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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of Korean Institute of Communications and Information Sciences
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The Korean Institute of Communications and Information Sciences
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Volume & Issues
Volume 32, Issue 12C - Dec 2007
Volume 32, Issue 12B - Dec 2007
Volume 32, Issue 12A - Dec 2007
Volume 32, Issue 11C - Nov 2007
Volume 32, Issue 11B - Nov 2007
Volume 32, Issue 11A - Nov 2007
Volume 32, Issue 10C - Oct 2007
Volume 32, Issue 10B - Oct 2007
Volume 32, Issue 10A - Oct 2007
Volume 32, Issue 9C - Sep 2007
Volume 32, Issue 9B - Sep 2007
Volume 32, Issue 9A - Sep 2007
Volume 32, Issue 8C - Aug 2007
Volume 32, Issue 8B - Aug 2007
Volume 32, Issue 8A - Aug 2007
Volume 32, Issue 7C - Jul 2007
Volume 32, Issue 7B - Jul 2007
Volume 32, Issue 7A - Jul 2007
Volume 32, Issue 6C - Jun 2007
Volume 32, Issue 6B - Jun 2007
Volume 32, Issue 6A - Jun 2007
Volume 32, Issue 5C - May 2007
Volume 32, Issue 5B - May 2007
Volume 32, Issue 5A - May 2007
Volume 32, Issue 4C - Apr 2007
Volume 32, Issue 4B - Apr 2007
Volume 32, Issue 4A - Apr 2007
Volume 32, Issue 3C - Mar 2007
Volume 32, Issue 3B - Mar 2007
Volume 32, Issue 3A - Mar 2007
Volume 32, Issue 2C - Feb 2007
Volume 32, Issue 2B - Feb 2007
Volume 32, Issue 2A - Feb 2007
Volume 32, Issue 1C - Jan 2007
Volume 32, Issue 1B - Jan 2007
Volume 32, Issue 1A - Jan 2007
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Performance Analysis of Effective Load Control Procedure for WiBro System
Kim, So-Hyoung ; Kim, Jeong-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 387~393
In this paper, we propose the load control procedure for WiBro system in order to keep the data traffic throughput maximum. The transmitter at a mobile terminal can estimate maximum available power for each user and then the maximum number of subchannels can be calculated considering the total available power. The data traffic throughput and the total throughput (the sum of signaling traffic and data traffic throughput) are considered. As the number of bandwidth requests per frame increases, the data traffic throughput can significantly decrease. Therefore, the load control procedure is indispensible to maintain the data throughput at the maximum level. So, we propose the load control procedure to prevent data traffic throughput from decreasing and evaluate the proposed procedure through the computer simulation under the multi-user environment. The maximum throughput can be maintained by applying the proposed procedure.
Adaptive MIMO Transmission Method based on the Optimal Combination of Antenna Diversity with Spatial Multiplexing
Kim, Dae-Hyun ; Kim, Hyung-Myung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 394~401
MIMO transmission systems can have various transmission modes, which result from the various combinations of the antenna diversity with spatial multiplexing. In this paper, we find the optimal mode to maximize the capacity with the BER constraint and the optimal selection (diversity transmission or spatial multiplexing transmission) for transmission of each transmission antenna, if necessary. The computer simulation results show that the proposed scheme has more capacity than the conventional scheme.
Efficient Security Mechanism using Light-weight Data Origin Authentication in Sensor Networks
Park, Min-Ho ; Lee, Chung-Keun ; Son, Ju-Hyung ; Seo, Seung-Woo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 402~408
There are many weaknesses in sensor networks due to hardware limitation of sensor nodes besides the vulnerabilities of a wireless channel. In order to provide sensor networks with security, we should find out the approaches different from ones in existing wireless networks; the security mechanism in sensor network should be light-weighted and not degrade network performance. Sowe proposed a novel data origin authentication satisfying both of being light-weighted and maintaining network performance by using Unique Random Sequence Code. This scheme uses a challenge-response authentication consisting of a query code and a response code. In this paper, we show how to make a Unique Random Sequence Code and how to use it for data origin authentication.
