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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 33, Issue 12C - Dec 2008
Volume 33, Issue 12B - Dec 2008
Volume 33, Issue 12A - Dec 2008
Volume 33, Issue 11C - Nov 2008
Volume 33, Issue 11B - Nov 2008
Volume 33, Issue 11A - Nov 2008
Volume 33, Issue 10C - Oct 2008
Volume 33, Issue 10B - Oct 2008
Volume 33, Issue 10A - Oct 2008
Volume 33, Issue 9C - Sep 2008
Volume 33, Issue 9B - Sep 2008
Volume 33, Issue 9A - Sep 2008
Volume 33, Issue 8C - Aug 2008
Volume 33, Issue 8B - Aug 2008
Volume 33, Issue 8A - Aug 2008
Volume 33, Issue 7C - Jul 2008
Volume 33, Issue 7B - Jul 2008
Volume 33, Issue 7A - Jul 2008
Volume 33, Issue 6C - Jun 2008
Volume 33, Issue 6B - Jun 2008
Volume 33, Issue 6A - Jun 2008
Volume 33, Issue 5C - May 2008
Volume 33, Issue 5B - May 2008
Volume 33, Issue 5A - May 2008
Volume 33, Issue 4C - Apr 2008
Volume 33, Issue 4B - Apr 2008
Volume 33, Issue 4A - Apr 2008
Volume 33, Issue 3C - Mar 2008
Volume 33, Issue 3B - Mar 2008
Volume 33, Issue 3A - Mar 2008
Volume 33, Issue 2A - Feb 2008
Volume 33, Issue 2C - Feb 2008
Volume 33, Issue 2B - Feb 2008
Volume 33, Issue 1C - Jan 2008
Volume 33, Issue 1B - Jan 2008
Volume 33, Issue 1A - Jan 2008
Selecting the target year
An Intelligent 1-Dimensional Channel Estimation Method and Its Application to a DVB-T System
Cho, Chang-Yeon ; Kim, Joon-Tae ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 91~97
In this paper, we propose a channel estimation method associated with the interpolation order for OFDM systems. We first analyze the time varying channel and frequency selective channels, and then derive the channel index which indicates the ratio of the time axis variation and the frequency axis variation. This index is used for determining the order of interpolation such as time axis followed by frequency axis interpolation or vice versa. The computer simulation over a DVB-T system shows that the proposed method can provide more accurate channel information, thereby improving the overall performance.
A Channel Estimation Method for Multipath Feedback Interference Signal Cancellation of RF Repeaters
Lee, Sang-Dae ; Park, Jin ; Sung, Won-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 98~106
To reduce the outage probability and to increase the transmission capacity, the importance of repeaters in cellular systems keeps increasing. Unlike optical repeaters which require wireline connections, RF repeaters are easy to install, have low limitations in location and also have a reduced operational expense such as the optical fiber maintenance cost. On the other hand, RF repeaters suffer the interference due to the feedback signals between the transmitter and receiver antennas, hence require an extra interference cancellation method when the amount of the feedback signal reduction by using the shielding is not sufficient. In this paper, a channel estimation method for two-path feedback interference signals in the ICS (Interference Cancellation System) repeaters using baseband signal processing is proposed and its performance is evaluated. When compared with the conventional method which estimates each multipath individually, the proposed method achieves 10 dB performance gain in terms of the normalized mean-squared-error.
