IEICE Transactions on Communications
Online ISSN : 1745-1345
Print ISSN : 0916-8516
Volume E93.B, Issue 1
Displaying 1-37 of 37 articles from this issue
Regular Section
  • Ya-Cheng LU, Erl-Huei LU
    Article type: PAPER
    Subject area: Fundamental Theories for Communications
    2010 Volume E93.B Issue 1 Pages 1-8
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    In order to reduce the iterative decoding delay of convolutional turbo codes, this paper presents a concurrent decoding algorithm for the hardware implementation of turbo convolutional decoders. Different than a general turbo code, the hardware turbo decoder based on the proposed algorithm can update the priori information of message for each component code in a bit-by-bit manner as soon as it is generated by the other component code. The two component codes in a turbo code can thus be decoded concurrently, by using a single MAP decoder, subsequently reducing the decoding latency by approximately half while maintaining the bit error rate performance and a comparable hardware complexity, as a general turbo decoder.
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  • Yiheng ZHANG, Qimei CUI, Ping ZHANG, Xiaofeng TAO
    Article type: PAPER
    Subject area: Fundamental Theories for Communications
    2010 Volume E93.B Issue 1 Pages 9-15
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    Dramatic gains in channel capacity can be achieved in the closed-loop MIMO system under the assumption that the base station (BS) can acquire the downlink channel state information (CSI) accurately. However, transmitting CSI with high precision is a heavy burden that wastes a lot of uplink bandwidth, while transmitting CSI within a limited bandwidth leads to the degradation of system performance. To address this problem, we propose a zero-overhead downlink CSI feedback scheme based on the hybrid pilot structure. The downlink CSI is contained in the hybrid pilots at mobile terminal (MT) side, fed back to BS via the uplink pilot channel, and recovered from hybrid pilot at BS side. Meanwhile the uplink channel is estimated based on the hybrid pilot at BS side. Since transmitting the hybrid pilots occupies the same bandwidth as transmitting traditional code division multiplexing based uplink pilots, no extra uplink channel bandwidth is occupied. Therefore, the overhead for downlink CSI feedback is zero. Moreover, the hybrid pilots are formed at MT side by superposing the received analog downlink pilots directly on the uplink pilots. Thus the downlink CSI estimation process is unnecessary at MT side, and MT's complexity can be reduced. Numerical Simulations prove that, the proposed downlink CSI feedback has the higher precision than the traditional feedback schemes while the overhead for downlink CSI feedback is zero.
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  • Umut YUNUS, Hai LIN, Katsumi YAMASHITA
    Article type: PAPER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2010 Volume E93.B Issue 1 Pages 16-21
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    Due to the importance of maintaining the orthogonality among subcarriers, the estimation of carrier frequency offset (CFO) is a crucial issue in orthogonal frequency division multiplexing (OFDM) systems. The CFO estimation becomes complicated in OFDM direct-conversion receivers (DCRs), where additional analog impairments such as I/Q imbalance and time-varying DC offset (TV-DCO) exist. In this paper, we propose a novel joint estimation method for CFO and I/Q imbalance in the presence of TV-DCO. By using the linear property of the TV-DCO and employing a periodic pilot sequence, the desired estimates can be obtained in closed-form. Simulation results confirm the validity of the proposed method.
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  • Ky LENG, Kei SAKAGUCHI, Kiyomichi ARAKI
    Article type: PAPER
    Subject area: Network
    2010 Volume E93.B Issue 1 Pages 22-28
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    The Wireless Sensor Network (WSN) uses autonomous sensor nodes to monitor a field. These sensor nodes sometimes act as relay nodesfor each other. In this paper, the performance of the WSN using fixed relay nodes and Multiple-Input Multiple-Output (MIMO) technology necessary for future wireless communication is evaluated in terms of the channel capacity of the MIMO system and the number of sensor nodes served by the system. Accordingly, we propose an optimum topology for the WSN backbone named Connected Relay Node Double Cover (CRNDC), which can recover from a single fault, the algorithms (exhaustive search and other two approximation methods) to find the optimum distance to place the relay nodes from sink node, and the height of the sink and relay nodes to be placed by using the pathloss model. The performances of different MIMO-WSN configurations over conventional WSN are evaluated, and the direct relationship between relay position and minimum required channel capacity are discovered.
