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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 35, Issue 12C - Dec 2010
Volume 35, Issue 12B - Dec 2010
Volume 35, Issue 12A - Dec 2010
Volume 35, Issue 11C - Nov 2010
Volume 35, Issue 11B - Nov 2010
Volume 35, Issue 11A - Nov 2010
Volume 35, Issue 10C - Oct 2010
Volume 35, Issue 10B - Oct 2010
Volume 35, Issue 10A - Oct 2010
Volume 35, Issue 9C - Sep 2010
Volume 35, Issue 9B - Sep 2010
Volume 35, Issue 9A - Sep 2010
Volume 35, Issue 8C - Aug 2010
Volume 35, Issue 8B - Aug 2010
Volume 35, Issue 8A - Aug 2010
Volume 35, Issue 7C - Jul 2010
Volume 35, Issue 7B - Jul 2010
Volume 35, Issue 7A - Jul 2010
Volume 35, Issue 6C - Jun 2010
Volume 35, Issue 6B - Jun 2010
Volume 35, Issue 6A - Jun 2010
Volume 35, Issue 5C - May 2010
Volume 35, Issue 5B - May 2010
Volume 35, Issue 5A - May 2010
Volume 35, Issue 4C - Apr 2010
Volume 35, Issue 4B - Apr 2010
Volume 35, Issue 4A - Apr 2010
Volume 35, Issue 3C - Mar 2010
Volume 35, Issue 3B - Mar 2010
Volume 35, Issue 3A - Mar 2010
Volume 35, Issue 2C - Feb 2010
Volume 35, Issue 2B - Feb 2010
Volume 35, Issue 2A - Feb 2010
Volume 35, Issue 1C - Jan 2010
Volume 35, Issue 1B - Jan 2010
Volume 35, Issue 1A - Jan 2010
Selecting the target year
QoS Guarantee for Service Classes based on Performance Analysis of Cross-Layer Retransmission Scheme
Go, Kwang-Chun ; Lee, Hyun-Jin ; Kim, Jae-Hyun ; Choo, Sang-Min ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 95~104
In wireless communication system, a variety of retransmission algorithms are used in order to improve the quality of service of users. But the system may be inefficient because retransmission algorithms operate independently with other layers. Also, the quality of service can be degraded due to the unnecessary retransmission of packets. To solve these problems, the study on the cross-layer retransmission schemes have been widely performed. However, in order to apply cross-layer retransmission schemes to wireless communication system, whether the performance of cross-layer retransmission schemes meets QoS requirements of each service class has to be verified. Thus, this paper proposes the mathematical model for analyzing the performance of the cross-layer retransmission schemes and derives both the suitable retransmission scheme and the optimal retransmission parameter on each service class. The proposed mathematical model selects the MCS level based on channel state information and The performance analysis is comparatively easy in case that HARQ, ARQ, and AMC schemes are combined. The proposed mathematical model also enables the analysis of the packet transmission delay. To utilize the analytical model, this paper derives the suitable retransmission scheme and the optimal retransmission parameter for delay sensitive services in WiMAX system. Also, the proposed analytical model can be used to analyze the performance of wireless communication system such as LTE and WLAN.
Spatial Multiplexing System based on Random Unitary Beamforming for MU-MIMO Broadcast Channel
Park, Seong-Ho ; Park, Ki-Hong ; Lee, Jin-Hee ; Ko, Young-Chai ; Kim, Sung-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 105~111
Random unitary beamforming (RUB) is a very low complexity and practical transmission scheme for multiuser MIMO broadcast channel. In this paper, we propose the scheme that obtains the spatial multiplexing gain on the extension of the conventional RUB, that is, the receiver with two antennas is compared to that with one antenna in a conventional RUB, which results in the increased capacity. So, we propose the new codebook and the minimum mean square error successive interference cancellation (MMSE-SIC) receiver filter. We show the simulation result that the sum-rate of proposed system is increased.
