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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
Analysis and Optimization of the Cross-Modulation Noise in Multi-Band CDMA Handset
Kwack, Jun-Ho ; Joung, In-Gun ; You, Chee-Hwan ; You, Jung-Ho ; Kim, Hak-Sun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 1~8
In this paper, we have derived the Noise-Equation to determine the level of cross-modulation noise that is required for designing multi-band CDMA handset from IS-98 standard. From this Noise-Equation, also we were able to determine each component's specification and forecast the performance(or margin) of designing handset. In conclusion, we have designed and implemented the multi-band CDMA handset of Qualcomm's Zero-IF structure and verified validity of the Noise-Equation. In result, we have got the result of
error between Noise-Equation and actual measurement. Therefore, this paper will give a guideline for design of the Multi-Band CDMA handset.
Improved Throughput of WCDMA Downlink using Power Ramping under Retransmissions for Type I Hybrid ARQ with in Rayleigh Fading Channel
Kim, Bong-Hoe ; Hwang, Seung-Hoon ; Hong, Yu-Pyo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 9~12
In this paper, we propose and analyze a scheme for wireless channels, which is a combination of a type I hybrid-automatic repeat request (H-ARQ) scheme and a power ramping. The power ramping is considered for more reliable downlink data transmission, in which the transmission power is gradually changed from a small level to a large level when the number of retransmissions increases. The simulation results demonstrate that, when the power ramping step size is 0.5dB, the average throughput gain may be as high as 2% to 5% with properly selected parameters.
An Efficient Packet Scheduling Scheme to support Real-Time Traffic in OFDMA Systems
Park, Jeong-Sik ; Cho, Ho-Shin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 13~23
In this paper, a packet scheduling scheme that supports real-time traffic having multi-level delay constraints in OFDMA systems is proposed. The proposed scheme pursues to satisfy the delay constraint first, and then manage the residual radio resource in order to enhance the overall throughput. A parameters named tolerable delay time (TDT) is newly defined to deal with the differentiated behaviors of packet scheduling according to the delay constraint level. Assuming that the packets violating the delay constraint are discarded, the proposed scheme is evaluated in terms of the packet loss probability, throughput, channel utilization. It is then compared with existing schemes for real-time traffic support such as the Exponential Scheduling (EXP) scheme, the Modified Largest Weighted Delay First (M-LWDF) scheme, and the Round robin scheme. The numerical results show that the proposed scheduling scheme performs much better than the aforementioned scheduling schemes in terms of the packet loss probability, while slightly better in terms of throughput and channel utilization.
Channel State-Aware Joint Dynamic Cell Coordination Scheme using Adaptive Modulation and Variable Reuse Factor in OFDMA
Byun, Dae-Wook ; Ki, Young-Min ; Kim, Dong-Ku ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 24~33
In this paper, two different dynamic cell coordination strategies for frequency flat and selective fading are proposed for efficient subcarrier allocation in the joint consideration of adaptive modulation and variable frequency reuse in the channel-aware OFDMA downlink multicellular environment. Compared to a conventional OFDMA system without cell coordination, where system throughput may become degraded due to the persistent interference from other cells, the proposed system dynamically allows RNC to apply different reuse factors on each subchannel and scheduling in consideration of channel and interference conditions of individual users so as to increase the system throughput and guarantee QoS of each user. In a frequency flat fading, the dynamic scheme with the proposed scheduling achieves on average three times larger throughput than the conventional dynamic scheme . In a selective fading channel, the proposed schemes showed 2.6 times as large throughput as that of a single reuse factor of one for all subchannels.
Performance Enhancement of IEEE 802.15.3 MAC for Simultaneously Operating Piconets
Peng, Xue ; Peng, Gong ; Kim, Duk-Kyung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 34~43
In the IEEE 802.15.3 Medium Access Control (MAC) protocol, Simultaneously Operating Piconets (SOPs) are linked by the parent/child (P/C) or parent/neighbor (P/N) configuration, which work on a Time Division Multiple Access (TDMA) basis. This provides interference mitigation but the overall throughput is limited because the SOPs share the channel time exclusively. The protocol is not efficient for SOPs if we focus on the combination of interference mitigation and high throughput maintenance. In this paper Public Channel Time Allocation (Public CTA) is proposed, which is able to greatly reduce the inter-piconet interference (IPI) and achieve greater throughput without much loss of link success probability (LSP) in the SOPs. The simulation results based on the SOPs of Direct Sequence Ultra Wideband (DS-UWB) system demonstrate that the proposed scheme effectively supports the coexistence of SOPs, and it can not only significantly improve the overall throughput of SOPs but also maintain high LSP.