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  • Md. Mustafizur RAHMAN, Choong Seon HONG, Sungwon LEE
    Article type: PAPER
    Subject area: Network
    2010 Volume E93.B Issue 1 Pages 29-39
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    Routing in wireless ad hoc networks is a challenging issue because it dynamically controls the network topology and determines the network performance. Most of the available protocols are based on single-rate radio networks and they use hop-count as the routing metric. There have been some efforts for multirate radios as well that use transmission-time of a packet as the routing metric. However, neither the hop-count nor the transmission-time may be a sufficient criterion for discovering a high-throughput path in a multirate wireless ad hoc network. Hop-count based routing metrics usually select a low-rate bound path whereas the transmission-time based metrics may select a path with a comparatively large number of hops. The trade-off between transmission time and effective transmission range of a data rate can be another key criterion for finding a high-throughput path in such environments. In this paper, we introduce a novel routing metric based on the efficiency of a data rate that balances the required time and covering distance by a transmission and results in increased throughput. Using the new metric, we propose an on-demand routing protocol for multirate wireless environment, dubbed MR-AODV, to discover high-throughput paths in the network. A key feature of MR-AODV is that it controls the data rate in transmitting both the data and control packets. Rate control during the route discovery phase minimizes the route request (RREQ) avalanche. We use simulations to evaluate the performance of the proposed MR-AODV protocol and results reveal significant improvements in end-to-end throughput and minimization of routing overhead.
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  • Chaegwon LIM, Myung-Sun HUH, Chong-Ho CHOI, Gu-Min JEONG
    Article type: PAPER
    Subject area: Network
    2010 Volume E93.B Issue 1 Pages 40-46
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    Recently, bluetooth technology has become widely prevalent so that many laptops and mobile phones are equipped with bluetooth capability. In order to meet the increasing demand to interconnect these devices a new scatternet formation protocol named GBSFP (General Bluetooth Scatternet Formation Protocol) is proposed in this paper. GBSFP is the result of efforts to overcome the two major limitations of the legacy scatternet formation protocols as regards their real implementation, that all of the nodes should be within the Bluetooth communication range or that they should be time synchronized. In GBSFP, a node goes through three phases; 1) the Init phase to establish a bluetooth link to as many of its neighbors as possible, 2) the Ready phase to determine the role of each node, i.e., master or slave, and remove any unnecessary bluetooth links, and 3) the Complete phase to finalize the formation of the scatternet and begin data transmission. The simulation results show that GBSFP provides higher connectivity in many scenarios compared with BTCP and BlueStars.
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  • Takeshi KITAHARA, Hiroki FURUYA, Hajime NAKAMURA
    Article type: PAPER
    Subject area: Internet
    2010 Volume E93.B Issue 1 Pages 47-55
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    Since traffic in IP access networks is less aggregated than in backbone networks, its variance could be significant and its distribution may be long-tailed rather than Gaussian in nature. Such characteristics make it difficult to forecast traffic volume in IP access networks for appropriate capacity planning. This paper proposes a traffic forecasting method that includes a function to control residual error distribution in IP access networks. The objective of the proposed method is to grasp the statistical characteristics of peak traffic variations, while conventional methods focus on average rather than peak values. In the proposed method, a neural network model is built recursively while weighting residual errors around the peaks. This enables network operators to control the trade-off between underestimation and overestimation errors according to their planning policy. Evaluation with a total of 136 daily traffic volume data sequences measured in actual IP access networks demonstrates the performance of the proposed method.
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  • B. A. Hirantha Sithira ABEYSEKERA, Takahiro MATSUDA, Tetsuya TAKINE
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 56-64
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    In the IEEE 802.11 MAC protocol, access points (APs) are given the same priority as wireless terminals in terms of acquiring the wireless link, even though they aggregate several downlink flows. This feature leads to a serious throughput degradation of downlink flows, compared with uplink flows. In this paper, we propose a dynamic contention window control scheme for the IEEE 802.11e EDCA-based wireless LANs, in order to achieve fairness between uplink and downlink TCP flows while guaranteeing QoS requirements for real-time traffic. The proposed scheme first determines the minimum contention window size in the best-effort access category at APs, based on the number of TCP flows. It then determines the minimum and maximum contention window sizes in higher priority access categories, such as voice and video, so as to guarantee QoS requirements for these real-time traffic. Note that the proposed scheme does not require any modification to the MAC protocol at wireless terminals. Through simulation experiments, we show the effectiveness of the proposed scheme.
