Brain computer interface based on Electroencephalogram can be used to control the external devices through the motor imagery, and may be the next-generation user computer interface. However, this system requires a significant amount of data for the supervised algorithm training. The collection of training data is time-consuming, which may impede the usage in the daily life. In this paper, the trade-off between the training data size and algorithm accuracy is first analyzed. Then the reusing of the generalized pre-recorded training data set is explored to further improve this trade off. According to the simulation results, 63.8% training data collection time can first be saved with only 3% accuracy degradation.

Theoretical analysis is formulated for a solid state laser based optical phase-locked loop (OPLL) disturbed by shot noise, amplitude modulated noise, and frequency noise. The frequency noise spectral density of solid state lasers is modeled to contain a white component, a 1/f component, and a strong 1/f/sup 2/ component at the laser output. This model is verified and the spectral content of each component is measured using an open-loop RF frequency discriminator. The choice of loop filter is made by considering the frequency noise components, transient effects, and the loop damping factor /spl zeta/. The total phase error variance as a function of loop bandwidth is displayed for several values of carrier signal-to-noise ratio for the measured frequency noise spectrum. Optimal loop bandwidth is also calculated as a function of carrier signal-to-noise ratio. An OPLL experiment is performed, and measured phase error variance is compared with the theoretical predictions using the measured frequency noise spectrum. The results show that the measured phase error variance closely matches the theoretical predictions.>

Given the RMS transmitter pointing error and the desired probability of bit error (PBE), it can be shown that an optimal transmitter antenna gain exists which minimizes the required transmitter power. Given the RMS local oscillator tracking error, an optimum receiver antenna gain can be found which optimizes the receiver performance. The impact of pointing and tracking errors on the design of direct-detection pulse-position modulation (PPM) and heterodyne noncoherent frequency-shift keying (NCFSK) systems is then analyzed in terms of constraints on the antenna size and the power penalty incurred. It is shown that in the limit of large spatial tracking errors, the advantage in receiver sensitivity for the heterodyne system is quickly offset by the smaller antenna gain and the higher power penalty due to tracking errors. In contrast, for systems with small spatial tracking errors, the heterodyne system is superior because of the higher receiver sensitivity.>

Receiver timing synchronization of an optical PPM communication system can be achieved using a phase-locked loop (PLL) if the photodetector output is properly processed. The synchronization performance is shown to improve with increasing signal power and decreasing loop bandwidth. The bit error rate performance of the PLL synchronized PPM system is analyzed and compared to that of the perfectly synchronized system. It is shown that the increase in signal power needed to compensate for the imperfect synchronization is small (less than 0.1 dB) for loop bandwidths less than 0.1 percent of the slot frequency.