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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 30, Issue 12C - Dec 2005
Volume 30, Issue 12B - Dec 2005
Volume 30, Issue 12A - Dec 2005
Volume 30, Issue 11C - Nov 2005
Volume 30, Issue 11B - Nov 2005
Volume 30, Issue 11A - Nov 2005
Volume 30, Issue 10C - Oct 2005
Volume 30, Issue 10B - Oct 2005
Volume 30, Issue 10A - Oct 2005
Volume 30, Issue 9C - Sep 2005
Volume 30, Issue 9B - Sep 2005
Volume 30, Issue 9A - Sep 2005
Volume 30, Issue 8C - Aug 2005
Volume 30, Issue 8B - Aug 2005
Volume 30, Issue 8A - Aug 2005
Volume 30, Issue 7C - Jul 2005
Volume 30, Issue 7B - Jul 2005
Volume 30, Issue 7A - Jul 2005
Volume 30, Issue 6C - Jun 2005
Volume 30, Issue 6B - Jun 2005
Volume 30, Issue 6A - Jun 2005
Volume 30, Issue 5C - May 2005
Volume 30, Issue 5B - May 2005
Volume 30, Issue 5A - May 2005
Volume 30, Issue 4C - Apr 2005
Volume 30, Issue 4B - Apr 2005
Volume 30, Issue 4A - Apr 2005
Volume 30, Issue 3C - Mar 2005
Volume 30, Issue 3B - Mar 2005
Volume 30, Issue 3A - Mar 2005
Volume 30, Issue 2C - Feb 2005
Volume 30, Issue 2B - Feb 2005
Volume 30, Issue 2A - Feb 2005
Volume 30, Issue 1C - Jan 2005
Volume 30, Issue 1B - Jan 2005
Volume 30, Issue 1A - Jan 2005
Selecting the target year
Performance Evaluation of the Advanced Physical Layer Modulation Techniques for Cable Modem Upstream Channel
Cho, Byung-Hak ; Choi, Hyung-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 1~11
S-CDMA is the advanced physical layer modulation techniques of DOCSIS 2.0 specification. S-DMT is another challenging modulation technique for cable modem upstream channel due to the intrinsic robustness for fading and impulse noise. The BER performance of S-DMT and S-CDMA over the mixed channel model of AWGN and impulse noise were evaluated in comparison with TDMA. The mathematical BER derivation and the comparison of those three types of technique were performed based on the
non-Gaussian impulse noise model. The results of simulation show good compliance with those of analytic BER derivation. By the results of comparisons, it was verified that the performance of S-CDMA and S-DMT is almost the same, but the performance of S-DMT is far superior to that of TDMA at typical BER range of the practical data communications.
Study on Design of Internet Phon(VoIP) using the VPN
Yoo, Seung-Sun ; Kim, Sam-Tek ; Lee, Seung-Gi ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 12~19
The VoIP(Voice over IP) has been worldwide used and already put to practical use in many fields. However, it is needed to ensure secret of VoIP call in a special situation. It is relatively difficult to eavesdrop the commonly used PSTN in that it is connected with 1:1 circuit. However, it is difficult to ensure the secret of call on Internet because many users can connect to the Internet at the same time. Therefore, this paper suggests a new model of Internet telephone for eavesdrop prevention enabling VoIP(using SIP protocol) to use the VPN protocol and establish the probability of practical use comparing it with Internet telephone.
DESIGN OF A HIGH-THROUGHPUT VITERBI DECODER
Kim, Tae-Jin ; Lee, Chan-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 20~25
A high performance Viterbi decoder is designed using modified register exchange scheme and block decoding method. The elimination of the trace-back operation reduces the operation cycles to determine the merging state and the amount of memory. The Viterbi decoder has low latency, efficient memory organization, and low hardware complexity compared with other Viterbi decoding methods in block decoding architectures. The elimination of trace-back also reduces the power consumption for finding the merging state and the access to the memory. The proposed decoder can be designed with emphasis on either efficient memory or low latency. Also, it has a scalable structure so that the complexity of the hardware and the throughput are adjusted by changing a few design parameters before synthesis.
