IEICE Transactions on Communications
Online ISSN : 1745-1345
Print ISSN : 0916-8516
E91.B 巻, 2 号
選択された号の論文の48件中1~48を表示しています
Regular Section
  • Satoshi NARIKAWA, Hiroaki SANJOH, Naoya SAKURAI, Kiyomi KUMOZAKI
    原稿種別: PAPER
    専門分野: Fiber-Optic Transmission for Communications
    2008 年 E91.B 巻 2 号 p. 399-408
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル フリー
    We describe the transmission characteristics of a wavelength independent wavelength division multiplexing passive optical network (WDM-PON) based on a wavelength channel data rewriter (WCDR). The WCDR is composed of a linear amplifier (LA) and a saturated semiconductor optical amplifier (SOA), and by using the WCDR in optical network units (ONUs), we can erase the downstream signal and modulate the same wavelength channel with the upstream signal. In this paper, we analyze the data rewriting characteristic, the frequency chirp characteristic and the bit error rate (BER) degradation occasioned by the use of saturated SOAs. Furthermore, we report high-speed transmission with power penalty of less than 1dB at bit rates of 1.25Gbit/s, 2.5Gbit/s and 10Gbit/s for downstream signals and 1.25Gbit/s for upstream signals after transmission through 40km of single-mode fiber.
  • Masayuki MORITA, Hideki TODE, Koso MURAKAMI
    原稿種別: PAPER
    専門分野: Fiber-Optic Transmission for Communications
    2008 年 E91.B 巻 2 号 p. 409-417
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    An important issue in the realization of optical packetswitched (OPS) networks is the resolution of packet contention caused by the lack of RAM-like optical buffering. Although an optical buffer using fiber delay lines (FDLs) has been proposed, its capacity is extremely limited. There have been several studies of this problem. One approach is deflection routing, which is widely used in electronic packet-switched networks or optical burst-switched (OBS) networks. However, in OPS networks, packet lengths are short, so that the speed requirement for route lookup is very stringent. If the network topology is geometric, such as a Manhattan Street Network (MSN), hop-by-hop routing can be implemented by simple optical logic devices without an electronic routing table. However, if the topology is not geometric, it is hard to implement deflection routing electronically or optically. Another approach is reflection routing, which is easy to implement but has a higher probability of packet loss than does deflection routing. In this paper, we propose a packet contention resolution scheme, reflection-based deflection routing, which is based on reflection routing and enables switching the reflected packet to an alternate path if its primary path remains congested. Our method alleviates the time limitation on setting an alternate path by making use of the packet reflection latency and also reduces the probability of packet loss. We evaluate the performance of the proposed method by simulation experiments and show its effectiveness.
  • Yasuhiro YAMASAKI, Hideyuki SHIMONISHI, Tutomu MURASE
    原稿種別: PAPER
    専門分野: Network
    2008 年 E91.B 巻 2 号 p. 418-427
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    The advent of various quality-sensitive applications has greatly changed the requirements for IP network management and made the monitoring of individual traffic flows more important. Since the processing costs of per-flow quality monitoring are high, especially in high-speed backbone links, packet sampling techniques have been attracting considerable attention. Existing sampling techniques, such as those used in Sampled NetFlow and sFlow, however, focus on the monitoring of traffic volume, and there has been little discussion of the monitoring of such quality indexes as packet loss ratio. In this paper we propose a method for estimating, from sampled packets, packet loss ratios in individual TCP sessions. It detects packet loss events by monitoring duplicate ACK events raised by each TCP receiver. Because sampling reveals only a portion of the actual packet loss, the actual packet loss ratio is estimated statistically. Simulation results show that the proposed method can estimate the TCP packet loss ratio accurately from a 10% sampling of packets.
  • Chee-Onn CHOW, Hiroshi ISHII
    原稿種別: PAPER
    専門分野: Network
    2008 年 E91.B 巻 2 号 p. 428-436
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    Video multicast over wireless medium has gained increasing popularity in a wide range of applications, such as video-on-demand and group video conferencing. With mobile ad hoc networks emerging as a promising solution for future ubiquitous communications, supporting reliable video multicast over mobile ad hoc networks is a timely research topic. In this paper we tackle this issue by using multiple tree multicast routing protocol. Specifically, we introduce an extension to the Multicast Ad Hoc On-demand Distance Vector (MAODV) routing protocol to construct two optimally disjoint trees in a single routine. The extended protocol is called Multiple Tree Multicast Ad Hoc On-demand Distance Vector (MT MAODV) routing protocol. In order to distribute the video evenly and independently between these disjoint trees, the Multiple Description Coding (MDC) scheme is used for video coding. Simulation shows that the proposed protocol demonstrates video multicast with better quality than the conventional video multicast using a single tree only.
