IEICE Transactions on Communications
Online ISSN : 1745-1345
Print ISSN : 0916-8516
Volume E92.B, Issue 6
Displaying 1-50 of 71 articles from this issue
Special Section on 3rd Pan-Pacific EMC Joint Meeting - PPEMC'08 -
  • Yoshio Kami
    2009 Volume E92.B Issue 6 Pages 1919
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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  • Yoshiki KAYANO, Hiroshi INOUE
    Article type: PAPER
    2009 Volume E92.B Issue 6 Pages 1920-1928
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Printed circuit boards (PCBs) driven by a connected feed cable are considered to be one of the main sources of the electromagnetic interference (EMI) from electronic devices.In this paper, a method for predicting the electromagnetic (EM) radiation from a PCB driven by a connected feed cable at up to gigahertz frequencies is proposed and demonstrated. The predictive model is based on the transmission line theory and current- and voltage-driven CM generation mechanisms with consideration of antenna impedance. Frequency responses of differential-mode (DM) and common-mode (CM) currents and far-electric field were investigated experimentally and with finite-difference time-domain (FDTD) modeling. First, the dominant component in total EM radiation from the PCB was identified by using the Source-Path-Antenna model. Although CM can dominate the total radiation at lower frequencies, DM is the dominant component above 3GHz. Second, the method for predicting CM component at lower frequencies is proposed. And its validity was discussed by comparing FDTD calculated and measured results. Specifically, the relationship between the CM current and the terminating resistor was focused as important consequence for the prediction. Good agreement between the measured and predicted results shows the validity of the predicted results. The proposed model can predict CM current with sufficient accuracy, and also identify the primary coupling-mechanism of CM generation. Then far-electric field was predicted by using the proposed method, and it was demonstrated that outline of the frequency response of the undesired EM radiation from the PCB driven by the connected feed cable can be predicted with engineering accuracy (within 6dB) up to 18GHz. Finally, as example of application of equivalent circuit model to EMC design, effect of the width of the ground plane was predicted and discussed. The equivalent circuit model provides enough flexibility for different geometrical parameters and increases our ability to provide insights and design guidelines.
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  • Tohlu MATSUSHIMA, Tetsushi WATANABE, Yoshitaka TOYOTA, Ryuji KOGA, Osa ...
    Article type: PAPER
    2009 Volume E92.B Issue 6 Pages 1929-1936
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    A guard trace placed near a signal line reduces common-mode radiation from a printed circuit board. The reduction effect is evaluated by the imbalance difference model, which was proposed by the authors, when the guard trace has exactly the same potential as the return plane. However, depending on interval of ground connection of the guard trace, the radiation can increase when the guard trace resonates. In this paper, the authors show that the increase of radiation is caused by the common mode, and extend the imbalance difference model to explain a mechanism of increase of common-mode radiation. Additionally, the effective via location of the guard trace is proposed to reduce the number of vias. The guard trace voltage due to the resonance excites the common mode at the interface where the cross-sectional structure of the transmission line changes since the common-mode excitation is expressed by the product of the voltage and the difference of current division factors. To suppress the common-mode excitation, the guard trace should be grounded at the point where the cross-sectional structure changes. As a result, the common-mode radiation decreases even when the guard trace resonates.
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  • Umberto PAOLETTI, Takashi HISAKADO, Osami WADA
    Article type: PAPER
    2009 Volume E92.B Issue 6 Pages 1937-1944
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Power and ground planes on multilayer PCBs can effectively radiate electromagnetic fields excited by the IC simultaneous switching noise. The high frequency electromagnetic radiation is often calculated from the electric field along the edge of the PCB, which can be estimated with a cavity model using magnetic walls. The excitation of the cavity modes is related to the via current passing through the power bus planes at the interconnection between IC package and PCB. Usually the attention is focused on the differential-mode current of the package pins, but in the present paper it is shown that the common-mode current flowing out from package pins plays a very important role in the excitation of cavity modes, and its neglect implies a fatal underestimation of the electromagnetic radiation from the power bus planes in some circumstances. A second important contribute to the radiation is given by the common mode current on the pins, together with the current flowing on the PCB ground plane. With the proposed equivalent circuit, the effectiveness of decoupling inductors depending on their location and on the value of the parasitic capacitance is studied.
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  • Sang-Wook PARK, Fengchao XIAO, Yoshio KAMI
    Article type: PAPER
    2009 Volume E92.B Issue 6 Pages 1945-1952
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    An analytical method for estimating coupling between microstrip lines in arbitrary directions on adjacent layers in multi-layer printed circuit boards is studied: one line is embedded and the other is on the surface layer. Coupling or crosstalk has been estimated by development of a circuit-concept approach based on modified telegrapher's equations of the Agrawal approach instead of the Taylor approach for some computational advantages. Electromagnetic fields from the embedded microstrip line and the microstrip line on the surface can be obtained by using the electric image method for dielectric substrates. To verify the proposed approach, we conducted some experiments and compared the results of our approach with those of measurement and a commercial electromagnetic solver.
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  • Fengchao XIAO, Kimitoshi MURANO, Yoshio KAMI
    Article type: PAPER
    2009 Volume E92.B Issue 6 Pages 1953-1959
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    In this paper the time-domain analysis of two parallel traces is investigated. First, the telegrapher's equations for transmission line are applied to the parallel traces on printed circuit board (PCB), and are solved by using the mode decomposition technique. The time-domain solutions are then obtained by using the inverse Laplace transform. Although the Fourier-transform technique is also applicable for this problem, the solution is given numerically. Contrarily, the inverse Laplace transform successfully leads to an analytical expression for the transmission characteristics. The analytical expression is represented by series, which clearly explains the coupling mechanism. The analytical expression for the fundamental section of a meander delay line is investigated in detail. The analytical solution is validated by measurements, and the characteristics of the distortions in the output waveforms of meander delay lines due to the crosstalk are also investigated.
