著者

Kotaro KATAOKA Keisuke UEHARA Masafumi OE Jun MURAI

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Communications (ISSN:09168516)

巻号頁・発行日

vol.E95-B, no.7, pp.2200-2209, 2012-07-01

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In disaster sites of 2011 Tohoku Earthquake, digital communication was virtually unavailable due to the serious damage to the existing Internet and ICT resources. Thus there were urgent demands for recovering the Internet connectivity and first aid communication tools. This paper describes the design and deployment of networking systems that provide Internet connectivity using 3G mobile links or VSAT satellite links. In this paper we examine two approaches for post-disaster networking: quickly deployable package and on-demand networking. Based on a comparison of their characteristics and deployment experiences, this paper tries to extract lessons that contribute to improving the preparedness to another disaster. This paper also shares our significant operational experience acquired through supporting a maximum of 54 sites in Tohoku area including evacuation shelters, temporary hospitals and local government offices.

著者

Gaolei FEI Guangmin HU

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Communications (ISSN:09168516)

巻号頁・発行日

vol.E95-B, no.6, pp.1974-1977, 2012-06-01

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In this letter, we address the issue of estimating the temporal dependence characteristic of link loss by using network tomography. We use a k-th order Markov chain (k > 1) to model the packet loss process, and estimate the state transition probabilities of the link loss model using a constrained optimization-based method. Analytical and simulation results indicate that our method yields more accurate packet loss probability estimates than existing loss inference methods.

著者

Hyungjin KIM Min-Chul SUN Hyun Woo KIM Sang Wan KIM Garam KIM Byung-Gook PARK

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Electronics (ISSN:09168516)

巻号頁・発行日

vol.E95-C, no.5, pp.820-825, 2012-05-01

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Although the Tunnel Field-Effect Transistor (TFET) is a promising device for ultra-low power CMOS technology due to the ability to reduce power supply voltage and very small off-current, there have been few reports on the control of VT for TFETs. Unfortunately, the TFET needs a different technique to adjust VT than the MOSFET by channel doping because most of TFETs are fabricated on SOI substrates. In this paper, we propose a technique to control VT of the TFET by putting an additional VT-control doping region (VDR) between source and channel. We examine how much VT is changed by doping concentration of VDR. The change of doping concentration modulates VT because it changes the semiconductor work function difference, ψs,channel-ψs,source, at off-state. Also, the effect of the size of VDR is investigated. The region can be confined to the silicon surface because most of tunneling occurs at the surface. At the same time, we study the optimum width of this region while considering the mobility degradation by doping. Finally, the effect of the SOI thickness on the VDR adjusted VT of TFET is also investigated.

著者

Zhisheng LI Johan BAUWELINCK Guy TORFS Xin YIN Jan VANDEWEGE

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Electronics (ISSN:09168516)

巻号頁・発行日

vol.E95-C, no.4, pp.765-767, 2012-04-01

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This paper presents a new common-mode stabilization method for a CMOS differential cascode Class-E power amplifier with LC-tank based driver stage. The stabilization method is based on the identification of the poles and zeros of the closed-loop transfer function at a critical node. By adding a series resistor at the common-gate node of the cascode transistor, the right-half-plane poles are moved to the left half plane, improving the common-mode stability. The simulation results show that the new method is an effective way to stabilize the PA.

著者

Hitoshi YOSHINO

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Communications (ISSN:09168516)

巻号頁・発行日

vol.E95-B, no.4, pp.1036-1043, 2012-04-01

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Cognitive radio is an emerging technology to further improve the efficiency of spectrum use. Due to the nature of the technology, it has many facets, including its enabling technologies, its implementation issues and its regulatory implications. In ITU-R (International Telecommunications Union – Radiocommunication sector), cognitive radio systems are currently being studied so that ITU-R can have a clear picture on this new technology and its potential regulatory implications, from a viewpoint of global spectrum management. This paper introduces the recent results of the ITU-R studies on cognitive radio on both regulatory and technical aspects. This paper represents a personal opinion of the author, but not an official view of the ITU-R.

