Aufgaben:Exercise 3.4: Different Voice Codecs - Revision history

Hwang at 11:28, 23 January 2023

2023-01-23T11:28:35Z

Javier: Text replacement - "”" to """

2021-05-28T14:47:23Z

Text replacement - "”" to """

Javier: Text replacement - "„" to """

2021-05-28T14:46:59Z

Text replacement - "„" to """

Javier: Text replacement - "Category:Exercises for Mobile Communications" to "Category:Mobile Communications: Exercises"

2021-03-23T12:37:10Z

Text replacement - "Category:Exercises for Mobile Communications" to "Category:Mobile Communications: Exercises"

Guenter at 12:13, 20 February 2021

2021-02-20T12:13:33Z

Guenter at 16:54, 20 January 2021

2021-01-20T16:54:23Z

Guenter at 16:31, 20 January 2021

2021-01-20T16:31:33Z

Guenter at 16:21, 20 January 2021

2021-01-20T16:21:38Z

Guenter at 16:04, 20 January 2021

2021-01-20T16:04:21Z

Javier: Text replacement - "===Sample Solution===" to "===Solution==="

2020-12-15T14:10:45Z

Text replacement - "===Sample Solution===" to "===Solution==="

@@ Line 6: / Line 6: @@
 [[File:P_ID2221__Mob_A_3_4.png|right|frame|Audiosignale von "Narrow–Band" <br>und "Wide–Band"]]
 The development of the GSM standard after 1990 was accompanied by the standardization of various voice codecs:
-*With the first&nbsp; "Full-Rate Codec"&nbsp; $\rm (FR)$&nbsp; from 1991 a reduction to the data rate&nbsp; $13 \ \rm kbit/s$&nbsp; was achieved, sufficiently low to be able to transmit a voice signal over a single traffic channel.
+*With the first&nbsp; "Full Rate Codec"&nbsp; $\rm (FR)$&nbsp; from 1991 a reduction to the data rate&nbsp; $13 \ \rm kbit/s$&nbsp; was achieved, sufficiently low to be able to transmit a speech signal over a single traffic channel.
-*In 1994 the&nbsp; "Half-Rate Codec"&nbsp; $\rm (HR)$&nbsp; with the bitrate&nbsp; $5.6 \ \rm kbit/s$&nbsp; was developed with the aim of being able to transmit two calls simultaneously in one traffic channel if required.&nbsp; However, the quality does not quite reach the full-rate codec.
+*In 1994 the&nbsp; "Half Rate Codec"&nbsp; $\rm (HR)$&nbsp; with the bitrate&nbsp; $5.6 \ \rm kbit/s$&nbsp; was developed with the aim of being able to transmit two calls simultaneously in one traffic channel if required.&nbsp; However, the quality does not quite reach the full rate codec.
-*The&nbsp; "Enhanced Full-Rate Codec"&nbsp; $\rm (EFR)$&nbsp; from 1995 represented a significant development based on the data reduction method&nbsp; $\rm  ACELP$&nbsp; ("Algebraic Code Excited Linear Prediction"). The EFR codec delivers a data rate of&nbsp; $12.2 \ \rm kbit/s$&nbsp; and stands for the common quality standard in mobile communications nowadays.
+*The&nbsp; "Enhanced Full Rate Codec"&nbsp; $\rm (EFR)$&nbsp; from 1995 represented a significant development based on the data reduction method&nbsp; $\rm  ACELP$&nbsp; ("Algebraic Code Excited Linear Prediction"). The EFR codec delivers a data rate of&nbsp; $12.2 \ \rm kbit/s$&nbsp; and stands for the common quality standard in mobile communications nowadays.
-*In 1999, ETSI standardized the&nbsp;Adaptive Multi-Rate Codec"&nbsp; $\rm  (AMR)$&nbsp; for GSM.&nbsp; This provides eight different modes with data rates between&nbsp; $4.75 \ \ \rm kbit/s$&nbsp; and&nbsp; $12.2 \ \ \rm kbit/s$&nbsp;.&nbsp; The AMR codec uses the ACELP method like the EFR codec.
+*In 1999, ETSI standardized the&nbsp;Adaptive Multi Rate Codec"&nbsp; $\rm  (AMR)$&nbsp; for GSM.&nbsp; This provides eight different modes with data rates between&nbsp; $4.75 \ \ \rm kbit/s$&nbsp; and&nbsp; $12.2 \ \ \rm kbit/s$&nbsp;.&nbsp; The AMR codec uses the ACELP method like the EFR codec.
 *The&nbsp; "Wideband AMR"&nbsp; $\rm(WB-AMR)$&nbsp; is a further development of the original AMR.&nbsp; It was standardized by the 3GPP consortium in 2001 and by ITU-T in 2002 and uses the frequency range from&nbsp; $50 \ \rm Hz$&nbsp; to&nbsp; $7 \rm kHz$.&nbsp; This corresponds to a "'''W'''ide'''B'''and signal".
@@ Line 64: / Line 64: @@
 '''(2)'''&nbsp; Correct are the <u>answers 2 and 3</u>:
-*The EFR codec from 1995 is a significant development of the "Full&ndash;Rate Codecs" from 1991, whereby, among other things, speech quality is less impaired by background noise.
+*The EFR codec from 1995 is a significant development of the "Full Rate Codecs" from 1991, whereby, among other things, speech quality is less impaired by background noise.
 *Like the AMR, the EFR codec is based on the data reduction method ACELP ("Algebraic Code Excited Linear Prediction").
 *The first proposed solution is wrong.&nbsp; Like the FR and AMR codecs, the EFR codec is only designed for the telephone channel &nbsp; $(300 \ \rm Hz$&nbsp;&ndash; $3.4 \ \rm kHz)$.
@@ Line 74: / Line 74: @@
 *The advantage of the AMR codec over the EFR is its greater flexibility.
 *If the channel quality deteriorates significantly, it is possible to switch smoothly to a low-rate mode where transmission errors are less disturbing.
-*In addition, as with the "Half&ndash;Rate Codec", it is possible to have two conversations in one traffic channel.
+*In addition, as with the "Half Rate Codec", it is possible to have two conversations in one traffic channel.
 *The highest mode at&nbsp; $\rm 12.2 \ kbit/s$&nbsp; - and not the lowest - is identical to the EFR codec.&nbsp; It is therefore obvious that AMR cannot provide better voice quality than EFR.
@@ Line 81: / Line 81: @@
 '''(4)'''&nbsp;  <u>All answers are correct</u>:
 *Nine modes are provided in wideband&ndash;AMR, but only five of them are used for mobile communications, namely those with data rates of&nbsp; $6.60$,&nbsp; $8.85$,&nbsp; $12.65$,&nbsp; $15.85$,&nbsp; and&nbsp; $\text{23.65 kbit/s}$.
-*The modes up to&nbsp; $\text{12.65 kbit/s}$&nbsp; have the advantage that a voice signal encoded in this way can be accommodated in a single GSM traffic channel.&nbsp; For the higher rate modes, GSM/EDGE or UMTS is required.
+*The modes up to&nbsp; $\text{12.65 kbit/s}$&nbsp; have the advantage that a speech signal encoded in this way can be accommodated in a single GSM traffic channel.&nbsp; For the higher rate modes, GSM/EDGE or UMTS is required.
 *The higher rate modes&nbsp; $(15.85$&nbsp; and&nbsp; $\text{23.65 kbit/s})$&nbsp; provide only a slight improvement for speech, but due to the larger frequency range, they provide a noticeable improvement for the transmission of music.
 *Both the wideband AMR and the higher modes of narrowband AMR show weaknesses here.&nbsp; An even lower data rate gives extremely poor results with music signals.

