analysis to p eak - to -a verage p ower r atio in ofdm systems
DESCRIPTION
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). - PowerPoint PPT PresentationTRANSCRIPT
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
OUTLINE
What is PAPR Why PAPR happens Simulations How to solve the PAPR problem Conclusion
What is PAPR
Definition
2
2
max x tPAPR N
E x t
1 1
0 0
1
0
2 2
exp( 2 ) exp( 2 )N N
n nn n
N
nn
n
x t X j n ft X j n ft
X N
X N
2 22 x t N
E x t NN N
Why PAPR happens(1/2)
Large peaks cause saturation in power amplifiers
Why PAPR happens(2/2)
Hard to extend the linear working area of amplifier
PAPR depends on the number of subcarriers
Simulations(1/3)
Transmit block using QPSK
Simulations(2/3)
QPSK Discrete-time Scatter Plot Scope
Simulations(3/3)
Spectrum Scope after IFFT
How to solve the PAPR problem(1/6) Signal distortion
Clipping, Peak windowing, Peak cancellation Coding
Error correction, Use lower PAPR signals Scrambling
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
How to solve the PAPR problem(3/6) Different window with same window length (time domain)
rectangular kaisar hamminghanning
How to solve the PAPR problem(4/6) Different window with same window length (frequency domain)
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
How to solve the PAPR problem(6/6) Same window with different window length-hamming window (frequency
domain)
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