IEICE Transactions on Communications
Online ISSN : 1745-1345
Print ISSN : 0916-8516
Volume E92.B, Issue 2
Displaying 1-50 of 50 articles from this issue
Special Section on Medical Information and Communications Technologies
  • Ryuji KOHNO
    2009 Volume E92.B Issue 2 Pages 365
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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  • Arthur W. ASTRIN, Huan-Bang LI, Ryuji KOHNO
    Article type: INVITED PAPER
    2009 Volume E92.B Issue 2 Pages 366-372
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    Body Area Networks (BAN) can provide a wide range of applications including medical support, healthcare monitoring, and consumer electronics with increased convenience or comfort. To harmonize with the strong demands from both medical and healthcare societies, and information and communications technology (ICT) industries, IEEE 802.15.6 task group (TG6) was set up to develop an IEEE wireless standard on BAN. This paper presents a general guidance to TG6. Some pre-works to set up TG6 are reviewed. The objectives, main topics, current status are described in details.
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  • Matti HÄMÄLÄINEN, Attaphongse TAPARUGSSANAGORN, Jari II ...
    Article type: INVITED PAPER
    2009 Volume E92.B Issue 2 Pages 373-378
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    The average age of population is predicted to be raised universally but the number of nursing staff is not increasing at the same rate. This leads us to the situation where, e.g., we have too many patients for one nurse. On the other hand, sparse population in some regions, such as Northern or Eastern Finland, causes a severe problem that doctors are far away from patient. In this paper, we summarize the possibilities and applications that utilize wireless technologies in healthcare sector and which can be useful in nursing activities. The use of new innovations is one way to solve the problems that are based on the expected lack of professional staff in the future. Despite of the very natural hospital link, the developed technical solutions have applications outside hospital. Remote care of aging people and other special groups need to be done daily and almost real-time. Keeping people home instead of hospital is one way to decrease the entire care costs. In addition to the obvious human context, we derive some other applications where we can benefit wireless nursing and remote sensing techniques.
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  • Po-Hsun CHENG, Sao-Jie CHEN, Jin-Shin LAI
    Article type: PAPER
    2009 Volume E92.B Issue 2 Pages 379-386
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    This work elucidates the evolution of three generations of the laboratory information system in the National Taiwan University Hospital, which were respectively implemented in an IBM Series/1 mini-computer, a client/server and a plug-and-play HL7 interface engine environment respectively. The experience of using the HL7 healthcare information exchange in the hospital information system, laboratory information system, and automatic medical instruments over the past two decades are illustrated and discussed. The latest design challenge in developing intelligent laboratory information services is to organize effectively distributed and heterogeneous medical instruments through the message gateways. Such experiences had spread to some governmental information systems for different purposes in Taiwan; besides, the healthcare information exchange standard, software reuse mechanism, and application service provider adopted in developing the plug-and-play laboratory information system are also illustrated.
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  • Changle LI, Huan-Bang LI, Ryuji KOHNO
    Article type: PAPER
    2009 Volume E92.B Issue 2 Pages 387-395
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    The medical body area network (MBAN) is an emerging technology to resolve the small area connection issues around human body, especially for the medical applications. This paper proposes a dynamic TDMA (DTDMA) protocol for MBAN with focus on the dependability and power efficiency. In DTDMA, the slots are allocated by the MBAN coordinator only to the devices which have buffered packets and released to other devices after the current allocation. Through the adaptive allocation of the slots in a DTDMA frame, the MBAN coordinator adjusts the duty cycle adaptively with the traffic load. Comparing with the IEEE 802.15.4 MAC protocol, the DTDMA provides more dependability in terms of lower packet dropping rate and less energy consumption especially for an end device of a MBAN.
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  • Chien-Sheng CHEN, Szu-Lin SU, Yih-Fang HUANG
    Article type: PAPER
    2009 Volume E92.B Issue 2 Pages 396-402
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In this paper we present hybrid positioning schemes that combine time of arrival (TOA) and angle of arrival (AOA) measurements from only two base stations (BSs) to locate the mobile station (MS) in non-line-of-sight (NLOS) environments. The proposed methods utilize two TOA circles and two AOA lines to find all the possible intersections to locate the MS without requiring a priori information about the NLOS error. The commonly known Taylor series algorithm (TSA) and the hybrid lines of position algorithm (HLOP) have convergence problems, and the relative positioning between the MS and the BSs greatly affects the location accuracy. The resulting geometry creates a situation where small measurement errors can lead to significant errors in the estimated MS location. Simulation results show that the proposed methods always perform better than TSA and HLOP for different levels of NLOS errors, particularly when the MS/BSs have an undesirable geometric layout.
