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![Page 1: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/1.jpg)
Adaptive modulation schemes for frequency selective fading channels
Mª Carmen Aguayo Torres, José Paris Angel,
José Tomás Entrambasaguas Muñoz
Universidad de MálagaEscuela Técnica Superior de Ingeniería de Telecomunicación
![Page 2: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/2.jpg)
2Universidad de Málaga
Conclusions
Conclusions
AOFDM,ADFE,ATHP
AOFDM,ADFE,ATHP
Contents
Adaptive QAM
(AQAM)
Adaptive QAM
(AQAM)
OFDM, DFE and THP
OFDM, DFE and THP
Introduction
Introduction
![Page 3: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/3.jpg)
3Universidad de Málaga
Introduction
• Time spread– Frequency selectivity
• Multipath– Time selectivity or fading
Time and frequency
selective channel
At an instant of time, distinct frequencies have different gains and phases
At a single frequency: the channel change with time
Mobile environment
![Page 4: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/4.jpg)
4Universidad de Málaga
Time selectivity
Adaptive transmission techniques
Simple way to face fading: use enough power or transmit slowly enough
Inefficient
Possibility: Modify the transmitted signal depending on the instantaneous channel conditions
Any signal parameter can be modified: power, symbol period, modulation scheme...
![Page 5: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/5.jpg)
5Universidad de Málaga
Adaptive QAMHigh bit rates when channel is suitableSlow down the transmission when the channel gets worse
Time selectivity
Modify constellation sizePower and symbol period are kept
Adaptive modulation levelR
ece
ive
d s
ign
al
time
Used constellatio
n: BPSK
Used constellatio
n: BPSK
Used constellatio
n:16QAM
Used constellatio
n:16QAM
![Page 6: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/6.jpg)
6Universidad de Málaga
Frequency selectivity
Several techniques against frequency selectivity
Equalization
Decision feedback equalization
Problem:error propagation
Tomlinson-Harashima pre-equalization
Linear equalization enhances noise
Disadvantage:transmitter needs knowledge about the channelTDD
![Page 7: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/7.jpg)
7Universidad de Málaga
Other possibility:
splitting up the whole band width in narrow flat subbands
Frequency selectivity
Overlapped but orthogonal spectra
Multicarrier modulation or OFDM
Problem:time selective channels destroy the orthogonality
![Page 8: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/8.jpg)
8Universidad de Málaga
Time and frequency selective channel
Time and frequency selective channel
Adaptive DFE, THP or
OFDM
Adaptive DFE, THP or
OFDM
Adaptive QAM
Adaptive QAM
FadingchannelFadingchannel
Adaptive OFDM, DFE and THP
DFE, THP orOFDM
DFE, THP orOFDM
Frequency selective channel
Frequency selective channel
Adaptive modulation can be used over each subcarrier in OFDM or over the equivalent channel after equalization
![Page 9: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/9.jpg)
9Universidad de Málaga
Time and frequency selective channel
Conclusions
Conclusions
AOFDM,ADFE,ATH
AOFDM,ADFE,ATH
Fixed constellationFrequency selective
Flat fading channel
Contents
OFDM, DFE and THP
OFDM, DFE and THP
Adaptive QAM
(AQAM)
Adaptive QAM
(AQAM)
Introduction
Introduction
![Page 10: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/10.jpg)
10Universidad de Málaga
Channel model
System model
Efficiency and BER
Conclusions
Conclusions
AOFDM,ADFE,ATH
AOFDM,ADFE,ATH
Contents
OFDM, DFE and THP
OFDM, DFE and THP
Adaptive QAM
(AQAM)
Adaptive QAM
(AQAM)
Introduction
Introduction
![Page 11: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/11.jpg)
11Universidad de Málaga
Flat fading channel model
Propagation model
The signal arrives through a multitude of rays of different gains and phases but similar lengths
Channel model
System model
Efficiency and BER
Flat fading channel
![Page 12: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/12.jpg)
12Universidad de Málaga
Flat fading channel model
x(t)
h(t)
y(t)
FLAT FADING CHANNEL
Flat fading channel
Propagation model
The signal arrives through a multitude of rays of different gains and phases but similar lengths
Complex Gaussian distributionTime variations: fD
![Page 13: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/13.jpg)
13Universidad de Málaga
AQAM system model
Modify the bit rate to get closer the variable channel capacity
Channel model
System model
Efficiency and BER
![Page 14: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/14.jpg)
14Universidad de Málaga
AQAM system model
Return channel
R[n] bits/segSymbol period: T
b[n] x[n]
h[n] nAWGN[n]
Adaptive transmitter
Adaptive receiver
Channel
y[n] [n]b̂
Modify the bit rate to get closer the variable channel capacity
![Page 15: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/15.jpg)
15Universidad de Málaga
AQAM transmitter model
m[n+1]
1
U2
Adaptivemodulator
x[n]
m[n]
b[n] To the direct channel
From return channel
S/P
m[n] is variable and under receiver controlU constellations and no-transmission
U+1 modulation regions
