1. (Semi) Blind Channel Estimation & Data Recovery in OFDM Presented by: Ahmed Abdul Quadeer Electrical Engineering Department 2 nd Graduates Seminar Day

2. Outline

3. Wireless Communication System TransmitterChannel Receiver

4. OFDM

5. Problem TransmitterChannel Receiver XH Y = H ʘ X X = Y./ H

6. Channel Estimation Techniques Training basedBlindSemi-blind Data Aided

7. = HELLO Training Based Technique TransmitterChannel Receiver HELLOЧҒҐЮҨ XH Y = H ʘ X Y and X known H = Y./ X  Wireless channel is time variant.  Necessary to train periodically  Low Bandwidth Efficiency. HELLO = HELLO ℏℱℰℳℭ

8. Blind Technique TransmitterChannel Receiver  No training used.  Utilize structure of the communication system:  Finite Alphabet Set  Time Correlation  Coding Data Transmitted = {A, B, C, D} A  000 and B  111 t

9. Semi-Blind Technique TransmitterChannel Receiver  Hybrid of Training and Blind techniques.  Training signal as well as other constraints of communication system are utilized.

10. Data Aided Technique  Use the refined channel estimate to detect data again.  Joint Channel Estimation and Data Detection.  Use detected data to improve the channel estimate. XH

11. Conclusion LOWHIGH Trade off between Computational Complexity and Bandwidth Efficiency Complexity Bandwidth Efficiency

13. Explanation