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

Outline

Wireless Communication System TransmitterChannel Receiver

OFDM

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

Channel Estimation Techniques Training basedBlindSemi-blind Data Aided

= 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

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

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

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

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

Explanation