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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 34, Issue 12C - Dec 2009
Volume 34, Issue 12B - Dec 2009
Volume 34, Issue 12A - Dec 2009
Volume 34, Issue 11C - Nov 2009
Volume 34, Issue 11B - Nov 2009
Volume 34, Issue 11A - Nov 2009
Volume 34, Issue 10C - Oct 2009
Volume 34, Issue 10B - Oct 2009
Volume 34, Issue 10A - Oct 2009
Volume 34, Issue 9C - Sep 2009
Volume 34, Issue 9B - Sep 2009
Volume 34, Issue 9A - Sep 2009
Volume 34, Issue 8C - Aug 2009
Volume 34, Issue 8B - Aug 2009
Volume 34, Issue 8A - Aug 2009
Volume 34, Issue 7C - Jul 2009
Volume 34, Issue 7B - Jul 2009
Volume 34, Issue 7A - Jul 2009
Volume 34, Issue 6C - Jun 2009
Volume 34, Issue 6B - Jun 2009
Volume 34, Issue 6A - Jun 2009
Volume 34, Issue 5C - May 2009
Volume 34, Issue 5B - May 2009
Volume 34, Issue 5A - May 2009
Volume 34, Issue 4C - Apr 2009
Volume 34, Issue 4B - Apr 2009
Volume 34, Issue 4A - Apr 2009
Volume 34, Issue 3C - Mar 2009
Volume 34, Issue 3B - Mar 2009
Volume 34, Issue 3A - Mar 2009
Volume 34, Issue 2C - Feb 2009
Volume 34, Issue 2B - Feb 2009
Volume 34, Issue 2A - Feb 2009
Volume 34, Issue 1C - Jan 2009
Volume 34, Issue 1B - Jan 2009
Volume 34, Issue 1A - Jan 2009
Selecting the target year
A New Constant Modulus Algorithm based on Maximum Probability Criterion
Kim, Nam-Yong ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 85~90
In this paper, as an alternative to constant modulus algorithm based on MSE, maximization of the probability that equalizer output power is equal to the constant modulus of the transmitted symbols is introduced. The proposed algorithm using the gradient ascent method to the maximum probability criterion has superior convergence and steady-state MSE performance, and the error samples of the proposed algorithm exhibit more concentrated density functions in blind equalization environments. Simulation results indicate that the proposed training has a potential advantage versus MSE training for the constant modulus approach to blind equalization.
Performance Analysis of Selection Combining Technique for MPSK over Independent But Non-Identically Distributed Rayleigh Fading Channels
Bao, Vo Nguyen Quoc ; Kong, Hyung-Yun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 91~98
This paper provides new exact-closed form expressions for average SER and average BER as well as outage probability for M-PSK signaling with selection combining over independent but non-identically distributed Rayleigh fading paths. The validity of these expressions is verified by the Monte-Carlo simulations. All of numerical results are in excellent agreement with simulation results.
Performance of Frequency Planning and Channel Allocation Algorithm for Unified Inter-Cell Interference Avoidance and Cancellation in OFDMA Cellular Systems
Lee, Jae-Hoon ; Kim, Dong-Woo ; Lee, Hee-Soo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 99~106
In this paper, we propose UCA algorithms that are applied to the unified inter-cell interference mitigation through frequency plannings in OFDMA cellular systems. Under three frequency plannings, UCA algorithms allocate frequency channels to UEs(User Equipments). Proposed UCA algorithms require the information of received signal power from home sector and neighbor sectors respectively. We compare all possible combinations of UCA algorithms and frequency plannings through compute simulation. A primary performance measure is the low 5th percentile of SINR at UEs. The proposed UCA algorithms can avoid the interference to neighbor cells by allocating relatively low transmit power to centrally-located UEs and cancel inter-cell interference at cell-edge UEs by a coordinated symbol repetition. We show that UCA algorithm 2 applied in frequency planning 1 is promising among other combinations of UCA algorithms and frequency palnnings in terms of the low 5th percentile of SINR at UEs.