![Page 16: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/16.jpg)
16Universidad de Málaga
AQAM receiver model
m[n]
1 S/P
y[n]
U2
Adaptivedetector
m[n]
m[n+1]To the return channel
From the direct
channel
[n]
Grid adjust
Channel estimation
Contellation selector
[n]b̂
![Page 17: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/17.jpg)
17Universidad de Málaga
Adaptation algorithm
• 5 modulation regions– No transmission– QPSK– 16QAM– 64QAM– 256QAM
ber(
m,
)
10-6
10-5
10-4
10-3
10-2
10-1
100
5 10 15 20 25 30 35
(dB)
m = 2
QPSK
Average BER
Po
![Page 18: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/18.jpg)
18Universidad de Málaga
Adaptation algorithm
ber(
m,
)
10-6
10-5
10-4
10-3
10-2
10-1
100
5 10 15 20 25 30 35
(dB)
ber() m()
2
4
6
8
0
1 2 43
442
4332
3222
2112
1
M
M
M
M
00
)m
)(log
)(log
)(log
)(log
(
• 5 modulation regions– No transmission– QPSK– 16QAM– 64QAM– 256QAM
![Page 19: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/19.jpg)
19Universidad de Málaga
Average efficiency and BER
Average efficiency
Average of m()
Channel model
System model
Efficiency and BER
![Page 20: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/20.jpg)
20Universidad de Málaga
Average efficiency and BER
10-6
10-5
10-4
10-3
10-2
10-1
100
5 10 15 20 25 30 35 (dB)
2
4
6
8
0
ber() m()
Average efficiency
Average of m()
![Page 21: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/21.jpg)
21Universidad de Málaga
Average efficiency and BER
Po = 10-2
Average efficiency
Average of m()
![Page 22: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/22.jpg)
22Universidad de Málaga
Average BER
Average of the instantaneous BER ber()
Average efficiency and BER
10-6
10-5
10-4
10-3
10-2
10-1
100
5 10 15 20 25 30 35 (dB)
2
4
6
8
0
ber() m()
![Page 23: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/23.jpg)
23Universidad de Málaga
Average efficiency and BER
Average BER
Average of the instantaneous BER ber()
![Page 24: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/24.jpg)
24Universidad de Málaga
Average efficiency and BER
At 23 dB, QPSK has the same BER than AQAM, but half efficiency
![Page 25: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/25.jpg)
25Universidad de Málaga
Conclusions
Conclusions
AOFDM,ADFE,ATH
AOFDM,ADFE,ATH
Contents
OFDM, DFE and THP
OFDM, DFE and THP
Adaptive QAM
(AQAM)
Adaptive QAM
(AQAM)
Introduction
Introduction
Channel model
OFDM
DFE and THP
![Page 26: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/26.jpg)
26Universidad de Málaga
Frequency selective fading channel model
Small symbol period propagation paths can be distinguished
frequency selective fading channel
Channel model
OFDM
DFE and THP
![Page 27: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/27.jpg)
27Universidad de Málaga
Frequency selective fading channel model
x(t) y(t)
FREQUENCY SELECTIVE FADING CHANNEL
h0 (t)
Retardo 0Retardo 0
hL-1 (t)
Retardo L-1Retardo L-1
Channel output comes from adding L different echos which passed through a flat fading channel
Small symbol period propagation paths can be distinguished
frequency selective fading channel
![Page 28: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/28.jpg)
28Universidad de Málaga
Frequency selective fading channel model
number, delay and average power of each ray
0 1 2 3 4 50
0.1
0.2
0.3
0.4
Ray delay, l (s)
Nor
mal
ized
pow
er
Typical Urban Channel
Power profile
![Page 29: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/29.jpg)
29Universidad de Málaga
Frequency selective fading channel model
Frequency responseAt each frequency, the response is different and variable in time
In average, SNR is the same for all
frequencies
![Page 30: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/30.jpg)
30Universidad de Málaga
OFDM system model
s0a
,ˆ
s1a
,ˆ
s1Na
,ˆ
IDF
Ta1,s
x[n]
nW [n]
h[n,i]y[n]P/S
+Ext
DF
TExt+
S/P
aN-1,s
a0,s
Channel model
OFDM
DFE and THP
![Page 31: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/31.jpg)
31Universidad de Málaga
OFDM system model
s0a
,ˆ
s1a
,ˆ
s1Na
,ˆ
IDF
Ta1,s
x[n]
nW [n]
h[n,i]y[n]P/S
+Ext
DF
TExt+
S/P
aN-1,s
a0,s
Cyclic extension
Eliminates ISI
Linear convolution with the channel appears as circular
Total period Tt = T + TgUseful period: N Ts
mmmmNHaa ˆ
For a constant channel, OFDM can be considered as N parallel channels Fourier transform of the channel
impulse response sampled at each subcarrier frequency
![Page 32: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/32.jpg)
32Universidad de Málaga
OFDM system model
s0a
,ˆ
s1a
,ˆ
s1Na
,ˆ
IDF
Ta1,s
x[n]
nW [n]
h[n,i]y[n]P/S
+Ext
DF
TExt+
S/P
aN-1,s
a0,s
f
f = fs/N
f
Fourier transform of the pulse
![Page 33: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/33.jpg)
33Universidad de Málaga
m
1N
mk0kmkkmmmm
NHaHaa,
,,ˆ Intercarrier Interference (ICI)
Doppler spread effects
f
The transference function Hm,m results from the average over a symbol period
Received pulses over fading channels are not orthogonal
![Page 34: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/34.jpg)
34Universidad de Málaga
Interference analysis
Signal to Interference Ratio, SIR
1N
mk0k
2
mk
2
mm
H E
H E
,.