Multiuser Bit-Interleaved Coded OFDM with Limited Feedback Infonnation
Sung, Chang-Kyung ; Kim, Ji-Hoon ; Lee, In-Kyu ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 107~114
In wireless access systems, there has been much interest in enhancing the performance of orthogonal frequency division multiplexing OFDM) in a frequency selective fading channel. If the channel is static and is perfectly known to both the transmitter and the receiver, the water-filling technique with adaptive modulation is known to be optimal. However, for OFDM systems, this requires intensive traffic overheads for reporting channel side information on all subcarriers to the transmitter In this paper, we propose an adaptive modulation and coding scheme for bit-interleaved coded OFDM (BIC-OFDM) for downlink packet transmissions with reduced feedback information. To minimize the feedback information, we employ a rate adaptation method based on the OFDM symbol rather than on each subcarrier. To illustrate the performance gap between the optimal water-filling and the proposed scheme, we will compare cutoff rates for both schemes. It is shown that the loss is less than 2dB while the proposed scheme significantly reduces the feedback payloads. Also, the OFDM system in multiuser environment with subcarrier grouping is considered. It is shown that by exploiting multiuser diversity the throughput of the proposed scheme approaches the channel outage capacity as the number of users and the number of subcarrier groups increase.
A Full Utilization of Space-time Block Code in Cooperative Communications
Tin, Luu Quoc ; Kong, Hyung-Yun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 115~120
We propose a cooperative transmission scheme that uses Hurwitz-Radon space-time code for the relays which help the source to transmit signals to the destination, the full utilization here is that the destination utilizes the broadcast symbols from the source. We present the 2 transmit antennas case in detail because of its simplicity and high data rate. Analysis and simulations show that the proposed scheme achieves full diversity order of 3. The maximum likelihood receiver is also derived and the combining scheme is shown to be very simple.
Performance Analysis for Spatial Multiplexing MIMO in MB-OFDM UWB Receivers
Suh, Jung-Won ; Kwon, Yang-Soo ; Kim, Seok-Hyeon ; Chung, Jea-Hak ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 121~129
This paper presents the spatial multiplexing MIMO system to increase data rate to double in MB-OFDM UWB system, which is ECMA standards, and compares BER performance of various receiver structures. The complexity and BER performance of various types of spatial multiplexing receivers are compared and analyzed using diagonal and horizontal encoding techniques for
antennas systems. Computer simulations exhibit that
ZF method show better BER performance than that of SISO system with simple complexity.
On Opportunistic Beamforming with Multiple-User Selection
Ku, Mi-Hyeon ; Kim, Dong-Woo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 130~138
In this paper, we propose a user selection method to maximize the sum-rate of downlink over opportunistic beamforming. The throughput of an opportunistic beamforming with non-uniformly distributed or a small number of users can decrease. In order to improve the throughput, we propose a scheduling method that does not use SINR or SNR but uses the effective channel gain of each user obtained from the SINR or SNR feedback. The proposed method makes it possible to select users flexibly according to the distribution of users. In numerical results, we show that the proposed methods improve the average sum-rate about 60% when users are distributed non uniformly.
Performance Analysis of Frame Synchronization and Structure Detection Utilizing Multiple Frames of the DVB-S2 Satellite Broadcasting System
Kim, Sang-Tae ; Kang, Seok-Heon ; Sung, Won-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 139~147
DVB-S2 (Digital Video Broadcasting-Satellite, Version 2) system transmits frames which adapt their structures based on the channel conditions, thus requiring simultaneous detection of the start of the Same (SoF) and the frame structure at the initial acquisition stage of the receiver. Also, a very low value of the minimum operating signal-to-noise ratio (SNR) for the acquisition necessitates a method utilizing multiple received frames to meet the required performance. In this paper, performance of joint time synchronization and frame structure detection methods using multiple DVB-S2 frames is evaluated by deriving the detection error probability. In particular, we evaluate the performance and complexity variations when the soft- and hard-decision values of the signal correlation output are used, present the synchronization parameters to optimize the performance, and verify the analysis results via computer simulations.