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  • Makoto KAWASAKI, Ryuji KOHNO
    Article type: PAPER
    2009 Volume E92.B Issue 2 Pages 403-409
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    Wireless communication devices in the field of medical implant, such as cardiac pacemakers and capsule endoscopes, have been studied and developed to improve healthcare systems. Especially it is very important to know the range and position of each device because it will contribute to an optimization of the transmission power. We adopt the time-based approach of position estimation using ultra wideband signals. However, the propagation velocity inside the human body differs in each tissue and each frequency. Furthermore, the human body is formed of various tissues with complex structures. For this reason, propagation velocity is different at a different point inside human body and the received signal so distorted through the channel inside human body. In this paper, we apply an adaptive template synthesis method in multipath channel for calculate the propagation time accurately based on the output of the correlator between the transmitter and the receiver. Furthermore, we propose a position estimation method using an estimation of the propagation velocity inside the human body. In addition, we show by computer simulation that the proposal method can perform accurate positioning with a size of medical implanted devices such as a medicine capsule.
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  • Kamya Yekeh YAZDANDOOST, Ryuji KOHNO
    Article type: PAPER
    2009 Volume E92.B Issue 2 Pages 410-417
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    The medical care day by day and more and more is associated with and reliant upon concepts and advances of electronics and electromagnetics. Numerous medical devices are implanted in the body for medical use. Tissue implanted devices are of great interest for wireless medical applications due to the promising of different clinical usage to promote a patient independence. It can be used in hospitals, health care facilities and home to transmit patient measurement data, such as pulse and respiration rates to a nearby receiver, permitting greater patient mobility and increased comfort. As this service permits remote monitoring of several patients simultaneously it could also potentially decrease health care costs. Advancement in radio frequency communications and miniaturization of bioelectronics are supporting medical implant applications. A central component of wireless implanted device is an antenna and there are several issues to consider when designing an in-body antenna, including power consumption, size, frequency, biocompatibility and the unique RF transmission challenges posed by the human body. The radiation characteristics of such devices are important in terms of both safety and performance. The implanted antenna and human body as a medium for wireless communication are discussed over Medical Implant Communications Service (MICS) band in the frequency range of 402-405MHz.
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  • Norihiko KATAYAMA, Kenichi TAKIZAWA, Takahiro AOYAGI, Jun-ichi TAKADA, ...
    Article type: PAPER
    2009 Volume E92.B Issue 2 Pages 418-424
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    Body Area Network (BAN) is considered as a promising technology in supporting medical and healthcare services by combining with various biological sensors. In this paper, we look at wearable BAN, which provides communication links among sensors on body surface. In order to design a BAN that manages biological information with high efficiency and high reliability, the propagation characteristics of BAN must be thoroughly investigated. As a preliminary effort, we measured the propagation characteristics of BAN at frequency bands of 400MHz, 600MHz, 900MHz and 2400MHz respectively. Channel models for wearable BAN based on the measurement were derived. Our results show that the channel model can be described by using a path loss model for all frequency bands investigated.
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  • Qiong WANG, Jianqing WANG
    Article type: PAPER
    2009 Volume E92.B Issue 2 Pages 425-430
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    With the rapid progress of electronic and information technology, an expectation for the realization of body area network (BAN) by means of ultra wide band (UWB) techniques has risen. Although the signal from a single UWB device is very low, the energy absorption may increase significantly when many UWB devices are simultaneously adorned to a human body. An analysis method is therefore required from the point of view of biological safety evaluation. In this study, two approaches, one is in the time domain and the other is in the frequency domain, are proposed for the specific energy absorption (SA) and the specific absorption rate (SAR) calculation. It is shown that the two approaches have the same accuracy but the time-domain approach is more straightforward in the numerical analysis. By using the time-domain approach, SA and SAR calculation results are given for multiple UWB pulse exposure to an anatomical human body model under the Federal Communications Commission (FCC) UWB limit.
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  • Satoru KIKUCHI, Kazuyuki SAITO, Masaharu TAKAHASHI, Koichi ITO, Hiroo ...
    Article type: PAPER
    2009 Volume E92.B Issue 2 Pages 431-439
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    This paper presents the computational electromagnetic dosimetry inside an anatomically based pregnant woman models exposed to electromagnetic wave during magnetic resonance imaging. The two types of pregnant woman models corresponding to early gestation and 26 weeks gestation were used for this study. The specific absorption rate (SAR) in and around a fetus were calculated by radiated electromagnetic wave from highpass and lowpass birdcage coil. Numerical calculation results showed that high SAR region is observed at the body in the vicinity of gaps of the coil, and is related to concentrated electric field in the gaps of human body such as armpit and thigh. Moreover, it has confirmed that the SAR in the fetus is less than International Electrotechnical Commission limit of 10W/kg, when whole-body average SARs are 2W/kg and 4W/kg, which are the normal operating mode and first level controlled operating mode, respectively.
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  • Tetsuyuki MICHIYAMA, Yoshio NIKAWA
    Article type: LETTER
    2009 Volume E92.B Issue 2 Pages 440-444
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    The body area network (BAN) has attracted attention because of its potential for high-grade wireless communication technology and its safety and high durability. Also, human area transmission of a BAN propagating at an ultra-wide band (UWB) has been demonstrated recently. When considering the efficiency of electromagnetic (EM) propagation inside the human body for BAN and hyperthermia treatment using RF, it is important to determine the mechanism of EM dissipation in the human body. A body heating system for hyperthermia must deposit EM energy deep inside the body. Also, it is important that the EM field generated by the implant system is sufficiently strong. In this study, the specific absorption rate (SAR) distribution is simulated using an EM simulator to consider the biological transmission mechanism and its effects. To utilize the EM field distribution using an implant system for hyperthermia treatment, the SAR distribution inside the human body is simulated. As a result, the SAR distribution is concentrated on the surface of human tissue, the muscle-bolus interface, the pancreas, the stomach, the spleen and the regions around bones. It can also be concentrated in bone marrow and cartilage. From these results, the appropriate location for the implant system is revealed on the basis of the current distribution and differences in the wave impedance of interfacing tissues. The possibility of accurate data transmission and suitable treatment planning is confirmed.
