IEICE Transactions on Communications
Online ISSN : 1745-1345
Print ISSN : 0916-8516
Volume E93.B, Issue 5
Displaying 1-44 of 44 articles from this issue
Special Section on Technology and Architecture for Sustainable Growth of the Internet
  • Katsuyuki YAMAZAKI
    2010 Volume E93.B Issue 5 Pages 1077
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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  • Shin MIYAKAWA
    Article type: INVITED PAPER
    2010 Volume E93.B Issue 5 Pages 1078-1084
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    According to the recent observations of IPv4 (Internet Protocol version 4) address allocation status, it will be running out within few years. Consequently, to ensure the continuous extension of the Internet operation, introducing IPv6 (Internet Protocol version 6) protocol is surely needed. But at the same time, such transformation must be “smooth” for every Internet users and be compatible with today's IPv4 based practices. This paper describes several techniques and usage scenario which are discussed mainly in the IETF — Internet Engineering Task Force — and tried to be implemented as prototype products to transform today's Internet towards the IPv6 based one.
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  • Kazuya SUZUKI, Masahiro JIBIKI, Kenichi YOSHIDA
    Article type: PAPER
    2010 Volume E93.B Issue 5 Pages 1085-1094
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    The availability of IP networks has increased its importance due to the evolving use of real-time and mission-critical applications on IP networks. Methods for preparing alternate routing tables that can be used for fast restoration from link failures have been investigated. In such methods, each node has to compute a number of alternate routing tables in advance since they have to prepare for each potential failure. The resulting huge number of alternate routing tables has prevented these methods from being deployed. In this paper, we propose a method for reducing the number of alternate routing tables for link failure. It analyzes three types of shortest path trees on the basis of link-state information. We show that the number of alternate routing tables can be reduced to 1/100, on average, from that with the conventional method, and that they are small enough to be stored in the memory of IP routers.
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  • John Russell LANE, Akihiro NAKAO
    Article type: PAPER
    2010 Volume E93.B Issue 5 Pages 1095-1103
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    Multipath routing and the ability to simultaneously use multiple network paths has long been proposed as a means for meeting the reliability and performance improvement goals of a next generation Internet. However, its use causes out-of-order packet delivery, which is well known to hinder TCP performance. While next-generation transport protocols will no doubt better cope with this phenomenon, a complete switch to these new protocols cannot be made on all devices “overnight”; the reality is that we will be forced to continue using TCP on such multipath networks well after deployment of a future Internet is complete.In this paper, we investigate the use of best-effort packet reordering — an optional network layer service for improving the performance of any TCP session in the presence of out-of-order packet delivery. Such a service holds the promise of allowing unmodified TCP to take advantage of the reliability and performance gains offered by a future multipath-enabled Internet without suffering the adverse performance effects commonly associated with out-of-order packet delivery. Our experiments test the performance of two common TCP variants under packet dispersion with differing numbers of paths and amounts of inter-path latency variance. They were conducted using multipath network and packet reorderer implementations implemented within the Emulab testbed. Our results demonstrate that a simple best-effort reordering service can insulate TCP from the type of reordering that might be expected from use of packet dispersion over disjoint paths in a wide-area network, and is capable of providing significant performance benefits with few ill side-effects.
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  • Suguru YOSHIMIZU, Hiroyuki KOGA, Katsushi KOUYAMA, Masayoshi SHIMAMURA ...
    Article type: PAPER
    2010 Volume E93.B Issue 5 Pages 1104-1112
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    With the emergence of bandwidth-greedy application services, high-speed transport protocols are expected to effectively and aggressively use large amounts of bandwidth in current broadband and multimedia networks. However, when high-speed transport protocols compete with other standard TCP flows, they can occupy most of the available bandwidth leading to disruption of service. To deploy high-speed transport protocols on the Internet, such unfair situations must be improved. In this paper, therefore, we propose a method to improve fairness, called Kyushu-TCP (KTCP), which introduces a non-aggressive period in the congestion avoidance phase to give other standard TCP flows more chances of increasing their transmission rates. This method improves fairness in terms of the throughput by estimating the stably available bandwidth-delay product and adjusting its transmission rate based on this estimation. We show the effectiveness of the proposed method through simulations.
