaltet je ein Tief– und Hochpassfilter und kann damit die niedrigen Frequenzen (Telefonsignal) von den höheren Frequenzen (xDSL–Signal) trennen.
 
  
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'''(4)'''&nbsp; Richtig sind die <u>Aussagen 1 und 3</u>: Bei ADSL–Systemen werden tatsächlich stets $32 \ \rm kbit/s$ für Verwaltungsdaten reserviert. Dagegen kann bei ADSL2 die Länge des Overheads zwischen $4$ und  $32 \ \rm kbit/s$ variieren. Bei einer Reduzierung erreicht man eine höhere Nutzdatenrate.
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'''(4)'''&nbsp; Correct are<u>statements 1 and 3</u>:  
 +
*In fact, ADSL systems always reserve 32 kbit/s for administrative data.  
 +
*In contrast, with ADSL2 the length of the overhead can vary between 4 kbit/s and 32 kbit/s. If it is reduced, a higher user data rate is achieved.
 +
*Statement 3 is correct: By including ''Seamless Rate Adaptation'' in the standard, a possible loss of synchronization in case of a variation of the channel quality can be avoided.
  
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Die Aussage 3 ist richtig: Durch die Aufnahme von ''Seamless Rate Adaption'' in den Standard kann ein eventueller Verlust der Synchronisation bei einer Variation der Kanalgüte vermieden werden.
 
  
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Dagegen ist die letzte Aussage falsch. Die maximal erreichbare Datenrate beträgt bei VDSL(2) zwar (theoretisch) $250 \ \rm Mbit/s$. Die Datenrate sinkt aber bei einer Entfernung von $500  \ \rm m$ auf bis zu $100 \  \rm Mbit/s$. Bei $2000 \ \rm m$ Kupferleitung beträgt sie sogar weniger als $10 \  \rm Mbit/s$. ADSL2+ erreicht dagegen maximal „nur” $ 25 \  \rm Mbit/s$, aber die Datenrate nimmt bei größerer Entfernung deutlich langsamer ab als VDSL(2) und beträgt bei $2000 \  \rm m$ ungefähr noch $15 \ \rm Mbit/s$. Der „Schnittpunkt” liegt bei ungefähr $1500 \  \rm m$.
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In contrast, the last statement is incorrect:
 +
*The maximum achievable data rate for VDSL(2) is indeed (theoretically) 250 Mbit/s. However, the data rate drops to as low as 100 Mbit/s at a distance of 500 meters. At 2000 meters of copper line, it is even less than 10 Mbit/s.  
 +
*ADSL2+, on the other hand, achieves a maximum of "only" 25 Mbit/s, but the data rate decreases much more slowly than VDSL(2) at greater distances and is still approximately 15 Mbit/s at 2000 meters. The "intersection point" is at about 1500 meters.
  
  
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[[Category:Aufgaben zu Beispiele von Nachrichtensystemen|^2.2 xDSL–Systeme
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[[Category:Examples of Communication Systems: Exercises|^2.2 xDSL Systems
 
^]]
 
^]]

Latest revision as of 11:16, 22 March 2023

ADSL connection from the end customer to the local exchange

$\rm xDSL$  is a very broad generic term that includes a whole range of different system variants for fast Internet access:

  • $\rm ADSL$:  Asymmetric Digital Subscriber Line,
  • the extensions  $\rm ADSL2$  and  $\rm ADSL2+$,
  • $\rm VDSL$:  Very high-speed Digital Subscriber Line, in Germany the system  $\rm VDSL(2)$.


The exercise includes some general questions about the three system variants mentioned above.



Hints:

  • This exercise belongs to the chapter  "xDSL Systems".
  • The graphic shows the local exchange as well as the cable branch of one of the above mentioned variants.




Questions

1

Which xDSL variant is shown in the graphic?

ADSL,
VDSL.

2

Which statements are true:  With xDSL, the optical fiber termination point is located

always in the local exchange,
in the so-called DSLAM,
at the end customer.

3

the telephone signal (analog or ISDN) and the xDSL signal are separated

with the help of a router,
the DSLAM,
the DSL modem,
the splitter.

4

Which of the following statements are correct?

With ADSL, 32 kbit/s are always reserved for management data.
With ADSL2, 32 kbit/s are always reserved for management data.
An innovation in ADSL2 is  Seamless Rate Adaption.
VDSL(2) always offers a higher data rate than ADSL2+.


Solution

Solution

(1)  Correct is the proposed solution 1: The graphic shows ADSL.

  • In VDSL, the DSLAM (Digital Subscriber Line Access Multiplexer) is located in the cable branch.


(2)  Only the proposed solution 2 is correct:

  • The fiber termination point is usually in the DSLAM in DSL. Only in the ADSL variant is the DSLAM located in the local exchange.
  • In contrast, the DSLAM in the VDSL variant is located in the cable distribution frame (or for the VDSL(2) variant in the Outdoor DSLAM next to the cable distribution frame) in order to reduce the "last mile" (length of the copper line) and thus achieve higher data rates.
  • The fiber optic termination is located at the end customer only if FttH or FttB technologies are used.
  • However, it is then no longer DSL.


(3)  Only the proposed solution 4 is correct:

  • The splitter contains one low-pass and one high-pass filter.
  • It can thus separate the low frequencies (telephone signal) from the higher frequencies (xDSL signal).


(4)  Correct arestatements 1 and 3:

  • In fact, ADSL systems always reserve 32 kbit/s for administrative data.
  • In contrast, with ADSL2 the length of the overhead can vary between 4 kbit/s and 32 kbit/s. If it is reduced, a higher user data rate is achieved.
  • Statement 3 is correct: By including Seamless Rate Adaptation in the standard, a possible loss of synchronization in case of a variation of the channel quality can be avoided.


In contrast, the last statement is incorrect:

  • The maximum achievable data rate for VDSL(2) is indeed (theoretically) 250 Mbit/s. However, the data rate drops to as low as 100 Mbit/s at a distance of 500 meters. At 2000 meters of copper line, it is even less than 10 Mbit/s.
  • ADSL2+, on the other hand, achieves a maximum of "only" 25 Mbit/s, but the data rate decreases much more slowly than VDSL(2) at greater distances and is still approximately 15 Mbit/s at 2000 meters. The "intersection point" is at about 1500 meters.


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