• IE interfaces
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• v.13 no.2
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• pp.178-187
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• 2000

In this paper, we investigate the system performance when the voice traffic is constructed as the ATM Adaptation Layer type 2(AAL-2) and then it is transmitted to the Base Station Controller(BSC) from the Base Station Transceiver Subsystem(BTS) through El link in International Mobile Telecommunication-2000 (IMT-2000) network. For this purpose, we first briefly describe the architecture of the BTS and the BSC, and then model it as a queueing network. By simulation study, we present the required processing time at traffic control blocks and the timeout time which should be set for multiplexing the user packets in the LIU(Line Interface Unit). Further, we evaluate the performance of physical links and the timeout probability that user packets can not be multiplexed within the established timeout time, and the multiplexing gain. Finally, we present the number of voice users who can be simultaneously admitted on one El link and 99.9% value of the transmission delay from the Radio Channel Element(RCE) to the Selector & Transcoder Subsystem(STS).

• Proceedings of the KSPS conference
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• 2005.11a
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• pp.147-150
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• 2005

The performance of speech recognition in car environment is severely degraded when there is music or news coming from a radio or a CD player. Since reference signals are available from the audio unit in the car, it is possible to remove them with an adaptive filter. In this paper, we present experimental results of speech recognition in car environment using the echo canceller. For this, we generate test speech signals by adding music or news to the car noisy speech from Aurora2 DB. The HTK-based continuous HMT system is constructed for a recognition system. In addition, the MMSE-STSA method is used to the output of the echo canceller to remove the residual noise more.

• IEMEK Journal of Embedded Systems and Applications
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• v.6 no.2
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• pp.62-67
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• 2011

In this paper, Multi Mode Receiver Module is designed in one H/W module for Multi-mode Digital Broadcasting. Multi mode means Digital TV, Mobile TV and Digital Radio on the Broadcasting. and T-DMB, DAB(+), ISDB-T and DVB-T standard. Our Module can receive various broadcasting signal such as ISDB-T, DVB-T and DAB. The Multi mode Receiver Module & demuxer was implemented using the one SoC Chip has good performances to receive the multi mode signals as well as standard interface such as SPI, to connect the main CPU Unit.

• Journal of Positioning, Navigation, and Timing
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• v.8 no.1
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• pp.1-12
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• 2019

In this paper, we implement a navigation software of a Global Navigation Satellite System (GNSS) receiver based on a commercial purpose GNSS software receiver platform and verify its performance by performing experimental tests for various GNSS signals available in Korea region. The SX3, employed in this paper, is composed of an application program and a Radio Frequency (RF) frontend, and can capture and process multi-constellation and multi-frequency GNSS signals. All the signal processing procedure of SX3 is accessible by the receiver software designer. In particular for an easy research and development, the Application Programing Interface (API) of the SX3 has a flexible architecture to upgrade or change the existing software program, equipped with a real-time monitoring function to monitor all the API executions. Users can easily apply and experiment with the developed algorithms using a form of Dynamic Link Library (DLL) files. Thus, by utilizing this flexible architecture, the cost and effort to develop a GNSS receiver can be greatly reduced.

• Journal of Advanced Navigation Technology
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• v.15 no.1
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• pp.97-103
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• 2011

This paper presents a dual-band balanced mixer using nonlinear phase characteristic of composite right/left-handed (CRLH) transmission line. This metamaterial structure provides low LO leakage and high RF to LO isolation without additional filters for LO and RF path. The balanced mixer consists of balun and Wilkinson divider with dual-band characteristic of unit-cell which behaves like a CRLH metamaterial. Experimental results are used to verify the proposed metamaterial functions. The balanced mixer design results in an operating frequency of 870 MHz and 1660 MHz with an optimum mixer conversion loss of 15.2 dB at 870 MHz and 21.2 dB at 1660 MHz.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.6
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• pp.809-814
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• 2011

The major resource problem in sensor networks is energy efficiency. There are two major access methods to efficiently use energy. The first is to use dynamic power management (DPM). The second is to use energy efficient protocols. In DPM methods, the OS, the power manager, is responsible for managing the proper power state of CPU and each I/O with respect to the events, but the OS is not largely concerned about the internal operation of each network protocols. Also, energy efficient protocols are mainly focused on the power saving operation of the radio PHY. In addition, in wireless sensor network most of tasks are connected to communication. In such a situation, traditional power managers can waste unpredicted power. In this paper, we introduce an efficient power manger that can reduce a lot of unwanted power consumption through cooperative power management (CPM) in communication-related tasks between each units, such as radio, sensing unit, and CPU, for ad hoc wireless sensor nodes.