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  • Soichiro TAIRA, Osamu FUJIWARA
    Article type: PAPER
    2009 Volume E92.B Issue 6 Pages 1960-1964
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    The electromagnetic fields emitted from an electrostatic discharge (ESD) event occurring between charged metals cause seriously damage high-tech equipment. In order to clarify the generation mechanism of such ESD fields and also to reduce them, we previously proposed a finite-difference time-domain (FDTD) algorithm based on a delta-gap feeding method and a frequency dispersion characteristic formula (Naito's formula) of ferrite material for simulating the ESD fields due to a spark between the charged metals with ferrite core attachment. In the present study, by integrating the above FDTD algorithm and a spark-resistance formula, we simulated both of the ESD itself and the resultant fields for the metal bars with ferrite core attachment, and demonstrated that the core attachment close to the spark gap suppresses the magnetic field level. This finding was also validated via 6-GHz wide-band measurement of the magnetic near-field.
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  • Ken KAWAMATA, Shigeki MINEGISHI, Yoshinori TAKA, Osamu FUJIWARA
    Article type: PAPER
    2009 Volume E92.B Issue 6 Pages 1965-1968
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    The very fast transients of micro-gap discharges driven by low voltage electrostatic discharging (ESDs) are investigated in the time domain. We previously developed a 12GHz wideband measurement setup consisting of a distributed constant line system, however the observed transients due to micro-gap discharges had very fast rise times of 34ps or less, which reached the limitation on our system. In this paper, we proposed a method for estimating wideband transients beyond the measurement limit by using the transmission loss of a high performance coaxial transmission line. The proposed method is validated by estimating an impulsive voltage waveform with rise/fall time of 16ps from the waveform measured through a semi-rigid coaxial cable with a length of 10m.
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  • Yu-ichi HAYASHI, Hideaki SONE
    Article type: PAPER
    2009 Volume E92.B Issue 6 Pages 1969-1973
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    A transmission line created by cables adjoined by connectors is influenced by noise from connectors with contact failure, and such noise degrades communication quality. The authors used a model of a connector with increased contact resistance in a coaxial cable and measured the electromagnetic near-field around a cable while changing positions of the model. In this paper, the result shows that the radiated electromagnetic field has no relationship with the position along the cable of a connector with increased contact resistance, when the contact condition of connector, contact resistance value, measurement position, and length of a transmission line are constant.
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  • Nobuo KUWABARA, Yasuhiro ISHIDA, Masato KAWABATA
    Article type: PAPER
    2009 Volume E92.B Issue 6 Pages 1974-1980
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    The electromagnetic field emitted from UTP cable has been calculated by the 4-port network method from 30MHz to 1GHz. However it has not been clarified as to whether this method was effective in the frequency range of more than 1GHz or not. In this paper, the electromagnetic field emitted from UTP cable was calculated by the moment method and it was compared with the calculated results by the 4-port network method. The wire grid model was developed to represent the propagation constants of UTP cable. The comparison of calculated and measured results confirms the validity of the model. A hybrid coupler was used to generate differential mode signal for the measurement. The comparison indicated that the calculated results by the moment method closely agreed with the measured results in the frequency range of 0.3 to 2GHz and the difference was smaller than the results by the 4-port network method.
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Regular Section
  • Jungsuk SONG, Hiroki TAKAKURA, Yasuo OKABE, Yongjin KWON
    Article type: PAPER
    Subject area: Fundamental Theories for Communications
    2009 Volume E92.B Issue 6 Pages 1981-1990
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Intrusion detection system (IDS) has played an important role as a device to defend our networks from cyber attacks. However, since it is unable to detect unknown attacks, i.e., 0-day attacks, the ultimate challenge in intrusion detection field is how we can exactly identify such an attack by an automated manner. Over the past few years, several studies on solving these problems have been made on anomaly detection using unsupervised learning techniques such as clustering, one-class support vector machine (SVM), etc. Although they enable one to construct intrusion detection models at low cost and effort, and have capability to detect unforeseen attacks, they still have mainly two problems in intrusion detection: a low detection rate and a high false positive rate. In this paper, we propose a new anomaly detection method based on clustering and multiple one-class SVM in order to improve the detection rate while maintaining a low false positive rate. We evaluated our method using KDD Cup 1999 data set. Evaluation results show that our approach outperforms the existing algorithms reported in the literature; especially in detection of unknown attacks.
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  • Ya-Ting WU, Wai-Ki WONG, Shu-Hung LEUNG, Yue-Sheng ZHU
    Article type: PAPER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2009 Volume E92.B Issue 6 Pages 1991-1999
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    This paper presents the performance analysis of a De-correlated Modified Code Tracking Loop (D-MCTL) for synchronous direct-sequence code-division multiple-access (DS-CDMA) systems under multiuser environment. Previous studies have shown that the imbalance of multiple access interference (MAI) in the time lead and time lag portions of the signal causes tracking bias or instability problem in the traditional correlating tracking loop like delay lock loop (DLL) or modified code tracking loop (MCTL). In this paper, we exploit the de-correlating technique to combat the MAI at the on-time code position of the MCTL. Unlike applying the same technique to DLL which requires an extensive search algorithm to compensate the noise imbalance which may introduce small tracking bias under low signal-to-noise ratio (SNR), the proposed D-MCTL has much lower computational complexity and exhibits zero tracking bias for the whole range of SNR, regardless of the number of interfering users. Furthermore, performance analysis and simulations based on Gold codes show that the proposed scheme has better mean square tracking error, mean-time-to-lose-lock and near-far resistance than the other tracking schemes, including traditional DLL (T-DLL), traditional MCTL (T-MCTL) and modified de-correlated DLL (MD-DLL).