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Regular Section
  • Kinji MORI, Akio SHIIBASHI
    Article type: INVITED SURVEY PAPER
    Subject area: Network Management / Operation
    2009 Volume E92.B Issue 2 Pages 445-460
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    The advancement of technology is ensured by step-by-step innovation and its implementation into society. Autonomous Decentralized Systems (ADSs) have been growing since first proposed in 1977. Since then, the ADS technologies and their implementations have interacted with the evolving markets, sciences, and technologies. The ADS concept is proposed on biological analogy, and its technologies have been advanced according to changing and expanding requirements. These technologies are now categorized into six generations on the basis of requirements and system structures, but the ADS concept and its system architecture have not changed. The requirements for the system can be divided in operation-oriented, mass service-oriented, and personal service-oriented categories. Moreover, these technologies have been realized in homogeneous system structure and, as the next step, in heterogeneous system structure. These technologies have been widely applied in manufacturing, telecommunications, information provision/utilization, data centers, transportation, and so on. They have been operating successfully throughout the world. In particular, ADS technologies have been applied in Suica, the IC card ticket system (ICCTS) for fare collection and e-commerce. This system is not only expanding in size and functionality but also its components are being modified almost every day without stopping its operation. This system and its technologies are shown here. Finally, the future direction of ADS is discussed, and one of its technologies is presented.
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  • DinhTrieu DUONG, Min-Cheol HWANG, Byeong-Doo CHOI, Jun-Hyung KIM, Sung ...
    Article type: PAPER
    Subject area: Fundamental Theories for Communications
    2009 Volume E92.B Issue 2 Pages 461-472
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In low bit-rate video transmission, the payload of a single packet can often contain a whole coded frame due to the high compression ratio in both spatial and temporal domains. Thus, the loss of a single packet can lead to the loss of a whole video frame. In this paper, we propose a novel error concealment algorithm that can effectively reconstruct the lost frame and protect the quality of video streams from the degradation caused by propagation errors. The proposed algorithm employs a bilateral motion estimation scheme where the weighted sum of the received motion vectors (MVs) in the neighboring frames is utilized to construct the MV field for the concealed frame. Unlike the conventional algorithms, the proposed scheme does not produce any overlapped pixel and hole region in the reconstructed frame. The proposed algorithm can be applied not only to the case of single frame loss but also adaptively extended to the case of multiframe loss. Experimental results show that the proposed algorithm outperforms other conventional techniques in terms of both peak signal-to-noise ratio (PSNR) performance and subjective visual quality.
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  • Naohiro KAWABATA, Hisao KOGA, Osamu MUTA, Yoshihiko AKAIWA
    Article type: PAPER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2009 Volume E92.B Issue 2 Pages 473-482
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    As a method to realize a high-speed communication in the home network, the power-line communication (PLC) technique is known. A problem of PLC is that leakage radiation interferes with existing systems. When OFDM is used in a PLC system, the leakage radiation is not sufficiently reduced, even if the subcarriers corresponding to the frequency-band of the existing system are never used, because the signal is not strictly band-limited. To solve this problem, each subcarrier must be band-limited. In this paper, we apply the OQAM based multi-carrier transmission (OQAM-MCT) to a high-speed PLC system, where each subcarrier is individually band-limited. We also propose a pilot-symbol sequence suitable for frequency offset estimation, symbol-timing detection and channel estimation in the OQAM-MCT system. In this method, the pilot signal-sequence consists of a repeated series of the same data symbol. With this method, the pilot sequence approximately becomes equivalent to OFDM sequence and therefore existing pilot-assisted methods for OFDM are also applicable to OQAM-MCT system. Computer simulation results show that the OQAM-MCT system achieves both good transmission rate performance and low out-of-band radiation in PLC channels. It is also shown that the proposed pilot-sequence improves frequency offset estimation, symbol-timing detection and channel estimation performance as compared with the case of using pseudo-noise sequence.
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  • Chang Wu YU, Tung-Kuang WU, Rei-Heng CHENG, Kun-Ming YU, Shun Chao CHA ...
    Article type: PAPER
    Subject area: Network
    2009 Volume E92.B Issue 2 Pages 483-490
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    A mobile node in ad hoc networks may move arbitrarily and act as a router and a host simultaneously. Such a characteristic makes nodes in MANET vulnerable to potential attacks. The black hole problem, in which some malicious nodes pretend to be intermediate nodes of a route to some given destinations and drop packets that pass through it, is one of the major types of attack. In this paper, we propose a distributed and cooperative mechanism to tackle the black hole problem. The mechanism is distributed so that it suits the ad hoc nature of network, and nodes in the protocol cooperate so that they can analyze, detect, and eliminate possible multiple black-hole nodes in a more reliable fashion. Simulation results show that our method achieves a high black hole detection rate and good packet delivery rate, while the overhead is comparatively lower as the network traffic increases.