• 한국해양학회지
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• v.30 no.1
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• pp.27-38
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• 1995

For the study of oceanic surface current, this work presents a system design which is composed of three parts, a Global Positiong System(GPS) unit, a transmitter with radio frequency (RF) modem and an antenna which are housed in a plastic spherical buoy, and computerised of VHF receiving system. The key idea for this study is to employ a commercially available GPS on a drifting buoy and to utilize the receiver position information from the buoy in determining the Lagrangian motion of surface ocean waters. Great efforts has been paid to the system design which would demand several points in harsh conditions common in the sea surface, that is power supply problems housed inside of a plastic buoy, optimizing transmitting radio frequency which limits transmitting distance to a receiving station. for all these difficulties, the system appears to be promising in future oceanic applications and is considered to economical compared to ARGOS drift buoy which is being used by commercial base. We believe that the system needs to be improved in terms of several aspects such as a longer transmitting distance, a power supply and software. for the test experiments in situ, the system has employed off the coast of Ku Ryong Po int the southeast part of Korea and successfully collected the surface current data. The results are presented for two cases from 21 to 31, March 1994 and 21 to 25, June 1994 in terms of current statistics and trajectories of drifting buoys.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.504-511
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• 2016

In this paper, MIMO system based on turbo equalization techniques which LDPC codes were outer code and space time trellis codes (STTC) were employed as an inner code are studied. LDPC decoder and STTC decoder are connected through the interleaving and de-interleaving that updates each other's information repeatedly. In conventional turbo equalization of MIMO system, BCJR decoder which decodes STTC coded bits required two-bit wise decoding processing. Therefore duo-binary turbo codes are optimal for MIMO system combined with STTC codes. However a LDPC decoder requires bit unit processing, because LDPC codes can't be applied to these system. Therefore this paper proposed turbo equalization for MIMO system based on LDPC codes combined with STTC codes. By the simulation results, we confirmed performance of proposed turbo equalization model was improved about 0.6dB than that of conventional LDPC codes.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.54.1-54.1
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• 2014

Kyung Hee University has been developing a CubeSat for the space science mission called SIGMA (Scientific cubesat with Instrument for Global Magnetic field and rAdiation), which includes TEPC (Tissue Equivalent Proportional Counter) and a magnetometer. SIGMA has a 3-unit CubeSat, and the weight is about 3.2 kg. The main payload is TEPC which can measure the Linear Energy Transfer (LET) spectrum and calculate the equivalent dose for the complicated radiation field in the space. The magnetometer is a secondary payload using a miniaturized fluxgate magnetometer. We expect it to have a 1 nT resolution in the dynamic range of ${\pm}65535$ nT. An Attitude Control System (ACS) spins the SIGMA spacecraft 4 rpm with the spin axis perpendicular to the ecliptic plane. Full duplex communication is consists of VHF uplink and S-band and UHF downlink. In this paper, we introduce the system design and the scientific purpose of the SIGMA CubeSat mission.

• Journal of Advanced Navigation Technology
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• v.8 no.2
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• pp.98-104
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• 2004

When a straight-in landing from an instrument approach using ILS or VOR/DME is not possible or desirable because of topographical reason or bad weather, a circling approach maneuver is initiated by the pilot to align the aircraft with a runway for landing. Visual contact with the runway is necessary while conducting a circle to land maneuver. This research is to develop a new warning system based on a convention marker system which alerts pilots to watch out for exceeding the circling approach area. The airborne system also uses the same receiver unit without any new installations. The objective of this research is to design and develop a Yagi antenna in a special form. The research includes computer simulations to determine the size of antenna radiation pattern and to compute an expected flight path in case of alarm to validate effectiveness of the system.