Hardware Design of SNR Estimator for Adaptive Satellite Transmission System
Lee, Jae-Ung ; Kim, Soo-Seong ; Park, Eun-Woo ; Im, Chae-Yong ; Yeo, Sung-Moon ; Kim, Soo-Young ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 148~158
This paper proposes an efficient signal to noise ratio (SNR) estimation algorithm and its hardware implementation for adaptive transmission system using M-ary modulation scheme. In this paper, we present the implementation results of the proposed algorithm for the second generation digital video broadcasting via satellite (DVB-S2) system, and the proposed algorithm can be tailored to the other communication systems using adaptive transmissions. We built a look-up table (LUT) using the theoretical background of the received signal distribution, and by using this LUT we need just two comparators and a counter for the hardware implementation. For this reason, the hardware of the proposed scheme produces accurate estimation results even with extremely low complexity. The simulation results investigated in this paper reveal that the proposed method can produce estimation results within the specified SNR range in the DVB-S2 system, and it requires a few hundreds of samples for average estimation error of about 1 dB.
A Synchronization Tracking Algorithm to Compensate the Drift of Satellite in FH-FDMA Satellite Communication System
Bae, Suk-Neung ; Kim, Su-Il ; Choi, Young-Kyun ; Jin, Byoung-Il ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 159~166
In this paper, we proposed an algorithm to solve the problem that can't maintain hop synchronization using only early-late gate tracking loop due to the drift of geo-stationary satellite in frequency hopping satellite communication system. When the signal is transferred to downlink through DRT(Dehop-Rebop Transponder), the problem with synchronization loss is occurred periodically when using only early-late gate tracking loop, because of energy loss in each side portion of hop due to orbital variation of the satellite. To solve this problem, we have developed Anti-Shrink synchronization tracking algorithm which uses the prediction value of transmission timing and the structure of inner-outer gate instead of early-late gate with the ranging information. Through simulations, we showed that the performance of the Anti-Shrink algorithm is better than that of simple inner-outer energy ratio algorithm and similar to that of conventional early-late tracking loop algorithm with ranging information. No synchronization failure in the proposed algorithm was occurred because of less energy loss and robustness without the ranging information.
Design of a 5.8 GHz Narrow Band-pass Filter with Harmonics Suppression
Yoon, Ki-Cheol ; Lee, Jong-Chul ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 167~173
In this paper, the flexible narrow bandpass filters (BPFs) with
g/4 short and
g/2 open stubs by microstrip line on duroid substrate are suggested. These BPFs with narrow bandwidth show flexible bandwidth with variation of the position of the stubs using the Qe (external quality factor) without changing the impedance value at microwave range. On the other hand, by replacing the series quarter-wavelength connecting lines with the equivalent T-shaped line of bandstop filter(BSF), the compact stub bandpass filter with harmonics suppression can be realized. The BPF with
g/4 short stubs shows the insertion loss of 2.1 dB and the return loss of 18 dB and BPF with
g/2 open stubs shows the insertion loss of 1.2 dB and the return loss of 21.9 dB at the center frequency of 5.8 GHz and the bandwidth of 10 %.
EPC C1 Gen2 RFID System with Channel Coding
Jeon, Ki-Yong ; Cho, Sung-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 174~182
For the UHF EPC C1 Gen2 RFID system, to overcome the performance degradation in wireless channel environments, we proposed a modified tag structure which supports channel coding and its applied methodology. The reader consistently monitors the wireless channel status and sets to use channel coding functions for tags and reader only if wireless channel is corrupted. Compared with previous tag complexity, only negligible gates are needed to implement channel coding. By simulation we showed an obvious performance improvement of the identification reliability.
The Combined Tx. Diversity of STBC Tx. Diversity and Balanced Tx. Diversity
Chun, Kwang-Ho ; Min, Seung-Hyun ; Liu, Lijun ; Lim, Myoung-Seob ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 183~190
The balanced Tx diversity with same data on two antennas can have better or lower performance than STBC Tx diversity, depending on the difference between each phase of two channels when the received signal is processed with MRRC. Therefore, using the feedback information based on the phase estimation in each channels, the better scheme of the balanced Tx diversity and STBC Tx diversity can be selected. However, when the phase condition changes during the transmission as the selected Tx. diversity scheme, the decoded bit can be erroneous because the previously estimated phase and newly estimated phase is different. In this case, the receiver should request the re-transmission of the just received signal to the transmitter part. Through computer simulation, it is shown that the combined scheme of the balanced Tx diversity and STBC Tx. diversity has better performance than STBC Tx diversity.