Co-Channel Interference Cancellation in Cellular OFDM Networks - PART I : Maximum-Likelihood Co-Channel Interference Cancellation with Power Control for Cellular OFDM Networks
Mohaisen, Manar ; Chang, Kyung-Hi ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 409~416
In cellular orthogonal frequency division multiplexing (OFDM) networks, co-channel interference (CCI) leads to severe degradation in the BER performance. To solve this problem, maximum-likelihood estimation (MLE) CCI cancellation scheme has been proposed in the literature. MLE CCI cancellation scheme generates weighted replicas of the transmitted signals where weights represent the estimated channel transfer functions. The replica with the smallest Euclidean distance from the received signal is selected and data are detected. When the received power of the desired and interference signals are nearly the same, the BER performance is degraded. In this paper, we propose a closed-loop power control (PC) scheme capable of detecting the equal received power situation at the mobile station (MS) receiver by using the newly introduced parameter power ratio (PR). When this situation is detected, the MS sends a feedback to the desired base station (BS) which boosts the transmission power in the next frame. At cell edge where signal to interferer ratio (SIR) is considered to have average value between -5 dB and 10 dB, computer simulations show that the proposed CCI cancellation scheme has a gain of 7 dB at 28 Km/h.
Guard Interval Extension for Individual Users in Uplink OFDMA Mobile Communication Systems
Rim, Min-Joong ; Lim, Dae-Woon ; Jeong, Byung-Jang ; Noh, Tae-Gyun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 417~425
While the cyclic prefix lengths of downlink OFDMA(Orthogonal Frequency Division Multiple Access) systems are determined based on the maximum delay spreads encountered in cellular environments, the guard interval of uplink OFDMA systems should consider the timing offsets of uplink signals as well as the delay spread lengths. Especially in the cases of initial accesses, handovers, and considerable time elapsed without data transmissions between base and mobile stations in a large cell, uplink timing offsets can be large and a very long guard interval length may be required. In order to keep the small size of the cyclic prefix in uplink OFDMA systems, the systems require a method of extending the guard intervals for users with large timing offsets without affecting the cyclic prefix length of the system. This paper proposes a method extending the guard intervals of individual users in uplink OFDMA systems.
A Study of MAP Architecture Adopting the Sliding Window Method for Turbo Decoding
Choi, Goang-Seog ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 426~432
The MAP algorithm is designed and implemented through the sliding window method for turbo decoding. First, the implementation issues, which are the length of the sliding window and the normalization method of state metrics are reviewed, and their optimal values are obtained by the simulation. All component schemes of the decoder including the branch metric evaluator are also presented. The proposed MAP architecture can be easily redesigned according to the size of sliding window, that is, sub-frame length because of its simplicity on buffer control.
Performance analysis of Wireless Internet system employing joint adaptive array antennas
Park, Hyun-Hwa ; Kim, Jeong-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 433~440
In this paper, we have proposed WiBro receiver structure employing joint adaptive antenna scheme at the base station (BS) and the mobile station (MS) and evaluated its performance. In WiBro system, the joint use of transmit beamforming at BS and receive beamforming at MS can improve the SINR significantly and increase the capacity compared to the conventional system. Moreover, power allocation level can be decreased because channel variation can be reduced by using the jointly updated weight. However, it needsthe calculation of the antenna weights in every subcarrier for performance improvement. This could imply an enormous computational burden. However, the computational complexity can be reduced significantly by using the same set of the antenna weights for the adjacent subcarriers instead of calculating antenna weights for every subcarrier. We have analyzed the impact of subcarrier grouping for weight calculation on the system performance.