Adaptive Parallel and Iterative QRDM Detection Algorithms based on the Constellation Set Grouping
Mohaisen, Manar ; An, Hong-Sun ; Chang, Kyung-Hi ; Koo, Bon-Tae ; Baek, Young-Seok ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 112~120
In this paper, we propose semi-ML adaptive parallel QRDM (APQRDM) and iterative QRDM (AIQRDM) algorithms based on set grouping. Using the set grouping, the tree-search stage of QRDM algorithm is divided into partial detection phases (PDP). Therefore, when the treesearch stage of QRDM is divided into 4 PDPs, the APQRDM latency is one fourth of that of the QRDM, and the hardware requirements of AIQRDM is approximately one fourth of that of QRDM. Moreover, simulation results show that in
system and at Eb/N0 of 12 dB, APQRDM decreases the average computational complexity to approximately 43% of that of the conventional QRDM. Also, at Eb/N0 of 0dB, AIQRDM reduces the computational complexity to about 54% and the average number of metric comparisons to approximately 10% of those required by the conventional QRDM and AQRDM.
A Computationally Efficient Scheduling Algorithm Capable of Controlling Throughput-Fairness Tradeoff
Lee, Min ; Oh, Seong-Keun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 121~127
In this paper, we propose a computationally efficient scheduling algorithm that can arbitrarily control the throughput-fairness tradeoff in a multiuser wireless communication environment. As a new scheduling criterion, we combine linearly two well-known scheduling criteria such as one of achieving the maximum sum throughput and the other of achieving the maximum fairness, so as to control the relative proportion of the throughput and the fairness according to a control factor. For linear combining two different criteria, their optimization directivenesses and the units should be unified first. To meet these requirements, we choose an instantaneous channel capacity as a scheduling criterion for maximizing the sum throughput and the average serving throughput for maximizing the fairness. Through a unified linear combining of two optimization objectives with the control factor, it can provide various throughput-fairness tradeoffs according to the control factors. For further simplification, we exploit a high signal-to-noise ratio (SNR) approximation of the instantaneous channel capacity. Through computer simulations, we evaluate the throughput and fairness performances of the proposed algorithm according to the control factors, assuming an independent Rayleigh fading multiuser channel. We also evaluate the proposed algorithm employing the high SNR approximation. From simulation results, we could see that the proposed algorithm can control arbitrarily the throughput-fairness performance between the performance of the scheduler aiming to the maximum sum throughput and that of the scheduler aiming to the maximum fairness, finally, we see that the high SNR approximation can give a satisfactory performance in this situation.
Optimal Chip Rate of Power and Rate Adapted DS/CDMA Communication Systems in Nakagami Fading Channels
Lee, Ye-Hoon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 128~133
We investigate the optimal chip rate of power or rate adapted direct-sequence code division multiple access (DS/CDMA) communication systems in Nakagami fading channels. We find that the optimal chip rate that maximizes the spectral efficiency depends upon both the channel parameters, such as multipath intensity profile (MIP) and line-of-sight (LOS) component, and the adaptation scheme itself. With the rate adaptation, the optimal chip rate is less than
, irrespective of the channel parameters, where
is multipath delay spread. This indicates that with the rate adaptation, correlation receiver achieves higher spectral efficiency than RAKE receiver. With the power adaptation, however, the optimal chip rate and the corresponding number of tabs in RAKE receiver are sensitive to MIP and LOS component.
Centralized Downlink Scheduling using Directional Antennas in IEEE 802.16 based Wireless Mesh Networks
Lee, Sang-Joon ; Lee, Hyong-Woo ; Cho, Choong-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 134~141
In this paper, we propose a scheduling algorithm to improve the performance of IEEE 802.16 based wireless mesh networks using directional antenna. The performance is presented in terms of throughput of system and delay between each node by varying number of users. The result show that proposed scheduling algorithm improving the performance by reducing the delay of mesh network system. Our work may be useful as a guideline to control the fairness between SSs for multi-hop systems such as multi-hop relay and mesh networks.