.
SIR depends on fDTbut not on the power profile
Useful signal power
Interference of the k subcarrier on the m one
![Page 35: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/35.jpg)
35Universidad de Málaga
High SNR are limited by interference
Interference analysis
Intercarrier interference added Gaussian noise
Signal to Noise and Interference ratio, SNIR 1
11
![Page 36: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/36.jpg)
36Universidad de Málaga
Performance results
BER
QPSKRayleigh channel
![Page 37: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/37.jpg)
37Universidad de Málaga
DFE system model
Channel model
OFDM
DFE and THP
x[n]b[n]
DFE TX
![Page 38: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/38.jpg)
38Universidad de Málaga
nW [n]
y[n]h[n,i]
DFE system model
[n]b̂Feedforward Filter
Feedback FilterDFE RX
x[n]b[n]
DFE TX
Error propagation:Depends on specific channel
![Page 39: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/39.jpg)
39Universidad de Málaga
DFE system model
ZF DFE
For FIR channels, only feedback filter is necessary
[n]b̂
Feedback Filter
ZF DFE RX
nW [n]
y[n]h[n,i]
x[n]b[n]
DFE TX
Grid adjustment
![Page 40: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/40.jpg)
40Universidad de Málaga
THP system model
Moving the feedback filter to the transmitter: no error propagation
Preequalizer Filter
s[n]b[n]
THP TX
xy[n]
Gk
x[n]
v[n]
x
GainControl
+u[n]
Mod{·}
Gk-1
![Page 41: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/41.jpg)
41Universidad de Málaga
THP system model
nW [n]
r[n]h[n,i]
y[n]
ZF THP RX
x
GainControl
Mod{·}[n]b̂
A[n]^
![Page 42: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/42.jpg)
42Universidad de Málaga
THP system model
Moving the feedback filter to the transmitter: no error propagation
Preequalizer Filter
s[n]b[n]
THP TX
xy[n]
Gk
x[n]
v[n]
x
GainControl
+u[n]
Mod{·}
Gk-1
Transmitted signal is like-QAM but continuous
Power penalty QPSK:Average: 1.0 dBMaximum: 5.6 dB
![Page 43: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/43.jpg)
43Universidad de Málaga
5 10 15 20 25 30 35 10-5
10-3
10-2
10-1
10-0 B
ER
(dB)
DFE-I
DFE
THP
10-4
Performance results
QPSKTU channel
BER
Power penalty
Error propagation
![Page 44: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/44.jpg)
44Universidad de Málaga
Adaptive QAM
(AQAM)
Adaptive QAM
(AQAM)
AOFDM
ADFE
ATHP
Conclusions
Conclusions
AOFDM,ADFE,ATH
AOFDM,ADFE,ATH
Contents
OFDM, DFE and THP
OFDM, DFE and THP
Introduction
Introduction
![Page 45: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/45.jpg)
45Universidad de Málaga
System model
Return channel
R[n] bits/sec
Adaptive receiver
Adaptivetransmitter
x[n]b[n]
nAWGN[n]
h[n,i]y[n]
Channel
[n]b̂
Modifying the bits per second transmitted depending on the instantaneous channel conditions
![Page 46: Adaptive modulation schemes for frequency selective fading channels Mª Carmen Aguayo Torres, José Paris Angel, José Tomás Entrambasaguas Muñoz Universidad.](https://reader033.fdocuments.us/reader033/viewer/2022052701/56649dbe5503460f94ab1eb8/html5/thumbnails/46.jpg)
46Universidad de Málaga
Adaptive OFDM
Signal properties can be selected depending on gain and noise at each subcarrier
OFDM splits up the whole bandwidth in parallel flat channels
AOFDM
ADFE
ATHP
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47Universidad de Málaga
Adaptive OFDM
f
SNR(f)
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48Universidad de Málaga
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49Universidad de Málaga
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50Universidad de Málaga
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51Universidad de Málaga
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52Universidad de Málaga
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53Universidad de Málaga
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54Universidad de Málaga
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55Universidad de Málaga
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56Universidad de Málaga
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57Universidad de Málaga
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58Universidad de Málaga
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59Universidad de Málaga
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60Universidad de Málaga
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61Universidad de Málaga
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62Universidad de Málaga
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63Universidad de Málaga
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64Universidad de Málaga
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65Universidad de Málaga
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66Universidad de Málaga
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67Universidad de Málaga
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68Universidad de Málaga
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69Universidad de Málaga
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70Universidad de Málaga
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71Universidad de Málaga
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72Universidad de Málaga
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