(Semi) Blind Channel Estimation

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(Semi) Blind Channel Estimation Data Recovery
in OFDM
2nd Graduates Seminar Day

• Presented by Ahmed Abdul Quadeer
• Electrical Engineering Department

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Outline
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Wireless Communication System
4
OFDM
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Problem
Y H ? X
X
H
X Y ./ H
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Channel Estimation Techniques
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Training Based Technique
HELLO
HELLO
HELLO
?????
HELLO
?FEMC
Transmitter
Channel
Receiver
Y H ? X
X
H
Y and X known
H Y ./ X

• Wireless channel is time variant.

• Necessary to train periodically ? Low Bandwidth
  Efficiency.

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Blind Technique

• No training used.

• Utilize structure of the communication system

• Finite Alphabet Set

Data Transmitted A, B, C, D

• Coding

A ? 000 and B ? 111

• Time Correlation

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Semi-Blind Technique
Transmitter
Channel
Receiver

• Hybrid of Training and Blind techniques.

• Training signal as well as other constraints of
  communication system are utilized.

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Data Aided Technique

• Use the refined channel estimate to detect data
  again.

• Joint Channel Estimation and Data Detection.

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Conclusion
Trade off between Computational Complexity and
Bandwidth Efficiency
Complexity
LOW
HIGH
Bandwidth Efficiency
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Explanation