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  • Dalia NASHAT, Xiaohong JIANG, Michitaka KAMEYAMA
    Article type: PAPER
    2010 Volume E93.B Issue 5 Pages 1113-1121
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    The Distributed Denial of Service attack (DDoS) is one of the major threats to network security that exhausts network bandwidth and resources. Recently, an efficient approach Live Baiting was proposed for detecting the identities of DDoS attackers in web service using low state overhead without requiring either the models of legitimate requests nor anomalous behavior. However, Live Baiting has two limitations. First, the detection algorithm adopted in Live Baiting starts with a suspects list containing all clients, which leads to a high false positive probability especially for large web service with a huge number of clients. Second, Live Baiting adopts a fixed threshold based on the expected number of requests in each bucket during the detection interval without the consideration of daily and weekly traffic variations. In order to address the above limitations, we first distinguish the clients activities (Active and Non-Active clients during the detection interval) in the detection process and then further propose a new adaptive threshold based on the Change Point Detection method, such that we can improve the false positive probability and avoid the dependence of detection on sites and access patterns. Extensive trace-driven simulation has been conducted on real Web trace to demonstrate the detection efficiency of the proposed scheme in comparison with the Live Baiting detection scheme.
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  • Takeshi YAGI, Naoto TANIMOTO, Takeo HARIU, Mitsutaka ITOH
    Article type: PAPER
    2010 Volume E93.B Issue 5 Pages 1122-1130
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    Vulnerabilities in web applications expose computer networks to security threats, and many websites are used by attackers as hopping sites to attack other websites and user terminals. These incidents prevent service providers from constructing secure networking environments. To protect websites from attacks exploiting vulnerabilities in web applications, service providers use web application firewalls (WAFs). WAFs filter accesses from attackers by using signatures, which are generated based on the exploit codes of previous attacks. However, WAFs cannot filter unknown attacks because the signatures cannot reflect new types of attacks. In service provider environments, the number of exploit codes has recently increased rapidly because of the spread of vulnerable web applications that have been developed through cloud computing. Thus, generating signatures for all exploit codes is difficult. To solve these problems, our proposed scheme detects and filters malware downloads that are sent from websites which have already received exploit codes. In addition, to collect information for detecting malware downloads, web honeypots, which automatically extract the communication records of exploit codes, are used. According to the results of experiments using a prototype, our scheme can filter attacks automatically so that service providers can provide secure and cost-effective network environments.
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  • Mitsuaki AKIYAMA, Makoto IWAMURA, Yuhei KAWAKOYA, Kazufumi AOKI, Mitsu ...
    Article type: PAPER
    2010 Volume E93.B Issue 5 Pages 1131-1139
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    Nowadays, the number of web-browser targeted attacks that lead users to adversaries' web sites and exploit web browser vulnerabilities is increasing, and a clarification of their methods and countermeasures is urgently needed. In this paper, we introduce the design and implementation of a new client honeypot for drive-by-download attacks that has the capacity to detect and investigate a variety of malicious web sites. On the basis of the problems of existing client honeypots, we enumerate the requirements of a client honeypot: 1) detection accuracy and variety, 2) collection variety, 3) performance efficiency, and 4) safety and stability. We improve our system with regard to these requirements. The key features of our developed system are stepwise detection focusing on exploit phases, multiple crawler processing, tracking of malware distribution networks, and malware infection prevention. Our evaluation of our developed system in a laboratory experiment and field experiment indicated that its detection variety and crawling performance are higher than those of existing client honeypots. In addition, our system is able to collect information for countermeasures and is secure and stable for continuous operation. We conclude that our system can investigate malicious web sites comprehensively and support countermeasures.
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  • Masanori TAKAOKA, Masato UCHIDA, Kei OHNISHI, Yuji OIE
    Article type: PAPER
    2010 Volume E93.B Issue 5 Pages 1140-1150
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    In this paper, we propose a file replication method to achieve load balancing in terms of write access to storage device (“write storage access load balancing” for short) in unstructured peer-to-peer (P2P) file-sharing networks in which the popularity trend of queried files varies dynamically. The proposed method uses a write storage access ratio as a load balance index value in order to stabilize dynamic P2P file-sharing environments adaptively. In the proposed method, each peer autonomously controls the file replication ratio, which is defined as a probability to create the replica of the file in order to uniform write storage access loads in the similar way to thermal diffusion phenomena. Theoretical analysis results show that the behavior of the proposed method actually has an analogy to a thermal diffusion equation. In addition, simulation results reveal that the proposed method has an ability to realize write storage access load balancing in the dynamic P2P file-sharing environments.