An Energy Saving Cooperative Communications Protocol without Reducing Spectral Efficiency for Wireless Ad Hoc Networks
Xuyen, Tran Thi ; Kong, Hyung-Yun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 107~112
Spectral efficiency of current two-phase cooperative communications protocols is low since in the second time the relay forwards the same signal received from the source to the destination, the source keeps silent in this time. In this paper, we propose a novel cooperative communications protocol where the signal needed to transmit to the destination is sent in both phases, the source and the relay also transmit different signal to the destination thus no loss of spectral efficiency. This protocol performs signal selection based on log-likelihood ratio (LLR) at relay and maximum likelihood (ML) detection at destination. While existing protocols pay for a worse performance than direct transmission in the low SNR regime which is of special interest in ad hoc networks, ours is better over the whole range of SNR. In addition, the proposal takes advantages of bandwidth efficiency, long delay and interference among many terminals in ad hoc network. Simulation results show that the proposed protocol can significantly save total energy for wireless ad hoc networks.
A Seamless Layer-2 Handover Scheme for mobile WiMAX based Wireless Mesh Networks
Kim, Min ; Kim, Hwa-Sung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 113~123
Wireless mesh networks have been studied as the next generation technology to solve problems of conventional wireless networks. Particularly, mobile WiMAX based wireless mesh networks are noticed due to many advantages. In this paper, we propose a layer-2 handover scheme for mobile WiMAX based wireless mesh networks. A layer-2 handover scheme based on mobile WiMAX causes many handover failures over mobile WiMAX based wireless mesh networks because it does not consider the characteristics of wireless mesh networks. The proposed scheme does not bring about packet losses achieving lower handover latency than a conventional handover scheme. Simulation results show that the proposed scheme achieves loss-free and low handover latency during the layer-2 handover.
Performance of DF Protocol for Distributed Cooperative Spectrum Sensing in Cognitive Radio
Zou, Mingrui ; Bae, Sang-Jun ; Kwak, Kyung-Sup ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 124~131
Cognitive radio has been proposed to mitigate the spectrum scarcity problem by allowing the secondary users to access the under-utilized frequency bands and opportunistically transmit. Spectrum sensing, as a key technology in cognitive radio, is required to reliably detect the presence of primary users to avoid the harmful interference. However, it would be very hard to reliably detect the presence of primary users due to the channel fading, shadowing. In this paper, we proposed a distributed cooperative spectrum sensing scheme based on conventional DF (decode-and-forward) cooperative diversity protocol. We fist consider the cooperation between two secondary users to illustrate that cooperation among secondary users can obviously increase the detection performance. We then compare the performance of DF based scheme with another conventional AF (amplify-and-forward) protocol based scheme. And it is found that the proposed scheme based on DF has a better detection performance than the one based on AF. After that, we extend the number of cooperative secondary users, and demonstrate that increasing the cooperation number can significantly improve the detection performance.
An Improved Combining of Hard Decisions for Cooperative Spectrum Sensing in Cognitive Radio Systems
Shin, Oh-Soon ; Shin, Yo-An ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 132~138
Cognitive radio is considered as a promising solution to scarce spectrum problem. The primary object of cognitive radio is to increase spectral efficiency, while causing limited interference to primary users who are using the spectrum. Hence, an essential part of cognitive radio systems is spectrum sensing which determines whether a particular spectrum is occupied or not by a primary user at a particular time. However, sensing decision of each individual secondary user alone may not be reliable enough due to shadowing and multipath fading of wireless channels. The so called hidden terminal problem makes the problem even worse, possibly yielding undesired interference to the primary users. Recently, cooperative spectrum sensing is emerging as a remedy to these problems of individual sensing. Cooperative sensing allows a group of secondary users to share local sensing information to extract a global decision with high fidelity. In this paper, we investigate a cooperative spectrum sensing algorithm based on hard decisions of local sensing outcomes. Specifically, we propose an effective scheme for combining local decisions by introducing weighting factors that reflect reliability of the corresponding secondary user. Through computer simulations, the performance of the proposed combining scheme is compared with that of the conventional scheme without weighting factors in various environments.
Average Internal Loop-back Antenna Calibration Method for Array Antenna Systems
Lee, Il-Shin ; Kim, Hyun-Su ; Lee, Hong-Won ; Chung, Jae-Hak ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 139~146
This paper presents an average internal loop-back antenna calibration method for array antenna in TDD(Time Division Duplex) systems. The proposed method calibrates the amplitude and the phase of RF systems using into mal coupler and switches without aids of external calibration systems. The average calibration scheme of the proposed method also increases reliability of calibration performance. Computer simulation demonstrates that the proposed method corrects beamforming angles of DOA estimation algorithm and BER performance in transmit power allocation scheme.
