1. 2004/12/231 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. 2004/12/232 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. 2004/12/233 LS Estimator LS estimation objective Channel matrix considering pilot carriers only: The Transform can reformulated : LS estimator

4. 2004/12/234 Interpolation in Frequency domain  Linear Interpolation The need for interpolation Mathematical expression: Example

5. 2004/12/235 Interpolation in Frequency domain  Second-Order Interpolation Mathematical expression: Example

6. 2004/12/236 Interpolation in Time domain  2-D Interpolation We have pilots to do interpolation.

7. 2004/12/237 Interpolation in Time domain 2-D Interpolation Using previous symbol information with 2 kinds of formulas : (1) Formula 1: (2) Formular 2:

8. 2004/12/238 Channel Model ATTC (Advanced Television Technology Center) and the Grande Alliance DTV Laboratory’s ensemble E model: 6-tap multi-path channel:

9. 2004/12/239 Simulation on Static Channel Comparison between 1st and 2nd formulas by using linear interpolation MSE SER

10. 2004/12/2310 Simulation on Static Channel Comparison between 1st and 2nd formulas by using 2nd-order interpolation MSE SER

11. 2004/12/2311 Simulation on Static Channel Comparison between linear and 2 nd -order interpolation by using 1st formula. MSE SER

12. 2004/12/2312 Simulation on Static Channel Comparison between linear and 2 nd -order interpolation by using 2nd formula. MSE SER

13. 2004/12/2313 Simulation on Rayleigh Fading Channel fdT=0.01, V=27km/h Comparison between linear and 2 nd -order interpolation by using 2nd formula. MSE SER

14. 2004/12/2314 Simulation on Rayleigh Fading Channel fdT=0.02, V=54km/h Comparison between linear and 2 nd -order interpolation by using 2nd formula. MSE SER

15. 2004/12/2315 Summation 1st formula works better than 2nd one when suffering static channel condition. Linear interpolation performs almost the same with 2 nd -order one on static channel but better on rayleigh fading channel. Besides, it is of low complexity.

16. 2004/12/2316 DSP Acceleration Data type modification. Using intrinsic functions. Coding style optimization.

17. 2004/12/2317 Different Data Types Simulation Results Floating-point v.s. Fixed-point 32 bits Function Name Floating- point Code size (Bytes) Floating- point Executetion Cycles Fixed-point 32bits Code size (Bytes) Fixed-point 32bits Executetio n Cycles Improve- ment Complex_Multiplier 284899,60348488,51390.16% Complex_Divier4041,900,051440688,85063.75% Linear_Interpolation 548579,794632441,42323.87% 64QAM58092,169456104,458-13.33% De-64QAM24721,305,2391088225,01682.76%

18. 2004/12/2318 Different Data Types Simulation Results Fixed-point 32 bits v.s. Fixed-point 16 bits Function Name Fixed- point 32bits Code size (Bytes) Fixed-point 32bits Executetion Cycles Fixed- point 16bits Code size (Bytes) Fixed-point 16bits Executetion Cycles Improve- ment Complex_Multiplier 48488,51332471,49319.23% Complex_Divier440688,850280283,12258.89% Linear_Interpolation 632441,423356139,36568.43% 64QAM456104,458440104,4580% De-64QAM1088225,0161076224,0550.4%

19. 2004/12/2319 Different Coding Style Simulation Results Function Name Fixed- point 16bits Code size (Bytes) Before Fixed-point 16bits Executetion Cycles Before Fixed- point 16bits Code size (Bytes) After Fixed-point 16bits Executetion Cycles After Improve- ment Complex_Multiplier 32471,4934887,68689.25% Complex_Divier280283,122348201,42728.86% Linear_Interpolation 356139,365308132,4424.97% 64QAM440104,458404104,4580% De-64QAM1076224,0551052218,8942.3%

20. 2004/12/2320 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. 2004/12/2321 Using Intrinsic Functions (2)_dotp2 & _dotpn2: Works for complex multiplier. (3)_add2: 32 bits adder.

22. 2004/12/2322 Simulation Results by Using Intrinsic Functions Function Name Fixed- point 16bits Code size (Bytes) Before Fixed-point 16bits Executetion Cycles Before Fixed- point 16bits Code size (Bytes) After Fixed-point 16bits Executetion Cycles After Improve- ment Complex_Multiplier 4887,6862683,42655.42% Complex_Divier348201,427428193,7643.8% Linear_Interpolation 308132,442308132,4420% 64QAM404104,458404104,4580% De-64QAM1052218,8941052218,8940%

23. 2004/12/2323 Different Coding Style Simulation Results (Interpolation, De-QAM) Function Name Fixed- point 16bits Code size (Bytes) Before Fixed-point 16bits Executetion Cycles Before Fixed- point 16bits Code size (Bytes) After Fixed-point 16bits Executetion Cycles After Improve- ment Complex_Multiplier 268342627234210% Complex_Divier428193,764428162,96015.89% Linear_Interpolation 308132,44233274,06644.08% 64QAM404104,458396101,3083.02% De-64QAM1052218,8941068148,16932.31%

24. 2004/12/2324 Performance Comparison between Floating-point and Fixed-point version MSE SER

25. 2004/12/2325 Future Work More optimization of DSP code.

26. 2004/12/2326 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.