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  • Bong Joo KIM, Gang Uk HWANG
    Article type: PAPER
    Subject area: Network
    2009 Volume E92.B Issue 6 Pages 2000-2007
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    In this paper, we analyze the extended real-time Polling Service (ertPS) algorithm in IEEE 802.16e systems, which is designed to support Voice-over-Internet-Protocol (VoIP) services with data packets of various sizes and silence suppression. The analysis uses a two-dimensional Markov Chain, where the grant size and the voice packet state are considered, and an approximation formula for the total throughput in the ertPS algorithm is derived. Next, to improve the performance of the ertPS algorithm, we propose an enhanced uplink resource allocation algorithm, called the e2rtPS algorithm, for VoIP services in IEEE 802.16e systems. The e2rtPS algorithm considers the queue status information and tries to alleviate the queue congestion as soon as possible by using remaining network resources. Numerical results are provided to show the accuracy of the approximation analysis for the ertPS algorithm and to verify the effectiveness of the e2rtPS algorithm.
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  • Ngo Anh VIEN, Nguyen Hoang VIET, SeungGwan LEE, TaeChoong CHUNG
    Article type: PAPER
    Subject area: Network
    2009 Volume E92.B Issue 6 Pages 2008-2022
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    In this paper, we solve the call admission control (CAC) and routing problem in an integrated network that handles several classes of calls of different values and with different resource requirements. The problem of maximizing the average reward (or cost) of admitted calls per unit time is naturally formulated as a semi-Markov Decision Process (SMDP) problem, but is too complex to allow for an exact solution. Thus in this paper, a policy gradient algorithm, together with a decomposition approach, is proposed to find the dynamic (state-dependent) optimal CAC and routing policy among a parameterized policy space. To implement that gradient algorithm, we approximate the gradient of the average reward. Then, we present a simulation-based algorithm to estimate the approximate gradient of the average reward (called GSMDP algorithm), using only a single sample path of the underlying Markov chain for the SMDP of CAC and routing problem. The algorithm enhances performance in terms of convergence speed, rejection probability, robustness to the changing arrival statistics and an overall received average revenue. The experimental simulations will compare our method's performance with other existing methods and show the robustness of our method.
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  • Ayong YE, Jianfeng MA, Xiaohong JIANG, Susumu HORIGUCHI
    Article type: PAPER
    Subject area: Network
    2009 Volume E92.B Issue 6 Pages 2023-2031
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Secure sensor localization is a prerequisite for many sensor networks to retrieve trustworthy data. However, most of existing node positioning systems were studied in trust environment and are therefore vulnerable to malicious attacks. In this work, we develop a robust node positioning mechanism(ROPM) to protect localization techniques from position attacks. Instead of introducing countermeasures for every possible internal or external attack, our approach aims at making node positioning system attack-tolerant by removing malicious beacons. We defeat internal attackers and external attackers by applying different strategies, which not only achieves robustness to attacks but also dramatically reduces the computation overhead. Finally, we provide detailed theoretical analysis and simulations to evaluate the proposed technique.
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  • Weiwei XIA, Lianfeng SHEN
    Article type: PAPER
    Subject area: Network
    2009 Volume E92.B Issue 6 Pages 2032-2043
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    We propose two vertical handoff schemes for cellular network and wireless local area network (WLAN) integration: integrated service-based handoff (ISH) and integrated service-based handoff with queue capabilities (ISHQ). Compared with existing handoff schemes in integrated cellular/WLAN networks, the proposed schemes consider a more comprehensive set of system characteristics such as different features of voice and data services, dynamic information about the admitted calls, user mobility and vertical handoffs in two directions. The code division multiple access (CDMA) cellular network and IEEE 802.11e WLAN are taken into account in the proposed schemes. We model the integrated networks by using multi-dimensional Markov chains and the major performance measures are derived for voice and data services. The important system parameters such as thresholds to prioritize handoff voice calls and queue sizes are optimized. Numerical results demonstrate that the proposed ISHQ scheme can maximize the utilization of overall bandwidth resources with the best quality of service (QoS) provisioning for voice and data services.
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  • Chi Jia HUANG, Chien CHEN
    Article type: PAPER
    Subject area: Internet
    2009 Volume E92.B Issue 6 Pages 2044-2053
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Internet routers need to classify incoming packets quickly into flows in order to support features such as Internet security, virtual private networks and Quality of Service (QoS). Packet classification uses information contained in the packet header, and a predefined rule table in the routers. Packet classification of multiple fields is generally a difficult problem. Hence, researchers have proposed various algorithms. This study proposes a multi-dimensional encoding method in which parameters such as the source IP address, destination IP address, source port, destination port and protocol type are placed in a multi-dimensional space. Similar to the previously best known algorithm, i.e., bitmap intersection, multi-dimensional encoding is based on the multi-dimensional range lookup approach, in which rules are divided into several multi-dimensional collision-free rule sets. These sets are then used to form the new coding vector to replace the bit vector of the bitmap intersection algorithm. The average memory storage of this encoding is Θ (L · N · log N) for each dimension, where L denotes the number of collision-free rule sets, and N represents the number of rules. The multi-dimensional encoding practically requires much less memory than bitmap intersection algorithm. Additionally, the computation needed for this encoding is as simple as bitmap intersection algorithm. The low memory requirement of the proposed scheme means that it not only decreases the cost of packet classification engine, but also increases the classification performance, since memory represents the performance bottleneck in the packet classification engine implementation using a network processor.
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  • Komwut WIPUSITWARAKUN, Sanon CHIMMANEE
    Article type: PAPER
    Subject area: Internet
    2009 Volume E92.B Issue 6 Pages 2054-2064
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Overlay networks which are dynamically created over underlying IP networks are becoming widely used for delivering multimedia contents since they can provide several additional user-definable services. Multiple overlay paths between a source-destination overlay node pair are designed to improve service robustness against failures and bandwidth fluctuation of the underlying networks. Multimedia traffic can be distributed over those multiple paths in order to maximize paths' utilization and to increase application throughputs. Most of flow-based routing algorithms consider only common metrics such as paths' bandwidth or delay, which may be effective for data applications but not for real-time applications such as Voice over IP (VoIP), in which different levels of such performance metrics may give the same level of the performance experienced by end users. This paper focuses on such VoIP overlay networks and proposes a novel alternative path based flow routing algorithm using an application-specific traffic metric, i.e. “VoIP Path Capacity (VPCap), ” to calculate the maximum number of QoS satisfied VoIP flows which may be distributed over each available overlay path at a moment. The simulation results proved that more QoS-satisfied VoIP sessions can be established over the same multiple overlay paths, comparing to traditional approaches.
