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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 31, Issue 12C - Dec 2006
Volume 31, Issue 12B - Dec 2006
Volume 31, Issue 12A - Dec 2006
Volume 31, Issue 11C - Nov 2006
Volume 31, Issue 11B - Nov 2006
Volume 31, Issue 11A - Nov 2006
Volume 31, Issue 10C - Oct 2006
Volume 31, Issue 10B - Oct 2006
Volume 31, Issue 10A - Oct 2006
Volume 31, Issue 9C - Sep 2006
Volume 31, Issue 9B - Sep 2006
Volume 31, Issue 9A - Sep 2006
Volume 31, Issue 8C - Aug 2006
Volume 31, Issue 8B - Aug 2006
Volume 31, Issue 8A - Aug 2006
Volume 31, Issue 7C - Jul 2006
Volume 31, Issue 7B - Jul 2006
Volume 31, Issue 7A - Jul 2006
Volume 31, Issue 6C - Jun 2006
Volume 31, Issue 6B - Jun 2006
Volume 31, Issue 6A - Jun 2006
Volume 31, Issue 5C - May 2006
Volume 31, Issue 5B - May 2006
Volume 31, Issue 5A - May 2006
Volume 31, Issue 4C - Apr 2006
Volume 31, Issue 4B - Apr 2006
Volume 31, Issue 4A - Apr 2006
Volume 31, Issue 3C - Mar 2006
Volume 31, Issue 3B - Mar 2006
Volume 31, Issue 3A - Mar 2006
Volume 31, Issue 2C - Feb 2006
Volume 31, Issue 2B - Feb 2006
Volume 31, Issue 2A - Feb 2006
Volume 31, Issue 1C - Jan 2006
Volume 31, Issue 1B - Jan 2006
Volume 31, Issue 1A - Jan 2006
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Implementation and Performance Evaluation of Self-Similar Traffic Generator Using OPNET
Han Kyeong-Eun ; Jung Kwang-Bon ; Lee Seung-Hyun ; Kim Young-Chon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 5A, 2006, Pages 441~450
Recently, with the exponential growth of the number of Internet users, IP traffic which occupies more than 90 percent of the entire Internet traffic affects significantly to the performance of networks. Therefore, the design of the self-similar traffic generator reflected the feature of IP traffic is very important to design the networks efficiently and evaluate the performance of it correctly. In this paper, we design the self-similar traffic generator using OPNET. In order to implement the self-similar characteristics, ON-OFF sources with Pateto distribution are employed and aggregated. The designed self-similarity traffic generator is evaluated and verified with R/S plot, variance time(VT) plot under the various offered loads and the number of sources. It is expected that the designed self-similar traffic generator can be put to practical use when wire or wireless networks is designed and verified as well as it can be useful to decide the specific parameter value for Internet traffic modeling.
An Efficient Downlink Scheduling Scheme Using Prediction of Channel State in an OFDMA-TDD System
Kim Se-Jin ; Won Jeong-Jae ; Lee Hyong-Woo ; Cho Choong-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 5A, 2006, Pages 451~458
In this paper, we propose a novel scheduling algorithm for downlink transmission which utilizes scarce wireless resource efficiently in an Orthogonal Frequency Division Multiple Access/Time Division Duplex system. Scheduling schemes which exploit channel information between a Base Station and terminals have been proposed recently for improved performance. Time series analysis is used to estimate the channel state of mobile terminals. The predicted information is then used for prioritized scheduling of downlink transmissions for improved throughput, delay and jitter performance. Through simulation, we show that the total throughput and mean delay of the proposed scheduling algorithm are improved compared with those of the Proportional Fairness and Maximum Carrier to Interference Ratio schemes.
A routing Algorithm by Broadcasting a Bitmap in Wireless Sensor Networks
Jung Sang-Joon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 5A, 2006, Pages 459~468
Current routing in sensor networks focuses on finding methods for energy-efficient route setup and reliable relaying of data from the sensors to the sink so that the lifetime of the network is maximized. The existing routing protocols do not have routing tables to determine a path when packets are transferred. A sensor network by a routing table increases a cost of maintaining and updating a path, because sensor nodes have characteristics to be mobile and constrained capacity and resources. This paper proposes a new routing algorithm by broadcasting a bitmap in order to reduce the number of messages transferred when routing paths are established. Each node has a routing table with a bitmap, which contains link information. A bitmap is formed two-dimensional array, which consists of each row and column represented with a bit. The node only updates its own bitmap if it receives a bitmap from another adjacent nodes after the broadcasting. There by, each node has a bitmap with partial links information not total links information on the network. The proposed routing algorithm reduces the number of messages for routing establishment at least 10% compared with the previous algorithms.