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  • Jihoon LEE, Seungwoo JEON, Jaehoon KIM
    Article type: LETTER
    2010 Volume E93.B Issue 5 Pages 1151-1154
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    Multi-hop Wireless LAN-based mesh network (WMN) provides high capacity and self-configuring capabilities. Due to data forwarding and path selection based on MAC address, WMN requires additional operations to achieve global connectivity using IPv6 address. The neighbor discovery operation over WLAN mesh networks requires repeated all-node broadcasting and this gives rise to a big burden in the entire mesh networks. In this letter, we propose the proxy neighbor discovery scheme for optimized IPv6 communication over WMN to reduce network overhead and communication latency. Using simulation experiments, we show that the control overhead and communication setup latency can be significantly reduced using the proxy-based neighbor discovery mechanism.
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  • Pi-Chung WANG
    Article type: LETTER
    2010 Volume E93.B Issue 5 Pages 1155-1158
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    In the last decade, the technique of packet classification has been widely deployed in various network devices, including routers, firewalls and network intrusion detection systems. In this work, we improve the performance of packet classification by using multiple hash tables. The existing hash-based algorithms have superior scalability with respect to the required space; however, their search performance may not be comparable to other algorithms. To improve the search performance, we propose a tuple reordering algorithm to minimize the number of accessed hash tables with the aid of bitmaps. We also use pre-computation to ensure the accuracy of our search procedure. Performance evaluation based on both real and synthetic filter databases shows that our scheme is effective and scalable and the pre-computation cost is moderate.
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  • Saeyoung AHN, Sunshin AN
    Article type: LETTER
    2010 Volume E93.B Issue 5 Pages 1159-1162
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    We define the term sensor node profile (SNP) in IEEE 802.15.4, which considers the transmitting data type as well as a variety of nodal characteristics which are able to manage the channels of each node by using the SNP. Through the use of the SNP the nodes are able to maximize the channel resource usage, which could form the basis of algorithms that can provide the required Quality of Service (QoS).
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Regular Section
  • Thai Hoa DUONG, Kye San LEE, Ihn S. KIM
    Article type: PAPER
    Subject area: Devices/Circuits for Communications
    2010 Volume E93.B Issue 5 Pages 1163-1171
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    In this paper, we utilize low temperature co-fired ceramic technology (LTCC) to realize a modified short-circuited stub bandpass filter suitable for ultra-wideband (UWB) applications. By modifying the conventional short-circuited stub bandpass filter structure with stubs and connecting lines of lower characteristic impedances, the number of stubs has been reduced from 5 to 2 on a high dielectric constant substrate (εr=40). A wireless local area network (WLAN) stopband in the frequency range of 5.15 to 5.825GHz has been inserted into the filter characteristic using three short-circuited coupled lines. The filter is fabricated and measurement results show that it has an insertion loss less than 1.0dB and return loss better than 10dB in the pass bands. A bandwidth ratio of 109.49% has been achieved. Measurement results agree well with simulation results. The dimensions of the filter are 4×8×0.57mm3.
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  • Masahiro HAYASHITANI, Masahiro SAKAUCHI, Kiyoshi FUKUCHI
    Article type: PAPER
    Subject area: Fiber-Optic Transmission for Communications
    2010 Volume E93.B Issue 5 Pages 1172-1179
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    We propose a high-speed protection scheme for multiple-priority-class traffic transmission in WDM ring networks. This scheme achieves high-speed protection by quickly suspending transmission of low-priority traffic when a failure is detected. Each node suspends transmission of the low-priority traffic being sent over the backup path corresponding to the impaired primary path after receiving a failure notification and checking a table that includes the primary paths passing through the node, the backup paths corresponding to the primary paths, and low-priority traffic transmitted by the node. If a node detects a failure, it sends a single failure notification for each ring to the source node of the primary path, and the nodes on the route sequentially suspend low-priority traffic. Simulation shows that the proposed scheme reduces the failure-recovery time by up to 60% compared with the conventional scheme.