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  • Yohei KOJIMA, Kazuaki TAKEDA, Fumiyuki ADACHI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 6 Pages 2065-2071
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can provide better downlink bit error rate (BER) performance of direct sequence code division multiple access (DS-CDMA) than the conventional rake combining in a frequency-selective fading channel. FDE requires accurate channel estimation. In this paper, we propose a new 2-step maximum likelihood channel estimation (MLCE) for DS-CDMA with FDE in a very slow frequency-selective fading environment. The 1st step uses the conventional pilot-assisted MMSE-CE and the 2nd step carries out the MLCE using decision feedback from the 1st step. The BER performance improvement achieved by 2-step MLCE over pilot assisted MMSE-CE is confirmed by computer simulation.
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  • Tarkesh PANDE, Heon HUH, James KROGMEIER, David LOVE
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 6 Pages 2072-2084
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Continuous phase modulation (CPM) is a non-linear modulation technique whose power and bandwidth efficiency make it an attractive choice for mobile communication systems. Current research has focused on devising encoding rules for using CPM over multiple-input multiple-output (MIMO) systems in order to obtain the improved bit error rate (BER) and high data rates promised by MIMO technology. In this paper, optimal and suboptimal non-coherent receivers for a class of CPM signals called orthogonal space-time CPM (OST-CPM) are derived under a quasi-static fading channel assumption. The performance of these receivers is characterized and shown to achieve the same diversity order as that of the corresponding optimal coherent receiver.
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  • Chantima SRITIAPETCH, Seiichi SAMPEI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 6 Pages 2085-2094
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    This paper proposes a frequency domain nulling filter and Turbo equalizer to suppress interference in the uplink of one-cell reuse single-carrier time division multiple access (TDMA) systems. In the proposed system, the desired signal in a reference cell is interfered by interference signals including adjacent-channel interference (ACI), co-channel interference (CCI), and intersymbol interference (ISI). At the transmitter, after a certain amount of spectrum is nulled considering the expected CCI, the suppressed power due to nulling is reallocated to the remaining spectrum components so as to keep the total transmit power constant. In this process, when mitigation of ACI is necessary, after a certain amount of spectrum at both edges is nulled using an edge-removal filter, the aforementioned process is conducted. At the receiver, frequency domain SC/MMSE Turbo equalizer (FDTE) is employed to suppress ISI due to spectrum nulling process in the transmitter as well as the multipath fading. Computer simulations confirm that the proposed scheme is effective in suppression of CCI, ACI and ISI in one-cell reuse single-carrier TDMA systems.
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  • Sangchul OH, Namhoon PARK, Ohjun KWON, Yeongjin KIM
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 6 Pages 2095-2101
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    In this paper, we have shown a major element occupying the large portion of software communications architecture (SCA)-based software defined radio (SDR) handheld embedded system and an important feature for implementing a high speed broadband radio to an SCA waveform through a couple of experiments. First, this paper identifies the main items possessing the large portion of SCA-based SDR handheld embedded system by the experiment on the target platform which is similar to a commercial mobile handheld system. Both the world interoperabillity for microwave access (WiMAX) and high speed downlink packet access (HSDPA) waveform software packages are used as an SCA waveform application. This paper also presents the results of the relative binary size distribution of SCA software resources for looking for the major elements making an SCA-based SDR handheld embedded system heavier. As a result, when focusing on the relative weight portion of SCA core framework (CF), the SCA CF takes 16% up and others have 84% out of the whole binary size distribution of SCA software resources. The results of the experiment give us notice that the weight portion of SCA CF is minor and compatible with the overall software binary size needs of an SCA-based SDR handheld embedded system, on the other hand, the practical problem on the lightweight is in a common object request broker architecture (CORBA) and extensible markup language (XML) parser resources. Second, this paper describes an important feature for implementing a high speed broadband radio to an SCA waveform and presents the performance evaluation results of the SCA port communication on both power PC (PPC) 405 and x86 processor platforms. The PPC 405 platform, which is similar to a commercial mobile handset, takes the value of average round trip time (RTT) with a maximum of thirty six millisecond. The x86 platform, however, which is analogous to a server platform, maintains stable micro-second resolution. From our experiments, we observe that rapid SCA port communication, sufficiently less than the frame length of high-speed broadband radios, should be provided for serving those radio services in a commercial handheld system based on the SCA.
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  • Hao ZHANG, T. Aaron GULLIVER
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 6 Pages 2102-2111
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    In this paper, we study the capacity and performance of nonorthogonal pulse position modulation (NPPM) for Ultra-Wideband (UWB) communication systems over both AWGN and IEEE802.15.3a channels. The channel capacity of NPPM is determined for a time-hopping multiple access UWB communication system. The error probability and performance bounds are derived for a multiuser environment. It is shown that with proper selection of the pulse waveform and modulation index, NPPM can achieve a higher capacity than orthogonal PPM, and also provide better performance than orthogonal PPM with the same throughput.