Mode Selection Technique Between Antenna Grouping and Beamforming for MIMO Communication Systems
Kim, Kyung-Chul ; Lee, Jung-Woo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 147~154
Antenna grouping algorithm is hybrid of beamforming and spatial multiplexing. In antenna grouping system, we partition
transmit antennas into
groups and use beamforming in a group, spatial multiplexing between groups. We can transmit
data streams in the
antenna grouping system. With antenna grouping, we can achieve diversity gain through beamforming, and high spectral efficiency through spatial multiplexing. But if channel is ill-conditioned or there are some correlations between antennas, the performance of antenna grouping is seriously degraded and in that case, beamforming is the best transmit strategy. By selecting the antenna grouping mode when channel is well-conditioned and by selecting the beamforming mode when channel is ill-conditioned, we can prevent serious fluctuation of BER performance caused by varying channel condition and achieve the best BER performance. In this paper, we investigate mode selection algorithm which can select antenna grouping mode or beamforming mode. we also propose a simple mode selection criterion.
An Efficient ICI Self-Cancellation Method with Frequency Offset and Phase Noise in OPDM Systems
Park, Jeong-Hwan ; Kim, Hyung-Myung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 155~163
OFDM System is a promising transmission technique due to its spectral efficiency But, a major disadvantage of the OFDM system is its sensitivity to frequency offset and phase noise that makes intercarrier interference (ICI), which degrades the system performance severely The ICI self-cancellation method has a good performance with frequency offset or phase noise. This paper proposed the N/2 spacing data-conjugate method that works well in large frequency offset and phase noise (normalized frequency offset=0.2-0.4, phase noise standard deviation=about lodes). Also, an efficiency ICI cancellation method using pilot was proposed. Simulation results confirm that performance of the proposed scheme is better than conventional schemes.
A Novel Ranging Algorithm for WiBro/WiMAX in Array Antenna System
Kim, Jae-Hwan ; Choi, Seung-Won ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 164~169
This paper presents a fast and accurate ranging algorithm for the WiBro system. The proposed algorithm detects a received ranging code and estimates its propagation delay using the correlation characteristics of the PRBS (Pseudo Random Binary Sequence) and the circular shift property of the discrete Fourier transform operator. The proposed ranging algorithm was applied to array antenna systems to show how it could improve the ranging performance of an array antenna system compared to a conventional base station system, which uses only a single antenna.
CQI Quantization Scheme in Random Beamforming System
Ko, Kyeong-Jun ; Lee, Jung-Woo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 170~176
It has been known that multiuser MIMO systems have better performance than single-user MIMO systems. However, multiuser MIMO systems should eliminate inter-user interferences which are generated by allocating data to multiple users simultaneously There is zero-forcing beamforming (ZFBF) as scheme used widely among algorithms to eliminate inter-user interferences. But, it needs many feedback bits since BS knows quite exact channel state information to use this scheme in real systems. Random beamforming (RBF) was proposed to cope with a defect of ZFBF. RBF is a multiuser scheme to send data to users who have optimal performance with predetermined codebook, each receiver feeds back a index of codeword which has optimal performance within the codebook and its CQI information.  assumes that the BS knows perfect CQI information of each receiver but CQI information should be quantized in the real systems. Therefore, in this paper, efficient CQI quantization scheme for RBF system is proposed.
Design of an Improved Anti-Collision Unit for an RFID Reader System Based on Gen2
Sim, Jae-Hee ; Lee, Yong-Joo ; Lee, Yong-Surk ;
The Journal of Korean Institute of Communications and Information Sciences, volume 34, issue 2A, 2009, Pages 177~183
In this paper, we propose an improved anti-collision algorithm. We have designed an anti-collision unit using this algorithm for the 18000-6 Type C Class 1 Generation 2 standard (Gen2). The Gen2 standard uses a Q-algorithm for incremental method on the Dynamic Slot-Aloha algorithm. It has basically enhanced performance over the Slot-Aloha algorithm. Unfortunately, there are several non-clarified parts: initial
value, weighted C, and the ending point of the algorithm. If an incorrect value is selected, it causes degradation in performance. Thus we propose an improved anti-collision algorithm by clearly defining the vague parts of the existing algorithm. Simulation results showed an improved performance of up to 34.8% using an optimized value of C and the initial
value. With the ending condition, performance is 34.7%. The anti-collision unit is designed using the Verilog HDL. The module was synthesized using Synopsys' Design Compiler and the TSMC
standard cell library. The synthesized result yielded 3,847 gates, and was guaranteed under the proposed working frequency of 19.2MHz.