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  • Kaoru FUKUDA, Akinori NAKAJIMA, Fumiyuki ADACHI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 491-498
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    Multi-carrier code division multiple access (MC-CDMA) is a promising wireless access technique for the next generation mobile communications systems, in which broadband packet data services will dominate. Hybrid automatic repeat request (HARQ) is an indispensable error control technique for high quality packet data transmission. The HARQ throughput performance of multi-code MC-CDMA degrades due to the presence of residual inter-code interference (ICI) after frequency-domain equalization (FDE). To reduce the residual ICI and improve the throughput performance, a frequency-domain soft interference cancellation (FDSIC) technique can be applied. An important issue is the generation of accurate residual ICI replica for FDSIC. In this paper, low-density parity-check coded (LDPC-coded) MC-CDMA HARQ is considered. We generate the residual ICI replica from a-posteriori log-likelihood ratio (LLR) of LDPC decoder output and evaluate, by computer simulation, the throughput performance in a frequency-selective Rayleigh fading channel. We show that if the residual ICI is removed, MC-CDMA can provide a throughput performance superior to orthogonal frequency division multiplexing (OFDM).
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  • Tao LIU, Shihua ZHU
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 499-506
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    This paper is concerned with timing synchronization of high rates UWB signals operating in a dense multipath environment, where access must tackle inter-frame interference (IFI), inter-symbol interference (ISI) and even multi-user interference (MUI). A training-based joint timing and channel estimation scheme is proposed, which is resilient to IFI, ISI, MUI and pulse distortion. A low-complexity detection scheme similar to transmit-reference (TR) scheme comes out as a by-product. For saving the training symbols, we further develop an extended decision-directed (DD) scheme. A lower bound on the probability of correct detection is derived which agrees well with the simulated result for moderate to high SNR values. The results show that the proposed algorithm achieves a significant performance gain in terms of mean square error and bit error rate in comparison to the “timing with dirty templates” (TDT) algorithms.
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  • Igor JELOVCAN, Gorazd KANDUS, Tomaz JAVORNIK
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 507-516
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    An adaptive zero forcing maximum likelihood soft input soft output (AZFML-SISO) detector for multiple input multiple output (MIMO) wireless systems is presented. Its performance in an iterative MIMO receiver is analyzed. The AZFML-SISO detector calculates the soft outputs, applying the ML approach to the list that contains only those signal vectors limited by a hypersphere around the zero forcing (ZF) solution. The performance of the algorithm is evaluated on a communication system based on the standard for single carrier broadband wireless communication IEEE 802.16, with three transmit and three receive antennas. It is shown by computer simulation that the computational complexity in an average sense of the receiver running the AZFML-SISO algorithm is reduced by 90% at the SNR values of 30dB and by 50% for SNR values of 15dB in comparison to the receiver with an ML detector, while the system performance degrades by less than 1dB.
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  • JunHwan LEE, Tomoaki OHTSUKI, Masao NAKAGAWA
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 517-526
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In orthogonal frequency division multiplexing (OFDM) the multipath exceeding the guard interval (GI) causes inter-symbol interference (ISI) and inter-carrier interference (ICI), thereby making it difficult to achieve high data rate transmission. In this paper, the double window cancellation and combining (DWCC), introduced in [14], is analyzed by investigating SINR distribution under different delay spread channels. The analysis indicates that the extension of processing window in iterative cancellation can have an adverse effect on the performance for small interference levels. In addition, the optimal combining of DWCC and turbo equalization (TE), named TE-DWCC, is investigated by varying the iterative cancellation procedure between DWCC and channel decoder and the decision feedback type such as hard decision feedback (HDF) or soft decision feedback (SDF). Finally, by changing interference level, code rate, and decision feedback type, the performance of TE-DWCC is compared with the conventional canceller that adopts turbo equalization in the exponentially distributed slow fading channel.
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  • Jaehong KIM, Sangjae LEE, Sehun KIM
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 527-532
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    Multiple Input Multiple Output (MIMO) represents a highly promising technique for 4G communication networks as it uses multiple antennas at the transmitter and receiver to improve the reliability of transmissions and to provide a high data rate. This paper introduces an adjustable scheduling algorithm for multi-user MIMO systems that can provide an advantageous trade-off solution between throughput maximization and fair resource allocation among users. Specifically, our algorithm is proposed as a solution to system requirement issues through the flexible control of fairness factors.
