title: Time-frequency joint coding method for boosting information transfer rate in an SSVEP based BCI system.
abstract: Steady-State Visual Evoked Potential (SSVEP) based Brain-Computer Interface (BCI) system is an important BCI modality. It has advantages such as ease of use, little training and high Information Transfer Rate (ITR). Traditional SSVEP based BCI systems are based on the Frequency Division Multiple Access (FDMA) approach in telecommunications. Recently, Time Division Multiple Access (TDMA) was also introduced to SSVEP based BCI to enhance the system performance. This study designed a new time-frequency joint coding method to utilize the information coding from both time and frequency domains. TDMA using Different Frequency (DF) mode and Same Frequency (SF) mode were compared to the traditional FDMA mode in the offline experiment. The result showed that the DF mode had better performance than the other two modes. The mean and the standard deviation of accuracy and ITR of the online experiment was 83.3%±5.5% and 130.3 + 14.9 bits/min (trial time: 1.25s) and 92.0%±7.5% and 136.6 + 19.8 bit/min (trial time: 1.5s). The average typing speed for the word-copy spelling task was 14.9 characters per minute (cpm) (trial time: 1.25s) and 14.8 cpm (trial time: 1.5s). The overall results demonstrate the feasibility and advantage of the proposed time-frequency joint coding method.
authors.lastname: Ke Lin
authors.lastname: Yijun Wang
authors.lastname: Xiaorong Gao
mesh_terms: D000328:Adult; D000465:Algorithms; D062207:Brain-Computer Interfaces; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D055815:Young Adult