An Efficient Scanning Group and Order Decision Method Using Neighbor Network Information in Wireless LAN
Kang, Dong-Wan ; Choi, Jae-Kark ; Yoo, Sang-Jo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 142~152
When a mobile station(MS) performs a handover, in the IEEE 802.11 WLAN, MS's channel scanning for discovering new available APs is the dominating factor in handover latency, accounting 90% of overall latency. In order to reduce such a scanning latency, we focus on the method for reducing the number of channels for the MS in handover process to scan. With the help of IEEE 802.21 information server(IS), a proper order of groups of channels to be scanned is offered by the current AP depending on the information of neighbor APs in terms of the distance from serving AP, traffic load and network topology. By using this scanning order, the passive scanning of a MS in normal operation enables the MS to filter out the unavailable channels, and thus to classify the candidate channels of neighbor APs into three groups. Then, a handover-imminent MS can perform the active scanning from the most reliable group of channels. Simulation results show that the proposed scanning scheme reduce the scanning latency in comparison with the conventional scheme.
TDMA based Multi-channel MAC Protocol for Improving Channel Efficiency in Wireless Ad Hoc Networks
Kim, Jun-Ho ; Choi, Jae-Kark ; Yoo, Sang-Jo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 153~164
In this paper, we propose a multi-channel MAC protocol to improve the channel efficiency and network performance in wireless ad hoc networks. There are two main problems encountered in designing multi-channel MAC protocols. The first problem is the rendezvous problem and the second is multi-channel hidden node problem. In order to solve these problems, most of previous researches that have considered multi-channel MAC protocols use a common control channel to exchange control packets. However, they have a bottleneck problem at common control channel as increasing the number of data channels. The proposed MAC protocol solves the multi-channel hidden node problem using a TDMA scheme and increases the network throughput because transmitting and receiving data at the same time is possible. Also, since there is no common control channel, the network does not suffer from the common control channel saturation problem. Moreover, it achieves energy savings by allowing nodes that are not involved in communication to go into sleep mode. Simulation results show that the proposed MAC protocol improves the network throughput and channel efficiency and provides energy savings.
Mesh Network Implementation using DWDS-based Link Layer Routing
Yoon, Mi-Kyung ; Yang, Seung-Chur ; Kim, Jong-Deok ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 165~173
WMN(Wireless Mesh Network) is an wireless backbone network technology that is an easily configurable network in the low cost compared to the wireless LAN(Local Area Network). Most of the previous researches have evaluated their algorithms by the simulations rather than by the implementation. There exist some implementation papers, however, they have the limitations of the flexibility on the link establishment and the link quality utilization. Consequently, the benefit of the WMN - configuration flexibility is degraded and the performance deterioration occurs in the multi-hop wireless environment. In this paper, we introduce a Linux-based link layer Wireless Mesh Routing System - WBMR. The design and implementation of WBMR provides the dynamic link establishment and the effective multi-channel usage. We have modified the ntroof the original WLAN operation for the dynamic link establishment, and the Linux bridge for the link layer routing. The result of performance evaluation verifies that our WBMR supports fast self-configuration and increases data transmission throughput compared to the other researches of the wireless multi-hop environment.
A Seamless Voice Call Handover Scheme for the 3G LTE System
Kim, Kyung-Min ; Jung, Hyun-Duk ; Lee, Jai-Yong ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 174~185
A seamless handover between the 3G LTE and legacy 3G system is required for the smooth deployment of the 3G LTE system which is the next generation cellular network system. Especially on voice call handover, the service interruption time is very sensitive for user's satisfaction and therefore, a seamless voice call handover scheme is necessarily required. However, handover between the 3G LTE and the 3G CS system is hard to be achieved due to the lack of interface between two systems and the restriction of radio resource. In this paper, a new network entity called SCSE is proposed and inter-working between the 3G LTE and the 3G CS systems is enabled. Also contributed to the feature of the SCSE, the handover procedure is simplified and the service interruption time is minimized as a consequence. The evaluation result shows that the proposed SCSE scheme exclusively meets the service interruption time requirement which is smaller than 300 ms.