  • Masaki AIDA, Chisa TAKANO, Masayuki MURATA, Makoto IMASE
    原稿種別: PAPER
    専門分野: Network Management/Operation
    2008 年 E91.B 巻 2 号 p. 437-445
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    Recently problems with commercial IP telephony systems have been reported one after another, in Japan. One of the important causes is congestion in the control plane. It has been recognized that with the current Internet it is important to control not only congestion caused by overload of the data plane but also congestion caused by overload of the control plane. In particular, “retry traffic,” such as repeated attempts to set up a connection, tends to cause congestion. In general, users make repeated attempt to set up connections not only when the data plane is congested but also when the control plane in the network is overloaded. The latter is caused by user behavior: an increase in the waiting time for the processing of connection establishment to be completed tends to increase his or her initiation of reattempts. Thus, it is important to manage both data plane and control-plane resources effectively. In this paper, we focus on RSVP-based communication services including IP telephony, and introduce a model that takes account of both data-plane and control-plane systems, and we examine the behavior of retry traffic. In addition, we compare the system stability achieved by two different resource management methods, the hard-state method and the soft-state method.
  • Gagik MKRTCHYAN, Katsuhiro NAITO, Kazuo MORI, Hideo KOBAYASHI
    原稿種別: PAPER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 446-458
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    Multi-carrier code division multiple access (MC-CDMA) has been considered as one of the promising techniques for the next generation of mobile communication systems because of its efficient bandwidth usage, robustness to the multi-path fading and simple channel-sharing scheme. However, MC-CDMA cannot be employed in the uplink communication where the transmitted signal from each user propagates through the different multi-path fading channel, and the received signals are no longer orthogonal at the base station. As a result, bit error rate (BER) performance in the uplink MC-CDMA communication would be strongly degraded due to the occurrence of multi-user interference (MUI). To solve the MUI problem in the uplink MC-CDMA, the pre-equalization method was proposed in which the uplink signal is pre-equalized at the user terminal by using the channel response estimated from the downlink. Although the pre-equalization method is very effective for the stationary uplink channel with fixed users, it is hard to be employed in the time varying fading channel with mobile users, because there is a big difference in the channel responses between downlink and uplink. For the efficient MUI compensation, each user terminal would be required to predict the future channel conditions based on the current observation. This paper proposes a method for model based uplink channel response prediction by employing the spectral decomposition of the downlink channel impulse response. Computer simulation results show that the proposed method can achieve the accurate prediction of channel response for mobile users during the uplink transmission and allows the effective MUI compensation.
  • Kenichi KOBAYASHI, Takao SOMEYA, Tomoaki OHTSUKI, Sigit P. W. JAROT, T ...
    原稿種別: PAPER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 459-465
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    Multiple-Input Multiple-Output (MIMO) systems that realize high-speed data transmission with multiple antennas at both transmitter and receiver are drawing much attention. In line-of sight (LOS) environments, the performance of MIMO systems depends largely on the difference of the phase difference of direct paths from transmit antennas to each receive antenna. When the phase difference of direct paths are close to each other, the spatial division multiplexing (SDM) channels are not orthogonal to each other so signal detection becomes difficult. In this paper, we propose a MIMO system with relative phase difference time-shift modulation (RPDTM) in Rician fading environments. The proposed scheme transmits independent signals from each antenna at each time slot where the relative phase difference between signal constellations used by transmit antennas varies in a pre-determined pattern. This transmission virtually changes the phase difference of direct paths from transmit antennas to each receive antenna without lowering data rate and without knowledge of the channels. In addition, forward error correction coding (ECC) is applied to exploit the time slots where the receiver can detect the signals easily to improve the detection performance. If there are time slots where the receiver can separate the received signal, the receiver can decode the data by using the time slots and the correlation between data. From the results of computer simulation, we show that MIMO system with RPDTM can achieve the better bit error rate (BER) than the conventional MIMO system. We also show that the MIMO system with RPDTM is effective by about Rician factor K=10dB.
  • Franco CHIARALUCE, Ennio GAMBI, Giorgia RIGHI
    原稿種別: PAPER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 466-478
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    This paper extends previous analytical approaches for the study of CDMA systems to the relevant case of multipath environments where users can operate at different bit rates. This scenario is of interest for the Wideband CDMA strategy employed in UMTS, and the model permits the performance comparison of classic and more innovative spreading signals. The method is based on the characteristic function approach, that allows to model accurately the various kinds of interferences. Some numerical examples are given with reference to the ITU-R M. 1225 Recommendations, but the analysis could be extended to different channel descriptions.