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  • Jae Soong LEE, Jae Young LEE, Soobin LEE, Hwang Soo LEE
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 533-543
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    Although each application has its own quality of service (QoS) requirements, the resource allocation for multiclass services has not been studied adequately in multiuser orthogonal frequency division multiplexing (OFDM) systems. In this paper, a total transmit power minimization problem for downlink transmission is examined while satisfying multiclass services consisting of different data rates and target bit-error rates (BER). Lagrangian relaxation is used to find an optimal subcarrier allocation criterion in the context of subcarrier time-sharing by all users. We suggest an iterative algorithm using this criterion to find the upper and lower bounds of optimal power consumption. We also propose a prioritized subcarrier allocation (PSA) algorithm that provides low computation cost and performance very close to that of the iterative algorithm. The PSA algorithm employs subcarrier selection order (SSO) in order to decide which user takes its best subcarrier first over other users. The SSO is determined by the data rates, channel gain, and target BER of each user. The proposed algorithms are simulated in various QoS parameters and the fading channel model. Furthermore, resource allocation is performed not only subcarrier by subcarrier but also frequency block by frequency block (comprises several subcarriers). These extensive simulation environments provide a more complete assessment of the proposed algorithms. Simulation results show that the proposed algorithms significantly outperform existing algorithms in terms of total transmit power consumption.
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  • Wenjie JIANG, Yusuke ASAI, Shuji KUBOTA
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 544-558
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In multiple antenna systems that use spatial multiplexing to raise transmission rates, it is preferable to use maximum likelihood (ML) detection to exploit the full receive diversity and minimize the error probability. In this paper, we present two tree based approximate ML detectors that use new two ordering criteria in conjunction with efficient search strategies. Unlike conventional tree detectors, the new detectors closely approximate the error performance of the exact ML detector while achieving a dramatic reduction in complexity. Moreover, they ensure a fixed detection delay and high level of parallelization in the tree search.
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  • Wannaree WONGTRAIRAT, Pornchai SUPNITHI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 559-566
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In this paper, we derive the average bit error probability (BEP) for common digital modulation schemes and the outage probability of double Nakagami-m channels with MRC diversity. First, the probability density function (PDF) and moment generating function (MGF) of received signal with maximal ratio combining (MRC) receiver diversity are computed. The derived MGF results are simplified in terms of a generalized hypergeometric function 2F0. The derived BEP expressions find applications in existing wireless systems such as satellite mobile communication system, mobile-to-mobile communication system and multiple-input multiple-output (MIMO) wireless communication system. In addition, the obtained general MGF expression considers combined Rayleigh × Nakagami-m, double Rayleigh, single Rayleigh, single Nakagami-m, and non-fading or additive white Gaussian noise (AWGN) channels as special cases. The simulation results agree well with the theoretical results.
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  • Yi CHU
    Article type: PAPER
    Subject area: Antennas and Propagation
    2009 Volume E92.B Issue 2 Pages 567-577
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In this paper, we propose a set of constraints for adaptive broad-band beamforming in the presence of angular errors. We first present spatial and frequency derivative constraints (SFDC) for the design of the quiescent beamformer response. With the wavelet-based blocking matrices, the proposed generalized sidelobe canceller (GSC) preserves the desired signal, and it is less sensitive to the broad-band noise. To make this beamformer more robust to the directional mismatch, we add a pseudo-interference algorithm in the weight adaptive process. Analysis and simulation results demonstrate that the angular beamwidth is insensitive to the input signal-to-noise ratio (SNR).
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  • Eiichi YOSHIKAWA, Tomoaki MEGA, Takeshi MORIMOTO, Tomoo USHIO, Zen KAW ...
    Article type: PAPER
    Subject area: Sensing
    2009 Volume E92.B Issue 2 Pages 578-584
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    The purpose of this study is the real-time estimation of Doppler spectral moments for precipitation in the presence of ground clutter overlap. The proposed method is a frequency domain approach that uses a Gaussian model both to remove clutter spectrum and to estimate weather spectrum. The main advantage of this method is that it does not use processes like several fitting procedures and enables to estimate profiles of precipitation in a short processing time. Therefore this method is efficient for real-time radar observation with high range and time resolution. The performance of this method is evaluated based on simulation data and the observation data acquired by the Ku-band broad band radar (BBR) [1].
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  • M. Ali Akber DEWAN, M. Julius HOSSAIN, Oksam CHAE
    Article type: PAPER
    Subject area: Multimedia Systems for Communications
    2009 Volume E92.B Issue 2 Pages 585-598
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    Background modeling is one of the most challenging and time consuming tasks in motion detection from video sequence. This paper presents a background independent moving object segmentation algorithm utilizing the spatio-temporal information of the last three frames. Existing three-frame based methods face challenges due to the insignificant gradient information in the overlapping region of difference images and edge localization errors. These methods extract scattered moving edges and experience poor detection rate especially when objects with slow movement exist in the scene. Moreover, they are not much suitable for moving object segmentation and tracking. The proposed method solves these problems by representing edges as segments and applying a novel segment based flexible edge matching algorithm which makes use of gradient accumulation through distance transformation. Due to working with three most recent frames, the proposed method can adapt to changes in the environment. Segment based representation facilitates local geometric transformation and thus it can make proper use of flexible matching to provide an effective solution for tracking. To segment the moving object region from the detected moving edges, we introduce a watershed based algorithm followed by an iterative background removal procedure. Watershed based segmentation algorithm helps to extract moving object with more accurate boundary which eventually achieves higher coding efficiency in content based applications and ensures a good visual quality even in the limited bit rate multimedia communication.