Frequency Domain Scrambling Code Allocation for MC-CDMA Based Communication Systems
Kim, Houng-Soo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 44~50
In typical MC-CDMA systems, different frequency-domain scrambling codes are randomly chosen from a given code set and then assigned to different subscriber stations using the same subcarrier set. When orthogonal codes are employed for the frequency-domain scrambling, the choice of the scrambling code does not affect the detection performance if the timing and frequency synchronizations are perfect and the channel characteristic is flat. However, in practical cases, inter-code interference often appears due to the broken code orthogonality. In this paper, the optimal order of allocating the orthogonal frequency-domain scrambling codes to new subscriber stations is derived under non-negligible timing offsets in MC-CDMA system.
Performance Analysis of UMM-S/OFDM with Multi-level Modulation in the Rayleigh Fading Channel
Kim, Nam-Soo ; Cho, Sung-Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 51~56
Unitary matrix modulation (UMM) is investigated in multiple antennas system that is called unitary space-time modulation (USTM). When we consider only diagonal components of UMM with splitting over the coherence bandwidth, the system can obtain frequency diversity in a single antenna system. In Rayleigh fading channel, we compared USTM/OFDM with 2Tx-antenna with UMM-S/OFDM with 1Tx-antenna, conventional multi-level OFDM and UMM-S/OFDM with changing bit rate per Hz. Also, we analyzed SNR for between multi-level modulation STBC/OFDM and multi-level modulation UMM-S/OFDM with changing transmission rate. When it was adaptive multi-level modulation to improve SNR, we did the UMM-S/OFDM system performance analysis of N-ary PSK and M-ary QAM.
Design and Implementation HDTV Relay Transmission System for Overlay Multicast
Son, Seung-Chul ; Kwag, Yong-Wan ; Heo, Kwon ; Lee, Hyung-Ok ; Nam, Ji-Seung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 57~65
The overlay multicast that has been recently presented as IP alternative for the IP multicast has been getting much persuasion by the computing power of the hardware and the advancement of the network techniques to enforce Routing in application-level. In an overlay multicast, the system resource and the network bandwidth must be utilized efficiently to service real-time HDTV images. Specifically, the system must consider the delay and the jitter that can be incurred at the application-level. In this paper, we implement a server and a client to broadcast HDTV, in the session composed by the existing overlay multicast protocol. The broadcasting server performs the service using a TV tuner, An HDTV camcorder, and files, clients constituting a multicast group relay the received data to other clients. At this time, the information that the clients report periodically, including their delay and the network state, to the server is used as an important information to maintain an overlay session. The implementation is based on the DirectX and its performance is evaluated by the LAN test bed that has been set.
Efficient Spectrum Utilization Scheme Using Adjacent Cell's Incumbent User Cognition In Cognitive Ratio System
Lee, Myeong-Geol ; Song, Jeong-Ig ; Sohn, Sung-Hwan ; Kim, Jae-Moung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 66~74
Cognitive Radio system can guarantee available channel whenever, wherever by sensing surrounding channel condition. Therefore, there is a strict rule that have to use allocated channel efficiently without any interference from incumbent User. In this paper, to avoid interference which can occur during uplink transmission in CR system, we propose reporter using scheme which informs incumbent user's situation to adjacent cell to limit channel usage. Therefore, we can use more channel in each cell without interference. With this scheme we can expect better throughput using more channel in a large space with same resource.
Sampling time-based Adaptive Beacon Interval and Superframe Duration Control in IEEE 802.15.4
Kim, Jeong-Ah ; Jeon, Yeong-Ho ; Park, Hong-Seong ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 75~82
This paper proposes the way that reduces power consumption of the IEEE 802.15.4-based sensor network. To reduce power consumption, we consider following two schemes; first scheme is the Adaptive Beacon Interval Control. The next is the Adaptive Superframe Duration Control. Our results show that these guarantee reducing power consumption in ns-2 simulator.
Implementation of a Jitter and Glitch Removing Circuit for UHF RFID System Based on ISO/IEC 18000-6C Standard
Kim, Sang-Hoon ; Lee, Yong-Joo ; Sim, Jae-Hee ; Lee, Yong-Surk ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 83~90
In this paper, we propose an implementation and an algorithm of 'Jitter and Glitch Removing Circuit' for UHF RFID reader system based on ISO/IEC 18000-6C standard. We analyze the response of TI(Texas Instrument) Gen2 tag with a reader using the proposed algorithm. In ISO/IEC 18000-6C standard, a bit rate accuracy(tolerance) is up to +/-22% during tag-to-interrogator communication and +/-1% during interrogator-to-tag communication. In order to solve tolerance problems, we implement the Jitter and Glitch Removing Circuit using the concept of tolerance and tolerance-accumulation instead of PLL(DPLL, ADPLL). The main clock is 19.2MHz and the LF(Link Frequency) is determined as 40kHz to meet the local radio regulation in korea. As a result of simulations, the error-rate is zero within 15% tolerance of tag responses. And in the case of using the adaptive LF generation circuit, the error-rate varies from 0.000589 to zero between 15% and 22% tolerance of tag responses. In conclusion, the error-rate is zero between 0%-22% tolerance of tag response specified in ISO/IEC 18000-6C standard.