  • Yoshitaka HARA, Kazuyoshi OSHIMA
    原稿種別: PAPER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 479-487
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    This paper proposes a new partial channel state information (CSI) reporting method for spatial scheduling in TDD/MIMO systems. In the proposed method, a terminal transmits pilot signals using transmit beams which have large channel gains between the base station (BS) and the terminal. Then, the BS can obtain partial CSI through responses of the pilot signals. Furthermore, adaptive allocation of pilot signals is proposed, in which pilot signals for CSI reporting are adaptively allocated to terminals depending on the number of terminals. We evaluate system throughput of spatial scheduling under the partial CSI reporting from multiple terminals. Numerical results show that the proposed method reduces uplink signalling for CSI reporting effectively, keeping high system throughput of spatial scheduling.
  • Yong-Seok KIM
    原稿種別: PAPER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 488-493
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    In this paper, we consider a method to enhance the throughput of HSDPA systems in the mixed traffic scenario. A channel-dependent adaptive delay barrier (DB) function is proposed to maximize throughput of best-effort (BE) traffic while satisfying the delay latency of voice over internet protocol (VoIP) service. Simulations show that the proposed channel-adaptive DB function raises the throughput of BE traffic service by 30% compared to the conventional scheme, without degrading the capacity of VoIP service over HSDPA system.
  • Maung SANN MAW, Iwao SASASE
    原稿種別: PAPER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 494-504
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    In the subcarrier and power allocation schemes in Multi-Input Multi-Output and Orthogonal Frequency Division Multiple Access (MIMO-OFDMA) systems, only equal fairness among users has been considered and no scheme for proportional data rate fairness has been considered. In this paper, a subcarrier, bit and power allocation scheme is proposed to maximize the total throughput under the constraints of total power and proportional data rate fairness among users. In the proposed scheme, joint subchannel allocation and adaptive bit loading is firstly performed by using singular value decomposition (SVD) of channel matrix under the constraint of users' data throughput requirements, and then adaptive power loading is applied. Simulation results show that effective performance of the system has been improved as well as each throughput is proportionally distributed among users in MIMO-OFDMA systems.
  • Quoc Tuan TRAN, Shinsuke HARA, Kriangsak SIVASONDHIVAT, Jun-ichi TAKAD ...
    原稿種別: PAPER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 505-517
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    The combination of Multiple-Input Multiple-Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) technologies gives wireless communications systems the advantages of lower bit error rate (BER) and higher data rate in frequency-selective fading environments. However, the main drawbacks of MIMO systems are their high complexity and high cost. Therefore, antenna selection in MIMO systems has been shown to be an effective way to overcome the drawbacks. In this paper, we propose two receive antenna selection methods for a MIMO-OFDM system with radio frequency (RF) switches and polarization antenna elements at the receiver side, taking into consideration low computational complexity. The first method selects a set of polarization antenna elements which gives lower correlation between received signals and larger received signal power, thus achieves a lower BER with low computational complexity. The second method first selects a set of polarization antenna elements based on the criterion of the first method and another set of polarization antenna elements based on the criterion of minimizing the correlation between the received signals; it then calculates the signal-to-interference-plus-noise power ratio (SINR) of the two sets and selects a set with larger SINR. As a result, the second method achieves a better BER than the first one but it also requires higher computational complexity than the first one. We use the measured channel data to evaluate the performance of the two methods and show that they work effectively for the realistic channel.
  • Ryosuke FUJIWARA, Akira MAEKI, Kenichi MIZUGAKI, Goichi ONO, Tatsuo NA ...
    原稿種別: PAPER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 518-526
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    A direct-sequence ultra-wideband impulse radio (DSUWB-IR) system is developed for low-power wireless applications such as wireless sensor networks. This system adopts impulse radio characterized by a low duty cycle, and a direct-sequence 0.7-GHz bandwidth, which enables low-power operation and extremely precise positioning. Simulation results reveal that the system achieves a 250-kbps data rate for 30-mdistance wireless communications using realistic specifications. We also conduct an experiment that confirms the feasibility of our system.
  • A. K. M. BAKI, Kozo HASHIMOTO, Naoki SHINOHARA, Tomohiko MITANI, Hiros ...
    原稿種別: PAPER
    専門分野: Antennas and Propagation
    2008 年 E91.B 巻 2 号 p. 527-535
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    The Earth will require sustainable electricity sources equivalent to 3 to 5 times the commercial power presently produced by 2050. Solar Power Satellite (SPS) is one option for meeting the huge future energy demand. SPS can send enormous amounts of power to the Earth as the form of microwave (MW). A highly efficient microwave power transmission (MPT) system is needed for SPS. A critical goal of SPS is to maintain highest Beam Efficiency (BE) because the microwaves from SPS will be converted to utility power unlike the MW from communication satellites. Another critical goal of SPS is to maintain Side Lobe Levels (SLL) as small as possible to reduce interference to other communication systems. One way to decrease SLL and increase BE is the edge tapering of a phased array antenna. However, tapering the excitation requires a technically complicated system. Another way of achieving minimum SLL is with randomly spaced element position but it does not guarantee higher BE and the determination of random element position is also a difficult task. Isosceles Trapezoidal Distribution (ITD) edge tapered antenna was studied for SPS as an optimization between full edge tapering and uniform amplitude distribution. The highest Beam Collection Efficiency (BCE) and lowest SLL (except maximum SLL) are possible to achieve in ITD edge tapering and ITD edge tapered antenna is technically better. The perfor-mance of ITD is further improved from the perspective of both Maximum Side Lobe Level (MSLL) and BE by using unequal spacing of the antenna elements. A remarkable reduction in MSLL is achieved with ITD edge tapering with Unequal element spacing (ITDU). BE was also highest in ITDU. Determination of unequal element position for ITDU is very easy. ITDU is a newer concept that is experimented for the first time. The merits of ITDU over ITD and Gaussian edge tapering are discussed.
