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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
Selecting the target year
Design of New Quasi-Orthogonal Space-Time Block Code with Minimum Decoding Complexity
Chae, Chang-Hyeon ; Choi, Dae-Won ; Jung, Tae-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1219~1225
In this paper, we propose a new quasi-orthogonal space-time block code(QO-STBC) achieving full rate and full diversity for general QAM and quasi-static Rayleigh fading channels with four transmit antennas. This code possesses the quasi orthogonal property like the conventional minimum decoding complexity QO-STBC(MDC-QO-STBC), which allows independently a maximum likelihood(ML) decoding to only require joint detection of two real symbols. By computer simulation results, we show that the proposed code exhibits the identical BER performance with the existing MDC-QO-STBC. However, the proposed code has an advantage in the transceiver implementation since the original coding scheme may be modified so that increases of peak-to-average power ratio occur at only two transmit antennas, but the MDC-QO-STBC does at all of transmit antennas.
QoS Mesh Routing Protocol for IEEE 802.16 based Wireless Mesh Networks
Kim, Min ; Kim, Hwa-Sung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1226~1237
This paper proposes QoS mesh routing protocol for IEEE 802.16 based wireless mesh networks. QoS mesh routing protocol proposed in this paper is a proactive hop-by-hop QoS routing protocol. The goal of our routing protocol is not only to find a route from a source to a destination, but also optimal route that satisfies QoS requirements, given in terms of bandwidth and delay as default QoS parameters. In this paper, we first analyze possible types of routing protocols that have been studied for MANET and show proactive hop-by-hop routing protocols are the most appropriate for wireless mesh networks. Then, we present a network model for IEEE 802.16 based wireless mesh networks and propose a proactive hop-by-hop QoS routing protocol. Through our simulation, we represent that our routing protocol outperforms QOLSR protocol in terms of end-to-end delay, packet delivery ratio and routing overhead.
Recursive Nullspace Calculation for Multiuser MIMO Systems
Joung, Jin-Gon ; Lee, Yong-Hoon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1238~1243
The computational complexity for the zero-forcing (ZF)-based multiuser (MU) multiple-input multiple-output(MIMO) preprocessing matrices can be immoderately large as the number of transmit antennas or users increases. In this paper, we show that the span of singular vector space of a matrix can be obtained from the singular vectors of the parted rows of that matrix with computational saving and propose a computationally efficient recursive-algorithm for achieving the ZF-based preprocessing matrices. Analysis about the complexities shows that a new recursive-algorithm can lighten the computational load.
Exact BER Expressions for Decode-and-Forward Relaying in Rayleigh Fading Channels
Lee, In-Ho ; Kim, Dong-Woo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1244~1250
User cooperation provides high reliability in wireless communication systems by employing relay nodes to transmit the same information. In this paper, a bit error rate (BER) study is presented for decode-and-forward (DF) relaying for user cooperation in independent and identically distributed Rayleigh fading channels. For an arbitrary number of relays, exact and closed-form expressions of the BER are proposed for M-ary PAM (Pulse Amplitude Modulation), QAM (Quadrature Amplitude Modulation) and PSK (Phase Shift Keying), respectively. It is also shown that the analytic results are perfectly matched with the simulated ones.
Cooperation Method for Cellular Communication Systems
Kim, Eung-Sun ; Kim, Young-Doo ; Park, Sang-Kyu ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1251~1259
A scheme for selecting the mode with the maximum system capacity is proposed for cooperative relaying. Three possible modes are presented based on decode-and-forward relaying, and the time required by each mode is evaluated. Based on these results, a method is then developed for selecting the optimal mode with the minimum time duration (or maximum channel capacity). Computer simulations confirm that the optimal mode outperforms the other modes.
Relay Position in Decode-and-Forward Relay Systems to Achieve Full Diversity Gain
Kwak, Kyung-Chul ; Seo, Woo-Hyun ; Hong, Dae-Sik ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1260~1266
Error propagation of source-relay (S-R) link limits the performance of decode-and-forward (DF) relay and prohibits DF relay from achieving full diversity gain. In order to solve this problem, the proposed deployment strategy focuses on two objectives. One is to achieve full diversity gain, and the other is to minimize the used power of the DF relay system. In order to achieve full diversity, the error probability of S-R link should be lower than that of maximal ratio combining (MRC) at destination without error propagation since the error probability of the weaker link dominates the total error probability. The proposed strategy of relay positioning points out the range of the relay position for achieving full diversity, and the used power of the relay is minimized by this range. Analysis of error probability and simulation results prove that the two objectives are achieved by the proposed strategy of the relay position.