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  • Lei WANG, Baoyu ZHENG, Qingmin MENG, Chao CHEN
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 65-72
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    Based on Free Probability Theory (FPT), which has become an important branch of Random Matrix Theory (RMT), a new scheme of frequency band sensing for Cognitive Radio (CR) in Direct-Sequence Code-Division Multiple-Access (DS-CDMA) multiuser network is proposed. Unlike previous studies in the field, the new scheme does not require the knowledge of the spreading sequences of users and is related to the behavior of the asymptotic free behavior of random matrices. Simulation results show that the asymptotic claims hold true even for a small number of observations (which makes it convenient for time-varying topologies) outperforming classical energy detection scheme and another scheme based on random matrix theory.
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  • Che-Sheng CHIU, Chia-Chi HUANG
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 73-81
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    A number of inter-cell interference coordination schemes have been proposed to mitigate the inter-cell interference problem for orthogonal frequency division multiple access (OFDMA) systems and among them, partial frequency reuse is considered one of the most promising approaches. In this paper, we propose an inter-cell interference mitigation scheme for an OFDMA downlink system, which makes use of both partial frequency reuse and soft handover. The basic idea of this hybrid scheme is to dynamically select between a partial frequency reuse scheme and a soft handover scheme to provide better signal quality for cell edge users. Compared with the standard partial frequency reuse scheme, simulation results show that approximately one quarter of cell edge users can get improvements in signal quality as well as link spectral efficiency from using the proposed hybrid scheme. We also observe that by using our approach, there is a significant cell edge throughput gain over the standard partial frequency reuse scheme. Furthermore, based on a well defined data rate fairness criterion, we show that our method achieves higher overall system capacity as compared with the standard partial frequency reuse scheme.
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  • Kan ZHENG, Lijie HU, Ling WANG, Wenbo WANG, Lin HUANG
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 82-89
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    Cooperative communication provides a new way of introducing spatial diversity to wireless systems. In order to increase the spectral efficiency of coded cooperative relaying system, the adaptive modulation technique is presented under Rayleigh fading channel in this paper. The source and relay adapt their modulation schemes based on the channel condition of all three links, i.e. source to relay, source to destination and relay to destination. Furthermore, since the available channel knowledge of the source to relay link is usually non-ideal at the destination in practice, a simplified estimation of this link quality is also given. Simulation demonstrates the effectiveness of the proposed technique in improving the data throughput.
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  • Ziyan JIA, Shiro HANDA, Fumihito SASAMORI, Shinjiro OSHITA
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 90-98
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    In this paper, multiple-symbol differential detection (MSDD) is applied to the differential unitary space-time-frequency coding (DUSTFC) scheme over frequency selective fading multiple-input multiple-output (MIMO) channels. The motivation of applying MSDD is to compensate for the performance loss of conventional (two-symbol observation) differential detection comparing with coherent detection, by extending the observation interval and considering the fading autocorrelations. Since the differential coding of DUSTFC can be performed in time or frequency domain, both the time-domain and frequency-domain MSDD are investigated. After calculating the frequency-domain fading autocorrelation, the decision metrics of MSDD considering appropriate fading autocorrelations are derived in time and frequency domain respectively. Bit error rate (BER) performances of the two kinds of MSDD are analyzed by computer simulations. Simulation results demonstrate that a considerable performance gain can be got by applying MSDD in both cases, and the transmit diversity gain can also be enhanced by applying MSDD. So that it is proved that full advantage of transmit diversity with DUSTFC can be taken by applying MSDD.
