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Analysis to P eak - to -A verage P ower R atio in OFDM Systems

Analysis to P eak - to -A verage P ower R atio in OFDM Systems. 指導老師 : 黃文傑 博士 研究生 : 吳濟廷 2003.7.30. OUTLINE. What is PAPR Why PAPR happens Simulations How to solve the PAPR problem Conclusion. What is PAPR. Definition. Why PAPR happens(1/2).

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Analysis to P eak - to -A verage P ower R atio in OFDM Systems

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  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) rectangular kaisar hanning hamming

  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=11 N=7 N=15 N=13

  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

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