• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.371-379
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• 2011

Active phased array antenna structure is used for modern multi-function radars. To search targets in high clutter environment, the radar receiver needs high dynamic range performance. Though active phased array antenna structure lead to increase of SNR, the SFDR is not increased. In this paper, high SFDR receiver of X-band active phased array radar was designed and manufactured. One channel digital receiver is connected to 32 T/R modules and one PCB assembly is composed to 2 channel digital receivers with RF part, ADC part, LO distribution part and digital down conversion part. A commercial FIFO board was used for digital receiver measurement about major performance in digital output signal condition. The measured digital receiver gain and SFDR is 33 dB and more than 81 dBc each.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.6
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• pp.653-663
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• 2014

To cope with an increasing amount of data traffic, research efforts are being made to maximize the data rate by reducing the interference between the transmission nodes. This paper also focuses on interference control schemes utilizing antenna sub-array beam-forming. The first scheme relies on horizontal beam rotation which utilizes three types of narrow beam patterns. Different beam patterns are applied to transmit signals in rotating fashion to control the interference. The second scheme is based on user-specific sub-array beamforming, which uses the precoding matrix based on users' location and controls the amount of interference in the multi-user environment. The performance of the proposed schemes is evaluated using the computer simulation to demonstrate the performance enhancement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.425-431
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• 2015

Beamspace Multiple-Input Multiple Output(MIMO) system can transmit multiple data by using Electronically Steerable Parasitic Array Radiator(ESPAR) antenna which has single Radio Frequency(RF)-chain. Beamspace MIMO system can reduce complexity of the system and size of antenna in comparison with the conventional MIMO system because of characteristic of ESPAR antenna using the single antenna and the RF-chain. Heretofore, only the research of transmitting single-carrier has been conducted by the use of beamspace MIMO system. Therefore, in this paper, we propose beamspace MIMO system based on Orthogonal Frequency Division Multiplexing(OFDM) for transmitting the multi-carrier and analysis the performance of this system. We find a proper reactance value which has good performance because proposed system changes the performance by the reactance values of parasitic elements. and we confirm that performance of the proposed system is similar to conventional MIMO system based on OFDM.

• Journal of Sensor Science and Technology
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• v.20 no.2
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• pp.137-144
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• 2011

Wireless sensor network(WSN) has the potential to greatly effect many aspects of u-healthcare. By outfitting the potential with WSN, wearable sensor node can collects real-time data on physiological status and transmits through base station to server PC. However, there is a significant gap between WSN and healthcare. WSN has the limited resource about computing capability and data transmission according to bio-sensor sampling rates and channels to apply healthcare system. If a wearable node transmits ECG and accelerometer data of 4 channel sampled at 100 Hz, these data may occur high loss packets for transmitting human activity and ECG to server PC. Therefore current wearable sensor nodes have to solve above mentioned problems to be suited for u-healthcare system. Most WSN based activity and ECG monitoring system have been implemented some algorithms which are applied for signal vector magnitude(SVM) algorithm and ECG noise algorithm in server PC. In this paper, A wearable sensor node using integrated ECG and 3-axial accelerometer based on wireless sensor network is designed and developed. It can form multi-hop network with relay nodes to extend network range in WSN. Our wearable nodes can transmit 1-channel activity data processed activity classification data vector using SVM algorithm to 3-channel accelerometer data. ECG signals are contaminated with high frequency noise such as power line interference and muscle artifact. Our wearable sensor nodes can remove high frequency noise to clear original ECG signal for healthcare monitoring.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.331-335
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• 2020

In this study, through the accumulated technologies such as real-time monitoring of power consumption using power line communication (PLC) method, power control, and automatic blocking of standby power, to commercialize them, we developed the hardware design, algorithm, protocol and module along with data transmission using PLC. We conducted the study to develop advanced products. We also proposed cloud-based smart outlet products with a novel type of outlet. These products can measure the internal power consumption through the H/W modules and the modules that control the power of household appliances connected to the smart outlets and smart plugs. Subsequently, they transmit the measurements to the energy saving system server via a communication module. This system can control the terminal device connected to the Gateway (G/W) server through a mobile phone. This will allow the customer to check the power consumption of the building at any given time, to turn the terminal on/off, and to maximize the energy efficiency during the construction of new apartments or multi-family housing in an area.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.1
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• pp.77-82
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• 2015

