Post on 03-Apr-2020
PLC Transmission PLC Transmission Prototype using TDS-O d Ch lOFDM and MV Channel ModelingModeling
Jian SongDept Of Electronic EngineeringDept. Of Electronic Engineering
Tsinghua University2012-03-29
OutlineOutline
Introduction
TDS-OFDM based PLC Prototype
Medium-Voltage Channel Modeling
Summary and Future Plan
DTV Technology R&D Center
OutlineOutline
Introduction
TDS-OFDM based PLC Prototype
Medium-Voltage Channel Modeling
Summary and Future Plan
DTV Technology R&D Center
ObjectiveObjective
Major system parameters j y pBandwidth: 20MHz (with scalability)Length of frame body: 4096 data symbolsLength of frame head: 350 and 700 symbolsModulation: QPSK/16QAM/64QAM/256QAMFEC rate: 0 4/0 6FEC rate: 0.4/0.6
Performance specificationsMax. throughput: 160 Mbps (W/O PN)Max. payload: >100MbpsMax multi path delay: 25usMax. multi-path delay: 25usMax. frequency offset: 300Hz
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OutlineOutline
Introduction
TDS-OFDM based PLC Prototype
Medium-Voltage Channel Modeling
Summary and Future Plan
DTV Technology R&D Center
System block diagramSystem block diagramFrame Head
FECMappingInterleaver
Scrambler
MUX
FrameBodyPro-
i
BasebandProcessing
Datainput
CombinePowerLine
SystemInformation
X cessing
SynchronizerDigital Signal
Processor
ADC SRRC filterChannel Estimator
and EqualizerPower Line
De-interleaverDe-mappingLDPC decoder
De-scramblerOutput data
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Characteristic of TDS-OFDMCharacteristic of TDS OFDM
PN sequence is used as the guard interval, PN sequence is used as the guard interval, as well as the training sequence for the channel acquisition, time synchronization, and channel estimationMain featureFast channel acquisition since this can be done directly
in the time domain, robust for timing variable channel
High spectrum efficiency as it avoids both continuousHigh spectrum efficiency as it avoids both continuous and scattered pilot insertion into the frame body by CP-OFDM approach
More accurate channel estimation due mainly to the good correlation of PN sequence (spreading gain)
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TDS-OFDM vs C-OFDMC-OFDM
Copy
CP IDFT D t Pil t CP IDFT D t Pil t
Copy
C-OFDM
CP IDFT Data+Pilots CP IDFT Data+Pilots
IDFT DataGI ZP could be another possible padding
C-OFDM:Process in Frequency domainIDFT=Inverse Discrete Fourier Transform
ZP could be another possible padding
TDS-OFDM Symbol
PN IDFT Data IDFT DataPNTDS-OFDM
PN IDFT Data IDFT DataPN
TDS-OFDM:Process in Time/Frequency domain
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Interference Cancellation is NEEDED
Channel estimation is challengingChannel estimation is challenging- Mutual interference between Data and PN sequence
Transmitted Signal
DATA DATAPN PN
g
ConvolutionReceived Signal
DATA PN DATA PN
?PN signal without
PN
?g
interference from dataDouble PN to avoid
mutual interference?