LMS-Wiener Model for Resources Prediction of Handoff Calls in Multimedia Wireless IP Networks
Lee, Jin-Yi ; Lee, Kwang-Hyung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 26~33
Exact prediction of resource demands for future calls enhances the efficiency of the limited resource utilization in resource reservation methods for potential calls in wireless IP networks. In this paper, we propose a LMS-Wiener resource(bandwidth) prediction for future handoff calls, and then an the proposed method is compared with an existing Wiener-based method in terms of prediction error through our simulations. In our simulations, we assume that handoff call arrivals follow a non-Poisson process and each handoff call has an non-exponentially distributed channel holdingtime in the cell, considering that handoff call arrival pattern is not Poisson distribution but non-Poisson for long periods of time in wireless picocellular IP networks. Simulation results show that the prediction error in the proposed method converges to the lower value while in an existing method increase as time is passed. Therefore we may conclude that the proposed method improves the efficiency of resource utilization by more exactly predicting resource demands for future handoff calls than an existing method.
Performance Analysis of Asynchronous OFDMA Uplink Systems with Timing Misalignments over Frequency-selective Fading Channels
Park, Myong-Hee ; Ko, Kyun-Byoung ; Park, Byung-Joon ; Lee, Young-Il ; Hong, Dae-Sik ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 34~42
In orthogonal frequency-division multiple access (OFDMA) uplink environments, asynchronously received signals can cause multiple access interference (MAI). This paper focuses on the performance degradation due to the MAI over frequency-selective fading channels. We first introduce the timing misalignment, which is defined as the relative timing difference between asynchronous timing error of uplink user and reference time of the base station, and analytically derive the MAI using the power delay profile of wide-sense stationary uncorrelated scattering (WSSUS) channel model. Then, the effective signal-to-noise ratio (SNR) and the average symbol error probability (SEP) are derived. The proposed analytical results are verified through simulations with respect to the region of the timing misalignment and the number of asynchronous users.
Performance Improvement of LMMSE Channel Estimation Method for OFDM Systems
Kang, Yeon-Seok ; Kim, Young-Soo ; Suh, Doug-Young ; Kim, Jin-Sang ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 43~50
In this paper, we present an improved channel estimation method for orthogonal frequency division multipexing systems using pilot symbol assisted modulation(PSAM). Conventional linear minimum mean square error(LMMSE) channel estimation method uses only pilot symbols for channel estimation. So, as the fading channel varies rapidly, the system performance is degraded. The basic idea of the proposed scheme is that we firstly estimate channel coefficients at the middle point between two pilot symbols and then compute the channel attenuation by using LMMSE method. Superior performance achieved with the proposed method is illustrated by simulation experiments with the Doppler frequency of 36Hz and 185Hz in comparison with conventional LMMSE channel estimator.
Design of an enhanced SIR measurement algorithm for WCDMA mobile station Modem
Han, Jung-Su ; Doo, Joo-Hyun ; Choi, Hyung-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 51~60
In this paper, we propose an enhanced SIR measurement algorithm for WCDMA mobile station modem. The proposed algorithm minimizes processing delay by applying velocity estimation-based channel estimator with IIR filter and reduces measured SIR offset by compensating attenuated signal power by using pilot channel(CPICH) in fading channel environment. To improve stability of SIR measurement, we also adopt an IIR filter which can properly reflect variation of fading channel in signal and interference power measurement. We prove that the proposed algorithm outperforms conventional SIR measurement algorithm in mean and jitter of measured SIR. Computer simulation shows that performance results using the proposed algorithm have improvement of approximately 8dB for measured mean and 2dB for measured jitter in the wireless mobile channel, especially in fast mobile speed environment.
Call Admission Control using Soft QoS-based Borrowing Scheme in DVB-RCS Networks
Lee, Hee-Bong ; Jang, Yeong-Min ; Lee, Ho-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 61~65
We propose a soft QoS-based borrowing scheme for call admission control(CAC) in DVB-RCS(Digital Video Broadcast-Return Channel via Satellite). Some of the ongoing calls temporarily and fairly release bandwidths that can be used to accommodate a new call in an overloaded satellite network. The amount of bandwidth borrowed from each call is proportional to each user's critical bandwidth ratio, one of parameters for soft QoS mechanism. Simulation results show that the proposed scheme improves the system performance in terms of call blocking probability and bandwidth utilization.