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  • Xingzai LV, Jinkang ZHU, Ling QIU
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 6 Pages 2112-2121
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    We address the problem of multiuser co-channel interference scheduling in multicell interference-limited networks. Our target is to optimize the network capacity under the SIR-balanced power control policy. Since it's difficult to optimize the original problem, we derive a new problem which maximizes the lower bound of the network capacity. Based on the analysis of this new problem, we propose an interference matched scheduling algorithm. This algorithm considers the caused co-channel interference and the channel conditions to schedule the “matched” users at the same time. We prove that this interference matched scheduling algorithm optimizes the lower bound of the network capacity for any arbitrary numbers of cells and users. Moreover, this scheduling method is low-complexity and can be implemented in a fully distributed fashion. Simulation results reveal that the performance of the proposed algorithm achieves near optimal capacity, even though it does not optimize the network capacity directly. Finally, the proposed algorithm holds a great gain over formerly proposed round robin and power matched scheduling method, especially when the scale of the network is large.
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  • Subrata Kumar BISWAS, Tetsuki TANIGUCHI, Yoshio KARASAWA
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 6 Pages 2122-2130
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    In recent years, the space-time block coding (STBC) method has attracted attention to provide transmission diversity in mobile communication systems. Although the STBC method is very effective in slow fading environments, its performance in fast fading environments has yet to be clearly verified. In this paper we propose a railway radio communication system using space-time coding in cooperation with two base stations. Here, we considered the differential STBC (D-STBC) method in railway communication system to overcome difficulties caused by the fast fading environment. We have compared the performance of STBC and D-STBC method where there is frequency offset between two base stations. Moreover, we have presented the simulation result of overall performance of the system including frequency offset and transmission time delay when operating D-STBC method. The overall evaluation on this paper shows that the D-STBC method is suitable for realizing highly reliable railway communication systems.
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  • Yung-Yi WANG, Wen-Hsien FANG, Jiunn-Tsair CHEN
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 6 Pages 2131-2141
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    We propose a dimension reduction algorithm for the receiver of the downlink of direct-sequence code-division multiple access (DS-CDMA) systems in which both the transmitters and the receivers employ antenna arrays of multiple elements. To estimate the high order channel parameters, we develop a layered architecture using dimension-reduced parameter estimation algorithms to estimate the frequency-selective multipath channels. In the proposed architecture, to exploit the space-time geometric characteristics of multipath channels, spatial beamformers and constrained (or unconstrained) temporal filters are adopted for clustered-multipath grouping and path isolation. In conjunction with the multiple access interference (MAI) suppression techniques, the proposed architecture jointly estimates the direction of arrivals, propagation delays, and fading amplitudes of the downlink fading multipaths. With the outputs of the proposed architecture, the signals of interest can then be naturally detected by using path-wise maximum ratio combining. Compared to the traditional techniques, such as the Joint-Angle-and-Delay-Estimation (JADE) algorithm for DOA-delay joint estimation and the space-time minimum mean square error (ST-MMSE) algorithm for signal detection, computer simulations show that the proposed algorithm substantially mitigate the computational complexity at the expense of only slight performance degradation.
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  • Jun-Hee JANG, Jung-Su HAN, Sung-Soo KIM, Hyung-Jin CHOI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 6 Pages 2142-2152
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    To mitigate the asynchronous ICI (Inter-Cell Interference), SCM (Spatial Covariance Matrix) of the asynchronous ICI plus background noise should be accurately estimated for MIMO-OFDMA (Multiple-input Multiple-output-Orthogonal Frequency Division Multiple Access) system. Generally, it is assumed that the SCM of the asynchronous ICI plus background noise is estimated by using training symbols. However, it is difficult to measure the interference statistics for a long time and considering that training symbols are not appropriate for OFDMA system such as LTE (3GPP Long Term Evolution). Therefore, noise reduction method is required to improve the estimation accuracy. Although the conventional time-domain low-pass type weighting method can be effective for noise reduction, it causes significant estimation error due to the spectral leakage in practical OFDM system. Therefore, we propose a time-domain sinc type weighing method which can not only reduce noise effectively minimizing estimation error caused by the spectral leakage but also can be implemented using frequency-domain weighted moving average filter easily. We also consider the iterative CFR (Channel Frequency Response) and SCM estimation method which can effectively reduce the estimation error of both CFR and SCM, and improve the performance for LTE system. By using computer simulation, we show that the proposed method can provide up to 2.5dB SIR (Signal to Interference Ratio) gain compared with the conventional method, and verify that the proposed method is attractive and suitable for implementation with stable operation.
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  • Zhao LI, Hiroshi FURUKAWA
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 6 Pages 2153-2159
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Vector Coding (VC) is a novel vector modulation scheme that partitions a SISO (Single-Input Single-Output) channel into orthogonal subchannels by singular value decomposition (SVD). Because the orthogonal transmissions enabled by VC cannot cope with inter block interference (IBI) that is inevitable in delay spread channels, this paper proposes an IBI cancelling demodulator which can remove IBI by an iterative technique. We also show that code elimination in which insignificant eigencodes with lowermost eigenvalues are intentionally removed from transmission vectors greatly reduces BER (Bit Error Rate). The VC which utilizes the IBI cancelling demodulator and code elimination to reduce BER is compared with the original VC in not only delay spread SISO channels but also delay spread MIMO (Multi-Input Multi-Output) channels while emphasis is placed on the MIMO cases. Simulation results show that, under a predetermined BER, the enhanced MIMO-VC can improve effective transmission rate than the natural extension of VC to delay spread MIMO channels.
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  • Augusto FORONDA, Chikara OHTA, Hisashi TAMAKI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 6 Pages 2160-2167
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Several scheduling algorithms have been proposed for the downlink of a Code Division Multiple Access (CDMA) system with High Data Rate (HDR). Modified Largest Weighted Delay First (M-LWDF) scheduling algorithm selects a user according to the user current channel condition, user head-of-line packet delay and user Quality of Service (QoS) requirement. Proportional Fair (PF) scheduling algorithm has also been proposed for CDMA/HDR system and it selects a user according to the ratio of the user current channel rate and the user average channel rate, which provides good performance in terms of fairness. However, when variable bit rate (VBR) traffic is considered under different channel conditions for each user, both schedulers' performance decrease. M-LWDF scheduler can not guarantee the QoS requirement to be achieved and PF scheduler can not achieve a good fairness among the users. In this work, we propose a new scheduling algorithm to enhance M-LWDF and PF schedulers performance. Proposed scheduler selects a user according to the user input traffic characteristic, user current channel condition and user QoS requirement, which consists of a delay value with a maximum violation probability. We consider the well-known effective bandwidth expression, which takes into account the user QoS requirement and the user input traffic characteristics, to select a user to be scheduled. Properties of the proposed scheduling algorithm are investigated through simulations with constant bit rate (CBR) and VBR flows and performance comparisons with M-LWDF and PF schedulers. The results show a better performance of the proposed scheduler compared with M-LWDF and PF schedulers.