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  • Dong-Chul GO, Jong-Moon CHUNG, Su Young LEE
    Article type: LETTER
    Subject area: Fundamental Theories for Communications
    2009 Volume E92.B Issue 2 Pages 599-603
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    An adaptive algorithm to optimize the packet size in wireless mobile networks with Gauss-Markov mobility is presented. The proposed control algorithm conducts adaptive packet size control for mobile terminals that experience relatively fast changing channel conditions, which could be caused by fast mobility or other rapidly changing interference conditions. Due to the fast changing channel conditions, the packet size controller uses short channel history for channel status estimation and takes advantage of a pre-calculated probability density function (PDF) of the distance of the mobile nodes in the estimation process. The packet size is adapted to maximize the communication performance through automatic repeat request (ARQ). The adaptive packet size controlling algorithm is based on an estimation of the channel error rate and the link statistics obtained from the mobility pattern. It was found that the distribution of the link distance among mobile nodes following the Markov-Gauss mobility pattern in a circular communication range well fits the Beta PDF. By adapting the Beta PDF from the mobility pattern, the results show that it is possible to estimate the channel condition more accurately and thereby improve the throughput and utilization performance in rapidly changing wireless mobile networking systems.
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  • Chang-Rae JEONG, Hyo-Yol PARK, Kwang-Soon KIM, Keum-Chan WHANG
    Article type: LETTER
    Subject area: Fundamental Theories for Communications
    2009 Volume E92.B Issue 2 Pages 604-607
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In this paper, an efficient partial incremental redundancy (P-IR) scheme is proposed for an H-ARQ using block type low density parity check (B-LDPC) codes. The performance of the proposed P-IR scheme is evaluated in an HSDPA system using IEEE 802.16e B-LDPC codes. Simulation results show that the proposed H-ARQ using IEEE 802.16e B-LDPC codes outperforms the H-ARQ using 3GPP turbo codes.
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  • Ki Yong JEON, Sung Ho CHO
    Article type: LETTER
    Subject area: Devices/Circuits for Communications
    2009 Volume E92.B Issue 2 Pages 608-611
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In this letter, we propose a new scheme for the tag structure of the EPCglobal Class-1 Generation-2 (EPC C1 Gen2) standard equipped with a channel encoding block and the corresponding decoding block in the receiver of the reader system. The channel coded tag is designed to fully accommodate the EPC C1 Gen2 standard. The use of the proposed channel encoding block increases the number of logic gates in the tag by no more than 5%. The proposed reader system is designed to be used in the mixed tag modes as well, where the channel coded tags and existing tags co-exist in the same inventory round. The performances of the proposed tags and the corresponding reader systems are also presented by comparing the number of EPC error frames and the tag identification time with those of the conventional tags and reader systems.
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  • Gicheol WANG, Gihwan CHO
    Article type: LETTER
    Subject area: Network
    2009 Volume E92.B Issue 2 Pages 612-615
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In the proposed scheme, every sensor establishes communications keys with its neighbors after deployment. They are selectively employed for intra-cluster communications, and the employed keys are determined by local topology of clusters. Thus, our scheme periodically changes the local topology of clusters so as to renew the intra-cluster communication keys. Besides, new Cluster Heads (CHs) easily share a key with the Base Station (BS) by informing the BS of their member information without sending key materials. Simulation results prove that our approach has strong resiliency against the increase of compromised sensors. It also achieves a performance gain in terms of energy.
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  • Yong LEE, Goo-Yeon LEE, Hwa-Jong KIM, Choong-Kyo JEONG
    Article type: LETTER
    Subject area: Network
    2009 Volume E92.B Issue 2 Pages 616-619
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In this letter, we propose a hybrid authentication algorithm to alleviate the latent security problems of mobile multi-hop networks. The proposed scheme uses centralized authentication when a node first joins the network, and uses distributed authentication for the hop-by-hop authentication among multi-hop nodes. We also analyze performance of the proposed scheme.
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  • Myung Ho YEO, Yu Mi KIM, Jae Soo YOO
    Article type: LETTER
    Subject area: Network
    2009 Volume E92.B Issue 2 Pages 620-623
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    Clustering the sensor nodes is one of the most popular and effective approaches for applications that must support hundreds or thousands of nodes. The conventional algorithms consider various parameters to evenly distribute the energy load. However, energy consumption problem of the cluster head still remains. In this paper, we propose a novel clustering approach that periodically elects cluster heads with assistant nodes. The assistant nodes substitute for each cluster head to transmit sensor readings to the base station. Performance evaluations show that our proposed clustering algorithm achieves about 10-40% better performance than the existing clustering algorithms in terms of lifetime.
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  • Jaejoon CHO, Sunshin AN
    Article type: LETTER
    Subject area: Network
    2009 Volume E92.B Issue 2 Pages 624-627
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    An energy-efficient clustering scheme to maximize the network lifetime is presented in IEEE 802.15.4 networks. In the proposed clustering scheme, even though the cluster is divided into several sub-clusters in order to decrease data redundancies, the sub-CH does not transmit the beacon frame due to the problem of beacon collision. Our clustering scheme also allows the CH to control the size of the sub-cluster according to the residual energy of the sub-CH. The performance of the proposed scheme is verified by simulations that demonstrate how our scheme provides a better network lifetime than the conventional scheme.