The Analysis of RF System and Communication Link for improvement in reliability of Smart UAV Data-Link
Hwang, In-Yong ; Yu, Kap-Seon ; Kim, Hak-Sun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 66~79
In this paper, we have performed the analysis of RF transceiver system and communication link for the improvement in reliability of Smart-UAV(Unmanned Aerial Vehicles) Data-Link. The system analysis performed using the development specification of the data link and data sheet of using components through the system simulation tool that is Agilent EEsof ADS. Also, the communication link analysis peformed using a variety of propagation models for the smart UAV operation environments. As a result, we have presented problems appeared in the simulation results and development specification. As well as, we have presented about several problems and consideration issue for system design through the communication link analysis.
A Priority-based MAC Protocol to Support QoS in Ad-hoc Networks
Wang, Weidong ; Seo, Chang-Keun ; Yoo, Sang-Jo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 80~89
In IEEE 802.11 and 802.11e for ad hoc networks, DCF and EDCA use a contention-based protocol called CSMA/CA, which is simple to implement efficient when the system is light loaded. But the performance of CSMA/CA decreases dramatically when the system load is heavy because of increasing collisions. In PCF and HCF modes, stations are controlled by a base station by polling, no collision ever occurs. However, when the system load is light, the performance is poor because few stations have data to transfer. More important, PCF and HCF can not be used in the ad hoc networks. In this paper, we address a priority-based distributed polling mechanism (PDPM) that implements polling scheme into DCF or EDCA modes for ad hoc networks by adding a polling approach before every contention-based procedure. PDPM takes the advantages of polling mechanism that avoids most of collisions in a high load condition. At the same time, it also keeps the contention-based mechanism for a light loaded condition. PDPM provides quality of service (QoS) with fewer collisions and higher throughput compared with IEEE 802.11e.
Design and Implementation of USB Interface Bridge for PC-based DAB Receiver
Park, Nho-Kyung ; Jin, Hyun-Joon ; Park, Sang-Pong ; Kim, Sang-Pok ; Han, Sung-Ho ; Lee, Sang-Chul ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 90~97
Generally, DAB systems are divided into two categories, a stand-alone type and a PC/PDA-based type. The PC/PDA-based type has less mobility comparing to the stand-alone type, nevertheless, it has the advantage of using memory, audio/video decoder, or other resources of PC/PDA. The DAB receiver implemented in this paper is a PC-based receiver system employing USB interface. The USB interface bridge is designed using FPGA and EZ-USB development kit and the implemented DAB receiver adopts the bridge and makes use of the stand-alone typed DRK-026 receiver for experiments. The USB interface bridge transforms serial data into USB packets and all of related signals are controlled by hardware logics. The operation of the implemented DAB receiver is verified by sending audio data into the PC for decoding through USB interface bridge.
Wireless Packet Scheduling Algorithms based on Link Level Retransmission
Kim, Nam-Gi ; Yoon, Hyun-Soo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 98~106
We propose a new wireless fair queueing algorithm, WFQ-R (Wireless Fair Queueing with Retransmission), which is well matched with the LLR (Link Level Retransmission) algorithm and does not require channel prediction. In the WFQ-R algorithm, the share consumed by retransmission is regarded as a debt of the retransmitted flow to the other flows. Thus, the WFQ-R algorithm achieves wireless fairness with the LLR algorithm by penalizing flows that use wireless resources without permission under the MAC layer. Through simulations, we showed that our WFQ-R algorithm maintains fairness adaptively and maximizes system throughput. Furthermore, our WFQ-R algorithm is able to achieve flow separation and compensation.
Development of Small-sized Ceramic VCXO using the PECL
Lee, Jae-Kyung ; Yoon, Dal-Hwan ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 107~113
In this paper, we have developed the miniature ceramic PECL(positive emitter-coupled logic) VCXO of the
size for gratifying the requested specifications and the multilayer ceramic SMD(surface mounted device) package technology. The ceramic SMD PECL VCXO designed by the inverted Mesa type HFF is operating at the 3.3 Voltage and have the frequency range of 120MHz-180MHz. The Q factor is over 5K and it has the low jitter characteristics of 3.5 ps and low phase noise.