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  • Eiji OKI, Ayako IWAKI
    Article type: PAPER
    Subject area: Network
    2010 Volume E93.B Issue 5 Pages 1180-1189
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    This paper compares the performances of optimal routing as yielded by the pipe, hose, and intermediate models. The pipe model, which is specified by the exact traffic matrix, provides the best routing performance, but the traffic matrix is difficult to measure and predict accurately. On the other hand, the hose model is specified by just the total outgoing/incoming traffic from/to each node, but it has a problem in that its routing performance is degraded compared to the pipe model, due to insufficient traffic information. The intermediate model, where the upper and lower bounds of traffic demands for source-destination pairs are added as constraints, is a construction that lies between the pipe and hose models. The intermediate model, which lightens the difficulty of the pipe model, but narrows the range of traffic conditions specified by the hose model, offers better routing performance than the hose model. An optimal-routing formulation extended from the pipe model to the intermediate model can not be solved as a regular linear programming (LP) problem. Our solution, the introduction of a duality theorem, turns our problem into an LP formulation that can be easily solved. Numerical results show that the network congestion ratio for the pipe model is much lower than that of hose model. The differences in network congestion ratios between the pipe and hose models lie in the range from 27% to 45% for the various network topologies examined. The intermediate model offers better routing performance than the hose model. The intermediate model reduces the network congestion ratio by 34% compared to the hose model in an experimental network, when the upper-bound and lower-bound margins are set to 25% and 20%, respectively.
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  • Weiwei XIA, Lianfeng SHEN
    Article type: PAPER
    Subject area: Network
    2010 Volume E93.B Issue 5 Pages 1190-1204
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    We propose a call admission control scheme in cellular and wireless local area networks (WLANs) integration: integrated service-based admission control with load-balancing capability (ISACL). The novel aspects of the ISACL scheme include that load transfer in the cellular/WLAN overlapping areas is allowed for the admission of originating data calls from the area with cellular access only and vertical handoff requests to the cellular network. Packet-level quality of service (QoS) constraints in the WLANs and other-cell interference in the code division multiple access (CDMA) cellular network are taken into account to derive the WLANs and cellular capacity. We model the integrated networks using a multi-dimensional Markov chain and the important performance measures are derived for effective optimization of the admission parameters. The analytical model is validated by a computer simulation. The variation of admission parameters with traffic load and the dependence of resource utilization on admission parameters are investigated. It is shown that optimal balancing of the traffic load between the cellular network and WLANs results in the maximum resource utilization. Numerical results demonstrate that substantial performance improvements can be achieved by applying the proposed ISACL scheme.
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  • Hyun-Sung PARK, Dong-Hyun KIM, Jong-Doek KIM
    Article type: PAPER
    Subject area: Network Management/Operation
    2010 Volume E93.B Issue 5 Pages 1205-1215
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    ISO/IEC 18000-7 Active RFID standard, a single channel system operating at 433MHz, faces technical difficulties in supporting some recently introduced application demands because of its low transmission rates and vulnerability to radio interference between the readers. We propose a new multi-channel active RFID system operating at the 2.4GHz band. The special feature of the proposed system is that a reader makes use of multiple interfaces to improve its performance. However, if only a small part of the interfaces is actually used, the performance improvement would not meet expectations. To overcome this problem, a multi-channel multi-interface active RFID protocol that balances the loads among all available interfaces is necessary. Three protocols, “Aggregated, ” “LP-Combined” and “AP-Balanced” are proposed in this paper. We carry out simulations to compare them under various conditions by changing numbers of tags, numbers of interfaces and tag data size. The AP-Balanced shows the best and the most stable performance and its performance increases almost linearly in proportion to the number of interfaces, which meets our expectation.
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  • Enis KOCAN, Milica PEJANOVIC-DJURISIC, Diomidis S. MICHALOPOULOS, Geor ...
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1216-1223
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    We perform error probability analysis of the uncoded OFDM fixed gain Amplify-and-Forward (AF) relaying system with subcarrier permutation (SCP). Two SCP schemes, named: the best-to-best SCP (BTB SCP) and the best-to-worst SCP (BTW SCP) are considered. Closed-form expressions for the bit error rate (BER) of the above SCP methods are derived. Numerical results manifest that these SCP schemes may outperform one another, depending on the average channel conditions of the links involved. That is, BTB SCP is better at low signal-to-noise ratio (SNR) values, while BTW SCP prevails in the medium and high SNR regime. Thus, it could be concluded that OFDM AF relaying systems may switch from the BTB SCP to BTW SCP in order to achieve optimum BER performance. Moreover, using the derived end-to-end SNR probability density functions (PDF), tight upper bounds for the ergodic capacities of both SCP schemes are obtained.