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  • Hiroshi TOKITO, Masahiro SASABE, Go HASEGAWA, Hirotaka NAKANO
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 99-110
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    Wireless mesh networks have been attracting many users in recent years. By connecting base stations (mesh nodes) with wireless connections, these network can achieve a wide-area wireless environment with flexible configuration and low cost at the risk of radio interference between wireless links. When we utilize wireless mesh networks as infrastructures for Internet access, all network traffic from mobile nodes goes through a gateway node that is directly connected to the wired network. Therefore, it is necessary to distribute the traffic load by deploying multiple gateway nodes. In this paper, we propose a spanning tree construction algorithm for TDMA-based wireless mesh networks with multiple gateway nodes so as to maximize the traffic volume transferred between the mesh network and the Internet (system throughput) by taking account of the traffic load on the gateway nodes, the access link capacity and radio interference. Through a performance evaluation, we show that the proposed algorithm increases the system throughput regardless of the bottleneck position and achieves up to 3.1 times higher system throughput than a conventional algorithm.
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  • YuPeng WANG, KyungHi CHANG
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 111-124
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    In this paper, we analyze the coexistence issues of M-WiMAX TDD and WCDMA FDD systems. Smart antenna techniques are applied to mitigate the performance loss induced by adjacent channel interference (ACI) in the scenarios where performance is heavily degraded. In addition, an ACI model is proposed to capture the effect of transmit beamforming at the M-WiMAX base station. Furthermore, a MCS-based throughput analysis is proposed, to jointly consider the effects of ACI, system packet error rate requirement, and the available modulation and coding schemes, which is not possible by using the conventional Shannon equation based analysis. From the results, we find that the proposed MCS-based analysis method is quite suitable to analyze the system theoretical throughput in a practical manner.
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  • Hiroyuki KAWAI, Akihito MORIMOTO, Kenichi HIGUCHI, Mamoru SAWAHASHI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 125-134
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    This paper investigates the gain of inter-Node B macro diversity for a scheduled-based shared channel using single-carrier FDMA radio access in the Evolved UTRA (UMTS Terrestrial Radio Access) uplink based on system-level simulations. More specifically, we clarify the gain of inter-Node B soft handover (SHO) with selection combining at the radio frame length level (=10msec) compared to that for hard handover (HHO) for a scheduled-based shared data channel, considering the gains of key packet-specific techniques including channel-dependent scheduling, adaptive modulation and coding (AMC), hybrid automatic repeat request (ARQ) with packet combining, and slow transmission power control (TPC). Simulation results show that the inter-Node B SHO increases the user throughput at the cell edge by approximately 10% for a short cell radius such as 100-300m due to the diversity gain from a sudden change in other-cell interference, which is a feature specific to full scheduled-based packet access. However, it is also shown that the gain of inter-Node B SHO compared to that for HHO is small in a macrocell environment when the cell radius is longer than approximately 500m due to the gains from hybrid ARQ with packet combining, slow TPC, and proportional fairness based channel-dependent scheduling.
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  • Juinn-Horng DENG, Jeng-Kuang HWANG
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 135-143
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    Recently, a new multi-carrier CDMA (MC-CDMA) system with cyclic-shift orthogonal keying (CSOK) has been proposed and shown to be more spectral and power efficient than conventional MC-CDMA systems. In this paper, a novel extension called the multiplexed CSOK (MCSOK) MC-CDMA system is proposed to further increase the data rate while maintaining a low peak-to-average power ratio (PAPR). First, the data stream is divided into multiple parallel substreams that are mapped into QPSK-CSOK symbols in terms of cyclic shifted Chu sequences. Second, these sequences are repeated, modulated, summed, and placed on IFFT subcarriers, resulting in a constant-modulus multiplexed signal that preserves the desired orthogonality among substreams. The receiver performs frequency-domain equalization and uses efficient demultiplexing, despreading, and demapping schemes to detect the modulation symbols. Furthermore, an alternate MCSOK system configuration with high link quality is also presented. Simulations show that the proposed MCSOK system attains lower PAPR and BER, as compared to conventional MC-CDMA system using Walsh codes. Under a rich multipath environment, the high link quality configuration exhibits excellent performance with both diversity gain and MCSOK modulation gain.