@@ Line 4: / Line 4: @@
 }}
-[[File:P_ID2221__Mob_A_3_4.png|right|frame|Audiosignale von "Narrow–Band&rdquo; <br>und "Wide–Band&rdquo;]]
+[[File:P_ID2221__Mob_A_3_4.png|right|frame|Audiosignale von "Narrow–Band" <br>und "Wide–Band"]]
 The development of the GSM standard after 1990 was accompanied by the standardization of various voice codecs:
 *With the first&nbsp; "Full-Rate Codec"&nbsp; $\rm (FR)$&nbsp; from 1991 a reduction to the data rate&nbsp; $13 \ \rm kbit/s$&nbsp; was achieved, sufficiently low to be able to transmit a voice signal over a single traffic channel.

@@ Line 4: / Line 4: @@
 }}
-[[File:P_ID2221__Mob_A_3_4.png|right|frame|Audiosignale von &bdquo;Narrow–Band&rdquo; <br>und &bdquo;Wide–Band&rdquo;]]
+[[File:P_ID2221__Mob_A_3_4.png|right|frame|Audiosignale von "Narrow–Band&rdquo; <br>und "Wide–Band&rdquo;]]
 The development of the GSM standard after 1990 was accompanied by the standardization of various voice codecs:
 *With the first&nbsp; "Full-Rate Codec"&nbsp; $\rm (FR)$&nbsp; from 1991 a reduction to the data rate&nbsp; $13 \ \rm kbit/s$&nbsp; was achieved, sufficiently low to be able to transmit a voice signal over a single traffic channel.

