Yukihiro Kamiya

A simple signal detection and waveform estimation for biometrics using Doppler sensors

The abstract goes here. Doppler sensors are recently considered as an attractive tool for remotely measuring heartbeats and breathing. We have considered a sophisticated method based on blind signal processing to cope with the detection and parameter estimation for multiple signals applicable to the simultaneous measurement of multiple persons under noisy environment[1]. However, on that way, we found a very simple but effective method which enables us to estimate the number of source (NOS), the fundamental waveforms and the period for multiple signals polluted by noise. It is expected that this method is directly applicable to the biometrics using Doppler sensors. This paper provides the principle and some numerical examples as the first step of the research.

A new approach for joint parameter estimation of multiple phase-varying periodic signals in white Gaussian noise

This paper proposes a new approach for the parameter estimation of the randomly-phase varying multiple periodic signals. The phase-varying multiple signal is often observed in digital communication signals. The proposed method enables us to blindly and jointly estimate the period, the number of sources (NOS) and the fundamental waveform, for each of the multiple signals. The performance is verified through computer simulations.

A New Simple Preprocessing Method for MUSIC Suitable for Non-contact Vital Sensing Using Doppler Sensors

Non-contact vital sensing using Doppler sensor is emerging along with interests on its application as a means for monitoring patients in hospitals or the elderly living in home alone. We already proposed a signal processing scheme applicable to Doppler sensor which enables us to monitor multiple persons by a Doppler sensor. As its extended version, we also proposed a scheme measuring the direction of the persons by putting multiple antennas at the receiver. In this paper, we propose to use those schemes as a preprocessing for the multiple signal classification (MUSIC) aiming at the precise identification of the direction of the persons. The proposed scheme is to not only improve the resolution of the identification of directions but also enables MUSIC to identify the directions exceeding the degree-of-freedom. Some numerical examples are provided for performance evaluation.

A New Method to Apply BRAKE to Sensor Networks Aiming at Power Saving

Wireless sensor network is a powerful solution for improving the efficiency of agricultural industries. A main concern is the battery life of sensors. To reduce the power consumption of the sensors, we want to shorten the length of the signal as much as possible. BRAKE [7], a blind receiver for spread spectrum systems, is interesting to cope with this matter since it does not need preambles which are usually put at the head of packets for enabling the receiver to detect the packets and its timing. However, BRAKE is not suitable for sensor networks as it is, because BRAKE cannot work with short signals. In this paper, we propose a new simple method to apply BRAKE to the sensor networks. Computer simulations verify the drastic effect of the proposed method.

A New Approach for Subsurface Wireless Sensor Networks

Subsurface wireless sensor network is a sensor network in which sensors are installed under water or soil. This is to monitor earthquakes or Tsunami, to secure a society against natural disasters. The subsurface wireless communication is not easy since the power mitigation of the signal is severe due to the water and soil. In addition, the battery capacity in the sensor node is very limited. In this paper, based on the spread spectrum (SS) which is robust against low signal-to-noise power ratio (SNR), we propose a new transmitter and receiver configurations achieving code division multiplexing (CDM) for the subsurface wireless sensor networks. The proposed method is advantageous in terms of the following points. First, it realizes CDM by using a single spreading code. Second, the receiver does not need the training sequence to adjust the multiple antenna for the SNR improvement. This is effective to reduce the battery consumption at the sensor node since it does not need to send the training sequence. The performance is verified through computer simulations.

A Near-Far Resistant Preambleless Blind Receiver with Eigenbeams Applicable to Sensor Networks

BRAKE has been proposed as a preambleless blind receiver (PBR) applicable to spread spectrum (SS) signals. However, the performance is degraded under the near-far problem. In this paper, we propose an eigenbeam BRAKE, i.e., the combination of BRAKE with the pre-beamforming using the eigenvectors derived from the correlation matrix. This scheme is to avoid the performance degradation under the near-far problem. Although this combination is expected to be effective, a new algorithm for controlling BRAKE is required to make it work with eigenbeams. So this paper proposes the BRAKE control algorithm as well. The performance is verified through computer simulations.

A Simple Medium Access Scheme Based on Spread Spectrum Suitable for Wireless Ad Hoc Networks

We propose a simple medium access scheme for wireless ad hoc network (WAHN). The proposed method is based on the spread spectrum (SS) technique to take advantage of the robustness against fading and differentiation of signals. However, conventionally, SS needed a mechanism to allocate a unique spreading code to each node. Since WHAN does not include base stations, this problem must be solved. In this paper, we solve this problem by let each node share a unique code and use it after expanding the chip duration. Although this proposed scheme decreases the data rate if the node expands widely the chip duration, it is better than CSMA. The performance is verified through computer simulations.