Rika Ito

Towards ambulatory brain-computer interfaces: a pilot study with P300 signals

Brain-Computer Interfaces (BCI) are communication systems that enable users to interact with computers using only brain activity. This activity is generally measured by ElectroEncephaloGraphy (EEG). A major limitation of BCI is the electrical sensitivity of EEG which causes severe deterioration of the signals when the user is moving. This constrains current EEG-based BCI to be used only by sitting and still subjects, hence limiting the use of BCI for applications such as video games. In this paper, we proposed a feasibility study to discover whether a BCI system, here based on the P300 brain signal, could be used with a moving subject. We recorded EEG signals from 5 users in 3 conditions: sitting, standing and walking. Analysis of the recorded signals suggested that despite the noise generated by the users motion, it was still possible to detect the P300 in the signals in each of the three conditions. This opens new perspective of applications using a wearable P300-based BCI as input device, e.g., for entertainment and video games.

Optimal design of FIR filter with discrete coefficients based on integer semi-infinite linear programs

The purpose of the paper is to propose, a new design method of FIR filters with discrete coefficients considering optimality. In the proposed method, the design problem of FIR filters is formulated as a Mixed Integer Semi-Infinite Linear Programming problem (MISILP), which can be solved by a branch and bound technique. Then, it is possible to obtain the optimal discrete coefficients, and the optimality of the obtained solution can be guaranteed. It was confirmed that optimal coefficients of linear phase FIR filter with discrete coefficients could be designed in reasonable computational time with sufficient precision based on the results of computational experiments.

A new heuristic signed-power of two term allocation approach for designing of FIR filters

In this paper, we consider design problems of linear phase FIR filters with CSD (or SP2) coefficients. When the total number of non-zero SP2 terms is given for the design problem, we have to determine the number of non-zero SP2 terms allocated for each filter coefficient respectively, while maintaining the total number. However, this is considered to be an NP-hard problem. Hence, Lim et al. (1998) developed an heuristic method for this allocation problem. In this paper, we propose a new heuristic method for the problem and compare it with Lims method through numerical experiments.

New design methods of FIR filters with signed power of two coefficients based on a new linear programming relaxation with triangle inequalities

In this paper, we propose new design methods for linear phase FIR (finite impulse response) filters with signed power-of-two (SP2) coefficients based on a semi-definite programming (SDP) relaxation method. The proposed methods include a linear programming (LP) relaxation and a relaxation by adding triangle inequalities. Although such design problems are known as NP-hard problems, these methods can solve the design problems with low computational cost in comparison to traditional SDP relaxation methods. It is shown by several numerical experiments that these method are superior to the simple SDP relaxation method.

Optimal design method for FIR filter with discrete coefficients based on integer semi-infinite linear programs

The purpose of the paper is to propose a new design method of FIR filters with discrete coefficients considering optimality. In the proposed method, the design problem of FIR filters is formulated as a mixed integer semi-infinite linear programming problem (MISILP), which can be solved by a branch and bound technique. Then, it is possible to obtain the optimal discrete coefficients, and the optimality of the obtained solution can be guaranteed. It was confirmed that optimal coefficients of a linear phase FIR filter with discrete coefficients could be designed in reasonable computational time with sufficient precision based on the results of computational experiments.

A heuristic approach for design of FIR filters with SP2 coefficients

Since FIR filters can easily obtain a linear phase property, they are highly useful in many fields. In this work, we consider the design problems of linear phase FIR filter with signed power of two (SP2) coefficients. When the total number of non-zero SP2 terms is given for the design problem, we have to determine the number of nonzero SP2 terms allocated to each filter coefficient respectively while keeping the total number. However, it is considered that this problem is one of the NP-hard problems. Hence, several heuristic methods have been developed for this allocation problem. We propose a new heuristic method for this problem comparing it with traditional heuristic method through several numerical experiments.