← Older revision		Revision as of 12:37, 23 March 2021
Line 90:		Line 90:


−	[[Category:~~Exercises for~~ Mobile Communications\|^3.2 Similarities between GSM and UMTS	+	[[Category:Mobile Communications: Exercises\|^3.2 Similarities between GSM and UMTS
	^]]		^]]

@@ Line 65: / Line 65: @@
 '''(2)'''&nbsp; Correct are the <u>answers 2 and 3</u>:
 *The EFR codec from 1995 is a significant development of the "Full&ndash;Rate Codecs" from 1991, whereby, among other things, speech quality is less impaired by background noise.
-*Like the AMR, the EFR codec is based on the data reduction method ACELP (''Algebraic Code Excited Linear Prediction'').
+*Like the AMR, the EFR codec is based on the data reduction method ACELP ("Algebraic Code Excited Linear Prediction").
 *The first proposed solution is wrong.&nbsp; Like the FR and AMR codecs, the EFR codec is only designed for the telephone channel &nbsp; $(300 \ \rm Hz$&nbsp;&ndash; $3.4 \ \rm kHz)$.
 *For better intelligibility and to avoid a dull sound, there is also a mid-range boost and a low-frequency cut.

@@ Line 57: / Line 57: @@
 {{ML-Kopf}}
-'''(1)'''&nbsp; Correct are the <u>solution suggestions 1 and 3</u>:
+'''(1)'''&nbsp; Correct are the <u>answers 1 and 3</u>:
-*The required data rate is reduced by removing redundancy and irrelevance from the data signal
+*The required data rate is reduced by removing redundancy and irrelevance from the data signal.
-*The artificial word &bdquo;Codec&rdquo; indicates that the same functional unit is used for both encoding and decoding.
+*The artificial word "codec" indicates that the same functional unit is used for both encoding and decoding.
 '''(2)'''&nbsp; Correct are the <u>answers 2 and 3</u>:
-*The EFR&ndash;Codec from 1995 is a significant development of the ''Full&ndash;Rate Codecs'' from 1991, whereby, among other things, speech quality is less affected by background noise.
+*The EFR codec from 1995 is a significant development of the "Full&ndash;Rate Codecs" from 1991, whereby, among other things, speech quality is less impaired by background noise.
-*Like the AMR, the EFR&ndash;Codec is based on the data reduction method ACELP (''Algebraic Code Excited Linear Prediction'').
+*Like the AMR, the EFR codec is based on the data reduction method ACELP (''Algebraic Code Excited Linear Prediction'').
-*The first proposed solution is wrong. Like the FR and AMR codecs, the EFR codec is only designed for the telephone channel (300 Hz to 3.4 kHz).
+*The first proposed solution is wrong.&nbsp; Like the FR and AMR codecs, the EFR codec is only designed for the telephone channel &nbsp; $(300 \ \rm Hz$&nbsp;&ndash; $3.4 \ \rm kHz)$.
 *For better intelligibility and to avoid a dull sound, there is also a mid-range boost and a low-frequency cut.
-'''(3)'''&nbsp;Only the <u>solution 2</u> is correct:
+'''(3)'''&nbsp;Only the <u>answers 2</u> is correct:
-*The advantage of the AMR&ndash;codec over the EFR is its greater flexibility.
+*The advantage of the AMR codec over the EFR is its greater flexibility.
 *If the channel quality deteriorates significantly, it is possible to switch smoothly to a low-rate mode where transmission errors are less disturbing.
-*In addition, as with the Half&ndash Rate Codec, it is possible to have two conversations in one traffic channel.
+*In addition, as with the "Half&ndash;Rate Codec", it is possible to have two conversations in one traffic channel.
-*The highest mode at 12.2 kbit/s - and not the lowest - is identical to the EFR codec. It is therefore obvious that AMR cannot provide better voice quality than EFR.
+*The highest mode at&nbsp; $\rm 12.2 \ kbit/s$&nbsp; - and not the lowest - is identical to the EFR codec.&nbsp; It is therefore obvious that AMR cannot provide better voice quality than EFR.
 '''(4)'''&nbsp;  <u>All answers are correct</u>:
-*Nine modes are provided in wideband&ndash;AMR, but only five of them are used for mobile communications, namely those with data rates of 6.60, 8.85, 12.65, 15.85 and 23.65 kbit/s.
+*Nine modes are provided in wideband&ndash;AMR, but only five of them are used for mobile communications, namely those with data rates of&nbsp; $6.60$,&nbsp; $8.85$,&nbsp; $12.65$,&nbsp; $15.85$,&nbsp; and&nbsp; $\text{23.65 kbit/s}$.
-*The modes up to 12.65 kbit/s have the advantage that a voice signal encoded in this way can be accommodated in a single GSM&ndash;traffic channel. For the higher rate modes, GSM/EDGE or UMTS is required.
+*The modes up to&nbsp; $\text{12.65 kbit/s}$&nbsp; have the advantage that a voice signal encoded in this way can be accommodated in a single GSM traffic channel.&nbsp; For the higher rate modes, GSM/EDGE or UMTS is required.
-*The higher rate modes (15.85 and 23.65 kbit/s) provide only a slight improvement for speech, but due to the larger frequency range, they provide a noticeable improvement for the transmission of music.
+*The higher rate modes&nbsp; $(15.85$&nbsp; and&nbsp; $\text{23.65 kbit/s})$&nbsp; provide only a slight improvement for speech, but due to the larger frequency range, they provide a noticeable improvement for the transmission of music.
-*Both the WB-AMR 12.65 and the higher modes of (narrowband) AMR show weaknesses here. An even lower data rate gives extremely poor results with music signals.
+*Both the wideband AMR and the higher modes of narrowband AMR show weaknesses here.&nbsp; An even lower data rate gives extremely poor results with music signals.
-*The WB-AMR has a better voice quality than the NB-AMR with 12.2 kbit/s even at a comparable data rate (12.65 kbit/s). Due to the greater bandwidth, speech sounds more natural and sibilants such as "s", "f" and "sch" become more intelligible.
+*The WB-AMR has a better voice quality than the NB-AMR with  a comparable data rate&nbsp; $\text{(12.65 kbit/s)}$.&nbsp; Due to the greater bandwidth, speech sounds are more natural and sibilants such as "s", "f" and "sch" become more intelligible.
 {{ML-Fuß}}