HSDPA Sector Throughput Analysis With Modified Link Budget
Yi Yo-Serb ; Kim Sang-Bum ; Hong Dae-Hyung ; Jang Byung-Lyerl ; Moon Soon-Joo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 5A, 2006, Pages 469~474
In this paper, we develop a method that derive the average sector throughput of HSDPA system. This proposed method reflects the effects of AMC, scheduling and multi-code transmission, and is performed by simple calculation procedures such as link budget analysis. Link budget table is used to estimate a cell coverage in general. We modify the link budget table in order to calculate C/I of the user according to the location of the user in CDMA packet system employing AMC. Furthermore, we utilize the proposed method to analyze the effects of scheduling and multi-code transmission.
Channel Estimation Scheme Using Modified ICA in MIMO-OFDM Systems
Kim Jong-Deuk ; Byun Youn-Shik ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 5A, 2006, Pages 475~483
If channel coefficients errors exist in MIMO-OFDM systems, the performance degradation of systems will occurs. In order to improve the performance of MIMO-OFDM systems, the technique of obtaining accurate channel estimation in multipath fading channel is necessary. In this paper, we introduce and propose new channel estimation-modified ICA algorithm. Simulation results shows from BER and SER curves which compare the proposed algorithm under time-varying Rayleigh fading with perfect known channel. The result of channel estimation by the proposed algorithm in this simulation, it shows that PDF(amplitude of channel) are close to the case with perfect known channel at the receiver with respect to uncoded QPSK/16-QAM/64-QAM modulation. Also, we can see that BER and SER curves are very close to the case with perfect known channel. Therefore, we see that the proposed algorithm have a good performance in MIMO-OFDM systems.
Multi-code Biorthogonal Code Keying with Constant Amplitude Coding Combined with
to Increase Bandwidth Efficiency
Kim Sung-Pil ; Kim Myoung-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 5A, 2006, Pages 484~492
A multi-code biorthogonal code keying(MBCK) system consists of multiple waveform coding block, and the sum of output codewords is transmitted. Drawback of MBCK is that it requires amplifier with high linearity because its output symbol is multi-level. MBCK with constant amplitude preceding blcok(CA-MBCK) has been proposed, which guarantees sum of orthogonal codes to have constant amplitude. Redundant bits of CA-MBCK for constant amplitude coding are not only used to make constant amplitude signal but also used to improve the bit error rate(BER) performance at receiver. In this paper, we proposed a transmission scheme which combine CA-MBCK with
to improve bandwidth efficiency of CA-MBCK. The BER performance of the scheme is same that of CA-MBCK in additive white gaussian noise(AWGN). And we showed that BER performance of the proposed system can be improved using redundant bits of constant amplitude preceding.
Design of Downlink Beamforming Transmitter in OFDMA/ TDD system
Park Hyeong-Sook ; Park Youn-Ok ; Kim Cheol-Sung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 5A, 2006, Pages 493~500
This paper presents the efficient structure and parameter optimization of downlink beamforming transmitter in OFDMA/TDD system. To design downlink beamforming transmitter for multiple transmit antennas, an efficient beamforming structure for multiple users and the choice of word-length of each block are critical in the aspect of its performance and hardware complexity. We propose an efficient beamforming scheme, which stores the weights of subcarriers into memory without user identification at the receiver of base station and calculates the weights for corresponding user in a subcarrier unit of IFFT input at high speed. Also, we obtain the word-length of main data path and other design parameters by fixed-point simulation analysis. The proposed architecture could reduce the memory size proportional to the maximum number of users per frame, and the processing time of an OFDM symbol at the receiver of base station without the need of additional processing time for calculating the weights at the transmitter.