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  • Jinwon CHOI, Jun-Sung KANG, Yong-Hwa KIM, Seong-Cheol KIM
    Article type: LETTER
    Subject area: Network
    2009 Volume E92.B Issue 2 Pages 628-631
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    This letter presents the variation of localization error to network parameters, the number of range estimation results from anchor nodes (ANs) and average distance between ANs in centralized Wireless Sensor Network (WSN). In sensor network, ANs estimate the relative range to Target Node (TN) using Time-Of-Arrival (TOA) information of Ultra WideBand (UWB) radio and a fusion center determines the final localization of TN based on estimation results reported. From simulation results, the variation of localization error, which is defined as the difference between localization result of TN and its actual location, is represented as the function of number of estimation results to average distance between ANs. The distribution of localization error is matched to the Rician distribution whose K-factor value is given by the proposed formula as well. Finally, the normalized error function for the efficient localization network design is characterized.
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  • Junbeom HUR, Hyunsoo YOON
    Article type: LETTER
    Subject area: Network Management / Operation
    2009 Volume E92.B Issue 2 Pages 632-635
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    Scalability is one of the most important requirements for secure multicast in a multi-group environment. In this study, we propose a decentralized multi-group key management scheme that allows each multicast group sender to control the access to its group communication independently. Scalability is enhanced by local rekeying and inter-working among different subgroups. The group key secrecy and backward/forward secrecy are also guaranteed.
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  • Dongju KIM, Kyunbyoung KO, Jeongho PARK, Daesik HONG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 636-639
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    This letter presents an analytical method for 64-QAM CDMA systems equipped with a multipath interference canceler (MPIC) over multipath fading channels. Numerical results obtained from the proposed analysis indicate that an MPIC is required in order to mitigate the effects of multipath interference and to effectively increase the system capacity.
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  • Janghoon YANG, Dong Ku KIM
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 640-645
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In this letter, an equivalent uplink problem formulation is developed in the multi-cell environment such that the downlink beamforming throughput is maximized under the assumption that base station (BS) can only use the estimated receive signal to interference plus noise power ratio (SINR) of mobile station (MS) in computing beam vectors because of channel estimation error and delay feedback. Numerical results show that the proposed downlink beamforming throughput maximization offers noticeable improvement of 5% outage and average throughput over conventional minimum mean squared error (MMSE) beamforming in the presence of channel uncertainties whereas the performance degradation in the environment of the nominal channel uncertainty is significant compared to the case of no uncertainty.
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  • Jaewon CHANG, Gwuieon JIN, Wonjin SUNG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 646-649
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    Eigen-beamforming (EB) transmission for multiple-input multiple-output (MIMO) systems is an effective means to maximize the receiver signal-to-noise ratio (SNR) in a noise-limited environment, but suffers a performance degradation when strong interference signals exist. In this letter, we propose an interference cancellation method for EB signals by constructing a new receive beamforming vector which jointly utilizes the EB matrix and minimum mean-square error (MMSE) spatial demultiplexing. The proposed method is shown to outperform the conventional EB receiver in the entire cell range, with a significant increase in the effective signal-to-interference plus noise ratio (SINR) near the cell boundary.
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  • Won Joon LEE, Jae Han YOON, Sang Kyu PARK
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 650-653
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    Several quasi-orthogonal STBCs (QOSTBCs) designs using four transmit antennas have been proposed. However, these STBC codes do not maintain full diversity due to the limitations of their complex orthogonal design. In this paper, we propose a code selection method with single-phase feedback which eliminates most of the interference by selecting the QOSTBC with less interference from among two predefined QOSTBCs. The BER performance improvement is investigated in relation with the single-phase feedback scheme at the expense of one bit.
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  • Seung-Moo CHO, Tae-Jin LEE
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 654-657
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    We present a novel frequency partitioning technique of fractional frequency reuse (FFR) that reduces the effect of co-channel interference and increases the capacity of OFDM systems. The usable sub-channel sets are classified into the common sub-channel sets for all cells and the dedicated sub-channel sets for specific cell types in FFR. The proposed fractional frequency reuse with ordering scheme (FFRO) can decrease the amount of interference in the common sub-channel sets by specially designing the sub-channel sets and the order of sub-channel assignment for specific cell types. Simulation results show that the proposed FFRO yields enhanced performance for both uniform and non-uniform distributions of traffic load.
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  • Dongju KIM, Myonghee PARK, Jeongho PARK, Kyunbyoung KO
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 658-661
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    The authors present an accurate analysis for multicode code division multiple access (CDMA) systems equipped with a multipath interference canceler (MPIC) over multipath fading channels. This letter verifies that the previous analysis has used the additional Gaussian approximation (AGA) for multipath interferences so that there is the performance mismatch between the previous analysis and simulations. Furthermore, it is confirmed that the proposed analysis, which does not use AGA, provides an analytical bound.