  • Hiroaki TSUCHIYA, Navarat LERTSIRISOPON, Jun-ichi TAKADA, Takehiko KOB ...
    原稿種別: PAPER
    専門分野: Antennas and Propagation
    2008 年 E91.B 巻 2 号 p. 536-542
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    In this paper, the effects of Bragg scattering on ultra-wideband (UWB) signal transmission from periodic surfaces are reported. First, the frequency dispersive property of Bragg scattering is theoretically and experimentally confirmed. Next, the transfer function of both specular path and Bragg scattering are extracted. Then direct sequence UWB (DS-UWB) transmission simulations are conducted by using a raised cosine pulse that occupied 3.1 to 10.6GHz and a Gaussian pulse that occupied 8.75 to 9.25GHz. Finally, the effects of Bragg scattering on UWB systems are discussed.
  • Amir ZAIMBASHI, Mohammad Reza TABAN, Mohammad Mehdi NAYEBI
    原稿種別: PAPER
    専門分野: Sensing
    2008 年 E91.B 巻 2 号 p. 543-552
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    In Distributed detection systems, restricting the output of the local decision to one bit certainly implies a substantial information loss. In this paper, we consider the fuzzy detection, which uses a function called membership function for mapping the observation space of each local detector to a value between 0 and 1, indicating the degree of assurance about presence or absence of a signal. In this case, we examine the problem of distributed Maximum Likelihood (ML) and Order Statistic (OS) constant false alarm rate (CFAR) detections using fuzzy fusion rules such as “Algebraic Product” (AP), “Algebraic Sum” (AS), “Union” (Un) and “Intersection” (IS) in the fusion centre. For the Weibull clutter, the expression of the membership function based on the ML or OS CFAR processors in the local detectors is also obtained. For comparison, we consider a binary distributed detector, which uses the Maximum Likelihood and Algebraic Product (MLAP) or Order Statistic and Algebraic Product (OSAP) CFAR processors as the local detectors. In homogenous and non homogenous situations, multiple targets or clutter edge, the performances of the fuzzy and binary distributed detectors are analyzed and compared. The simulation results indicate the superior and robust performance of the distributed systems using fuzzy detection in the homogenous and non homogenous situations.
  • Chow-Sing LIN, Fang-Zhi YEN
    原稿種別: PAPER
    専門分野: Multimedia Systems for Communications
    2008 年 E91.B 巻 2 号 p. 553-561
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    With the rapid advances in wireless network communication, multimedia presentation has become more applicable. However, due to the limited wireless network resource and the mobility of Mobile Host (MH), QoS for wireless streaming is much more difficult to maintain. How to decrease Call Dropping Probability (CDP) in multimedia traffic while still keeping acceptable Call Block Probability (CBP) without sacrificing QoS has become an significant issue in providing wireless streaming services. In this paper, we propose a novel Dynamic Resources Adjustment (DRA) algorithm, which can dynamically borrow idle reserved resources in the serving cell or the target cell for handoffing MHs to compensate the shortage of bandwidth in media streaming. The experimental simulation results show that compared with traditional No Reservation (NR), and Resource Reservation in the six neighboring cells (RR-nb), and Resource Reservation in the target cell (RR-t), our proposed DRA algorithm can fully utilize unused reserved resources to effectively decrease the CDP while still keeping acceptable CBP with high bandwidth utilization.
  • Jung-Chieh CHEN, Cheng-Hsuan WU, Yao-Nan LEE, Chao-Kai WEN
    原稿種別: LETTER
    専門分野: Fundamental Theories for Communications
    2008 年 E91.B 巻 2 号 p. 562-566
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    Inspired by the success of the low-density parity-check (LDPC) codes in the field of error-control coding, in this paper we propose transforming the downlink multiuser multiple-input multiple-output scheduling problem into an LDPC-like problem using the normal graph. Based on the normal graph framework, soft information, which indicates the probability that each user will be scheduled to transmit packets at the access point through a specified angle-frequency sub-channel, is exchanged among the local processors to iteratively optimize the multiuser transmission schedule. Computer simulations show that the proposed algorithm can efficiently schedule simultaneous multiuser transmission which then increases the overall channel utilization and reduces the average packet delay.
