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:susi104@gmail.com

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

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

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

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

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

B3G-TDD system performance

B3G-TDD MIMO-OFDM system System model

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

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

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:

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;

Implementation of frequency synchronization

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

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

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

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