A Design of Pipelined Analog-to-Digital Converter with Multi SHA Structure
Lee, Seung-Woo ; Ra, Yoo-Chan ; Shin, Hong-Kyu ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 114~121
In this paper, Pipelined A/D converter with multi SHA structure is proposed for high speed operation. The proposed structure incorporates a multi SHA block that consists of multiple SHAs of identical characteristics in parallel to improve the conversion speed. The designed multi SHA is operated by non-overlapping clocks and the sampling speed can be improved by increasing the number of multiplexed SHAs. Pipelined A/D converter, applying the proposed structure, is designed to satisfy requirement of analog front-end of VDSL modem. The measured INL and DNL of designed A/D converter are
, respectively. It satisfies the design specifications for VDSL modems. The simulated SNR is about 66dB which corresponds to a 10.7 bit resolution. The power consumption is 24.32mW.
Parallel Feedback Oscillator for Strong Harmonics Suppression and Frequency Doubler
Lee, Kun-Joon ; Ko, Jung-Pil ; Kim, Young-Sik ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 122~128
In this paper, a low noise parallel feedback oscillator for harmonic suppression and a frequency doubler are designed and implemented. As the fundamental signal of the oscillator for frequency doubling is extracted between the dielectric resonator (DR) filter and the gate device of the active device, the undesired harmonics at the output of the oscillator is remarkably suppressed. The fundamental signal of the oscillator for frequency doubling directly feeds to the frequency doubler without an additional band pass filter for harmonic suppression. The second harmonic suppression of -47.7 dBc at the oscillator output is achieved, while the fundamental suppression of -37.5 dBc at the doubler output is obtained. The phase noise characteristics are -80.3 dBc/Hz and -93.5 dBc/Hz at the offset frequency of 10 KHz and 100 KHz from the carrier, respectively.
A module generator for variable-precision multiplier core with error compensation for low-power DSP applications
Hwang, Seok-Ki ; Lee, Jin-Woo ; Shin, Kyung-Wook ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 129~136
A multiplier generator, VPM_Gen (Variable-Precision Multiplier Generator), which generates Verilog-HDL models of multiplier cores with user-defined bit-width specification, is described. The bit-widths of operands are parameterized in the range of
with 1-bit step, and the product from multiplier core can be truncated in the range of
with 2-bit step, resulting that the VPM_Gen can generate 3,455 multiplier cores. In the case of truncating multiplier output, by eliminating the circuits corresponding to the truncation part, the gate counts and power dissipation can be reduced by about 40% and 30%, respectively, compared with full-precision multiplier. As a result, an area-efficient and low-power multiplier core can be obtained. To minimize truncation error, an adaptive error-compensation method considering the number of truncation bits is employed. The multiplier cores generated by VPM_Gen have been verified using Xilinx FFGA board and logic analyzer.
A Study on Automatic Generation of Interface Circuits Based on FSM between Standard Buses and Ips
Lee, Ser-Hoon ; Moon, Jong-Uk ; Hwang, Sun-Young ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 137~146
IP-based design methodology has been popularly employed for SoC design to reduce design complexity and to cope with time-to-market pressure. Interface modules for communication between system buses and IPs are required, since many IPs employ different protocols. Automatic generation of these interface modules would enhance designer's productivity and IP's reusability. This paper proposes an automatic interface generation system based on FSM generated from the protocol description of IPs. The proposed system provides the library modules for the standard buses to reduce the burdens of describing the protocols for data transfer from/to standard buses. Experimental results show that the area of the interface circuits generated by the proposed system had been increased slightly by 4.5% on the average when compared to manual designs. In the experiment, where bus clock is 100 Mhz and slave module clock is 34 Mhz, the latency of the interface had been increased by 7.1% in burst mode to transfer 16 data words. However, occupation of system bus can be reduce by 64.9%. A chip designer can generate an interface that improves the efficiency of system bus, by using this system.
Design of the Compact Microstrip Bandpass Filter by using DGS Resonator
Cho, Young-Bin ; Jun, Kye-Suk ;
The Journal of Korean Institute of Communications and Information Sciences, volume 30, issue 2A, 2005, Pages 147~152
In this paper, we have proposed a novel DGS(Defected Ground Structure) resonator and has designed the band -pass filter using the proposed
stub-I type DGS resonator. This structure has strong advantages that can vary the retune loss at the passband freely and also can easily tune the attenuation pole frequency at the stopband. The bandpass filter can be made more smaller than the existing filters and be used to find the various applications for eliminating the harmonics and spurious mode at IMT-2000 band.