  • June HWANG, Seong-Lyun KIM
    原稿種別: LETTER
    専門分野: Fundamental Theories for Communications
    2008 年 E91.B 巻 2 号 p. 567-571
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    In this Letter, we investigate the correlation rate of a random sequence data set which is collected by RFID (Radio Frequency IDen-tification) readers in an indoor location. Using a passive RFID tag introduces reading error, which causes a loss of original data. From the question of how sensing errors of RFID readers affect the location prediction algorithm used for context awareness services at home, we analyze the correlation rate of a collected data set with respect to RFID reader-sensing error rate. Through our analysis, we conclude that the prediction accuracy can be better or worse than the one of the original data streams according to the error rate. We suggest that the reader specification has to be satisfied by the error boundary which is found in this work for the tolerant location prediction.
  • Takuma NISHIMOTO, Kiichi YAMASHITA, Kenichi OHHATA
    原稿種別: LETTER
    専門分野: Devices/Circuits for Communications
    2008 年 E91.B 巻 2 号 p. 572-574
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    A sandwich structure type RF-MEMS variable capacitor is proposed, that consists of a movable middle plate, and fixed top and bottom plates having different areas. Simulation results show that the proposed capacitor can operate at a control voltage of less than 3.2V; it achieves a tuning range of 4.8:1 (capacitance: 630-130fF) in the range of 0 to 3.2V and at a frequency of 7.5GHz.
  • David ASANO, Mao OHARA
    原稿種別: LETTER
    専門分野: Devices/Circuits for Communications
    2008 年 E91.B 巻 2 号 p. 575-578
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    In this paper, an automatic identification method based on frequency discrimination is proposed. The proposed method can be used when the received signal is a constant envelope modulation scheme. To test the proposed method PSK and FSK are considered. Using computer simulations, the performance of the proposed method was evaluated and found to be able to distinguish between PSK and FSK well even in the presence of noise.
  • Tae-Won OH, Hak-Kyu LEE, Chang-Hee LEE
    原稿種別: LETTER
    専門分野: Fiber-Optic Transmission for Communications
    2008 年 E91.B 巻 2 号 p. 579-580
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    We demonstrate a wavelength division multiplexing passive optical network (WDM-PON) based on wavelength-locked Fabry-Pérot laser diodes and thin-film filters. Twelve Fast Ethernet signals are bi-directionally transmitted over the multi-branch optical distribution network (ODN). The ODN has distributed branch nodes and bus networks.
  • Changho YUN, Kiseon KIM
    原稿種別: LETTER
    専門分野: Fiber-Optic Transmission for Communications
    2008 年 E91.B 巻 2 号 p. 581-584
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    A new load balanced channel sharing method (CSM), namely Heuristic Traffic Load Balanced (HTLB) CSM, is proposed for metro-wavelength division multiple access (WDMA) networks. In particular, HTLB CSM is designed to be effective for pre-allocation based medium access control (MAC) protocols by balancing traffic loads corresponding to pre-assigned destinations per time slot. As a result, HTLB CSM is shown to provide lower time complexity than the well-known sub-optimal load balanced CSM, MULTIFIT CSM. Furthermore, the Jain Index of the HTLB CSM is shown to be higher and more consistent than the MULTIFIT CSM and other pre-fixed CSMs under diverse traffic conditions.
  • Man-Soo HAN
    原稿種別: LETTER
    専門分野: Fiber-Optic Transmission for Communications
    2008 年 E91.B 巻 2 号 p. 585-588
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    We suggest a dual thresholds method for the dynamic bandwidth allocation in EPON. In the suggested method, a buffer in ONU has two thresholds and ONU generates a normal request and a greedy request based on the two thresholds. Also, OLT estimates the overall traffic load and grants the greedy request when estimated traffic is light. We study upstream channel resource wastage and show the suggested method decreases the upstream channel resource wastage. Using simulation, we validate the dual thresholds method is superior to the existing methods in the mean delay.
  • Jun Young JEONG, Je-Myung JEONG
    原稿種別: LETTER
    専門分野: Switching for Mobile Communications
    2008 年 E91.B 巻 2 号 p. 589-592
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    We propose an asynchronous variable-length optical packet switch that is based on a packet compression scheme and delay-line loop buffers, and evaluate the packet loss probability of the proposed switch through simulation and analysis. Simulation results well the analytical results and show the accuracy of our analysis. When the packet compression ratio is low, optical packet interval regulators are useful to improve the packet loss probability characteristics.
  • Myoungju YU, Jongmin LEE, Tai-Won UM, Won RYU, Byung Sun LEE, Seong Go ...