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  • Sungho HWANG, Jeongsik PARK, Ho-Shin CHO
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1224-1231
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    In this paper, an efficient radio resource allocation scheme for OFDMA systems is proposed, which follows two steps to take care of real-time traffic characterized with multi-level delay constraints. Urgent packets, those with imminent deadlines, are released first in step 1. After that the remaining channel resources are managed in such a way that overall throughput is maximized at Step 2. In this work, 2-dimensional diversity over multiple sub-bands and multiple users are jointly considered. The proposed scheme is compared with existing schemes designed for real-time traffic such as Exponential Scheduling (EXP) scheme, Modified Largest Weighted Delay First (M-LWDF) scheme, and Round robin scheme in terms of the packet discard probability and throughput. Numerical results show that the proposed scheme performs much better than the aforementioned ones in terms of the packet discard probability, while slightly better in terms of throughput.
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  • Hyung-Yun KONG, ASADUZZAMAN
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1232-1239
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    This paper presents a novel cross-layer approach to explore selection diversity for distributed clustering based wireless sensor networks (WSNs) by selecting a proper cluster-head. We develop and analyze an instantaneous channel state information (CSI) based cluster-head selection algorithm for a distributed, dynamic and randomized clustering based WSN. The proposed cluster-head selection scheme is also random and capable to distribute the energy uses among the nodes in the network. We present an analytical approach to evaluate the energy efficiency and system lifetime of our proposal. Analysis shows that the proposed scheme outperforms the performance of additive white Gaussian noise (AWGN) channel under Rayleigh fading environment. This proposal also outperforms the existing cooperative diversity protocols in terms of system lifetime and implementation complexity.
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  • Yang-Ho CHOI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1240-1247
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    To handle coherent signals with unknown arrival angles, an adaptive beamforming method is proposed which can be applied to an arbitrary array. The proposed method efficiently solves a generalized eigenvalue problem to estimate the arrival angles of the desired coherent signal group, by exploiting the Brent method in conjunction with alternating maximization. We discuss the condition for the correct direction estimation without erroneously taking interference direction estimates for the desired ones. Simulation results show that the performance of the proposed beamformer is very similar to that of the beamformer with the exact composite steering vector (CSV).
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  • Satoshi YAMAGUCHI, Hiroaki MIYASHITA, Toru TAKAHASHI, Masataka OTSUKA, ...
    Article type: PAPER
    Subject area: Antennas and Propagation
    2010 Volume E93.B Issue 5 Pages 1248-1255
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    Owing to their ultra-wideband characteristics, tapered slot antennas (TSAs) are used as element antennas in wideband phased arrays. However, when the size of a TSA is reduced in order to prevent the generation of a grating lobe during wide-angle beam scanning, the original ultra-wideband characteristics are degraded because of increased reflections from the ends of the tapered slot aperture. To overcome this difficulty, we propose a new antenna structure in which parallel-plate waveguides are added to the TSA. The advantage of this new structure is that the reflection characteristics of individual antenna elements are not degraded even if the width of the antenna aperture is very small, i.e., approximately one-half the wavelength of the highest operating frequency. In this study, we propose a procedure for designing the new antenna through numerical simulations by using the FDTD method. In addition, we verify the performance of the antenna array by experiments.
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  • Meng XU, Xincun JI, Jianhui WU, Meng ZHANG
    Article type: LETTER
    Subject area: Fundamental Theories for Communications
    2010 Volume E93.B Issue 5 Pages 1256-1259
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    In this paper, a modified Belief Propagation (BP) decoding algorithm for low-density parity check (LDPC) codes based on minimum mean square error (MMSE) criterion is proposed. This modified algorithm uses linear equation to replace the hyperbolic function in the original BP algorithm and optimizes the linear approximation error based on MMSE criterion. As a result, compared with the standard BP algorithm the computational complexity is reduced significantly as the modified algorithm requires only addition operations to implement. Besides that simulation results show our modified algorithm can achieve an error performance very close to the BP algorithm on the additive white Gaussian noise channel.
