1. Analysis to Peak-to-Average Power Ratio in OFDM Systems 指導老師 : 黃文傑 博士 研究生 : 吳濟廷 2003.7.30

2. OUTLINE What is PAPR Why PAPR happens Simulations How to solve the PAPR problem Conclusion

3. What is PAPR Definition

4. Why PAPR happens(1/2) Large peaks cause saturation in power amplifiers

5. Why PAPR happens(2/2) Hard to extend the linear working area of amplifier PAPR depends on the number of subcarriers

6. Simulations(1/3) Transmit block using QPSK

7. Simulations(2/3) QPSK Discrete-time Scatter Plot Scope

8. Simulations(3/3) Spectrum Scope after IFFT

9. How to solve the PAPR problem(1/6) Signal distortion  Clipping, Peak windowing, Peak cancellation Coding  Error correction, Use lower PAPR signals Scrambling

10. How to solve the PAPR problem(2/6) Peak windowing  Multiplied by certain window function  Rectangular, Kasier, Hanning, Hamming ….. Let’s discuss …  Different window with same window length  Same window with different window length

11. How to solve the PAPR problem(3/6) Different window with same window length (time domain) rectangularkaisarhamminghanning

12. How to solve the PAPR problem(4/6) Different window with same window length (frequency domain)

13. How to solve the PAPR problem(5/6) Same window with different window length-hamming window (time domain) N=7 N=11 N=13 N=15

14. How to solve the PAPR problem(6/6) Same window with different window length-hamming window (frequency domain)

15. Conclusion Advantages  Simple to implement  Independent of number of carriers  Large reduction in PAPR Disadvantages  No longer orthogonal  Difficult to find the relation between windowing parameter and PAPR