@@ Line 20: / Line 20: @@
 *The task belongs to the chapter&nbsp; [[Mobile_Communications/Similarities_Between_GSM_and_UMTS|Similarities between GSM and UMTS]].
 *The graph shows the magnitude spectrum of an audio signal and defines the characteristics "narrowband" and "wideband".
-*We refer you to the interactive SWF applet&nbsp; [[Applets:Quality_of_different_voice_codecs_(Applet)|Qualität verschiedener  Sprachcodecs &nbsp; &rArr; &nbsp; Quality of different voice codecs]] &nbsp;  (based on "Shock Wave Flash",&nbsp; German language).
+*We refer you to the interactive SWF applet&nbsp; [[Applets:Quality_of_different_voice_codecs_(Applet)|Qualität verschiedener  Sprachcodecs &nbsp; &rArr; &nbsp; Quality of different voice codecs]] &nbsp;  <br>(based on "Shock Wave Flash",&nbsp; German language).
@@ Line 27: / Line 27: @@
 <quiz display=simple>
-{What tasks does a speech codec perform?
+{What tasks does a voice codec perform?
 |type="[]"}
 + It is used for rate reduction of digitised speech.
@@ Line 33: / Line 33: @@
 + It is used for coding and decoding.
-{What advantages does the EFR codec offer compared to the FR codec?
+{What advantages does the&nbsp; $\rm EFR$&nbsp; codec offer compared to the&nbsp; $\rm FR$&nbsp; codec?
 |type="[]"}
-- It is designed for broadband signals $($frequency range: &nbsp; $200 \ \ \rm Hz$&nbsp; bis&nbsp; $7 \ \rm kHz)$&nbsp;.
+- It is designed for broadband signals $($frequency range: &nbsp; $200 \ \ \rm Hz$&nbsp;&ndash; $7 \ \rm kHz)$&nbsp;.
-+ It provides better sound quality.
++ It provides better voice quality.
 + The improvement is due to the ACELP method.
-{What are the advantages of the AMR codec over the EFR codec?
+{What are the advantages of the&nbsp; $\rm AMR$&nbsp;  codec over the&nbsp; $\rm EFR$&nbsp; codec?
 |type="[]"}
 - It provides better voice quality.
@@ Line 45: / Line 45: @@
 - The lowest mode is identical to the EFR standard.
-{What are the characteristics of WB-AMR?
+{What are the characteristics of&nbsp; $\text{WB-AMR}$?
 |type="[]"}
-+ The audio frequency range is&nbsp; $50 \ \rm Hz$&nbsp; bis&nbsp; $7 \ \rm kHz$.
++ The audio frequency range is&nbsp; $50 \ \rm Hz$&nbsp;&ndash; $7 \ \rm kHz$.
-+ It provides modes between&nbsp; $6.60 \ \ \rm kHz$&nbsp; and&nbsp; $23.85 \ \rm kHz$&nbsp;.
++ It provides modes between&nbsp; $6.60 \ \ \rm kHz$&nbsp; and&nbsp; $23.85 \ \rm kHz$.
 + GSM is not sufficient for the higher rate modes.