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  • Sangmok OH, Inho HWANG, Adrish BANERJEE, Jeong Woo LEE
    Article type: LETTER
    Subject area: Fundamental Theories for Communications
    2010 Volume E93.B Issue 5 Pages 1260-1263
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    A novel turbo coded modulation scheme, called the turbo-APPM, for deep space optical communications is proposed. The proposed turbo-APPM is a serial concatenation of turbo codes, an accumulator and a pulse position modulation (PPM), where turbo codes act as an outer code while the accumulator and the PPM act together as an inner code. The generator polynomial and the puncturing rule for generating turbo codes are chosen to lower the bit error rate. At the receiver, the joint iterative decoding is performed between the inner decoder and the outer turbo decoder. In the outer decoder, local iterative decoding for turbo codes is conducted. Simulation results are presented showing that the proposed turbo-APPM outperforms all previously proposed schemes such as LDPC-APPM, RS-PPM and SCPPM reported in the literature.
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  • Sangbin LEE, Songmin KIM, Sungjun KIM, Doohyun KO, Bumjin KIM, Sunshin ...
    Article type: LETTER
    Subject area: Network
    2010 Volume E93.B Issue 5 Pages 1264-1267
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    A network of sensors can be used to obtain state based data from the area in which they are deployed. To reduce costs, the data sent via intermediate sensors to a sink are often aggregated. In this letter, we introduce Self-Construction of Aggregation Tree (SCAT) scheme which uses a novel data aggregation scheme utilizing the knowledge of the mobile node and the infrastructure (static node tree) in gathering the data from the mobile node. The static nodes can construct a near- optimal aggregation tree by themselves, using the knowledge of the mobile node, which is a process similar to forming the centralized aggregation tree.
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  • Logan VOLKERS, Neil BARAKAT, Thomas DARCIE
    Article type: LETTER
    Subject area: Network
    2010 Volume E93.B Issue 5 Pages 1268-1271
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    DOCSIS is the defacto industry standard for cable internet to the home. In this letter, we examine the delay characteristics of commercially deployed DOCSIS networks. We focus on four mechanisms of the DOCSIS MAC operation and develop a computationally simple simulator to reproduce the phenomena produced by these mechanisms. In reproducing these phenomena using our simulator, we demonstrate that the simulator properly encapsulates the core mechanisms of DOCSIS and effectively simulates the delay of packets.
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  • Pi-Chung WANG, Yi-Ting FANG, Tzung-Chian HUANG
    Article type: LETTER
    Subject area: Network
    2010 Volume E93.B Issue 5 Pages 1272-1275
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    In this work, we propose a scheme of routing table compaction for IP forwarding engines based on ternary content addressable memory (TCAM). Our scheme transforms the original routing table into a form with only disjoint prefixes. The most prevalent next hop of the routing table is then calculated and the route prefixes corresponding to the next hop are replaced by one TCAM entry. In combination with Espresso-II logic minimization algorithm, the proposed scheme reduces the TCAM storage requirements by more than 75% compared to the original routing tables. We also present an effective approach to support incremental updates.
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  • Weile ZHANG, Junsong WANG, Qinye YIN, Ang FENG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1276-1279
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    In this letter, a novel method is proposed for carrier-frequency offset (CFO) estimation for multiple users in orthogonal frequency division multiple access (OFDMA) uplink with the generalized carrier assignment scheme (GCAS). The base station (BS) is equipped with multiple antennas, and each user's CFO can be estimated by the ESPRIT-like method that utilizes the rotation invariance of the space-domain snapshot matrix. The method is still effective even in fully loaded system with all subcarriers allocated to users. Simulation results illustrate the high performance of the proposed algorithm.
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  • Sangho CHOE
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1280-1283
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    We present a predictive closed-loop power control scheme for delay-prone burst transmission systems. The scheme has a sample-by-sample predictor compensating burst delay and a built-in channel encoder reducing power control command bit error.
