Difference between revisions of "Aufgaben:Exercise 4.4Z: Physical Channels in LTE"

Frequency/time assignment of the channels PDCCH and PDSCH

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The diagram shows the assignment of the two channels PDCCH and PDSCH in frequency and time:

One frequency block comprises $180 \ \rm kHz$ and is divided into twelve $15 \ \rm kHz$ –subcarriers
A subframe is one millisecond long and includes $14$ symbols.
Red marked are so called reference symbols.

Notes:

The task belongs to the chapter Bitübertragungsschicht bei LTE.

Questionnaire

Sample solution

Solution

(1) Correct are the solutions 3 and 4:

The assignment to Downlink or Uplink can be recognized by the second letter. It means:

PDCCH: Physical Downlink Control Channel,
PDSCH: Physical Downlink Shared Channel,
PUCCH: Physical Uplink Control Channel,
PUSCH: Physical Uplink Shared Channel.

(2) Correct are the solutions 2 and 4:

A "C" ⇒ Control as third letter indicates a control channel.
User data are always transferred to the Shared Channels ⇒ "S",

(3) All statements are correct:

A block in the LTE downlink occupies $180 \ \ \rm kHz$ (twelve subcarriers at $15 \ \ \rm kHz$ each) and has a duration of $1 \ \ \rm ms$ .
The assignment with PDCCH and PDSCH shows that the downlink is being considered.
The reference symbols are needed to estimate the channel quality and calculate the Channel Quality Indicator (CQI).
These reference symbols are distributed over different frequencies or symbols (different times) in order to estimate the channel quality as comprehensively as possible.

(4) The statement 1 is true because only two of the $14$ columns are occupied by the control channel PDCCH.

However, this result cannot be generalized. Rather, the division between PDCCH– and PDSCH symbols is dependent on the user's requirements and therefore dynamic.

For many users with a low data rate, the PDCCH would include three or four symbols, because this requires more intensive tuning than for a few concurrent users with high data rates.
The information "How many PDCCH symbols" is communicated to the terminal device via the Physical Control Format Indicator Channel (PCFICH).

(5) All statementsabove are correct:

The data rate of each user depends directly on the number of blocks of width $180 \ \rm kHz$ assigned to him.
The total LTI frequency width is between $1.4 \ \rm MHz$ and $20 \ \rm MHz$ .
In the frequency band of $1.4 \ \ \rm MHz$ six blocks of $180 \ \ \rm kHz$ are placed.
The overhead is thus $(1.4 - 6 \cdot 0.18)/1.4 \approx 22.8 \%$ .
At $20 \ \rm MHz$ total frequency width, i.e. $100$ blocks, the overhead is $(20 - 100 \cdot 0.18)/26 = 10 \ \ \%$ .
The more blocks are available in total, the more can be allocated to each individual user if his channel is good and if many other users do not also have high demands at the same time.