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  • Ai-ichiro SASAKI, Akinori FURUYA, Mitsuru SHINAGAWA
    Article type: PAPER
    Subject area: Terrestrial Radio Communications
    2010 Volume E93.B Issue 1 Pages 144-153
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    We propose a novel short-range wireless communications technology that uses quasi-static electric fields; it enables data communication between devices separated by up to 10cm via dielectric media at a speed of 10Mbps. It is considered to be a secure wireless technology since communication area is restricted to below about 10cm. To suppress electromagnetic radiation, we adopted a baseband transmission scheme in which the quasi-static electric field is directly modulated by 10BASE-T data signals. Since the spectra of the data signals are concentrated to below 20MHz, the amplitude of the electric field rapidly decreases outside the communication area. This contributes to enhancing security of the communications system. In this paper, we explain a basic principle of the short-range wireless communications technology. Since baseband data signals are carried by the quasi-static electric field, the quality of the communication is easily degraded by the existence of the earth ground. To isolate the communications system from the earth ground, we introduce a novel electro-optic sensor to receive the quasi-static electric field. With the electro-optic sensor, stable data communication is possible at 10Mbps via dielectric materials, such as a wooden table.
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  • Shaoping CHEN, Guangfa DAI, Wengui RAO
    Article type: LETTER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2010 Volume E93.B Issue 1 Pages 154-157
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    This letter deals with the time-domain estimation of time-varying channels in orthogonal frequency-division multiplexing (OFDM) systems. The general complex exponential basis expansion model (GCE-BEM) is used to capture the time variation of the channel within an OFDM block. The design criterion of optimal training for OFDM systems in time-varying channels is derived. This optimal training enables the complete elimination of the interference from data symbols and minimizes the noise effect on channel estimation. The design criterion can be used for both pilot symbol aided modulation (PASM) and superimposed training OFDM systems over time-varying channels.
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  • Keisuke IKUSHIMA, Ryou SOUGEN, Osanori KOYAMA, Makoto YAMADA, Yutaka K ...
    Article type: LETTER
    Subject area: Optical Fiber for Communications
    2010 Volume E93.B Issue 1 Pages 158-161
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    A novel fiber jacket removing system by a CO2 laser has been proposed to realize compact packaging of optical components. It has been clarified experimentally that excess-fiber-free MT connectorization is possible for 4-fiber ribbon.
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  • YoungHwan KWON, Min-Gon KIM, Seong Gon CHOI, Jun Kyun CHOI
    Article type: LETTER
    Subject area: Network
    2010 Volume E93.B Issue 1 Pages 162-165
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    This letter proposes a new multicast traffic control policy in TDM-PON, which differentially classifies multicast flows which have relatively many associated receivers as high-class, and multicast flows which have relatively few associated receivers as low-class. Simulation results confirm that the proposed policy can effectively enhance multicast performance regarding delay and loss, specifically important to multimedia services, compared to the legacy policy.
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  • PyungSoo KIM
    Article type: LETTER
    Subject area: Network
    2010 Volume E93.B Issue 1 Pages 166-169
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    This paper considers a new reactive fast handover MIPv6 (FMIPv6) mechanism to minimize packet loss of the existing mechanism. The primary idea of the proposed reactive FMIPv6 mechanism is that the serving access router buffers packets toward the mobile node (MN) as soon as the link layer between MN and serving base station is disconnected. To implement the proposed mechanism, the router discovery message exchanged between MN and serving access router is extended. In addition, the IEEE 802.21 Media Independent Handover Function event service message is defined newly. Through analytic performance evaluation and experiments, the proposed reactive FMIPv6 mechanism can be shown to minimize packet loss much than the existing mechanism.
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  • Sungsoo KIM, Yonghwan KIM, Kwangseon AHN
    Article type: LETTER
    Subject area: Network
    2010 Volume E93.B Issue 1 Pages 170-173
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    This letter proposes the Inference Algorithm through Effective Slot Allocation (ESA-IA). In ESA-IA, the tags which match the prefix of the reader's request-respond in the corresponding slot; the group of tags with an even number of 1's responds in slot 0, while the group with an odd number of 1's responds in slot 1. The proposed algorithm infers ‘00’ and ‘11’ if there are two collided bits in slot 0, while inferring ‘01’ and ‘10’ if there are two collided bits in slot 1. The ESA-IA decreases the time consumption for tag identification by reducing the overall number of queries.