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  • Chao LIU, Mengtian RONG
    Article type: PAPER
    Subject area: Terrestrial Radio Communications
    2009 Volume E92.B Issue 6 Pages 2168-2174
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    The IEEE 802.11 standard has been extensively deployed all over the world. Many studies have been put on its performance, especially throughput. Most research focused on the analysis of saturated throughput, but non-saturated situation is more usual in practice. By extending a saturation throughput model, a concise and novel model is proposed in this paper, which can be used to analyze both saturated and non-saturated conditions. Moreover, the model can also deal with the heterogeneous condition, which allows stations to have different traffic. Different access mechanisms and packet payloads are used in simulation to validate it, and the results show that the model is accurate.
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  • Koshiro KITAO, Tetsuro IMAI
    Article type: PAPER
    Subject area: Antennas and Propagation
    2009 Volume E92.B Issue 6 Pages 2175-2181
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    In order to reduce the amount of interference to neighboring cells in cellular systems, we generally use base station (BS) antennas that have sharp beam patterns in the vertical plane; however, the distribution of incoming waves at the BS affects the effective gain of the BS antennas which have directional pattern. Therefore, we have to clarify the characteristics of the distribution of the incoming waves. A recent trend is decreasing the cell radius; therefore, clarifying the distribution of the incoming waves at the BS when mobile stations (MSs) are located within 1km from the BS is important. In this report, we evaluate the effective gains of the BS antennas, which are calculated using the measured vertical power angle profile (PAP). Moreover, we examine the application of a simple incoming wave model to the evaluation of the antenna effective gains. In the model, the average power of the incoming waves is set to the Laplacian function and each wave is changed to a lognormal distribution. The antenna effective gain calculated using the model agrees well with that calculated using the measured PAP.
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  • Masao MASUGI, Kazuo MURAKAWA
    Article type: PAPER
    Subject area: Electromagnetic Compatibility (EMC)
    2009 Volume E92.B Issue 6 Pages 2182-2192
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    This paper describes an analysis of the effects of electric field on nerve cells by using the Hodgkin-Huxley model. When evaluating our model, which combines an additional ionic current source and generated membrane potential, we derive the peak-to-peak value, the accumulated square of variation, and Kolmogorov-Sinai (KS) entropy of the cell-membrane potential excited by 10, 100, 1k, and 10kHz-sinusoidal electric fields. In addition, to obtain a comprehensive view of the time-variation patterns of our model, we used a self-organizing map, which provides a way to map high-dimensional data onto a low-dimensional domain. Simulation results confirmed that lower-frequency electric fields tended to increase fluctuations of the cell-membrane potential, and the additional ionic current source was a more dominant factor for fluctuations of the cell-membrane potential. On the basis of our model, we visually confirmed that the obtained data could be projected onto the map in accordance with responses of cell-membrane potential excited by electric fields, resulting in a combined depiction of the effects of KS entropy and other parameters.
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  • Tohlu MATSUSHIMA, Tetsushi WATANABE, Yoshitaka TOYOTA, Ryuji KOGA, Osa ...
    Article type: PAPER
    Subject area: Electromagnetic Compatibility (EMC)
    2009 Volume E92.B Issue 6 Pages 2193-2200
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Placing a guard trace next to a signal line is the conventional technique for reducing the common-mode radiation from a printed circuit board. In this paper, the suppression of common-mode radiation from printed circuit boards having guard traces is estimated and evaluated using the imbalance difference model, which was proposed by the authors. To reduce common-mode radiation further, a procedure for designing a transmission line with guard traces is proposed. Guard traces connected to a return plane through vias are placed near a signal line and they decrease a current division factor (CDF). The CDF represents the degree of imbalance of a transmission line, and a common-mode electromotive force depends on the CDF. Thus, by calculating the CDF, we can estimate the reduction in common-mode radiation. It is reduced not only by placing guard traces, but also by narrowing the signal line to compensate for the variation in characteristic impedance due to the guard traces. Experimental results showed that the maximum reduction in common-mode radiation was about 14dB achieved by placing guard traces on both sides of the signal line, and the calculated reduction agreed with the measured one within 1dB. According to the CDF and characteristic impedance calculations, common-mode radiation can be reduced by about 25dB while keeping the characteristic impedance constant by changing the gap between the signal line and the guard trace and by narrowing the width of the signal line.
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  • Yu-Chen KUO, Ji-Wei CHEN
    Article type: PAPER
    Subject area: Sensing
    2009 Volume E92.B Issue 6 Pages 2201-2208
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    The wireless sensor network is a resource-constrained self-organizing system that consists of a large number of tiny sensor nodes. Due to the low-cost and low-power nature of sensor nodes, sensor nodes are failure-prone when sensing and processing data. Most presented fault-tolerant research for wireless sensor networks focused on crash faults or power faults and less on Byzantine faults. Hence, in this paper, we propose a power-saving data aggregation algorithm for Byzantine faults to provide power savings and high success rates even in the environment with high fault rates. The algorithm utilizes the concept of Byzantine masking quorum systems to mask the erroneous values and to finally determine the correct value. Our simulation results demonstrate that when the fault rate of sensor nodes is up to 50%, our algorithm still has 48% success rate to obtain the correct value. Under the same condition, other fault-tolerant algorithms are almost failed.