QoS-Aware Group Scan Scheduling in WiMAX Networks
Choi, Jae-Kark ; Yoo, Sang-Jo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 186~195
For the fast target base station channel decision in WiMAX networks, fast group scanning scheme was suggested, in which mobile stations in proximity of each other form a group and scan the candidate channels dispersively. However, the previous group scanning scheme does not consider the different QoS requirements of each MS in a group. In this paper we propose the enhanced group scanning scheme, so-called QoS-aware group scan scheduling scheme, that makes mobile stations in a group scan the candidate channels without deteriorating the QoS requirements. We introduce the QoS-aware channel scanning concept of a individual mobile station and show the different scanning latencies due to the different QoS requirements. With the help of the efficient channel allocation by the serving BS, in the proposed scanning scheme, a mobile station with relatively higher QoS in a group scans less amount of candidate channels than the others with relatively lower QoS, while the mobile stations in a group still guarantees the fast target base station decision. The performance results show that our proposed scanning scheme results in the fast target base station decision while considering the QoS requirements of each MS.
Statistical Analysis of End-to-End Delay for VoIP Service in Mobile WiMAX Networks
Islam, Mohd. Noor ; Jang, Yeong-Min ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 196~201
Measurement of Quality of Service (QoS) parameters and its statistical analysis becomes a key issue for Mobile WiMAX service providers to manage the converged network efficiently and to support end-to-end QoS. In this paper, we investigate the population distribution of end-to-end one-way delay which is the most important QoS parameter in Mobile WiMAX networks. The samples are analyzed with Chi-Square Goodness-of-Fit test, Kolmogorov-Smirnov (K-S), and Anderson-Darling (A-D) test to verify the distribution of parent population. The relation with confidence level and the minimum number of sample size is also performed for logistic distribution. The statistical analysis is a promising approach for measuring the performance Mobile WiMAX networks.
Overcoming OBI Problem by Means of Heterodyne Detection in Upstream Transmission of WDM/SCM-PON
Jeon, You-Chan ; Shin, Hong-Seok ; Park, Jin-Woo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 202~208
The performance of upstream transmission in SCM-PON is generally limited by the presence of OBI which is caused by the beating of two or more lasers. In this paper, we propose a novel approach for reducing OBI problem by using heterodyne detection with an additional LD as a local oscillator, resulting that the RF signal is shifted to the other spectal band. In addition, it is possible that the proposed method can provide the cost-effective solution thanks to the loop-back mechanism using R-SOA in ONUs. The performance is superior when the spectral width of LD is smaller and the power difference between the transmission LD and the oscillation LD is bigger. System configuration and design consideration are discussed. Performance of the systems is evaluated by simulator called OptSim. It is expected to provide WDM/SCM-PON system not only cost-effective but also efficient in increasing the number of subscribers.
A Variable-Length FFT/IFFT Processor for Multi-standard OFDM Systems
Yeem, Chang-Wan ; Shin, Kyung-Wook ;
The Journal of Korean Institute of Communications and Information Sciences, volume 35, issue 2A, 2010, Pages 209~215
This paper describes a design of variable-length FFT/IFFT processor (VL_FCore) for OFDM-based multi-standard communication systems. The VL_FCore adopts in-place single-memory architecture, and uses a hybrid structure of radix-4 and radix-2 DIF algorithms to accommodate various FFT lengths in the range of
. To achieve both memory size reduction and the improved SQNR, a two-step conditional scaling technique is devised, which conditionally scales the intermediate results of each computational stage. The performance analysis results show that the average SQNR's of 64~8,192-point FFT's are over 60-dB. The VL_FCore synthesized with a
CMOS cell library has 23,000 gates and 32 Kbytes memory, and it can operate with 75-MHz@3.3-V clock. The 64-point and 8,192-point FFT's can be computed in
, respectively, thus it satisfies the specifications of various OFDM-based systems.