1. 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

2. Outline 1. Background introduction Project background System model
2. My frequency synchronization algorithm
3. My simplified frequency synchronization implementation in MIMO-OFDM system

3. 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 special 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

4. 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 3G

5. Key technologies of B3G-TDD PHY layer(1)
Frame structure:

6. 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

7. B3G-TDD system performance

8. B3G-TDD MIMO-OFDM system
System model

9. 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

10. Frequency synchronization algorithm
training sequences for CFO estimation in OFDM frame structure

11. Frequency Synchronization
Two steps
Estimation range
Coarse frequency offset estimation:
Here,
Using the value of coarse frequency estimation to compensate TI1 and TI2
Estimation range
Fine frequency offset estimation:

12. Results of Frequency Synchronization
Fig.3:MSE for frequency offset(120km/h vs. 250km/h)
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;

13. Implementation of frequency synchronization

14. My simplified scheme for MIMO-OFDM frequency synchronization
L×Y modules
only 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
Q×L×Y

15. Frequency synchronization implementation result
Services demo
Xilinx VirtexII Pro50 FPGA
Up to 14 channels case

16. Future work How to save more resources
Simplified implementation scheme in distributed MIMO systems

17. That’s all!
Thank you for your listening! 