• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10A
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• pp.788-795
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• 2003

We analyze the performance of a truncated power controlled CDMA(code division multiple access) cellular systems with base station antenna arrays. Erlang capacity and the channel capacity which is a maximum date rate to maintain almost error free communication are analytically derived. The numerical results show there can be a substantial increase in Erlang capacity and in channel capacity by antenna arrays incorporating with the truncated power control scheme.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.3
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• pp.249-258
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• 2010

This study seeks to improve NFRDI Serial Oceanographic observation (NSO) system which has been operated at current observation stations in the Korean Seas since 1961 and suggests the direction of NSO for practical use of Korean operational oceanographic system. For improvement, data handling by human after CTD (Conductivity-Temperature-Depth) observation on the deck, data transmission, data reception in the land station, and file storage into database need to be automated. Software development to execute QA/QC (Quality Assurance/Quality Control) of real-time oceanographic observation data and to transmit the data with conversion to appropriate format automatically will help to accomplish the automation. Inmarsat satellite telecommunication systems with which have already been equipped on board the current observation vessels can realize the real-time transmission of the data. For the near real-time data transmission, CDMA (Code Division Multiple Access) wireless telecommunication can provide efficient transmission in coastal area. Real-time QA/QC procedure after CTD observation will help to prevent errors which can be derived from various causes.

• Journal of information and communication convergence engineering
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• v.3 no.1
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• pp.1-4
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• 2005

This study proposes a new diversity algorithm to improve the signal-to-noise ratio. In the wireless channel, if fading occurs due to the multipaths, the performance of the system is apparently reduced. One of the methods to reduce fadings like this is the diversity method, and this study aims to improve the performance of the system by proposing a new diversity algorithm. This study applied rake receiver, and normalized the wireless channel from the Nakagami fading channel to the Rayleigh fading channel, which set the fading index as 1, because of the multipaths. It applied QPSK and OQPSK modulation methods and applied the convolutional codes, where the code rate is 1/2 and 1/3 and the constraint length is 9, and the turbo code where the constraint length is 4. Under these conditions, this study compared and analyzed the average error probability of direct spread multiple access system. The diversity algorithm proposed in this paper could be applied to the mobile communication and other wireless multimedia communications that require high quality and high reliability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.967-975
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• 1998

This paper presents a system to cancel the multi-user interference of synchronous DS/CDMA systems by using the estimation circuit and the reference correlator. In the code-division multiple access(CDMA) scheme, the spectrum of the user's signal is directly spreaded by means of the Simplex coed or the phase offsetted PN code. It is interesting for the Simplex code and the PN code to have a similar correalation property. It these codes are used in DS/CDMA systems, the number of acceptable users can be increased in comparison with conventioal DS/CDMA systems. This thesis presents a interference cancellation model to cancel the multi-use interference in DS/CDMA systems by using Simples code of PN code as a spreading sequence. In AWGN environment, we analyze interference generated from other users and compare the resulting performance with that of the conventioanl receiver in same user side.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.347-350
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• 2007

Adaptive arrays have been proposed as an effective means of mitigating Multiple Access Interference (MAI) and improving the performance of existing and future wireless communication systems. In this paper, we apply the analytical method proposed to analyse the theoretical Mean Bit Error Rate (BER) of an uncoded IS-95 based CDMA system with an array antenna at the BS in a Ricean fading environment. We present a modified expression for the Signal to Interference plus Noise (SINR) ratio as a function of the number of users, number of antennas and noise levels. We also verify the analytical results by means of simulations by considering different user and channel scenarios.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.4
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• pp.342-353
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• 1997

This paper presents an analytical evaluation of a hybrid direct-sequence/slow frequencyhopped code division multiple-access (DS/SFH-CDMA) system employing noncoherent M-ary frequency shift keying(MFSK) modulation in a multiple Nakagami fading (m) environment. Multipath interference (MPI) and multi-access interference (MAI) is taken into account and the spectral efficiency is calculated for uncoded as well as channel coding systems. Predetection multipath maximal ratio combining (MRC) diversity in conjunction with interleaved channel coding (Hamming(7,4) code, BCH(15, 7) code and RS (7, 4), (15, 9)) code ) is employed for improving the bit error rate (BER) performance. The BER of noncoherent hybrid system is obtained using a Gaussian interference approximation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.3
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• pp.309-315
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• 1998

This paper is analyzed the performance of coded MC-CDMA system using the multi-carrier with narrow band that is suggested to solve ISI and ICI of DS-CDMA system. In this paper, considered channel model is indoor mobile radio communication environment with Rician fading distribution and fading of multi-carrier have mutual independent characteristics. For the performance analysis of MC-CDMA system, first, bit error probability of uncoded system is simulated in the reverse and forward Rician channels. And then, it is simulated that bit error probability of coded MC-CDMA system for users, multicarriers and SNR, using (7,4) Hamming code, (15,7) BCH code and 1/2-convolutional code with 7 constraint length.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.10A
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• pp.1571-1578
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• 1999

In this paper, we present the Modulator Channel Card and VLSI chip for the Radio Transceiver Unit (RTU) of direct sequence code division multiple access (DS-CDMA) Wireless Local Loop (WLL) System. The Modulator Channel Card is designed and implemented using ASIC's, FPGA's and DSP's. The ASIC, compliance with Common Air Interface specification proposed by ETRI, has 40K gates which is designed to operate at 32MHz, and is fabricated using $0.6\mu\textrm{m}$ CMOS process. The ASIC carries out for I- or Q- phase data channel signal processing at a time, where each data channel processing consists of channel coding, block interleaving, scrambling, Walsh modulation, Pseudo-Noise (PN) spreading, and baseband filtering. The Modulator Channel Card has been integrated as a part of RTU of WLL system and is confirmed that it meets all functional and performance requirements.

• Korean Journal of Optics and Photonics
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• v.27 no.4
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• pp.133-142
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• 2016

This paper presents the design and simulation of a three-dimensional pixel-by-pixel scanning light detection and ranging (LIDAR) system with a microelectromechanical system (MEMS) scanning mirror and direct sequence optical code division multiple access (DS-OCDMA) techniques. It measures a frame with $848{\times}480$ pixels at a refresh rate of 60 fps. The emitted laser pulse waves of each pixel are coded with DS-OCDMA techniques. The coded laser pulse waves include the pixel's position in the frame, and a checksum. The LIDAR emits the coded laser pulse waves periodically, without idle listening time to receive returning light at the receiver. The MEMS scanning mirror is used to deflect and steer the coded laser pulse waves to a specific target point. When all the pixels in a frame have been processed, the travel time is used by the pixel-by-pixel scanning LIDAR to generate point cloud data as the measured result.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.6
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• pp.1207-1213
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• 2007

This paper has researched water supply facilities management using real-time water utility monitoring system based on USN(Ubiquitous Sensor Network) which is consisted of wireless sensors transferring waterworks facilities md treatment information about a valve-room and flowmeter-room of water supply installation. In the manholes, it was installed with flowmeter, pressure sensors, vibration sensors, Co-sensors, and hydro-thermograph sensors. These measurement values which are received by PDA are used for facilities operation on the spot safely and conveniently. It has also provided safe installation management via CDMA(Code Division Multiple Access) network which transfers data to remote servers to monitoring at a distance place. With safety management system of water supply facilities on USN technology convenience and safety is increased in real situation, and it is expected that we can supply clean water to people as much safer and more effective water supply installation management.