Performance Improvement Techniques for an OFDM-CDMA System without Guard Interval
Lee Hyun-Woo ; Park Joong-Hoo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 5A, 2006, Pages 501~508
Orthogonal frequency division multiplexing-code division multiplexing access(OFDM-CDMA) systems without guard interval can enhance the bandwidth performance more efficiently than the systems with guard interval. In this paper, a new technique for an OFDM-CDMA system without guard interval, which can eliminate inter-symbol interference(ISI) and inter-channel interference(ICI), is presented. The proposed algorithm is a new demodulation technique, based on the Pseudo-Decorrelator, and it is named PD algorithm. Simulation results show that the PD algorithm can combat ISI and ICI efficiently for an OFDM-CDMA system without guard interval. The BER performance of the PD algorithm is much better than that of a conventional OFDM-CDMA system without guard interval.
Performance Evaluation of the Satellite-DMB system with a Frequency Domain Equalizer
Lee Jae-Sung ; Kim Duk-Kyung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 5A, 2006, Pages 509~516
Satellite-Digital Multimedia Broadcasting(S-DMB) systems are single frequency networks which consist of a satellite and gap fillers. Though gap fillers are required to extend the coverage to NLOS(Non Line-of-Sight) area, the receiver performance can be degraded with a limited number of fingers due to the increased number of multi-paths. The paper proposes to use frequency domain equalizer(FDE) instead of conventional Rake receiver, where the guard interval is not considered in order to minimize the impact on the current S-DMB systems. Through a campaign of simulations, it is found that the proposed FDE is less sensitive to the number of gap fillers compared to the conventional Rake receiver, and can achieve a greater channel capacity in most channel environments.
Design of a High-Speed RFID Filtering Engine and Cache Based Improvement
Park Hyun-Sung ; Kim Jong-Deok ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 5A, 2006, Pages 517~525
In this paper, we present a high-speed RFID data filtering engine designed to carry out filtering under the conditions of massive data and massive filters. We discovered that the high-speed RFID data filtering technique is very similar to the high-speed packet classification technique which is used in high-speed routers and firewall systems. Actually, our filtering engine is designed based on existing packet classification algorithms, Bit Parallelism and Aggregated Bit Vector(ABV). In addition, we also discovered that there are strong temporal relations and redundancy in the RFID data filtering operations. We incorporated two kinds of caches, tag and filter caches, to make use of this characteristic to improve the efficiency of the filtering engine. The performance of the proposed engine has been examined by implementing a prototype system and testing it. Compared to the basic sequential filter comparison approach, our engine shows much better performance, and it gets better as the number of filters increases.
Adaptive Indoor Location Tracking System Based on IEEE 802.15.4a
Jeon Hyeon-Sig ; Woo Sung-Hyun ; Cho Sang-Do ; Na Jong-In ; Kim Ki-Hwan ; Park Hyun-Ju ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 5A, 2006, Pages 526~536
According as Ubiquitous comes, interest for indoor location tracking system was more increased socially. However, existing indoor location tracking system doesn't correspond actively in frequent change of indoor environment, and there is a problem that correct location measurement of transfer object is difficult by NLOS property of indoor environment. Purpose of this paper proposes environment accommodation location tracking system that is improved location precision of transfer object and grasps location of indoor transfer object effectively that is essential element effectively to provide service to satisfy various user's request according as Ubiquitous comes.
Design and Implementation of a Splicer for Seamless Swiching between Programs in the Terrestrial DMB
Lee Yong-Hoon ; Lee Jin-Hwan ; Lee Gwang-Soon ; Lee Soo-In ; Kim Nam ;
The Journal of Korean Institute of Communications and Information Sciences, volume 31, issue 5A, 2006, Pages 537~545
As the T-DMB service is launched, some service requirements become necessary to send local programs such as advertisement and specific programs at the local broadcasting station while re-transmitting the broadcasting signal coming from the central or other station. In this paper, we propose a signalflow required for the effective splicing in the T-DMB system which usesboth MPEG-2 and MPEG-4 system specifications, and we illustrate the reconfiguring process into the ensemble stream that is widely used for the transmission of the T-DMB signal. Moreover, its performance is confirmed by comparing the images decoded at the recevier when the transport stream is swiched by using the splicer implemented through the proposed techniques.