Opportunistic Packet Scheduling and Media Access Control for Wireless LANs
Park, Hyung-Kun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 191~197
For the efficient transmission of burst data in the time varying wireless channel, opportunistic scheduling is one of the important techniques to maximize multiuser diversity gain. In this paper, we propose a distributed opportunistic scheduling scheme for wireless LAN network. A proportional fair scheduling, which is one of the opportunistic scheduling schemes, is used for centralized networks, whereas we design distributed proportional fair scheduling (DPFS) scheme and medium access control with distributed manner. In the proposed DPFS scheme, each receiver estimates channel condition and calculates independently its own priority with probabilistic manner, which can reduce excessive probing overhead required to gather the channel conditions of all receivers. We evaluate the proposed DPFS using extensive simulation and simulation results show that DPFS obtains higher network throughput than conventional scheduling schemes and has a flexibility to control the fairness and throughput by controlling the system parameter.
Channel Characteristics of Indoor Wireless Infrared Communication System Due to Different Transceiver Conditions
Peng, Chuan ; Wang, Zan ; Kim, Ji-Do ; Pan, Jae-Kyung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 198~203
In this paper, we consider the diffuse type of indoor wireless optical communication (WOC) system. To find the channel characteristics of indoor wireless infrared communication system, we investigate the simulation process to get the impulse response of diffuse type and analyze the scenario of the indoor structure which we have built. The simulation results of the impulse response include power ratio and time delay due to bounce times. We get and discuss the receiving power distribution according to six configurations which have different transmitter and receiver positions and reflection coefficients of the indoor structure assumed. The results of this paper are useful to design the indoor wireless optical communication systems.
A Priority-based Scheduling Approach for TPEG Applications
Joe, In-Whee ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 204~209
It is the most important in the traffic information system how fast to transmit the traffic conditions on each road, or event such as RTM (Road Traffic Message). In order to operate the event information more efficiently in the TPEG system, it is likely that the effective transmission system shall be needed, and this paper will propose the improved transmission system; Breaking away from the conventional method which is to transmit the traffic information by using simple FIFO method while encoding it into TPEG data, the improved transmission system is to transmit the important information more quickly or to advance the transmission cycle by scheduling according to degree of its importance after deciding which one is the important traffic information by comparing the importance ratings in between diverse information. The traffic information with low importance rating is to be transmitted slowly, and its transmission cycle shall become slow as well. In the computer simulations, it is shown that the proposed approach enables to transmit more quickly a sudden change of traffic conditions and the important traffic data.
Performance Evaluation of Equalization based On-Channel Repeater for Terrestrial Digital Multimedia Broadcast
Kim, Dong-Hyun ; Park, So-Ra ; Park, Sung-Ik ; Yoon, Seok-Hyun ; Lee, Yong-Tae ;
The Journal of Korean Institute of Communications and Information Sciences, volume 33, issue 2A, 2008, Pages 210~217
In this paper, the performance of equalization-based on-channel repeater for terrestrial DMB is analyzed. A primary concern in on-channel repeater is the performance degradation due to the echo and one of key component for on-channel repeater is the echo canceller, which usually employs LMS algorithm utilizing the repeater output as a reference for echo channel estimation and compensation. One problem using LMS algorithm is the tracking capability and there necessarily exists residual echo that has not been cancelled. To effectivelyremove the residual echo, we consider an equalization based on-channel repeater where the echo-cancellor is followed by an equalizer that performs channel estimation using pilot symbol and the channel inversion utilizing homomorphic decomposition. According to the simulation result, the performance degradation caused by the residual echo can be considerably alleviated by using the equalizer following the echo-canceller.