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  • Wan Yeon LEE, Soo KIM, Heejo LEE, Hyogon KIM
    Article type: LETTER
    Subject area: Internet
    2010 Volume E93.B Issue 1 Pages 174-177
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    Network resiliency has become crucial as the failure of a group of networks happens more frequently, being caused by either natural disasters or malicious attacks. In order to enhance the resiliency of the Internet, we show that changing the evolving strategy is more important than increasing the number of links by multihoming, which connects a single network with two or more links. From the simulation with Internet topologies, it is shown that the resiliency of the Internet can be enhanced by replacing the current evolving strategy only in part.
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  • Chang-Seop PARK
    Article type: LETTER
    Subject area: Internet
    2010 Volume E93.B Issue 1 Pages 178-181
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    Motivated by the fact that the existing FMIPv6 security scheme has several weaknesses in terms of security and efficiency, we propose a security-enhanced fast mobile IPv6 in this letter. Based on the concept of a secret key-based CGA (Cryptographically Generated Address), we show how to establish a new security association between the MN and AR (Access Router) whenever a handover occurs. We also show that the proposed scheme is robust against several types of security attacks feasible with the existing scheme. Our scheme is more efficient in that it requires fewer public key operations.
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  • Peng WANG, Xiaofeng ZHONG, Limin XIAO, Shidong ZHOU, Jing WANG, Yong B ...
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 182-186
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    In this letter, the performance improvement by the deployment of multiple antennas in cognitive radio systems is studied from a system-level view. The term opportunistic spectrum efficiency(OSE) is defined as the performance metric to evaluate the spectrum opportunities that can actually be exploited by the secondary user (SU). By applying a simple energy combining detector, we show that deploying multiple antennas at the SU transceiver can improve the maximum achievable OSE significantly. Numerical results also reveal that the improvement comes from the reduction of both the detection overhead and the false alarm probability.
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  • Bin FAN, Wenbo WANG, Yicheng LIN, Kan ZHENG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 187-191
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    This paper considers the proportional fair (PF) based subcarrier allocation problem in a multihop orthogonal frequency division multiple access (OFDMA) broadcast system with decode-and-forward (DF) relays. The problem is formulated as a mixed binary integer programming problem with the objective to achieve proportional fairness among users and exploit the diversity provided by the independent frequency selective fading among hops. Since it is prohibitive to find the optimal solution, two efficient heuristic schemes are proposed. Simulation results indicate that with the same fairness performance, the proposed schemes achieve considerable capacity gain over the conventional PF scheduling method.
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  • Bin SHENG, Pengcheng ZHU, Xiaohu YOU, Lan CHEN
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 192-194
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    In this letter, we propose a novel sparse channel estimation method for orthogonal frequency division multiplexing (OFDM) systems. The proposed method uses a discrete Fourier transform (DFT)-based technique for channel estimation and a sorted generalized Akaike information criterion (GAIC) to estimate the channel length and tap positions. Simulation results demonstrate that an improved channel estimation performance is obtained due to the reduction of signal space.
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  • Minjoong RIM
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 195-197
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    This paper addresses the relationships between diversity techniques and channel coding rates for OFDM systems. While a low channel coding rates is required if cyclic delay diversity is applied, the necessity of a low channel coding rate is alleviated with space time block coding.
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  • Lilin DAN, Yue XIAO, Wei NI, Shaoqian LI
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 198-202
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    This letter presents an improved peak cancellation (PC) scheme for peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems. The main idea is based on a serial peak cancellation (SPC) mode for alleviating the peak regrowth of the conventional schemes. Based on the SPC mode, two particular algorithms are developed with different tradeoff between PAPR and computational complexity. Simulation shows that the proposed scheme has a better tradeoff among PAPR, complexity and signal distortion than the conventional schemes.