著者

Yuki ATSUMI Manabu ODA Joonhyun KANG Nobuhiko NISHIYAMA Shigehisa ARAI

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Electronics (ISSN:09168516)

巻号頁・発行日

vol.E95-C, no.2, pp.229-236, 2012-02-01

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Photonic integrated circuits (PICs) produced by large-scale integration (LSI) on Si platforms have been intensively researched. Since thermal diffusion from the LSI logic layer is a serious obstacle to realizing a Si-based optical integrated circuit, we have proposed and realized athermal wavelength filters using Si slot waveguides embedded with benzocyclobutene (BCB). First, the athermal conditions were theoretically investigated by controlling the waveguide and gap width of the slot waveguides. In order to introduce the calculated waveguide structures to wavelength filters, the propagation losses and bending losses of the Si slot waveguides were evaluated. The propagation losses were measured to be 5.6 and 5.3 dB/cm for slot waveguide widths of 500 and 700 nm, respectively. Finally, athermal wavelength filters, a ring resonator, and a Mach-Zhender interferometer (MZI) with a slot waveguide width of 700 nm were designed and fabricated. Further, a temperature coefficient of -0.9 pm/K for the operating wavelength was achieved with the athermal MZI.

著者

Xiaodong DENG Mengtian RONG Tao LIU

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Communications (ISSN:09168516)

巻号頁・発行日

vol.E95-B, no.1, pp.152-159, 2012-01-01

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Large capacity tags are becoming available to meet the demands of industry, but the UHF RFID protocol is unable to reliably and efficiently read large data sets from tags. First of all, large data sets are not well protected. The tag merely relies on 16-bit CRC for ensuring the validity of up to 4,096-bit user-specific data in EPCglobal C1G2 protocol. Furthermore, the reliability will be even worse if large capacity tags are implemented using semi-active technology which is likely to prevail among sensor-integrated RFID tags. Since semi-active tags greatly alleviate the performance limitation imposed by the turn-on power of the tag chip, backscattering signal of semi-active tags could be a serious challenge for most readers because it is much weaker than signals emitted by passive tags due to longer reading distance. In this paper, Interim CRC is presented to enhance transmission reliability and efficiency when the tag is backscattering a large data set. By taking advantage of Interim CRC, the large data set can be divided into several blocks, and 16-bit checksum is calculated over each block. The tag backscatters all blocks at the first time and only retransmits certain blocks if CRC error occurs in those blocks. The result of simulation shows that the reading error rate can be confined to a preset threshold and the accumulative total of transmitted data are greatly reduced if optimal block size and transmission times are complied with. The simulation also conclusively proves that semi-active tags derive even longer reading range from Interim CRC. In addition, Interim CRC is totally compliant with the EPCglobal C1G2 protocol. It fully makes use of CRC-16 encoder and does not involve any other data encoding schematics and hardware modifications.

著者

Maciej SOBIERAJ Maciej STASIAK Joanna WEISSENBERG Piotr ZWIERZYKOWSKI

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Communications (ISSN:09168516)

巻号頁・発行日

vol.E95-B, no.1, pp.120-132, 2012-01-01

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This paper presents a new generalized single threshold model that can be used in communications and cellular networks. In the proposed model, called Single Hysteresis Model (SHM), it is assumed that the amount of resources accessible for a new call of a given class can depend on two load areas of the system. The switching between areas is modulated by the two-state Markov chain which determines the average time the system spends in a particular load area, i.e. the area in which calls of selected classes with a reduced amount of resources (high load area) and with the initial amount of resources (low load area) are serviced. The results obtained for the discussed analytical model are compared with the results of the simulation of an exemplary WCDMA radio interface carrying a mixture of different multi-rate traffic streams. The research study confirms high accuracy of the proposed model.

著者

Kentaro ISODA Teruyuki HARA

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Communications (ISSN:09168516)

巻号頁・発行日

vol.E94-B, no.11, pp.2969-2977, 2011-11-01

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A monopulse angle measurement method is often utilized to measure a target angle. However, this method cannot measure correct angles for multiple targets which cannot be distinguished by range, Doppler frequency and beamwidth. When the number of targets which cannot be distinguished by these parameters is restricted to two, a method which can measure two targets angles has been proposed. However, an approximation is utilized with this method, so that measured angles have errors even though the signal-to-noise ratio is infinite. Another method which can simultaneously measure azimuths and elevations for only two targets has also been proposed. However, this conventional method requires four receivers, and is therefore difficult to apply when there is a hard ware limitation. In this paper, we propose a method to measure azimuths and elevations of two targets by using two receivers and a time division system. A pairing problem has occurred due to the time division angle measurement with this method, so we also propose an algorithm to solve this pairing problem. We finally verify the proposed method by a numerical simulation and experimentation. The results show that the angles of two targets can be measured by our proposed method by using two receivers.