@@ Line 79: / Line 79: @@
 '''(2)'''&nbsp; Correct are the <u>solutions 2 and 4</u>:
-*Ein „C”  &nbsp; &rArr; &nbsp;   ''Control'' als dritter Buchstabe weist auf einen Kontrollkanal hin.
+*A "C" &nbsp; &rArr; &nbsp; ''Control'' as third letter indicates a control channel.
-* Nutzdaten werden stets in den ''Shared Channels''  &nbsp; &rArr; &nbsp; „S” übertragen,
+*User data are always transferred to the ''Shared Channels'' &nbsp; &rArr; &nbsp; "S",
+'''(3)'''&nbsp; <u>All statements</u> are correct:
+*A block in the LTE downlink occupies  $180 \ \ \rm kHz$  (twelve subcarriers at  $15 \ \ \rm kHz$  each) and has a duration of  $1 \ \ \rm ms$ .
+*The assignment with PDCCH and PDSCH shows that the downlink is being considered.
+*The reference symbols are needed to estimate the channel quality and calculate the ''Channel Quality Indicator'' (CQI).
+*These reference symbols are distributed over different frequencies or symbols (different times) in order to estimate the channel quality as comprehensively as possible.
-'''(3)'''&nbsp; <u>Alle Aussagen</u> sind zutreffend:
-*Ein Block im LTE–Downlink belegt im Frequenzbereich  $180 \ \rm kHz$  (zwölf Unterträger zu je  $15 \ \rm kHz$ ) und hat die Dauer  $1 \ \rm ms$ .
-*Die Belegung mit PDCCH und PDSCH zeigt, dass der Downlink betrachtet wird.
-*Die Referenzsymbole werden benötigt, um die Kanalqualität zu schätzen und den ''Channel Quality Indicator'' (CQI) zu berechnen.
-*Diese Referenzsymbole sind auf unterschiedliche Frequenzen bzw. Symbole (verschiedene Zeiten) verteilt, um die Kanalqualität möglichst umfassend schätzen zu können.
+'''(4)'''&nbsp; The <u>statement 1</u> is true because only two of the  $14$  columns are occupied by the control channel PDCCH.
-'''(4)'''&nbsp; Die <u>Aussage 1</u> stimmt, da hier nur zwei der  $14$  Spalten vom Kontrollkanal PDCCH belegt werden.
+However, this result cannot be generalized. Rather, the division between PDCCH&ndash; and PDSCH symbols is dependent on the user's requirements and therefore dynamic.
+*For many users with a low data rate, the PDCCH would include three or four symbols, because this requires more intensive tuning than for a few concurrent users with high data rates.
+*The information "How many PDCCH symbols" is communicated to the terminal device via the ''Physical Control Format Indicator Channel'' (PCFICH).
-Verallgemeinern kann man dieses Ergebnis allerdings nicht. Vielmehr ist die Aufteilung zwischen PDCCH&ndash; und PDSCH–Symbolen abhängig von den Anforderungen des Nutzers und damit dynamisch.
-*Bei vielen Nutzern mit niedriger Datenrate würde der PDCCH drei oder vier Symbole umfassen, weil hier eine intensivere Abstimmung nötig ist als bei wenigen gleichzeitigen Nutzern mit jeweils hoher Datenrate.
-*Dem Endgerät wird die Information „Wie viele PDCCH–Symbole” über den ''Physical Control Format Indicator Channel'' (PCFICH) mitgeteilt.
 '''(5)'''&nbsp; <u>All statements</u>above are correct:
-*Die Datenrate eines jeden Nutzers hängt direkt von der Anzahl der ihm zugewiesenen Blöcke der Breite  $180 \ \rm kHz$  ab.
+*The data rate of each user depends directly on the number of blocks of width  $180 \ \rm kHz$  assigned to him.
-*Die LTI–Gesamtfrequenzbreite liegt zwischen  $1.4 \ \rm MHz$  und  $20 \ \rm MHz$ .
+*The total LTI frequency width is between  $1.4 \ \rm MHz$  and  $20 \ \rm MHz$ .
-*In das Frequenzband von  $1.4 \ \rm MHz$  werden sechs Blöcke à  $180 \ \rm kHz$  untergebracht.
+*In the frequency band of $1.4 \ \ \rm MHz$ six blocks of $180 \ \ \rm kHz$ are placed.
-*Der Overhead beträgt somit  $(1.4 - 6 \cdot 0.18)/1.4 \approx 22.8 \%$ .
+*The overhead is thus  $(1.4 - 6 \cdot 0.18)/1.4 \approx 22.8 \%$ .
-*Bei  $20 \ \rm MHz$  Gesamtfrequenzbreite, also  $100$  Blöcken, ist der Overhead  $(20 - 100 \cdot 0.18)/26 = 10 \ \%$ .
+*At  $20 \ \rm MHz$  total frequency width, i.e.  $100$  blocks, the overhead is $(20 - 100 \cdot 0.18)/26 = 10 \ \ \%$.
-*Je mehr Blöcke insgesamt zur Verfügung stehen, desto mehr kann jedem einzelnen Nutzer zugewiesen werden, wenn sein Kanal gut ist und wenn nicht gleichzeitig viele andere Nutzer ebenfalls große Ansprüche stellen.
+*The more blocks are available in total, the more can be allocated to each individual user if his channel is good and if many other users do not also have high demands at the same time.
 {{ML-Fuß}}

	PDCCH,
	PDSCH,
	PUCCH,
	PUSCH.

	PDCCH,
	PDSCH,
	PUCCH,
	PUSCH.

	A transmission block for the downlink is shown.
	A block is the smallest addressable unit for LTE.
	The reference symbols are used to estimate the channel quality.

	In the example 6/7 of the symbols contain useful information.
	The statement "6/7 of the symbols carry useful information" applies generally.

	of the total available bandwidth,
	of the channel quality for this user,
	from the requirements of all users.

Difference between revisions of "Aufgaben:Exercise 4.4Z: Physical Channels in LTE"

Revision as of 20:00, 22 July 2020

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