fpga implementation of carrier frequency offset estimation in b3g mimo ofdm system speaker: yu he...
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FPGA Implementation of Carrier Frequency Offset Estimation in B3G
MIMO OFDM System
Speaker: Yu He
From: Beijing University of Posts and Telecommunications (BUPT),WTI lab
Email:[email protected]
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Outline
1. Background introduction Project background System model
2. My frequency synchronization algorithm
3. My simplified frequency synchronization implementation in MIMO-OFDM system
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Background----FuTURE project
Future Technologies for Universal Radio Environment Supported by the national 863 high-tech program China B3G network research and development Members :BUPT/Tsinghua/SJTU/SEU etc,also members of B3G spe
cial group of CCSA. Aims: Meet application requirement around 2010: frequency
efficiency is up to 10b/s/Hz,bandwidth is 20MHz,support IPv6, BER lower than 10e-6 for 100Mbps,vehicular speed 250km/h,flexible air interface can take full advantage of possible radio resources
Two branches: TDD & FDD
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B3G-TDD demo system architecture 3 MT、 2 AP、 1control domain
support all IP package transmission, data rate is up to 100Mbps
high vehicular speed :250km/h
high transmission performance, BER<10-6
high spectrum efficiency,5b/s/Hz.
high power efficiency, transmission power: 10dB lower than that of 3GIP Íø
A P 1 A P 2
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· ÓÉÆ÷
· ÓÉÆ÷ · ÓÉÆ÷
Inte r ne t
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Key technologies of B3G-TDD PHY layer(1)
Frame structure:
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key technologies of B3G-TDD PHY layer(2)
OFDM: has high spectrum efficiency due to orthogonal subcarrier and low implementation complexity with the help of FFT.
MIMO: taking advantage of spatial resources, can provide spectrum efficiency as high as 20-40b/s/Hz
Others: 64QAM,LDPC,Turbo,etc
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B3G-TDD system performance
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B3G-TDD MIMO-OFDM system
System model
IF F T
IF F T
T im in gS y n ch ro n izat io n 1 1
S 1 (k )
S Q (k )
R 1 (k )
...
R L(k )
......F F T
freq u en cys y n ch ro n izato n 1 1
T im in gS y n ch ro n izat io n L1
F F T
freq u en cys y n ch ro n izato n L1
T im in gS y n ch ro n izat io n 1 Q
freq u en cys y n ch ro n izato n 1 Q
T im in gS y n ch ro n izat io n LQ
freq u en cys y n ch ro n izato n LQ
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Frequency synchronization of MIMO-OFDM B3G-TDD system
What’s synchronization What’s the result if no accurate
synchronization ISI,FFT displacement ICI, carrier waveform distorting
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Frequency synchronization algorithm
training sequences for CFO estimation in OFDM frame structure
GP GPDL SYN UL SYN
TimingCodeCP
Coarse frequencyoffet estimation
TimingRecovery
TimingRecovery
T1CP T2 CP2 TI1 TI2
Fine frequencyoffet estimation
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Frequency Synchronization
'ˆ( ( ))ˆ angle P d
F
Using the value of coarse frequency estimation to compensate TI1 and TI2
/ 2 1
0
ˆ ˆ ˆ( ) ( ) ( )2
N
n
NP d r d n r d n
Here,
· Fine frequency offset estimation:
2
)(~)(~
ˆ
1
02
"1
N
nTT nrnrangle
F
· Coarse frequency offset estimation:
Two steps Estimation range( 1/ ,1/ )s sT T
Estimation range( 1/ 2 ,1/ 2 )s sT T
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Simulation condition:Fig.3: 6-path Rayleigh channel, v=120km/h vs. 250km/h, simulation length is 500 frames,normalized frequency offset is 0.5;
Results of Frequency Synchronization
Fig.3:MSE for frequency offset(120km/h vs. 250km/h)
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Implementation of frequency synchronization
R AM( T 1 1 r ea l)
R AM( T 1 1
im ag e)
R AM( T 1 2 r ea l)
R AM( T 1 2
im ag e)
M u ltip le£¨ I 1 * I 2 £©
M u tip le£¨ Q 1 * Q 2
£©
M u ltip le£¨ I 1 * Q 2 £©
M u ltip le£¨ I 2 * Q 1 £©
Ad d£¨ r ea l£©
Ad d£¨ im ag e
£©
+
+
+
-
R AM( r ec ip r o c a l
tab le )M u ltip le£¨ Q /I £©
R AM( ar c tan X
tab le )
d a ta _ re a l
data_ im ag e
M U X
M U XM u ltip le
dN
FN
2
C F O
d
t
N
FNRfff
2
arg
L
ndt NnrnrR
0
* )()(
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My simplified scheme for MIMO-OFDM frequency synchronization
IF F T
IF F T
T im in gS y n ch ro n izat io n 1 1
S 1 (k )
S Q (k )
R 1 (k )
...
R L(k )
......
F F T
freq u en cys y n ch ro n izato n 1 1
T im in gS y n ch ro n izat io n L1
F F T
freq u en cys y n ch ro n izato n L1
T im in gS y n ch ro n izat io n 1 Q
freq u en cys y n ch ro n izato n 1 Q
T im in gS y n ch ro n izat io n LQ
freq u en cys y n ch ro n izato n LQ
Q×L×Y
R A M
R A M
R A M
Fin ee s tim a tio n 1
C o a r see s tim a tio n 1
R e c ie v e A n te n n a 1
......
C o a r see s tim a tio n 2
C o a r see s tim a tio n Y
Fin ee s tim a tio n 2
Fin ee s tim a tio n L
R e c ie v e A n te n n a 2
R e c ie v e A n te n n a L
T im esy n c h r o n iza to n
T im esy n c h r o n iza to n
T im esy n c h r o n iza to n
L×Y modulesonly RX 1 calculates the Y users’ coarse frequency offsets ,the other antennas share the result and only need to do their different fine estimation ,so Y course frequency offset estimation modules and L fine frequency offset estimation modules are sufficient
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Frequency synchronization implementation result
Services demo
frequency synchronization implementation
Up to 14 channels
case
Xilinx VirtexII Pro50 FPGA
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Future work
How to save more resourcesSimplified implementation scheme in
distributed MIMO systems
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That’s all!Thank you for your listening!