著者

Masahiro FUNAHASHI Fapei ZHANG Nobuyuki TAMAOKI

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Electronics (ISSN:09168516)

巻号頁・発行日

vol.E94-C, no.11, pp.1720-1726, 2011-11-01

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Thin-film transistors based on Liquid-crystalline phenylterthiophenes, 3-TTPPh-5 and 3-TTPPhF4-6 are fabricated with a spin-coating method. The devices exhibit p-type operation with the mobility on the order of 10-2 cm2V-1s-1. The field-effect mobilities of the transistors using 3-TTPPh-5 and 3-TTPPhF4-6 are almost independent of the temperature above room temperature. In particular, the temperature range in which the mobility is constant is between 230 and 350 K for 3-TTPPh-5.

著者

TSUMURA Shigehiko VEHKAPERA Mikko LI Zexian TUJKOVIC Djordje JUNTTI Markku HARA Shinsuke

出版者

一般社団法人電子情報通信学会

雑誌

IEICE transactions on communications (ISSN:09168516)

巻号頁・発行日

vol.87, no.10, pp.3011-3020, 2004-10-01

被引用文献数

5

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In this paper, we evaluate the performance of single- and multi-antenna multi-carrier code division multiple access (MC-CDMA) downlink (base station to mobile terminal) systems in single- and multi-cell environments. We first propose a minimum mean square error (MMSE) filter with a Gaussian approximation for a single input single output (SISO) MC-CDMA downlink system. Then, we apply it to a SIMO (single input multiple output) system with a conventional turbo coding. Furthermore, we compare the performance of SISO (1×1) and SIMO (1×2) MC-CDMA systems with that of a multiple input multiple output (MIMO) (2×2) system employing space-time turbo coded modulation (STTuCM) in a multi-cell environment with 7 cells by computer simulation. Based on the computer simulation results, it is found that the considered MIMO system can achieve twofold capacity with the same transmission power in the multi-cell environment.

著者

Kentaro ISHIZU Homare MURAKAMI Stanislav FILIN Hiroshi HARADA

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Communications (ISSN:09168516)

巻号頁・発行日

vol.E93-B, no.12, pp.3311-3322, 2010-12-01

被引用文献数

4

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Selections of radio access networks by terminals are currently not coordinated and utilizations of the radio resources are not balanced. As a result, radio resources on some radio systems are occupied even though others can afford. In this paper, in order to provide a framework to resolve this issue, Cognitive Wireless Router (CWR) system is proposed for distributed management and independent reconfiguration of heterogeneous wireless networks. The proposed system selects appropriate operational frequency bands and radio systems to connect to the Internet in corporation between the CWRs and a server and therefore can provide optimized wireless Internet access easily even in environments without wired networks. The developed prototype system reconfigures the radio devices to connect to the Internet in 27 seconds at most. It is revealed that this reconfiguration time can be shortened to less than 100 ms by elaborating its procedure. It is also clarified that network data speed required at the server to deal with 10,000 CWRs is only 4.1 Mbps.

著者

LEE H.C. KYUNG C.M

出版者

一般社団法人電子情報通信学会

雑誌

IEICE transactions on communications (ISSN:09168516)

巻号頁・発行日

vol.80, no.1, pp.192-195, 1997-01-25

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A network with input and output buffer is proposed. It consists of several switching stages composed of 3×3 basic switching elements which are connected with perfect shuffle and horizontal connections. The proposed network reduces the required number of stages, and increases the fault tolerance due to its highly regular connection scheme. Its performance was evaluated with computer simulation under bursty traffic environment. For a 128×128 switch with 11 switching stages, a packet loss ratio of 10^lt-6gt was obtained when the input load is 0.8 and the burstiness is 10.