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  • Chung Ha KOH, Kang Jin YOON, Kyungmin PARK, Young Yong KIM
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 203-206
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    Femto cell systems have been the one of the key technologies for ubiquitous networks, and some of them are already serviced by manufacturers. Femto base stations are deployed randomly and without pre-planning, so the femto system has a wider variation in topology than cellular networks. Therefore, a specialized resource assignment algorithm is essential for efficient performance of the femto cell. In this paper, we propose a realtime channel assignment algorithm for adapting to the varying environments, including new cell deployment or power switch off. Our algorithm is a form of a sequential graph coloring problem which outperforms other fixed allocation algorithms. Simulation results show realtime assignment has better performance than the fixed allocation when the wireless environment changes faster than the tracking operation time.
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  • Dengbao DU, Jintao WANG, Jun WANG, Ke GONG, Zhixing YANG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 207-210
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    A differential inter-symbol interference (ISI) cancellation method for time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) systems is proposed. The differential output of an OFDM system can greatly reduce the impact of ISI in the frequency domain and it constructs a convolutional structure, thus the Viterbi decoding algorithm can be used to recover the transmitted information from the output signal. Simulation results show the effectiveness of the proposed method.
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  • Su HU, Gang WU, Teng LI, Yue XIAO, Shaoqian LI
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 211-214
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    In conventional preamble based channel estimation in OFDM/offset QAM (OFDM/OQAM) system, both the even index subcarriers and the odd index subcarriers are with identical value selected from {±1} respectively to avoid inter-carrier interference (ICI), if and only if channel frequency response in neighbor few subcarriers remain invariable. However, it requires larger coherent bandwidth. In this paper, we propose an effective preamble design with ICI cancellation for channel estimation in OFDM/OQAM system. With this structure, we only utilize even (or odd) index of subcarriers as reference signal to avoid ICI, and then the channel information of remaining subcarriers can be estimated by the interpolation approach. Based on the sampling theorem, the mean square error (MSE) performance of the proposed preamble design is analyzed, where channel estimation performance is same for all subcarriers. Simulation and analytical results demonstrate that the proposed preamble design with ICI cancellation method outperforms the conventional one in term of channel estimation accuracy in OFDM/OQAM system.
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  • Chia-Chun HUNG, Ching-Tai CHIANG, Shyh-Neng LIN, Rong-Ching WU
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 215-218
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    A simple closed-form approximation for the outage capacity of Transmit Antenna Selection/Maximal-Ratio Combining (TAS/MRC) systems over independent and identically distributed (i.i.d) Nakagami-m fading channels is derived while the fading index is a positive integer. When the Nakagami-m fading index is not an integer, the approximate outage capacity is derived as a single infinite series of Gamma function. Computer simulations verify the accuracy of the approximate results.
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  • Jieling WANG, Hong YANG, Kechu YI
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 1 Pages 219-221
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    A space-time and multipath diversity combining algorithm is presented for STBC single carrier block transmission system with two transmit and one receive antennas. The initial solution is achieved by an STBC-based frequency domain equalizer, and the multipath components in the received signal are decoupled by this initial solution and channel state information. Finally, STBC combining is carried out on each decoupled multipath component separately, and then the single carrier output branches are combined further using the maximal ratio combining (MRC) algorithm.
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  • Young-Ho JUNG
    Article type: LETTER
    Subject area: Terrestrial Radio Communications
    2010 Volume E93.B Issue 1 Pages 222-225
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    An orthogonal sequence based MIMO common feedback method for multicast hybrid automatic-repeat-request (H-ARQ) transmission is presented. The proposed method can obtain more diversity gain proportional to the number of transmit antennas than the conventional on-off keying (OOK) based common feedback method. The ACK/NACK detection performance gain of the proposed scheme over the OOK based method is verified by analysis and computer simulation results.
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  • Arturo Arvizu MONDRAGÓN, Juan-de-Dios Sáchez LÓPE ...
    Article type: LETTER
    Subject area: Optical Wireless Communications
    2010 Volume E93.B Issue 1 Pages 226-229
    Published: January 01, 2010
    Released on J-STAGE: January 01, 2010
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    We present a BPSK coherent optical wireless link in a multiple-beam, multiple-aperture configuration. The data are recovered using the signal obtained by the coherent addition of a set of maximum likelihood optical phase estimates and a select-largest stage. The proposal offers higher performance than the combining methods commonly used in optical wireless systems with diversity transmission and coherent detection.
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