    原稿種別: LETTER
    専門分野: Switching for Mobile Communications
    2008 年 E91.B 巻 2 号 p. 593-596
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    We propose a new mobility management scheme using Label Switched Path (LSP) of Multi Protocol Label Switching (MPLS) for seamless service in Broadband Convergence Network (BcN) in Korea, and verify that the proposed scheme has lower latency time than the existing ones through the separation of control plane from data plane for handover signaling.
  • Sangkyung KIM, Noyeul PARK, Changhwa KIM, Seung-sik CHOI
    原稿種別: LETTER
    専門分野: Network
    2008 年 E91.B 巻 2 号 p. 597-600
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    In case of link failures, many ad hoc routing protocols recover a route by employing source-initiated route re-discovery, but this approach can degrade system performance. Some use localized route recovery, which may yield non-optimal paths. Our proposal provides a mechanism that can enhance the overall routing performance by initiating route recovery at the destination node. We elucidate the effects through simulations including comparisons with AODV and AODV with local repair.
  • Yong LEE, Goo-Yeon LEE, Hwa-long KIM
    原稿種別: LETTER
    専門分野: Network
    2008 年 E91.B 巻 2 号 p. 601-604
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    Due to the proliferation of mobile devices connected to the Internet, implementing a secure and practical Mobile IP has become an important goal. A mobile IP can not work properly without authentication between the mobile node (MN), the home agent (HA) and the foreign agent (FA). In this paper, we propose a practical Mobile IP authentication protocol that uses public key cryptography only during the initial authentication. The proposed scheme is compatible with the conventional Mobile IP protocol and provides scalability against the number of MN's. We also show that the proposed protocol offers secure operation.
  • Jaeduck CHOI, Souhwan JUNG
    原稿種別: LETTER
    専門分野: Network
    2008 年 E91.B 巻 2 号 p. 605-608
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    This letter proposes a secure and efficient handover authentication scheme that requires a light-weight Diffie-Hellman operation at mobile nodes. Our scheme provides more enhanced securities like the PFS, PBS, and so on than the existing security-context-transfer schemes. Also, the mobile node delegates the exponent operation for the DH to the access router to reduce computational cost on it.
  • Yang-Ick JOO, Yeonwoo LEE
    原稿種別: LETTER
    専門分野: Network
    2008 年 E91.B 巻 2 号 p. 609-612
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    Energy-efficient transmission scheme is very essential for Wireless Personal Area Networks (WPNs) for maximizing the lifetime of energy-constrained wireless devices and assuring the required QoS in the actual physical transmission at each allocated TDMA time slot. We therefore propose the minimum energy (ME) criterion based adaptive transmission scheme which determines the optimum combination of transmit power, physical data rate and fragment size required to simultaneously minimize the energy consumption and satisfy the required QoS in each assigned time duration. The improved performances offered by the proposed algorithm are demonstrated via computer simulation in terms of throughput and energy consumption.
  • Insoo HWANG, Cheolwoo YOU, Dongho KIM, Yungsoo KIM, Vahid TAROKH
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 613-617
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    We propose a new broadcast strategy for a multiple-input multiple-output (MIMO) system with N transmit antennas at the transmitter and MN single antenna receivers. The proposed method, based on dirty-paper coding (DPC), spatially separates the M users but does not suffer from the power loss of classical spatial division multiple access (SDMA). For the special case of M=N=2 and when the two single antenna receivers are assumed to be co-located, the proposed scheme produces a 2 transmit, 2 receiver antenna MIMO transmission system that doubles the symbol rate of MIMO space-time block code (STBC) systems from one to two symbol per transmission time. It is proved theoretically and experimentally that the proposed scheme provides the same performance level as that of MIMO STBC systems (i. e., the Alamouti scheme) for the first symbol, and the same performance as the Bell labs layered space-time (BLAST) system for the second symbol. When compared to the BLAST system, the proposed scheme has the same symbol rate, but achieves significantly better performance, since it provides 2 level diversity per symbol on the first symbol while the BLAST system does not provide any diversity.
  • Sunwoo KIM
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 618-621
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    This letter considers multiuser time delay estimation in a sparse channel environment for radiolocation. The generalized successive interference cancellation (GSIC) algorithm is used to eliminate the multiple access interference (MAI). To adapt GSIC to sparse channels the alternating maximization (AM) algorithm is considered, and the continuous time delay of each path is estimated without requiring a priori known data sequences.
  • Xiao-lin CHE, Chen HE, Wen-feng LIN
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 622-627
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    In this letter, a Tomlinson-Harashima precoding (THP) scheme is proposed for the downlink of multiuser MIMO systems with multiple antennas at each receiver. Assuming single data stream communication for each user, joint transmitter and receiver design is done to maximize the signal to noise ratio (SNR) for each user. Furthermore, a heuristic user ordering algorithm is proposed to optimize the encoding order and improve the bit error rate (BER) performance. Simulation results have shown that the proposed approach is superior to some existing precoding schemes.
