Dong-Jo Park

A new antenna selection algorithm with low complexity for MIMO wireless systems

In this paper, we propose a new antenna selection algorithm with low complexity for multiple-input multiple-output (MIMO) wireless systems. We consider the selection only at the receiver (i.e., the transmitter employs the same number of RF chains as antenna elements, whereas the receiver utilizes a reduced number of RF chains). The selection goal is to maximize the channel capacity. We present the selection algorithm based on the norm and uncorrelation between rows of the channel matrix. Our algorithm requires low computational complexity and provides excellent performance. In the specific case, the proposed scheme shows near-optimal performance. We present simulation results that validate our algorithm and analysis.

Human detection using image fusion of thermal and visible image with new joint bilateral filter

We propose a novel human detection system with thermal and visible image sensors using a new joint bilateral filter. There is a limitation to the performance of devices which attempt to detect humans by using only one sensor. Therefore, we use two sensors: an infrared sensor and a color image sensor. To fuse the best features of both types of sensor in order to achieve superior performance in human detection, we use low-level image fusion. To carry out this image fusion process, we propose a new joint bilateral filter which is useful for fusion of the edge information in the visible image and the white region in the thermal image. This image fusion process effectively removes the regions of human shadow which is trouble of background subtraction. To achieve this effect, results from different pairs of fused images that are taken sequentially are subtracted to detect the human effectively. Experimental results show that effective and easy human detection can be achieved by the proposed algorithm.

A multi-user beamforming scheme in MIMO downlink channels for multi-cell networks

In this paper, a multi-user beamforming scheme is presented in multi-user multi-input multi-output (MIMO) downlink channels with other cell interference (OCI). The proposed scheme consists of maximizing signal-to-leakage-and-noise ratio (SLNR) and whitening the OCI for power allocation. The conventional scheme which eliminates perfectly intra-cell interference has several problems such as antenna constraints and noise enhancement. The proposed scheme has resolved these problems and could obtain an additional channel gain by the number of antennas. We confirm the increasing of the performance via numerical results.

Closed-form interpolations for MISO-OFDM beamforming codewords

We derive a spherical linear interpolation (SLI) with a closed-form phase term. The derived SLI is compared with the geodesic interpolation. Simulation results show that both schemes are efficient and similar when the channels are highly correlated, since their objectives are equivalent in a sense of minimizing the distance between two adjacent codewords.

A CSI feedback scheme for beamforming at AF relays

In cooperative wireless communications, beamforming at relays can be employed to increase the signal-to-noise ratio (SNR). Since beamforming at relays requires that channel state information (CSI) be exchanged, an efficient CSI feedback scheme is proposed to reduce the feedback overhead incorporating an optimization of the combining and beamforming weights. With 802.16e OFDMA time-division duplexing (TDD) systems, the proposed scheme feeds common information back to relays for beamforming, which should be acquired by a destination for combining. The simulation results verify that the proposed scheme reduces the feedback overhead and improves computational efficiency.

Visualization of Hyperspectral Images Using Bilateral Filtering with Spectral Angles

This paper presents an extended bilateral filter with spectral angles and a visualization scheme for hyperspectral image data. The conventional bilateral filter used to be implemented using a position vector and a luminance value at each pixel in the scene. Since hyperspectral image data can provide a spectrum vector that has hundreds of bands at each pixel, we propose an extended bilateral filter using spectral angles. The proposed bilateral filter can be used for extracting and preserving the spectrum edges of the hyperspectral image. A visualization scheme for hyperspectral images exploiting the proposed bilateral filter has been also proposed. When objects that have the similar tristimulus intensity but different spectrums are mixed, they can be separated through the proposed visualization scheme. The resulting images show that the proposed scheme facilitates anomaly detection in the hyperspectral scenes.

Design of multiple demeaning filters for small target detection in infrared imageries

In this paper, we propose multiple demeaning filters for small target detection in infrared (IR) images. The use of a demeaning filter is a promising method which detects a small object by removing the background components with a mean filter. The main factors in the design of a demeaning filter are two types of demeaning methods and the size of its window. We compare two demeaning methods, the sliding window method and the grid method, and we analyze the trade-off between the window size and the performance of the demeaning filters and present limitations related to their use. To overcome the drawbacks of a conventional demeaning filter, the use of multiple demeaning filters with filters of various sizes is considered. The proposed method not only has the advantage of being able to detect a small object in a densely cluttered environment, but it also can be used with low complexity with an integral image. Experimental results demonstrate the robustness and stability of the proposed multiple demeaning filters with low computational complexity compared with conventional methods.

Improved timing estimation for OFDM systems using preambles with repetitive patterns

We propose an improved timing estimation method for orthogonal frequency-division multiplexing (OFDM) systems that employ a preamble with time-domain repetitive patterns. The proposed method exploits the unique correlation property of the preamble including its cyclic prefix. Numerical results show that the proposed scheme is robust in fading multipath channels, achieving better performance than the existing methods.

MIMO precoding in the ad hoc networks

In this paper, multi-user multi-input multi-output (MIMO) precoding in the ad hoc networks is presented. The ad hoc channel model is considered and the leakage based concept extended centralized systems to distributed networks. The conventional scheme simply use own inverse channel matrices and can be suffered a noise enhancement problem. This paper presents that the leakage based precoding provides also strong performance in the ad hoc networks. It is proven using the achievable sum rate simulations.

Wireless image communication system for fire-fighting robots

Recently, it has sometimes been impossible for fire-fighting personnel to access the site of a fire, even as the fire causes tremendous property damage and loss of human life, due to high temperatures or the presence of explosive materials. In such environments, fire-fighting robots can be useful for extinguishing a fire, and they should be controlled by remote operators. In order to help a remote operator who is located far away from the fire-fighting robot, wireless image communication systems have been investigated in this study. The developed system uses a High-Speed Downlink Packet Access (HSDPA) network to transmit images, showing the view from a fire-fighting robot. The fire-fighting robots and remote controllers are equipped with industrial computers, and image-transmitting and image-receiving programs function according to various protocols to allow communication between the robots and controllers