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  • Xiaobo DENG, Yiming PI, Zhenglin CAO
    Article type: PAPER
    Subject area: Sensing
    2009 Volume E92.B Issue 6 Pages 2209-2217
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    This paper develops a complete architecture for constant false alarm rate (CFAR) detection based on a goodness-of-fit (GOF) test. This architecture begins with a logarithmic amplifier, which transforms the background distribution, whether Weibull or lognormal into a location-scale (LS) one, some relevant properties of which are exploited to ensure CFAR. A GOF test is adopted at last to decide whether the samples under test belong to the background or are abnormal given the background and so should be declared to be a target of interest. The performance of this new CFAR scheme is investigated both in homogeneous and multiple interfering targets environment.
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  • Jae Ho HWANG, Jae Moung KIM
    Article type: LETTER
    Subject area: Fundamental Theories for Communications
    2009 Volume E92.B Issue 6 Pages 2218-2221
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    This paper deals with a new ranging algorithm in an ultra-wideband system. The conventional ToA algorithm determines the distance between devices by estimating the propagation time. However, due to different timer offsets in each device, the accuracy of this estimation can be compromised. In this paper, a double reply ToA algorithm is proposed to increase the ranging accuracy without increasing hardware complexity.
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  • Moonseo PARK, Seong-Lyun KIM
    Article type: LETTER
    Subject area: Fundamental Theories for Communications
    2009 Volume E92.B Issue 6 Pages 2222-2225
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    When the joint source-channel (JSC) decoder is used for source coding over noisy channels, the JSC decoder may invent errors even though the received data is not corrupted by the channel noise, if the JSC decoder assumes the channel was noisy. A novel encoder algorithm has been recently proposed to improve the performance of the communications system under this situation. In this letter, we propose another algorithm based on conditional entropy-constrained vector quantizer to further improve the encoder. The algorithm proposed in this letter significantly improves the performance of the communications system when the hypothesized channel bit error rate is high.
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  • Wei FENG, Yifei ZHAO, Ming ZHAO, Shidong ZHOU, Jing WANG, Minghua XIA
    Article type: LETTER
    Subject area: Fundamental Theories for Communications
    2009 Volume E92.B Issue 6 Pages 2226-2230
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    This letter focuses on the simplified capacity evaluation for the downlink of a distributed antenna system (DAS) with random antenna layout. Based on system scale-up, we derive a good approximation of the downlink capacity by developing the results from random matrix theory. We also propose an iterative method to calculate the unknown parameters in the approximated expression of the downlink capacity. The approximation is illustrated to be quite accurate and the iterative method is shown to be quite efficient by Monte Carlo simulations.
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  • Abolfazl GHASSEMI, T. Aaron GULLIVER
    Article type: LETTER
    Subject area: Fundamental Theories for Communications
    2009 Volume E92.B Issue 6 Pages 2231-2234
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Tone reservation (TR) has been proposed for peak to average power reduction (PAPR) in real-baseband multicarrier systems [1]. In this technique, the peak reduction signal is computed by optimization via linear programming (LP). As shown in [1], the computational complexity of the LP optimization is largely determined by the complexity of the inverse fast Fourier transform (IFFT) algorithm. In this paper, we use submatrices of the inverse fast Fourier transform (IFFT) to reduce the number of constraints in the LP-based optimization. We show that a significant complexity reduction can be achieved compared to the conventional TR algorithm, with similar PAPR reduction.
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  • Ning HAN, Sung Hwan SOHN, Jae Moung KIM
    Article type: LETTER
    Subject area: Fundamental Theories for Communications
    2009 Volume E92.B Issue 6 Pages 2235-2238
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    The key issue in cognitive radio is to design a reliable spectrum sensing method that is able to detect the signal in the target channel as well as to recognize its type. In this paper, focusing on classifying different orthogonal frequency-division multiplexing (OFDM) signals, we propose a two-step detection and identification approach based on the analysis of the cyclic autocorrelation function. The key parameters to separate different OFDM signals are the subcarrier spacing and symbol duration. A symmetric peak detection method is adopted in the first step, while a pulse detection method is used to determine the symbol duration. Simulations validate the proposed method.
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  • Sang Hyun PARK, Quan LE, Bo-Hun CHOI
    Article type: LETTER
    Subject area: Devices/Circuits for Communications
    2009 Volume E92.B Issue 6 Pages 2239-2242
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    An inductive buffer peaking technique is proposed and demonstrated to extend the bandwidth of a 10-Gbit/s transimpedance amplifier (TIA) for optical communications. A TIA using this peaking technique is fabricated based on InGaP/GaAs HBT technology. The advantage of the proposed technique is verified by comparisons based on simulations and experiments. For these comparisons, three different types of TIAs using a basic gain stage, a shunt peaking gain stage and the proposed gain stage, respectively, are fabricated and measured. The measured performance of the proposed TIA shows that this bandwidth extension technique using inductive buffer peaking can be applied to circuit designs which demand wideband frequency response with low power consumption.
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  • Jaeho LEE, Taewon HWANG
    Article type: LETTER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2009 Volume E92.B Issue 6 Pages 2243-2246
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Multiple access based on energy spreading transform (EST) in [1] has been shown to effectively separate multiuser signals in an iterative manner. In this paper, an optimum hard-decision detector for the EST-based multiple access is proposed. The proposed scheme employs minimum mean square error (MMSE) processing at each iteration to enhance the performance of the original scheme. Analysis and simulation results show the significant performance improvement of the proposed scheme over the original method.