著者

Hajime TAZAKI Rodney Van METER Ryuji WAKIKAWA Thirapon WONGSAARDSAKUL Kanchana KANCHANASUT Marcelo DIAS DE AMORIM Jun MURAI

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Communications (ISSN:09168516)

巻号頁・発行日

vol.E93-B, no.8, pp.2004-2011, 2010-08-01

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Motivated by the deployment of post-disaster MANEMO (MANET for NEMO) composed of mobile routers and stations, we evaluate two candidate routing protocols through network simulation, theoretical performance analysis, and field experiments. The first protocol is the widely adopted Optimized Link State Routing protocol (OLSR) and the second is the combination of the Tree Discovery Protocol (TDP) with Network In Node Advertisement (NINA). To the best of our knowledge, this is the first time that these two protocols are compared in both theoretical and practical terms. We focus on the control overhead generated when mobile routers perform a handover. Our results confirm the correctness and operational robustness of both protocols. More interestingly, although in the general case OLSR leads to better results, TDP/NINA outperforms OLSR both in the case of sparse networks and in highly mobile networks, which correspond to the operation point of a large set of post-disaster scenarios.

著者

Hideharu AMANO Akiya JOURAKU Kenichiro ANJO

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS on Communications (ISSN:09168516)

巻号頁・発行日

vol.E86-B, no.12, pp.3385-3391, 2003-12-01

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A framework of dynamically adaptive hardware mechanism on multicontext reconfigurable devices is proposed, and as an example, an adaptive switching fabric is implemented on NEC's novel reconfigurable device DRP (Dynamically Reconfigurable Processor). In this switch, contexts for the full crossbar and alternative hadware modules, which provide larger bandwidth but can treat only a limited pattern of packet inputs, are prepared. Using the quick context switching functionality, a context for the full crossbar is replaced by alternative contexts according to the packet inputs pattern. If the context corresponding to requested alternative hadware modules is not inside the chip, it is loaded from outside chip to currently unused context memory, then replaced with the full size crossbar. If the traffic includes a lot of packets for specific destinations, a set of contexts frequently used in the traffic is gathered inside the chip like a working set stored in a cache. 4 4 mesh network connected with the proposed adaptive switches is simulated, and it appears that the latency between nodes is improved three times when the traffic between neighboring four nodes is dominant.

著者

CHANG Yeim-Kuan

出版者

一般社団法人電子情報通信学会

雑誌

IEICE transactions on communications (ISSN:09168516)

巻号頁・発行日

vol.88, no.1, pp.239-246, 2005-01-01

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Building next generation routers with the capability of forwarding multiple millions of packets per second is required for the increasing demand for high bandwidth on the Internet. Reducing the required memory size of the forwarding table is a possible solution since small forwarding table can be integrated into the application specific integrated circuit (ASIC). In this paper a hash technique is developed to reduce the size of the IP forwarding table. The proposed data structure is a compressed 8-8-8-8 multibit trie that is based on hash tables of 4-bit addresses. Two optimization techniques are also proposed to further improve the performance of the proposed schemes. Our experimental results show that the proposed hashing-based schemes are better than the Small Forwarding Table scheme [6] both in memory size and lookup latency.

著者

YASUDA Kinuko HAGINO Tatsuya

出版者

一般社団法人電子情報通信学会

雑誌

IEICE transactions on communications (ISSN:09168516)

巻号頁・発行日

vol.84, no.4, pp.920-929, 2001-04-01

被引用文献数

3

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In this paper, we propose a new filesystem named Ad-hoc Filesystem which targets ad-hoc wireless networks. Ad-hoc Filesystem is a serverless filesystem which automatically generates temporary shared space among multiple mobile machines when they gather in a communicable range. The generated space is freely available for participating machines and can be used for any temporary work there. The design of Ad-hoc Filesystem is strongly motivated by the recent wireless network technologies and advances of ad-hoc network techniques. However, targeting such an unstable network forces us a completely different design from existing filesystems. We have designed an initial prototype of Ad-hoc Filesystem and have evaluated the simulation results. Our design is strongly based on an assumption such that people who wish to work together would form a stable group in a range, and replicating data on two different machines would be enough to provide a proper level of availability. Hence, Ad-hoc Filesystem distributes files among multiple machines and duplicates them, in order to keep the files available even if some of participating machines arbitrarily leave the communication range. The directory entries are kept as a soft-state mechanism maintained by exchanging broadcast packets. The simulation results show that using broadcast to maintain system state hardly affects the overall system performance, and optimizations such that delaying replies with broadcast and sensing other packets promiscuously during the delay reduce the overhead significantly. Also the result indicates that our strategy that keeps two replicas for each data is promising to provide availability. Although further investigation based on real implementation remains important work, we believe that the prototype has a contribution to realize the possibility of ad-hoc filesystem by synthesizing number of previous works in areas such as network filesystems, server replication and ad-hoc wireless networks.