An Improved Backoff Algorithm for the Random Access Protocol for the Ranging Subchannel of IEEE 802.16 Networks
Kwon, Jeong-Min ; Lee, Hyong-Woo ; Cho, Choong-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1267~1275
An improved backoff algorithm for retransmission randomization for OFDMA/CDMA/slotted ALOHA used in the ranging subchannel of IEEE 802.16 network is proposed. Exploiting the fact that a base station coordinates channel access using UL-/DL-MAP in the IEEE 802.16 networks, we propose a minor modification of the existing IEEE 802.16 in order to increase throughput, decrease delay variation and achieve a graceful performance degradation in case of overload channel condition of the random access protocol. The algorithm basically estimates the number of backlogged users and arrival rate using which, the BS calculates retransmission probability for the subscriber stations involved in a collision. Computer simulation is performed to demonstrate the effectiveness of the proposed algorithm and to compare the performance with existing binary exponential backoff algorithm.
A Dynamic Channel Allocation Employing Smart Antenna to Resolve a Crossed Time-slot Problem in TD-SCDMA
Kim, Eun-Heon ; Park, Jae-Hyun ; Kim, Duk-Kyung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1276~1285
Since the TD-SCDMA (Time Division-Synchronous Code Division Multiple Access) system is based on TDD (Time Division Duplexing), the uplink and downlink can be allocated asymmetrically according to the traffic e.g. Web browsing. Although this asymmetric allocation can increase the frequency utilization, it may cause time slot opposing, which implies the time slot is assigned in opposing direction between cells. The time slot opposing can generate significant interference between cells, which results in severe performance degradation. In the paper, a novel dynamic channel allocation (DCA) is proposed in the TD-SCDMA system, to mitigate the impact of time slot opposing considering smart antenna. When the smart antenna is applied in the system, the inter-cell interference is largely affected by beam pattern and beam direction between neighboring cells. Therefore, the time slot opposing and smart antenna should be considered together in the DCA. The intensive simulations show that the proposed scheme can improve the system capacity compared to the conventional DCA schemes.
An Algorithm of Minimum Bandpass Sampling Selection with Guard-band Between Down-converted Adjacent IF signals
Bae, Jung-Hwa ; Cho, Jae-Wan ; Ko, Yong-Chae ; Cac, Tran Nguyen ; Park, Jin-Woo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1286~1295
This paper proposes, based on a bandpass sampling theory, a novel method to find valid sampling frequency range and minimum sampling rate with low computational complexity for downconversion of N bandpass radio frequency(RF) signals, under application of all possible signal placements(full permutations) in a IF stage. Additionally, we have developed a complexity-reducing method to obtaine the opttimal and minimal sampling rate for supporting the user-wanted guard-band or spacing between adjacent downconverted signal spectrums. Moreover, we have verified through comparisons with other methods that the proposed methods have more advantageous properties.
Joint Estimation Methods of Carrier Offset and Low-rank LMMSE Channel Estimation for MB-OFDM System
Shin, Sun-Kyung ; Nam, Sang-Kyun ; Sung, Tae-Kyung ; Kwak, Kyung-Sup ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1296~1302
In this paper, we propose joint estimation methods of carrier offset and channel estimation for MB-OFDM system with low complexity. The proposed methods estimate the channel by using low-rank LMMSE channel estimation which reduces the system complexity by applying the optimal number of rank to evaluate the frequency offset and additionally using the simple algorithm using the auto-correlation property of the estimated channel. We simulate the proposed algorithms under the IEEE 802.15 TG3a UWB channel model.