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  • Qing CHANG, Yongbo TAN, Wei QI, Dirong CHEN
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 662-665
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    This letter proposes a new transceiver for OFDM systems based on Smooth Local Trigonometric Transform (LTT). In our transceiver, the transmitter is realized by firstmodulating the original serial data using a constellation mapper, then feeding the results into the inverse LTT modulator. Unlike the conventional DFT-OFDM system, which always uses the roll cosine function as its window function, the proposed system needs no additional window function for the reason that LTT transform includes a bell-shaped window function by itself. Moreover, each LTT-OFDM symbol has a much more rapid attenuation rate outside of the spectral bandwidth and better spectrum convergence. In the receiver, the original data is recovered by demodulating the received data using forward LTT. Comparative simulation results from the conventional DFT-OFDM system, the system we proposed, and the recently proposed DCT based OFDM system are discussed in terms of bit error rate (BER).
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  • Eunchul YOON, Sun-Yong KIM, Suhan CHOI, Hichan MOON
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 666-670
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    The downlink beamforming weights which can suppress interfering signals toward out-of-cell mobile stations for a TDD-based OFDMA system are introduced. First, the downlink beamforming weights are optimally designed based on iteration. Then, the downlink beamforming weights are designed in a sub-optimal way. It is shown that the sub-optimally designed downlink beamforming weights have the same structure as that of the uplink beamforming weights which are derived based on MMSE. The performance of these schemes is compared based on the average receive SINR. The performance of a heuristic scheme which exploits uplink beamforming weights for downlink beamforming weights is also investigated.
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  • Huanfei MA, Haibin KAN, Hideki IMAI
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 671-674
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    Construction of quaternion design for Space-Time-Polarization Block Codes (STPBCs) is a hot but difficult topic. This letter introduces a novel way to construct high dimensional quaternion designs based on any existing low dimensional quaternion orthogonal designs(QODs) for STPBC, while preserving the merits of the original QODs such as full diversity and simple decoding. Furthermore, it also provides a specific schema to reach full diversity and maximized code gain by signal constellation rotation on the polarization plane.
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  • Daegun OH, Jong-Wha CHONG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 675-678
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In this paper, we propose a novel search and selection method for spreading code set of UWB system and apply it to IEEE 802.15.4a IR-UWB system. To find a spreading code with low spectral peak to average ratio (SPAR) and good auto-correlation property, the proposed method searches spreading codes in the frequency domain based on the time-frequency relation of the spreading code. Using evaluation parameters, we selected the code set which had SPAR reduced about 1.1079dB, Golay merit factor (GMF) improved by 49% and almost the same modified Golay merit factor (MGMF) compared to the code set used as preambles for IR-UWB system.
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  • Jie XU, Ling QIU
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 679-682
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In this letter, we propose a novel singular value decomposition zero-forcing beamforming (SVD-ZFBF) relaying scheme in the multiuser downlink MIMO broadcasting channel with fixed relays. Based on the processing scheme, we apply SUS [5] to select users at the relay station (RS) and develop a joint power allocation strategy at the base station (BS) and RS. By increasing the power at RS or selecting active users to obtain more multiuser diversity, SVD-ZFBF can approach an upper bound and outperform SVD-ZFDPC [1] with much lower complexity. Moreover, we show that the noise power ratio of RS to users significantly impacts the performance.
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  • Huan SUN, Sheng MENG, Yan WANG, Xiaohu YOU
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 683-686
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In this paper, the multi-user multiple-input multiple-output (MU-MIMO) relay channel is investigated, where the source node provides multi-beams to multi-users via a multi-antenna relay node. In this scenario, linear processing matrix at the relay node is designed around block diagonal (BD) scheme to improve the system sum-rate. Compared with the traditional linear processing matrix with zero-forcing (ZF) scheme at the relay node, the proposed matrix based on BD scheme can not only eliminate the multi-user interference to the same extent as the ZF scheme, but also realize optimal power allocation at the relay node. Numerical simulations demonstrate the BD scheme outperforms the ZF scheme and can significantly improve the sum-rate performance.
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  • Lei WANG, Dongweon YOON, Sang Kyu PARK
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 2 Pages 687-690
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    In order to reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals over fading channels, the selected mapping (SLM) scheme and channel estimation technique can be used. Because of the side information of SLM, however, the data rate decreases in the conventional transmission method. In this letter, to overcome this impairment, we propose a technique which transmits side information by using pilot tones. Numerical analysis and computer simulations show that this method can maintain the PAPR reduction ability of SLM while improving error performance.
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  • Xiaobo DENG, Yiming PI, Zhenglin CAO
    Article type: LETTER
    Subject area: Sensing
    2009 Volume E92.B Issue 2 Pages 691-694
    Published: February 01, 2009
    Released on J-STAGE: February 01, 2009
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    A new constant false alarm rate (CFAR) detection scheme based on the goodness-of-fit (GoF) test is proposed to deal with the problem of extended object detection in high resolution synthetic aperture radar (SAR) images. The performance of this detector is compared with that of the traditional detectors using the MSTAR database. Results show that the proposed detector is superior to the traditional detectors in controlling false alarms in nonhomogeneous environment where boundaries widely exist.
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