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  • Shaopeng WANG, Shihua ZHU, Yi LI
    Article type: LETTER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2009 Volume E92.B Issue 6 Pages 2247-2250
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    A method that jointly estimates the carrier frequency offset (CFO), channel and symbol timing for orthogonal frequency division multiplexing (OFDM) is proposed in this letter. Based on the characteristic of cyclic training symbols in the frequency domain, the joint estimation is divided into three separate estimations. The CFO and equivalent channel impulse response (CIR) are first estimated by an iterative joint maximum likelihood estimation (JMLE), then the symbol timing offset (STO) is obtained by the assistance of equivalent CIR, finally the CIR is calculated based on the equivalent CIR after known STO and CFO. In our proposed method, the effect of imperfect CIR is considered in the CFO estimator. Moveover, a procedure, which eliminates the inverse operation of a covariance matrix at each iterative process, was adopted to reduce the complexity of our proposed method. Simulations show that the proposed method is capable of retaining the same bit error rate as joint CFO and CIR maximum likelihood estimation without symbol timing error.
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  • Chisato FUKAI, Kazuhide NAKAJIMA, Takashi MATSUI
    Article type: LETTER
    Subject area: Optical Fiber for Communications
    2009 Volume E92.B Issue 6 Pages 2251-2253
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    We describe the applicability of photonic crystal fiber (PCF) with an enlarged effective area Aeff to a distributed Raman amplification (DRA) transmission. We investigate the DRA transmission performance numerically over a large Aeff PCF taking account of the signal-to-noise ratio (SNR) improvement RSNR in the S, C, and L bands. We show that an RSNR of 3dB can be expected by utilizing DRA with a maximum pump power of 500mW when the Aeff of the PCF is 230µm2.
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  • Soohyun OH, Jin Wook LEE, Taejoon PARK, Tae-Chang JO
    Article type: LETTER
    Subject area: Switching for Mobile Communications
    2009 Volume E92.B Issue 6 Pages 2254-2258
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    In wireless cellular networks, streaming of continuous media (with strict QoS requirements) over wireless links is challenging due to their inherent unreliability characterized by location-dependent, bursty errors. To address this challenge, we present a two-step scheduling algorithm for a base station to provide streaming of continuous media to wireless clients over the error-prone wireless links. The proposed algorithm is capable of minimizing the packet loss rate of individual clients in the presence of error bursts, by transmitting packets in the round-robin manner and also adopting a mechanism for channel prediction and swapping.
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  • Jeong Geun KIM, Ca Van PHAN, Wonha KIM
    Article type: LETTER
    Subject area: Network
    2009 Volume E92.B Issue 6 Pages 2259-2262
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    We analyze the performance of an opportunistic transmission strategy for Wireless Sensor Networks (WSNs). We consider a transmission strategy called Binary Decision-Based Transmission (BDT), which is a common form of opportunistic transmission. The BDT scheme initiates transmission only when the channel quality exceeds the optimum threshold to avoid unsuccessful transmissions that waste energy. We formulate the Markov Decision Process (MDP) to identify an optimum threshold for transmission decisions in the BDT scheme.
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  • Joonbok LEE, Kilnam CHON
    Article type: LETTER
    Subject area: Network
    2009 Volume E92.B Issue 6 Pages 2263-2266
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    In this paper, we propose a network-aware overlay multicast (NAOM) technique for large data dissemination in a well-managed overlay network. To improve the throughput, NAOM utilizes forward-only hosts; these hosts participate in the overlay network but are not members of the multicast. With the inclusion of the forward-only hosts, data slices can detour bottleneck links and more resources can be used to build efficient multicast trees. Large data are divided into fixed-size slices, and the slices are delivered simultaneously to multicast receivers along the multiple multicast trees. We model the problem of building efficient multicast trees with the inclusion of forward-only hosts. The problem is an NP-hard problem, and we introduce a polynomial time heuristic algorithm. Furthermore, we propose a dynamic scheduling scheme for the transfer of data along the evaluated multicast trees. Our experimental results in a real network environment show an improvement of the throughput but at the cost of additional resource consumption of forward-only nodes.
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  • Sang-Jo YOO, Nada GOLMIE
    Article type: LETTER
    Subject area: Network
    2009 Volume E92.B Issue 6 Pages 2267-2270
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    Channel scanning is an important aspect of seamless handovers since it is required in order to find a target point of attachment (PoA). However, channel scanning in single radio devices may cause severe service disruptions with the current PoA so that the provided QoS will be further degraded during a handover. In this letter, we propose a dynamic channel scanning algorithm that supports QoS. Simulation results show that the proposed mechanism reduces the service disruptions and provides the desired QoS to users during the scanning period.
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  • Cheolhyo LEE, Yoon-Seok NAM, Jae-Young KIM, You-Ze CHO
    Article type: LETTER
    Subject area: Network
    2009 Volume E92.B Issue 6 Pages 2271-2274
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    This paper proposes a one-way ranging method using reference-based broadcasting messages. The method is based on impulse radio UWB (Ultra-wideband) for wireless sensor networks. The proposed method reduces traffic overheads and increases the ranging accuracy using frequency offsets and counter information based on virtually synchronized counters between RNs (Reference Nodes) and MNs (Mobile Nodes). Simulation results show that the proposed method can alleviate the ranging errors comparing to SDS-TWR (Symmetric Double-Sided Two-Way Ranging) method in terms of the frequency offset.
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  • ASADUZZAMAN, Hyung-Yun KONG
    Article type: LETTER
    Subject area: Network
    2009 Volume E92.B Issue 6 Pages 2275-2278
    Published: June 01, 2009
    Released on J-STAGE: June 01, 2009
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    This letter proposes a simple modification of LEACH protocol to exploit its multi-hop scenario for user cooperation. Instead of a single cluster-head we propose M cluster-heads in each cluster to obtain the diversity of order M. All cluster-heads gather data from all sensor nodes within the cluster using the same technique as LEACH. Cluster-heads transmit gathered data cooperatively towards the destination or higher order cluster-head. We propose a code combining based cooperative protocol. We also develop the upper bounds on frame error rate (FER) for our proposal. Simulation and analysis show that our proposal can significantly prolong the system lifetime.
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