Dynamic Control of Timer for Receiving Beacon in Low Power Wireless Interface
Song, Myong-Lyol ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1303~1310
In IEEE 802.11b wireless network, stations synchronize themselves to the beacons periodically sent by the access point (AP) when they are running in low power mode. Stations stay awake for enough time to receive beacon because it is delayed in AP if the wireless channel has been being used by other traffic at each scheduled instant. In this paper, we propose a method that measures the delay of received beacons and calculates wake-up interval of station to receive the next one. Beacon transmission delay at the AP is analyzed. The proposed method is simulated and its characteristics are described in the analysis. The result measured in terms of station's wake-up interval shows some enhancement in energy consumption.
VHDL Implementation of GEN2 Protocol for UHF RFID Tag
Jang, Il-Su ; Yang, Hoon-Gee ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1311~1319
This paper presents the VHDL implementation procedure of the passive RFID tag operating in Ultra High Frequency. The operation of the tag compatible with the EPCglobal Class1 Generation2(GEN2) protocol is verified by timing simulation after synthesis and implementation. Due to the reading range with relatively large distance, a passive tag needs digital processor which facilitates faster decoding, encoding and state transition for enhancement of an interrogation rate. In order to satisfy linking time, the pipe-line structure is used, which can minimize latency to serial input data stream. We also propose the sampling strategy to decode the Preamble, the Frame-sync and PIE symbols in reader commands. The simulation results with the fastest data rate and multi tags environment scenario show that the VHDL implemented tag performs faster operation than GEN2 proposed.
Performance Comparisons of Two DCF Methods in the IEEE 802.11 Protocol
Park, Chul-Geun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1320~1328
In recent year, the popularity of WLAN has generated much interests on improvement and performance analysis of the IEEE 802.11 protocol. In this paper, we analyze two medium access methods of the IEEE 802.11 MAC protocol by investigating the MAC layer packet service times when arrival packet sizes have a general probability distribution. We use the M/G/1/K queueing model to analyze the throughput and the delay performance of IEEE 802.11 MAC protocol in a wireless LAN. We compare the performances of Basic access method and RTS/CTS access method. We take some numerical examples for the system throughput and the queue dynamics including the mean packet delay and packet blocking probability.
An Adaptive MAC Protocol considering Real Time in Wireless Sensor Networks
On, Jeong-Seok ; Kim, Jae-Hyun ; Oh, Young-Yul ; Lee, Jai-Yong ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1329~1338
Leading MAC protocols developed for duty-cycled WSNs such as B-MAC employ a long preamble and channel sampling. The long preamble introduces excess latency at each hop and suffers from excess energy consumption at non-target receivers. In this paper we propose AS-MAC (Asynchronous Sensor MAC), a low power MAC protocol for wireless sensor networks (WSNs). AS-MAC solves these problems by employing a series of preload approach that retains the advantages of low power listening and independent sleep schedule. Moreover AS-MAC offers an additional advantage such as flexible duty cycle as data rate varies. We demonstrate that AS-MAC is better performance than B-MAC through analysis and evaluation.
Lattice Reduction-aided Detection with Out-of-Constellation Point Correction for MIMO Systems
Choi, Kwon-Hue ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1339~1345
An important drawback in Lattice Reduction (LR) aided detectors has been investigated. For the solution, an improved LR aided detection with ignorable complexity overhead is proposed for MIMO system, where the additional correction operation is performed for the case of unreliable symbol decision. We found that LR aided detection errors mainly occur when the lattice points after the inverse lattice transform in the final step fall outside the constellation point set. In the proposed scheme, we check whether or not the lattice point obtained through LR detection is out of constellation. Only for the case of out of constellation, we additionally perform ML search with reduced search region restricted to the neighboring points near to the obtained lattice points. Using this approach, we can effectively and significantly improve the detection performance with just a slight complexity overhead which is negligible compared to full searched ML scheme. Simulation results show that the proposed scheme achieves the detection performance near to that of the ML detection with a lower computational complexity.
Coupling Matrix Synthesis Methods for RF/Microwave Filter Design
Choi, Dong-Muk ; Kim, Che-Young ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 12A, 2007, Pages 1346~1353
In this paper, the methods are presented for the calculation of general coupling coefficient matrixes used in the band pass filter design. They are calculated from transmission coefficient(
) and reflection coefficient(
) with desired characteristics derived from the poles of filter function and return loss(RL). The calculated matrixes from this method are transformed to the folded canonical filter structure using similarity transformation which lends us the practical filter design. Based on the resulting matrix, the folded canonical filter has been designed.