Juphil Cho

Fall detection by using K-nearest neighbor algorithm on WSN data

Falls are serious problem especially for elderly people. Day by day the elderly people are living alone and the children of these people want to get information in dangerous situations. With the alarm systems, someone in difficulty can be detected and emergency aid can be sent. We propose a system to detect falls by using a data mining approach on WSN data. The proposed system evaluated using data stream collected from sensor device and fall detection accuracy and precision are calculated. Our solution demonstrated promising results on WSN data stream.

Blind adaptive channel equalization using multichannel linear prediction-based cross-correlation vector estimation

Blind equalization of transmission channel is important in communication areas and signal processing applications because it does not need training sequences, nor does it require a priori channel information. In this paper, an adaptive blind MMSE channel equalization technique based on second-order statistics is investigated. We present an adaptive blind MMSE channel equalization using multichannel linear prediction error method for estimating cross-correlation vector. They can be implemented as RLS or LMS algorithms to recursively update the cross-correlation vector. Once cross-correlation vector is available, it can be used for MMSE channel equalization. Unlike many known subspace methods, our proposed algorithms do not require channel order estimation. Therefore, our algorithms are robust to channel order mismatch. Performance of our algorithms and comparison with existing algorithms are shown for real measured digital microwave channel.

A novel channel estimation method for OFDM in high-speed mobile system

In order to meet the requirements which are considered in an OFDM system under a high-speed mobile environment, lots of techniques have been studied. In mobile communication systems, fading distortion affects the overall performance. Furthermore, the higher the velocity of any mobile system, the more severe the effect of fading is. To solve this problem, in an OFDM system, exact channel estimation can be an important method. We propose a channel estimation method which outperforms conventional methods. The analytical results demonstrate that the proposed system has better performance than the conventional methods such as PSAM and ESAE.

Robust wireless transmission utilizing PPDU-based aggregation technique for next generation wireless LANs

In this paper, we propose a robust transmission scheme using aggregated physical protocol data units (APPDU). The proposed method includes a media access control (MAC) layer control for determining the number of preambles to be inserted based on the feed-back reply signal from a receiver; the generation of a multi-preamble aggregation frame by inserting the determined number of preambles into frames received from an upper layer; a physical layer for forming the multi-preamble aggregation frame generated in a data processing unit by using a physical layer frame; and the transmission of the formed multi-preamble aggregation frame. The proposed technique obtains performance improvement of about 3 dB in terms of SNR and 35% in terms of throughput efficiency.

Symbol Error Probability for Space-Time Block Codes Over Spatially Correlated Rayleigh Fading Channels

In general, multi-input multi-output (MIMO) channel is correlated by an amount that depends on the propagation environment as well as the polarization of the antenna elements and the spacing between them. In this paper, an exact error probability of orthogonal space-time block codes is considered in spatially correlated Rayleigh fading channels. We derive a general formula for the symbol error probability (SEP) of orthogonal space-time block codes for general PSK/PAM/QAM over spatially correlated Rayleigh fading channels.

Propagation Characterization Based on Geographic Location Variation for 5G Small Cells

Developments in next-generation wireless transmission technology and efficient frequency-use research are based on understanding the characteristics of the exact radio channel. With regard to developments in next-generation mobile communication systems, performance verification of the development system is essential, for which it is necessary to estimate the exact wireless-space channel. This paper presents results of the analysis of radio propagation characteristics based on location variation in outdoor environments for small-cell 5th generation (5G) mobile systems. Changes due to variation in location were measured using a channel sounder in a microcell environment with a 0.5 km radius in Korea. In order to analyze the propagation characteristics, the best distribution model reflecting the characteristics of the locations was derived. A comparison between actual measurements and three-dimensional ray-tracing simulation results confirmed the validity of the measurement result.

Link Relay H-ARQ mode for Throughput improvement in a Satellite Communication network

Satellite communication is a communication method using a satellite as a repeater communication on the air and have a communication range is wide and is possible to transmit high-speed data, so Satellite communication has been highlighted as the next generation communication. However, because the distance between the ground and the satellite is far away, there is a disadvantage that propagation delay time is very long and packet is damaged. Therefore, this study was applied to Link Relay H-ARQ system in order to complement the damage to the packet. Furthermore, we propose the Modified Link Relay H-ARQ scheme is a new scheme to supplementation the delay time. By applying the Markov channel for implementing a channel of satellite communications, the results of analyzing the performance, when applying the Link Relay HARQ scheme, BER and PER performance was improved, when applying the Modified Link Relay H-ARQ scheme, Throughput performance was confirmed improvement.

A Performance Comparison of Flooding Schemes in Wireless Sensor Networks

Broadcasting in multi-hop wireless sensor networks is a basic operation that supports many applications such as route search, setting up addresses and sending messages from the sink to sensor nodes. The broadcasting using flooding causes problems that can be mentioned as a broadcasting storm such as redundancy, contention and collision. A variety of broadcasting schemes using wireless sensor networks have been proposed to achieve superior performance rather than simple flooding scheme. Broadcasting algorithms in wireless sensor networks can be classified into six subcategories: flooding scheme, probabilistic scheme, counter-based scheme, distance-based scheme, location-based schemes, and neighbor knowledge-based scheme. This study analyzes a simple flooding scheme, probabilistic scheme, counter-based scheme, distance-based scheme, and neighbor knowledge-based scheme, and compares the performance and efficiency of each scheme through network simulation.

Features extraction of fluorescent light image for positioning information acquisition using steerable Gaussian filter

Indoor positioning technology has been a goal of ubiquitous computing research. In this paper, we show the feasibility of detecting fluorescent light based on the camera images received from a smart phone. We present a robust and real time approach to fluorescent light detection in indoor environments. It is based on taking a ceiling image by Smartphone image sensor, filtering using selective oriented Gaussian filters. Our algorithm can detect all fluorescent light in still images of indoor environments in various conditions.

Interference Analysis for DAB Service on the Advanced T-DMB System Environment

The advanced T-DMB is the digital broadcasting technique upgrading the T-DMB which has low effective data rate compared with other things. Since it applies the hierarchical modulation, it has maximally twice as much the effective data rate of a T-DMB, so it can provides the video service of high quality and many stations more than a T-DMB. Therefore, the study for DAB service on the AT-DMB environment will be advantageous better than the previous studies for it on the T-DMB environment. So, this paper proposes the method of the channel allocation for DAB service on the Advance T-DMB system environment and presents the results of the interference analysis in order to verify that.