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  • Osamu TAKYU, Yohtaro UMEDA, Masao NAKAGAWA
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1284-1288
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    Two novel frequency rotation techniques that suppress multipath interference and increase the frequency diversity gain are proposed for uplink IFDMA systems. These benefits are especially important as the performance of traditional IFDMA falls significantly when the number of simultaneous accessing users becomes large. Frequency rotation was originally proposed to suppress the multipath interference and enlarge the frequency diversity gain of downlink access. Unfortunately, it cannot be applied to the uplink due to the loss of orthogonality among users in the frequency domain. In the proposed frequency rotation techniques, users do not share the multiple frequency orthogonal channels and thus orthogonality among users is maintained. The proposed technique is verified by computer simulations.
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  • Ki-Ho LEE, Hyun-Ho CHOI, Dong-Ho CHO
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1289-1292
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    Hierarchical constellations offer a different property of robustness to the multiple bits that construct a symbol according to channel errors. We apply the characteristics of hierarchical constellations to a multi-user cellular system that has limited modulation levels, in order to improve cell capacity. We propose an adaptive resource allocation scheme based on the hierarchical constellation in which a symbol is shared by multiple users and each bit in a symbol is allocated adaptively according to the channel condition of each user. The numerical results show that the proposed resource allocation scheme provides mobile users with higher modulation levels so that the cell capacity is improved.
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  • Dongwook CHOI, Dongwoo LEE, Jae Hong LEE
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1293-1297
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    In this paper, we propose a new subcarrier allocation algorithm for a downlink OFDMA relay network with multicells. In the proposed algorithm, subcarriers are allocated to users and relays to maximize the overall sum of the achievable rate under fairness constraints. Simulation results show that the proposed algorithm achieves higher data rate than the static algorithm and reduces the outage probability compared to the static and greedy algorithms.
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  • In-Ho LEE, Joong-Hoo PARK, Dongwoo KIM
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1298-1301
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    In this letter, the outage performance of multi-hop multiple-input multiple-output (MIMO) relaying systems is analyzed for spatially correlated Rayleigh fading channels. We focus on nonregenerative MIMO decouple-and-forward (DCF) relaying in orthogonal space-time block code (OSTBC) transmission and provide its outage probability given the assumption of ideal relay gain. The outage obtained here is shown a lower bound for using practical gains, which gets tight at high SNR. We conduct numerical studies to assess the impact of the spatial correlation between antennas on the outage probability.
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  • Taeyoul OH, Seungheon HYEON, Hyunsung GO, Seungwon CHOI
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1302-1305
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    This letter presents an optimal user selection algorithm that provides a maximum sum-rate in a zero-forcing based Multiuser MIMO system for downlink. The proposed technique forms a primary group of users whose channel power exceeds a predetermined threshold. Through computer simulations, we have found that the proposed method outperforms the conventional technique yielding a sum rate that is 0.33bps/Hz higher when the transmit SNR is 10dB and the total number of users and transmit antennas in the cell is 100 and 4, respectively.
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  • Jang Hyun BAEK, Jong Hun PARK, Douglas C. SICKER, Taehan LEE
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1306-1309
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    This study examines movement-based registration (MBR). In MBR, a mobile station (MS) performs location registration whenever the number of entering cells reaches the specified movement threshold M. MBR is simple and its implementation is quite straightforward. However, it may result in more registrations than other similar schemes. We propose an improved MBR scheme, in which MBR combines with implicit registration (IR), to reduce registration cost. The performance of the proposed scheme is evaluated using a mathematical approach based on the 2-dimensional random walk mobility model in a hexagonal cell configuration. The numerical results for varying circumstances show that the proposed scheme performs better than conventional MBR.
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  • Taeung YOON, Youngpo LEE, So Ryoung PARK, Suk Chan KIM, Iickho SONG, S ...
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1310-1312
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    The relationship between the degree of overlap in direct modulation chirp spread spectrum systems with binary phase shift keying and intersymbol interference (ISI) is analyzed. It is observed that the ISI due to overlap fluctuates or monotonically increases as the number of overlaps changes and that, in some cases, the overlap does not incur ISI at all.
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  • Chenhao QI, Lenan WU
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1313-1316
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    In this letter, the sparse recovery algorithm orthogonal matching pursuit (OMP) and subspace pursuit (SP) are applied for MIMO OFDM channel estimation. A new algorithm named SOMP is proposed, which combines the advantage of OMP and SP. Simulation results based on 3GPP spatial channel model (SCM) demonstrate that SOMP performs better than OMP and SP in terms of normalized mean square error (NMSE).
