• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.1
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• pp.14-25
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• 1995

The main contribution of this paper can be summarized in two items as follws. Firstly, a modelling of mobile communication channel with Rayleigh fading characteristics is presented. Actual signal environments can be approximated as being real measurements by a proper mathematical representation of fluctuation of channel parameters due to Doppler effect, that is determined by the relative speed between transmitter and receiver, and noises, that vary at each sampling time. Secondly, an alternative procedure of synthesizing an adaptive equalizers is presented for recovering original signals that have been corrupted through the modelled channel. In order to compute the optimal tap coefficients for a high speed data(512 k symbol/sec) on a real-time basis, the CGM that guarantees fast and stable convergency is adopted during the training period of each frame. The coefficients obtained by the CGM are used as initial values for the LMS algorithm to trace the optimal coefficients during the data period that vary at each sampling time due to the mobility and noise at the receiver. Using the modelling presented in this paper, distributions of received signal power in various signal environments are demonstrated. The performance of the eqalizer proposed in this paper is shown as a function of BER under the various signal circumstances of mobile communications.

• ETRI Journal
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• v.39 no.2
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• pp.213-221
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• 2017

The advent of wireless access in vehicular environments (WAVE) technology has improved the intelligence of transportation systems and enabled generic traffic problems to be solved automatically. Based on the IEEE 802.11p standard for vehicle-to-anything (V2X) communications, WAVE provides wireless links with latencies less than 100 ms to vehicles operating at speeds up to 200 km/h. To date, most research has been based on field test results. In contrast, this paper presents a numerical analysis of the V2X broadcast throughput limit using a path loss model. First, the maximum throughput and minimum delay limit were obtained from the MAC frame format of IEEE 802.11p. Second, the packet error probability was derived for additive white Gaussian noise and fading channel conditions. Finally, the maximum throughput limit of the system was derived from the packet error rate using a two-ray path loss model for a typical highway topology. The throughput was analyzed for each data rate, which allowed the performance at the different data rates to be compared. The analysis method can be easily applied to different topologies by substituting an appropriate target path loss model.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.1
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• pp.12-21
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• 1999

All kinds of electronic machinery including portable communication system are being smaller size and are used at high frequency. It generates a lot of unwanted noise signals called electromagnetic interface (EMI). This paper presents an analysis result of EMI generation in VLSI and propose new circuits to minimize of EMI using I/O driver with parallel buffer architecture and distributed decoupling capacitor in a chip. The proposed circuits are evaluated with i8052 MCU which is shown reducing of delta current 1/3 times and improvement of EMI more 10dBuV compared with conventional processors.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.12
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• pp.1-10
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• 1999

In this paper, we analyzed the radiation patterns of a monopole antenna mounted on the complex structures by using FDTD method associated with 3-D PML absorbing boundary condition. In order to validate the proposed FDTD code, the radiation patterns of monopole antenna mounted on cylinders and spheres were compared with the exact solutions of $Carter^{[1]}$ and $Harrington^{[2]}$. For all case considered, the predicted radiation pattern exhibited excellent agreement with exact solution. To be able to model the more complex structures, the proposed FDTD methods are combined with BRL-CAD. And this procedures is applied to predict the radiation patterns of a wire antenna attached to the top of a Blackhawk helicopter.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.10
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• pp.34-41
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• 1998

In this paper, we evaluate synchronization techniques suitable for high-speed ATM satellite communications with a transmission rate of 155Mbit/s, and propose optimal algorithms that improve the tracking performance, where QPSK is selected for a modulation scheme, and the receiver is operated in burst mode. Based on these asumptions, we proposed modified algorithms and architectures for automatic frequency control(AFC), carrier recovery(CR), and symbol timing recovery(STR) for burst acquisition. Analysis is performed under AWGN environments with respect to the number of required symbol, steady-state stability, and hardware implementation for the proposed algorithms.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.9
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• pp.27-35
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• 1999

In this paper, we propose an error detection scheme of phase offsets for binary sequences including PN (Pseudo Noise) sequences based on the number theoretical approach. It is important to know phase offsets of spreading sequences in the CDMA (Code Division Multiple Access) mobile communication systems because phase offsets of the same spreading sequence are used to achieve the acquisition and are used to distinguish each base station. When the period of the sequence is not very long, the relative phase offset between the sequence and its shifted replica can be found by comparing them, but as the period of the sequence increases it becomes difficult to find the phase offset. The error detection failure probability of the proposed method is derived, and it is confirmed by the simulation results. We also discuss the circuit realization of the proposed method and show it can be easily implemented.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.11
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• pp.12-18
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• 1998

In non-geostationary orbit(NGSO) satellite communication links, satellite's elevation angle at terminal is changed continuously because of the satellite movement relative to earth surface. Therefore the characteristics of the fade-effected signal received by a terminal from a NGSO satellite is also varied continuously even if the terminal is operated at fixed location. In this paper, we determine a general statistic model for the fading characteristics over NGSO satellite communication links and set up the parameters of the fading model in terms of the elevation angle according to various propagation environment and find the parameter values using the data of fading margin for commercial NGSO mobile satellite communication systems. And the fading charateristics for each environment are analyzed using this model. These results can be applied to develop the compensation algorithm and to analyze the performance of the transmission schemes for NGSO mobile satellite communication systems.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.6
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• pp.1-12
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• 1999

This paper illustrates and analyzes system structure, link budget and cell coverage to accommodate Korea environment about LMDS systems that are expected to play an important role as the future wireless infrastructure of the information superhighway. In the mean time, many parameters used for the analysis apply to the allocated frequency bandwidth (Up-stream : 24.25GHz-24.75GHz, Down-stream : 25.5GHz-27.5GHz) of Ministry of Information and Communication. The modem and channel coding must be developed to accommodate specifications of DAVIC protocol. The materials about atmospheric phenomena refer to apply specifications of ITU-R. This paper will be need to disign the network structure and system configuration of LMDS system.

• Journal of information and communication convergence engineering
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• v.8 no.2
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• pp.163-167
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• 2010

In underwater acoustic communication, acoustic signals from transducers or hydrophones are used. And the underwater acoustic communication channels are very complicated, because of vertical distribution of acoustic velocity according depths, and reflections from boundaries like as surface or bottom. For the implementation of the underwater acoustic communication channel, the image method or ray tracing method have been used. In this paper, we introduce a new approach for implementation of underwater acoustic communication channel using the simulation of the Transmission Line Matrix Modeling and cross-correlations from the input and output signals.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.11
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• pp.79-85
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• 1995

In this paper, an epi layer and a device structure for InP/InGaAs p-i-n/HBT OEIC is designed for a receiving frontend of high speed optical communications. A 3 stage transimpedance circuit using the p-i-n/HBT device is also designed by SPICE simulations for a high sensitivity including ISI noises at a given bit rate. Our simulations show that the Personick's assumption which is not commonly satisfied have estimated a photoreceiver sensitivity too high, so thus we have to also consider ISI noises in OCIC receiver designs.