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PN
Hardware Platform
The highest payload data e g est pay oad datathroughput is 104 Mbps within 20MHz by using 256-QAM and LDPC rate of 0.6
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Prototype SetupPrototype Setup
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Frame Structure DesignFrame Structure Design
, 1 ,Lt
Lu
m i m i
p p
p p1, ,m i m i p p
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Multiple AccessMultiple Access
Scalable TDMA + TDS-OFDMA
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Scalable TDMA + TDS-OFDMA
Adaptive Bit LoadingAdaptive Bit Loading
Bit-loading algorithms for multi-rate Bit-loading algorithms for multi-rate LDPC coded OFDM system Optimization overOptimization overQPSK/16QAM/64QAM/256QAM
LDPC 0 4/0 6LDPC 0.4/0.6
Adapt the Constellation & coding mode according to the SNR estimation on each according to the SNR estimation on each sub-carrier and SNR threshold for each code rate and constellationcode rate and constellation
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OutlineOutline
Introduction
TDS-OFDM based PLC Prototype
Medium-Voltage Channel Modeling
Summary and Future Plan
DTV Technology R&D Center
Channel modelingChannel modeling
N
Approximation by the echo model:
0 1
1
2 /( ) i i pN
a a f
ii
k d j f d vH f g e e
attenuation delayh
1i attenuation delayweighting portion portion factor
E d fi itiError definition:
1 M
1
1 M
i ii
ERR H yM
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1iM
Channel measurementChannel measurement
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MV-Measurements
DTV Technology R&D Center 18Frequency (MHz)
MV-Measurements (cont’d)( )
DTV Technology R&D Center 19Frequency (MHz)
Average Attenuationg
10
-20
-10
Attenuation in three siteSite A--Site BSite B--Site ASite B--Site CSite C--Site B
-40
-30
B
-60
-50
Atte
nuat
ion:
dB
-80
-70
0 5 10 15 20 25 30 35 40-100
-90
Frequency:MHz
DTV Technology R&D CenterFrequency (MHz)
Frequency:MHz
Measurement (site B-> site A)
-20Station B --> Station A
meas
-30
meas.model
-40
dB
-60
-50
|H(f)
| in
-70
0 5 10 15 20 25 30-80
Frequency in MHz, ERR=0.697dB
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Measurement (site A-> site B)Measurement (site A > site B)
-20Station A --> Station B
-30
20meas.model
-40
B
-50
|H(f)
| in
dB
-70
-60
0 5 10 15 20 25 30-80
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Frequency in MHz, ERR=1.27dB
OutlineOutline
Introduction
TDS-OFDM based PLC prototype
Medium-voltage Channel Modeling
Summary and Future Plan
DTV Technology R&D Center
SummarySummary
TDS OFDM h l i f ibl b TDS-OFDM technology is feasible to be adopted by the powerline communication systems with potentially high spectrum efficiency
better capability to track the channel variation
Medium voltage channel is different from the low-voltage with the clear large scale effect
Research on power allocation algorithm can Research on power allocation algorithm can be conducted based on good channel modeling
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Future WorkTraining sequence in frequency domain helping
remove the noise enhancement effect for the remove the noise enhancement effect for the channel estimation
BICM-ID for better error correction performance
0.15
0.2
0.25
0.3
-2-1
01
23
-2
-1
0
1
2
30
0.05
0.1
-3-3
Only Gaussian inputs achieve the AWGNOnly Gaussian inputs achieve the AWGN channel capacity. circular APSK rather than square QAM constellations seem closer to
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Gaussian inputs.
Future work
X
p | ,λy x p | ,λy x
Λ
2.5QAM w/o SSD or Rotation
2.0
64-aryut (d
B)
QAM w/o SSD or Rotation QAM with SSD and 45o Rotation APSK w/o SSD APSK with SSD
Gaps between the DCMC
1.0
1.5
y
Gau
ssia
n in
pu 16-ary capacity and the channelcapacity. APSK plus SignalSpace Diversity (SSD) overi i d R l i h f di h l
0.5
Gap
to th
e G i.i.d. Rayleigh fading channels.
DTV Technology R&D Center1 2 3 4 5
0.0
AMI (bits/channel use)
ReferencesReferences
1. H. Liu, et al., “Channel Study for Medium-voltage Power Network”, IEEE International Symposium on PowerLine Communications and its Applications 2006, P.245-250, Florida, USA.
2. J. Song, et al., “Field Trial of Digital Video Transmission over Medium-Voltage Powerline with Time Domain Synchronous Orthogonal Frequency Division Multiplexing Technology”, IEEE International Symposium on PowerLine Communications and its Applications 2007, pp.559-564, Pisa, Italy
3. Z. Yang, et al., “Labeling optimization for BICM-ID systems,” IEEE Commun. Letters, vol. 14, no. 11, pp. 1047–1049, Nov. 2010.
4. H. Zhang, et al., “A Hughes-hartogs algorithm based bit loading algorithm for OFDM systems”, ICC 2010, Cape Town, South Africa.
5. Dai LingLong, et al., “A Novel Time Domain Synchronous 5. Dai LingLong, et al., A Novel Time Domain Synchronous Orthogonal Frequency Division Multiple Access Scheme”, IEEE Globecom 2009.
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Thanks to all the diligent work of Jian Fu, Jintao Wang, Fang Y H i Y Li l D i H i i Zh Qi W dYang, Hui Yang, Linglong Dai, Huimin Zhang, Qing Wu, and etc.