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  • Vo Nguyen Quoc BAO, Hyung Yun KONG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1317-1321
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    We propose an incremental relaying protocol in conjunction with partial relay selection with the aim of making efficient use of the degrees of freedom of the channels as well as improving the performance of dual hop relaying with partial relay selection (DRPRS). Specifically, whenever the direct link from the source to the destination is not favorable to decoding, the destination will request the help of the opportunistic relay providing highest SNR of the links from the source. Theoretical analyses, as well as simulation results, verify that our scheme outperforms the DRPRS scheme in terms of bit error probability.
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  • Jihoon CHOI, Young-Ho JUNG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1322-1325
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    A new adaptive algorithm is proposed by introducing some modifications to the recursive least squares (RLS) algorithm. Except for the noise variance, the proposed algorithm does not require any statistics or knowledge of the desired signal, thus, it is suitable for adaptive filtering for channel estimation in code division multiple access (CDMA) systems in cases where the standard RLS approach cannot be used. A theoretical analysis demonstrates the convergence of the proposed algorithm, and simulation results for CDMA channel estimation show that the proposed algorithm outperforms existing channel estimation schemes.
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  • Yi CHU
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1326-1329
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    This paper presents a new approach for the Capon beamformer to provide robustness against array pointing errors. This robustness is achieved by incorporating an uncertainty constraint with diagonal loading and injected pseudo-interference. A simple performance analysis of this new beamformer is also investigated. Simulation results demonstrate that the power estimator has excellent performance.
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  • Jae-Seon YOON, Jee-Hoon KIM, Hyoung-Kyu SONG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2010 Volume E93.B Issue 5 Pages 1330-1333
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    Recently, the orthogonal frequency-division multiple access (OFDMA) based wireless communication system is usually used in interactive digital video broadcasting environments or the wireless metropolitan area network (WMAN). Therefore, the relative condition of the inter-user channel can be easily deteriorated. This letter proposes and evaluates the mutual amplify-and-forward (AF) cooperation between two users using modified space time block code (STBC) to provide the reliability for an OFDMA system with a single antenna in an inferior inter-user channel environment. As a result, an OFDMA system adopting the proposed cooperation becomes more robust to inferior inter-user channels than our previously proposed decode-and-forward (DF) cooperation.
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  • Chang Wook AHN, Ju Yeop CHOI, Dong-Ha LEE, Jinung AN
    Article type: LETTER
    Subject area: Energy in Electronics Communications
    2010 Volume E93.B Issue 5 Pages 1334-1337
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    This paper presents an adaptive maximum power point tracking (MPPT) algorithm. The aim is to dynamically adjust the step length for updating duty ratio (or operating voltage) so as to make full utilization of the output power of photovoltaic (PV) systems, even under the rapidly changing atmospheric conditions. To this end, the average slope in terms of voltage and power is exploited for reducing the harmful effect of noise and error (incurred in measurement or quantization) on the slope. Also, a statistical decision-making scheme is employed for reliably deciding the time instant at which atmospheric conditions actually change. Empirical study has adduced grounds for its dominance over existing references.
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  • Won-Jae SHIN, Young-Hwan YOU
    Article type: LETTER
    Subject area: Broadcast Systems
    2010 Volume E93.B Issue 5 Pages 1338-1341
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    Cyclic delay diversity (CDD) is a simple technique to intentionally increase frequency selectivity of channels for orthogonal frequency division multiplexing (OFDM). This letter evaluates the performance of post-FFT fine frequency estimation scheme for OFDM-based FM system using CDD. A new and accurate mean square error expression of the fine frequency estimator is derived in the CDD-based OFDM system, and simulation results are provided to verify our analysis.
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  • Wonjong NOH
    Article type: LETTER
    Subject area: Broadcast Systems
    2010 Volume E93.B Issue 5 Pages 1342-1345
    Published: May 01, 2010
    Released on J-STAGE: May 01, 2010
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    In this paper, we study multi-layer transmission for wireless multimedia multicast in a cell. Under the assumptions that the users in a cell are uniformly well distributed and that the BS has no channel side information, we find the optimal number of transmission layers and power allocation. This result can be used in highly dynamic dense networks and jamming networks where channel side information at the transmitter is somewhat useless.
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