  • Sangchoon KIM, Jinyoung AN
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 628-632
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    This letter investigates the effects of using multiple transmit antennas on code acquisition for preamble search in the CDMA uplink when MIMO is used for signal transmission and reception. The performance of a ML code acquisition technique in the presence of MIMO channel is analyzed by considering the detection and miss probabilities. The acquisition performance is numerically evaluated on a frequency selective fading channel. It is found that the performance of code acquisition scheme for a SIMO system is better than that for the case of MIMO on the low thresholds in terms of detection performance and MAT.
  • Namseok CHANGE, Gye-Tae GIL, Joonhyuk KANG, Gangyoul YU
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 633-636
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    In this letter, a switched transmission technique is presented that can provide the orthogonal frequency division multiplexing (OFDM) systems with additional diversity gain. The space-time block coding (STBC) and space-frequency block coding (SFBC) are considered for the transmission of the OFDM signals. A proper coding scheme is selected based on the estimated normalized delay spread and normalized Doppler spread. The selection criterion is derived empirically. It is shown through computer simulations that the proposed switching technique can improve the bit error rate (BER) performance of an OFDM system when the corresponding wireless channel has some time variation of time selectivity as well as frequency selectivity.
  • Masaaki FUJII
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 637-640
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    A rate control scheme is described for zero-forcing beamforming (ZFBF) multiuser multiple-input and multiple-output (MU-MIMO) systems with a QR-decomposition maximum likelihood detector (MLD) at the receiver. For selected users, a modulation-and-coding set is selected for each substream by estimating the per-substream post-MLD signal-to-interference-plus-noise ratio. Iterative modified QR-decomposition MLD is employed at the receiver to achieve the throughput expected from the transmitter. The simulation results demonstrated that the proposed rate-control scheme achieved the target packet error rate while increasing the throughout for ZFBF-MU-MIMO systems as the number of user candidates increases.
  • Chang Woo LEE, Hyeonwoo CHO, Sang Woo KIM
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 641-645
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    The collision of ID signals from a large number of colocated passive RFID tags is a serious problem; to realize a practical RFID systems we need an effective anti-collision algorithm. This letter presents an adaptive algorithm to minimize the total time slots and the number of rounds required for identifying the tags within the RFID reader's interrogation zone. The proposed algorithm is based on the framed ALOHA protocol, and the frame size is adaptively updated each round. Simulation results show that our proposed algorithm is more efficient than the conventional algorithms based on the framed ALOHA.
  • Chul KIM, Sang-Heon SHIN, Sang Kyu PARK
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 646-648
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    We present a simple proactive time rearrangement scheme (PATRA) that reduces the interferences from multi-radio devices equipped in one platform and guarantees user-conceived QoS. Simulation results show that the interference among multiple radios in one platform causes severe performance degradation and cannot guarantee the user requested QoS. However, the PATRA can dramatically improve not only the userconceived QoS but also the overall network throughput.
  • Jihyung KIM, Sangho NAM, Dongjun LEE, Jonghan KIM, Jongae PARK, Daesik ...
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 649-652
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    In this letter, we propose a new preamble structure for channel estimation in a MIMO OFDM-based WLAN system. Both backward compatibility with IEEE 802.11a and low overhead are considered in designing the preamble. Simulation results show that the proposed preamble has low overhead and good performance gain for channel estimation.
  • Wei ZHANG, Jun SUN, Xinbing WANG
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 653-657
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    This paper addresses the problem of maximizing the protocol capacity of 802.11e networks, under the assumption that each access category (AC) has the same packet length. We prove that the maximal protocol capacity can be achieved at an optimal operating point with the medium idle probability of e-√2/T*c, where T*c is the duration of collision time in terms of slot unit. Our results indicate that the optimal operating point is independent of the number of stations and throughput ratio among ACs, which means the proposed analytical results still hold even when throughput ratio and station number are time-varying. Further, we show that the maximal protocol capacity can be achieved in saturated cases by properly choosing the protocol parameters. We present a parameter configuration algorithm to achieve both efficient channel utilization and proportional fairness in IEEE 802.11e EDCA networks. Extensive simulation and analytical results are presented to verify the proposed ideas.
  • Inwhee JOE
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 658-661
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    In this paper, we propose a novel MAC protocol with the patterned preamble technique to improve performance in terms of low power, channel utilization, and delay in wireless sensor networks. B-MAC is one of typical MAC protocols for wireless sensor networks using the duty cycle in order to achieve low-power operation. Since it works in an asynchronous fashion, B-MAC employs extended preamble and preamble sampling techniques. Even if it has outstanding performance in idle state, the overhead of these techniques is very large when packets are sent and received, because there is a lot of waste in the traditional preamble method. Instead of the simple preamble, our proposed MAC solution is to introduce more intelligent preamble with some patterns consisting of 2 phases (Tx phase & Ack phase). With this concept we implement real source code working on the mica2 platform with Tinyos-1.x version. Also, the test setup is presented, and the test results demonstrate that the proposed protocol provides better performance in terms of delay compared to B-MAC.
