Joint Maximum Likelihood Time Delay Estimation of Unknown Event-Related Potential Signals for EEG Sensor Signal Quality Enhancement.
Electroencephalograms (EEGs) measure a brain signal that contains abundant information about the human brain function and health. For this reason, recent clinical brain research and brain computer interface (BCI) studies use EEG signals in many applications. Due to the significant noise in EEG traces, signal processing to enhance the signal to noise power ratio (SNR) is necessary for EEG analysis, especially for non-invasive EEG. A typical method to improve the SNR is averaging many trials of event related potential (ERP) signal that represents a brain's response to a particular stimulus or a task. The averaging, however, is very sensitive to variable delays. In this study, we propose two time delay estimation (TDE) schemes based on a joint maximum likelihood (ML) criterion to compensate the uncertain delays which may be different in each trial. We evaluate the performance for different types of signals such as random, deterministic, and real EEG signals. The results show that the proposed schemes provide better performance than other conventional schemes employing averaged signal as a reference, e.g., up to 4 dB gain at the expected delay error of 10°.
Department of Information &amp; Communication Engineering, Daegu Gyeongbuk Institute of Science and Technology, Daegu 771-813, Korea. ssi09@dgist.ac.kr.
Kyungsoo
K
Kim
Department of Information &amp; Communication Engineering, Daegu Gyeongbuk Institute of Science and Technology, Daegu 771-813, Korea. ishdgist@dgist.ac.kr.
Sung-Ho
SH
Lim
Department of Information &amp; Communication Engineering, Daegu Gyeongbuk Institute of Science and Technology, Daegu 771-813, Korea. jayslee@dgist.ac.kr.
Jaeseok
J
Lee
Wellness Convergence Research Center, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 771-813, Korea. wskang@dgist.ac.kr.
Won-Seok
WS
Kang
Department of Brain &amp; Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 771-813, Korea. cmoon@dgist.ac.kr.
Cheil
C
Moon
Department of Information &amp; Communication Engineering, Daegu Gyeongbuk Institute of Science and Technology, Daegu 771-813, Korea. jwchoi@dgist.ac.kr.
Ji-Woong
JW
Choi
D001921:Brain / Q000502:physiology; D062207:Brain-Computer Interfaces; D004569:Electroencephalography / Q000379:methods*; D005071:Evoked Potentials / Q000502:physiology; D006801:Humans; D016013:Likelihood Functions; D008962:Models, Theoretical; D012815:Signal Processing, Computer-Assisted
EEG; ERP; maximum likelihood (ML); synchronization; time delay estimation (TDE)