The link performance analysis of the satellite communications system using satellite network simulator
Jang, Jae-Woong ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 441~450
In this paper, it is proposed the link performance analysis results using SNRAT(Satellite Network Resource Allocation & Analysis Tool) and verified the anticipated results by satellite communication network simulator. A communication satellite cannot be corrected or fixed for the error in orbit operation after launching unlike the ground operation equipment and has a restricted operation life. So, it is important to make possible to use satellite communications in the proper time. It is expected the link BER(Bit Error Rate), throughput and AJ(Anti-Jamming) performance using SNRAT tool before launching. And it is verified the performance of the repeaters and ground equipment specification using the satellite network simulator and is extracted the optimum operational scenarios through the tests of various network operational plans.
A Study on the Industrial Data Processing for Control System Middle Ware and Algorithm RFID is Expected
Kang, Jeong-Yong ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 451~459
RFID it reads information which is it writes, the semiconductor chip for and the radio frequency system which uses the hazard antenna it has built-in transmission of information it talks. Formation which is transmitted like this collection and America which it filtrates wey the RFID search service back to inform the location of the server which has commodity information which relates with an object past record server. The hazard where measurement analysis result the leader for electronic interference does not occur consequently together from with verification test the power level which is received from the antenna grade where it stands must maintain minimum -55dBm and the electronic interference will not occur with the fact that, antenna and reel his recognition distance the maximum 7m until the recognition which is possible but smooth hazard it must stand and and with the fact that it will do from within and and and 3-4m it must be used Jig it is thought.
Tone-Based Access Scheme with Repetitive Contention in Contention-Based Medium Access Control
Ahn, Jae-Hyun ; Yun, Jeong-Kyun ; Bahk, Sae-Woong ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 460~466
There are two coordination functions in IEEE 802.11 standard. One is PCF, polling based function, and the other is DCF, contention based function. DCF is simpler than PCF but the performance is similar with the latter. That's the reason why DCF is more popular than PCF. However, DCF has a risk of collision with other nodes in the network because the function is a distributed contention based one. CSMA/CA of DCF has collision avoidance algorithm in it, but the performance of avoidance algorithm has limitations. In this paper we proposed a new scheme called TAR(Tone-based Access scheme with Repetitive conention). In TAR, there is narrow contention-only channel other than original data transmitting channel, so that both a data transmission and the contention can be performed simultaneously. The TAR uses the same contention concept with the CSMA/CA, but it has the originality for the narrow contention channel and the repetitive contention scheme which greatly reduce the collision probability. We proved the performance of TAR by some simulations, and it showed good results.
Improved Soft-Decision Technique with Channel State Information in MB-OFDM System with DCM
Koo, Bon-Wook ; Kang, Byung-Su ; Song, Hyoung-Kyu ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 467~474
MB-OFDM (Multiband-orthogonal frequency division multiplexing) UWB (ultra wide band) system uses DCM (dual carrier modulation) scheme to achieve high-data rate transmission. The basic idea of DCM is that to transmit the 4 bits more reliably two 16-QAM (quadrature amplitude modulation) symbols are used and the two 16-QAM sysmbols are allocated to each subcarrier of OFDM with maximum-distance. In the case of using the DCM, if one 16-QAM symbol is broken by deep fadding channel, a receiver can detect the transmitted signal by using another 16-QAM symbol. In the conventional ML(maximum likelihood) decision scheme, since the receiver does not use the CSI (channel state information), loss in diversity can not be reduced. In this paper, we propose improved soft-decision scheme with CSI for higher performance of MB-OFDM UWB systemn.