  • Ming LUO, Qinye YIN, Ang FENG
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 662-665
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    We address pilot-aided channel estimation for a flat-fading spatially-correlated MIMO system, which employing Uniform Linear Arrays (ULA) on dual side and working in sparse scattering (multipath) environment. In case of sparse scattering, channel matrix and spatial correlation of flat-fading MIMO systems are parameterized by structure of multipaths, which is represented as Direction of Arrivals (DOAs), Direction of Departures (DODs) and complex path fading of each path. Based on this and block-fading property of channel, we design a channel estimation method via estimating multipath parameters using ESPRIT-like DOA-Matrix method which exploits shift-invariance property of ULA. The proposed method is able to obtain improved Mean-Square-Error performance than Least-Square method without prior information of spatial correlation.
  • Hyounkuk KIM, Hyuncheol PARK
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 666-668
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    This letter deals with computationally efficient maximumlikelihood (ML) detection for the quasi-orthogonal space-time block code (QOSTBC) with four transmit antennas. The proposed ML detector uses a permutation based real-valued equivalent channel matrix representation. As a result, the complexity of ML detection problem is moderated from O(2|A|2) to O(4|A|), where |A| is modulation order. Numerical results show that the proposed ML detector provides ML performance and achieves greatly high computational savings.
  • Chung Ha KOH, Young Yong KIM
    原稿種別: LETTER
    専門分野: Wireless Communication Technologies
    2008 年 E91.B 巻 2 号 p. 669-672
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    Recently, there has been extensive research on resource allocation schemes for multicast services that would satisfy the requirements of multimedia traffic. Although several schemes have been proposed to improve the performance of individual multicast groups, it is not easy to achieve both throughput efficiency and user fairness. In this study, we propose a new multicast scheduling scheme for achieving proportional fair (PF) allocation in wireless cellular systems. The basic idea of PF is to schedule the user whose corresponding instantaneous channel quality is the highest relative to the average channel condition over a given time scale. We first extend the PF metric to the extent that the scheduler can reflect the user's varying channel gain, and fairness, not only in the unicast case, but also in multicast transmissions. A multicast PF scheme maximizes the summation of the logarithmic average rate of all multicasting users. Thus, it improves the fairness to mobile users when compared to max-rate allocation, because the logarithmic rate gives more weight to lower rate users, while achieving high throughput. Moreover, the proposed scheme is less complex than max-rate allocation.
  • Masaaki HARADA, Keiji TANIGUCHI
    原稿種別: LETTER
    専門分野: Terrestrial Radio Communications
    2008 年 E91.B 巻 2 号 p. 673-676
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    The average bit error rate performances of M-ary orthogonal code shift keying (CSK) in Rician fading environments are analyzed in this letter. CSK is a digital modulation scheme that uses a code set as M-ary signals. In CSK, one code is selected from a code set containing M codes according to the information data. A signal is modulated by using this code and the effect of fading can be reduced by applying interleaving to the elements of the codes. In the analysis, the bit error probability is derived in closed form expression by using the Chernoff bound. The analysis results show that the error probability decreases when the code length is increased and that an arbitrarily small error probability is acheved as the code length approaches infinity, provided that Eb/N0 exceeds 1.42dB.
  • Jong Kyu KIM, Jung Su KIM, Hwan Sik YUN, Joon-Hyuk CHANG, Nam Soo KIMT
    原稿種別: LETTER
    専門分野: Multimedia Systems for Communications
    2008 年 E91.B 巻 2 号 p. 677-680
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    This letter presents a novel frame splitting scheme for an error-robust audio streaming over packet-switching networks. In our approach to perceptual audio coding, an audio frame is split into several subframes based on the network configuration such that each packet can be decoded independently at the receiver. Through a subjective comparison category rating (CCR) test, it is discovered that our approach enhances the quality of the decoded audio signal under the lossy packet-switching networks environment.
  • Jungwoo LEE
    原稿種別: LETTER
    専門分野: Multimedia Systems for Communications
    2008 年 E91.B 巻 2 号 p. 681-684
    発行日: 2008/02/01
    公開日: 2010/03/01
    ジャーナル 認証あり
    A single-pass rate control algorithm based on motion estimation error statistics is presented. The algorithm consists of two steps. The first step deals with the target bit allocation for each frame. The complexity measure which determines the target bit allocation is calculated by using the motion estimation error statistics. The second step is to compute the bit spending profile within a frame. A nonlinear profile based on motion estimation statistics is used to allocate bits for each macroblock more efficiently. Experimental results show that the performance in terms of PSNR is significantly improved over a conventional rate control algorithm. Compared to the conventional algorithm, the new algorithm has little added complexity because it uses existing information from motion estimation.
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