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Student: Chen, Ching Advisor: Prof. D. W. Lin Time: 2005/6/1

Techniques for and DSP Software Implementation of IEEE 802.16a TDD OFDMA Downlink Pilot-Symbol-Aided Channel Estimation. Student: Chen, Ching Advisor: Prof. D. W. Lin Time: 2005/6/1. Outline. Review of frequency and time domain interpolation approaches

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Student: Chen, Ching Advisor: Prof. D. W. Lin Time: 2005/6/1

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  1. Techniques for and DSP Software Implementation of IEEE 802.16a TDD OFDMA Downlink Pilot-Symbol-Aided Channel Estimation Student: Chen, Ching Advisor: Prof. D. W. Lin Time: 2005/6/1

  2. Outline • Review of frequency and time domain interpolation approaches • Frequency: Linear and 2nd-order interpolation • Time: 2-D interpolation • Simulation results • DSP code acceleration • Conclusion & future work • Reference

  3. LS Estimator LS estimation objective Channel matrix considering pilot carriers only: The Transform can reformulated : LS estimator

  4. Interpolation in Frequency domain Linear Interpolation • The need for interpolation • Mathematical expression: • Example

  5. Interpolation in Frequency domain Second-Order Interpolation • Mathematical expression: • Example

  6. Interpolation in Time domain 2-D Interpolation We havepilots to do interpolation.

  7. Interpolation in Time domain 2-D Interpolation • Using previous symbol information with 2 kinds of formulas : (1) Formula 1: (2) Formular 2:

  8. Channel Model • ATTC (Advanced Television Technology Center) and the Grande Alliance DTV Laboratory’s ensemble E model: 6-tap multi-path channel:

  9. Simulation on Static Channel • Comparison between 1st and 2nd formulas by using linear interpolation MSE SER

  10. Simulation on Static Channel • Comparison between 1st and 2nd formulas by using 2nd-order interpolation MSE SER

  11. Simulation on Static Channel • Comparison between linear and 2nd-order interpolation by using 1st formula. MSE SER

  12. Simulation on Static Channel • Comparison between linear and 2nd-order interpolation by using 2nd formula. MSE SER

  13. Simulation on Rayleigh Fading Channel fdT=0.01, V=27km/h • Comparison between linear and 2nd-order interpolation by using 2nd formula. MSE SER

  14. Simulation on Rayleigh Fading Channel fdT=0.02, V=54km/h • Comparison between linear and 2nd-order interpolation by using 2nd formula. MSE SER

  15. Summation • 1st formula works better than 2nd one when suffering static channel condition. • Linear interpolation performs almost the same with 2nd-order one on static channel but better on rayleigh fading channel . • Besides, it is of low complexity.

  16. DSP Acceleration • Data type modification. • Using intrinsic functions. • Coding style optimization.

  17. Different Data Types Simulation ResultsFloating-point v.s. Fixed-point 32 bits

  18. Different Data Types Simulation ResultsFixed-point 32 bits v.s. Fixed-point 16 bits

  19. Different Coding Style Simulation Results

  20. Using Intrinsic Functions • For TI C6000 DSP • Special functions which have best optimized assembly code on the TI DSP architecture (1)_amemd8_const: Allows aligned loads of 8 bytes to memory.

  21. Using Intrinsic Functions (2)_dotp2 & _dotpn2: Works for complex multiplier. (3)_add2: 32 bits adder .

  22. Simulation Results by Using Intrinsic Functions

  23. Different Coding Style Simulation Results(Interpolation, De-QAM)

  24. Performance Comparison between Floating-point and Fixed-point version • MSE SER

  25. Future Work • More optimization of DSP code.

  26. Reference • Chen, Ying Ying , “Study and Techniques of IEEE 802.16a TDD OFDMA Downlink Channel Estimation,” June 2004 • Texas Instrument, TMS320C6000 Optimizing Compiler User Guild, literature no. SPRU187K, Oct. 2002. • Texas Instrument, TMS320C6000 Programmer’s guide, literature no. SPRU198F, Feb. 2001.

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