Cooperative Transmission Scheme in OFDMA Uplink System
Yoon, Jae-Seon ; Song, Hyoung-Kyu ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 475~483
Recently, consumers demand high-quality wireless multimedia services via terrestrial and satellite network. And the interest for new services to sustain its successful commercial deployment grows tremendously. So, the MIMO schemes, such as STCs, MRC, has been used for realizing high reliability. However, MIMO schemes has some limitations. MIMO scheme needs more size, cost, and hardware complexity to employ additional antennas. Moreover, sufficient spaces between antennas are required to guarantee the independence of each channel and the devices which use multiple antennas should be enlarged. A cooperative transmission technique which is detect and forward type applying virtual MIMO with STBC matrix in DVB-RCT(Digital Video Broadcasting with Return Channel via Terrestrial) system based on OFDMA is also proposed.
Pilot-Aided Iterative Frequency Offset Estimation for Digital Video Broadcasting Systems
Lee, Kyung-Taek ; Seo, Jong-Soo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 484~489
The main disadvantage of orthogonal frequency division multiplexing (OFDM) systems is its sensitivity to carrier frequency offset and timing offset. This paper proposes a simple way of improving the performance of the integer frequency offset (IFO) estimator in OFDM-based digital video broadcasting (DVB) system. By modifying the conventional maximum likelihood (ML) estimator to have multi-stage estimation strategy, IFO estimator is derived. Simulations indicate that the proposed IFO estimator works robustly with reduced computational burden when compared to ML estimator.
Design of Integrated LTCC Front-End Module using Measurement-Based Behavioral Model for IEEE 802.11a WLAN Applications
Han, A-Reum ; Yoon, Kyung-Sik ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 490~496
This paper describes the design and implementation of an integrated LTCC front-end module for the IEEE802.11a WLAN applications by performing the behavioral-level simulation using measurement-based behavioral model. To meet the IEEE802.11a WLAN standard, a system transmitting 1024 symbols through 64-QAM process at the rate of 54Mbps should be implemented and nonlinear properties are confirmed by simulations of ACPR and EVM in this circumstance. The right offsets of ACPR which are 30MHz, 20MHz, and 11MHz distant from the center frequency of 5.8GHz are 49.36dBc, 36.90dBc, and 24.58dBc, respectively. The left offsets are 50.14dBc, 30.04dBc, and 28.85dBc, respectively and EVM is 2.94%. The size of the module implemented with LTCC five-layer substrates is
. The measured characteristics of the transmitter show P1dB of 16.2dBm and power gain of 16.73dB. Those of the receiver exhibit the small signal gain of 16.24dB and noise figure of 7.83dB.
Design & Fabrication of a Broadband SiGe HBT Variable Gain Amplifier using a Feedforward Configuration
Chae, Kyu-Sung ; Kim, Chang-Woo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 497~502
Broadband monolithic SiGe HBT variable gain amplifier with a feedforward configuration have been newly developed to improve bandwidth and dB-linearly controlled gain characteristics. The VGA has been implemented in a
BiCMOS process. The VGA achieves a dynamic gain-control range of 19.6 dB and a 3-dB bandwidth of 4 GHz (
) with the control-voltage range from 0.6 to 2.6 V. The VGA produces a maximum gain of 9.3 dB at 6 GHz and a output power of -3 dBm at 8 GHz.
VLSI Implementation of Low-Power Motion Estimation Using Reduced Memory Accesses and Computations
Moon, Ji-Kyung ; Kim, Nam-Sub ; Kim, Jin-Sang ; Cho, Won-Kyung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 5A, 2007, Pages 503~509
Low-power motion estimation is required for video coding in portable information devices. In this paper, we propose a low-power motion estimation algorithm and 1-D systolic may VLSI architecture using full search block matching algorithm (FSBMA). Main power dissipation sources of FSBMA are complex computations and frequent memory accesses for data in the search area. In the proposed algorithm, memory accesses and computations are reduced by using 1D PE (processing array) array architecture performing motion estimation of two neighboring blocks in parallel and by skipping unnecessary computations during motion estimation. The VLSI implementation results of the algorithm show that the proposed VLSI architecture can save 9.3% power dissipation and can operate two times faster than an existing low-power motion estimator.