A Study on the RF Shower System to Extend Interrogating Range on Mobile RFID Reader
Ahn, Si-Young ; Kim, Yong-Taek ; Bae, Sung-Woo ; Nae, Kwan-Kyu ; Roh, Hyoung-Hwan ; Kim, Gi-Beom ; Park, Jun-Seok ; Cho, Hong-Goo ; Oh, Ha-Ryoung ; Seong, Yeong-Rak ; Song, Ho-Jun ; Jang, Byung-Jun ; Lee, Jung-Suk ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 91~100
This paper presents the RF Shower System for increased read range on low power mobile RFID System with 20watts of power supply. From the experiment, by controlling the output power of shower system, the tripled read range between reader and Tag is possibly discovered. Thus we can expect on the significantly widen read range of RFID system by appropriate control of Shower Zone, though we only with the reader with its lower output power level of 20dBm.
Automatic Beacon Alignment Schemes Based on Short Address for WPANs
Jeon, Jong-Keun ; Yoon, Chong-Ho ; Kim, Se-Han ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 101~108
There nay be collisions among beacons from several full function devices in IEEE 802.15.4 sensor networks. These collision of beacons may cause devices to lose time synchronization, and thus be unable to association. To solve this problem, the IEEE 802.15.4b defines a new Post Beacon Period(PBP), but it does not still alleviate the beacon collision problem. In this paper, we propose two automatic beacon alignment schemes that a node itself can decide its beacon start time using its short address that has been assigned during association. We also simulate and investigate our proposed automatic beacon collision avoidance schemes using NS-2 simulator.
A New Space-Time Cooperative Diversity Relaying Strategy with Assistant and Management Terminals
Kim, Eun-Ki ; Kim, Young-Ju ; Lee, In-Sung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 109~114
A new space-time cooperative communication relaying strategy with assistant or management terminals is proposed in multi-hop wireless communication systems. More than one relaying terminals are included in one cooperative group to share the state information such as frame error rate and channel information. Among the cooperative group, the best ones are selected to send bit information using space-time codes. An implementation for the proposed scheme is also presented using a TDMA cooperative protocol. Receive signal to transmit signal ratio(
) and computer simulation show the strategy outperform the conventional cooperative system.
I/Q Performance Analysis for IEEE 802.11 b/g VoWLAN Terminal with New Matching Circuit
Kwoun, Sung-Su ; Lee, Jong-Chul ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 115~124
In this paper, the I/Q mismatch problem between the transmission line and antenna switch is solved by a new CPW matching circuit for a VoWLAN terminal with 54 Mbps communication speed through the IEEE 802.11 b/g CCK/OFDM. I/Q performances with the new matching circuit are analyzed and improved by the output spectrum mask, the characteristics of the EVM(Error Vector Magnitude) due to the nonlinear CCK/OFDM demodulation data, and receiver's sensitivity.
Frequency Sharing of Cellular TDD-OFDMA Systems beyond 3G with Terrestrial Fixed Systems
Jo, Han-Shin ; Yoon, Hyun-Goo ; Yook, Jong-Gwan ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 125~133
In this paper, the frequency sharing issue between cellular time division duplex-orthogonal frequency division multiple access (TDD-OFDMA) Systems and terrestrial Fixed Systems has been studied. The conventional advanced minimum coupling loss (A-MCL) includes only the formulation to calculate the interference from one interfering system. Therefore, A-MCL must be modified to assess the aggregated interference from base stations(BS) and mobile stations(MS). By applying the modified model, the coexistence analysis are done according to the average number of MS per sector, BS-to-BS distance, and the main beam direction of the terrestrial fixed system. In the case of 20 MS per sector, the BS-to-BS distance and the minimum distance between a terrestrial fixed system and BS are 5.8 km and 2.5 km, respectively. It is about 25dB that the difference between maximum and minimum interference signal power which varies with the main beam direction of the terrestrial fixed system. Moreover, for 40% of the main beam direction of the terrestrial fixed system, interference signal power is less than the maximum permissible interference.
Design of a 5.2GHz/2.4GHz Dual band CMOS Frequency Synthesizer for WLAN
Kim, Kwang-Il ; Lee, Sang-Cheol ; Yoon, Kwang-Sub ; Kim, Seok-Jin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 32, issue 1A, 2007, Pages 134~141
This paper presents a frequency synthesizer(FS) for 5.2GHz/2.4GHz dual band wireless applications which is designed in a standard
CMOS1P6M process. The 2.4GHz frequency is obtained from the 5.2GHz output frequency of Voltage Controlled Oscillator (VCO) by using the Switched Capacitor (SC) and the divider-by-2. Power dissipations of the proposed FS and VCO are 25mW and 3.6mW, respectively. The tuning range of VCO is 700MHz and the locking time is
. The simulated phase noise of PLL is -101.36dBc/Hz at 200kHz offset frequency from 5.0GHz with SCA circuit on.