Recently, multi-user massive MIMO (MU-Massive MIMO) network has attracted a lot of attention as a technology to accommodate explosively increasing mobile data traffic. However, the MU-Massive MIMO network causes a tremendous hardware complexity in a base station and computational complexity to select optimal set of users. In this paper, we thus propose a simple algorithm for selecting antennas and users while reducing the hardware and computational complexities simultaneously. The proposed scheme has a computational complexity of $O((N-S_a+1){\times}min(S_a,K))$, which is significantly reduced compared to the complexity of optimal scheme based on Brute-Force searching, $$O\left({_N}C_S_a\sum_{i=1}^{min(S_a,K)}_KC_i\right)$$, where N, $S_a$, and K denote the number of total transmit antennas, the number of selected antennas, and the number of all users, respectively.

• Journal of Advanced Navigation Technology
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• v.17 no.6
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• pp.616-624
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• 2013

When jamming signal is received, there would be malfunctions in GPS-based precise location systems. Especially, in aviation fields, these malfunctions may lead to more serious damages. Naturally, there are some research results about the prevention or location method for one jammer, but it is hard to identify and obtain measurements when multiple and various type signals are received. Therefore, we propose a method of identification and measurements acquisition algorithm in order to localize the multiple jammers which transmit CW, DSSS and SCW type signals. Also, a computer simulation is carried out so as to validate the feasibility of the proposed method by using MATLAB. From the simulation results, it is confirmed that the proposed method successfully identified the signal type and acquired the measurements of CW, DSSS and SCW type signals.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.11
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• pp.2022-2030
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• 2008

System such as FA and breakup TC is applied by real time and need to manage. This paper studies data processing skill that can divide TC and data of much quantity with collection by real time. Modularize to several system, and use of computer communication network that interlink computers that can achieve control function of each systems to network is spreading. Develop that can take advantage of Ideonet communication method and transmit signal of channel because do multiplex all. Do data that have semi-conductor equipment or many input of LCD equipment and output node multiplex, and several units real time Ideonet communication that control is available use that all input of point of contact and output module develop.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.962-977
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• 2019

The human voice is a convenient method of information transfer between different objects such as between men, men and machine, between machines. The development of information and communication technology, the voice has been able to transfer farther than before. The way to communicate, it is to convert the voice to another form, transmit it, and then reconvert it back to sound. In such a communication process, a vocoder is a method of converting and re-converting a voice and sound. The CELP (Code-Excited Linear Prediction) type vocoder, one of the voice codecs, is adapted as a standard codec since it provides high quality sound even though its transmission speed is relatively low. The EVRC (Enhanced Variable Rate CODEC) and QCELP (Qualcomm Code-Excited Linear Prediction), variable bit rate vocoders, are used for mobile phones in 3G environment. For the real-time implementation of a vocoder, the reduction of sound quality is a typical problem. To improve the sound quality, that is important to know the size and shape of noise. In the existing sound quality improvement method, the voice activated is detected or used, or statistical methods are used by the large mount of data. However, there is a disadvantage in that no noise can be detected, when there is a continuous signal or when a change in noise is large.This paper focused on finding a better way to decrease the reduction of sound quality in lower bit transmission environments. Based on simulation results, this study proposed a preprocessor application that estimates the SNR (Signal to Noise Ratio) using the spectral SNR estimation method. The SNR estimation method adopted the IMBE (Improved Multi-Band Excitation) instead of using the SNR, which is a continuous speech signal. Finally, this application improves the quality of the vocoder by enhancing sound quality adaptively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.197-199
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• 2016

In this paper, we investigate a market equilibrium in multi-channel sharing cognitive radio networks (CRNs): it is assumed that every subchannel is orthogonally licensed to a single primary user (PU), and can be shared with multiple secondary users (SUs). We model this sharing as a spectrum market where PUs offer SUs their subchannels with limiting the interference from SUs; the SUs purchase the right to transmit over the subchannels while observing the interference limits set by the PUs and their budget constraints. The utility function of SU is defined as least achievable transmission rate, and that of PU is given by the net profit. We define a market equilibrium in the context of extended Fisher model, and show that the equilibrium is yielded by solving an optimization problem, Eisenberg-Gale convex program.