In content services where people purchase and download large-volume contents, minimizing network traffic is crucial for the service provider and the network operator since they want to lower the cost charged for bandwidth and the cost for network infrastructure, respectively. Traffic localization is an effective way of reducing network traffic. Network traffic is localized when a client can obtain the requested content files from other a near-by altruistic client instead of the source servers. The concept of the peer-assisted content distribution network (CDN) can reduce the overall traffic with this mechanism and enable service providers to minimize traffic without deploying or borrowing distributed storage. To localize traffic effectively, content files that are likely to be requested by many clients should be cached locally. This paper presents a novel traffic engineering scheme for peer-assisted CDN models. Its key idea is to control the behavior of clients by using content-oriented incentive mechanism. This approach enables us to optimize traffic flows by letting altruistic clients download content files that are most likely contributed to localizing traffic among clients. In order to let altruistic clients request the desired files, we combine content files while keeping the price equal to the one for a single content. This paper presents a solution for optimizing the selection of content files to be combined so that cross traffic in a network is minimized. We also give a model for analyzing the upper-bound performance and the numerical results.

A high-speed low-complexity time-multiplexing Reed-Solomon-based forward error correction architecture based on the pipelined truncated inversionless Berlekamp-Massey algorithm is presented in this paper. The proposed architecture has very high speed and very low hardware complexity compared with conventional Reed-Solomon-based forward error correction architectures. Hardware complexity is improved by employing a truncated inverse Berlekamp-Massey algorithm. A high-speed and high-throughput data rate is facilitated by employing a three-parallel processing pipelining technique and modified syndrome computation block. The time-multiplexing method for pipelined truncated inversionless Berlekamp-Massey architecture is used in the parallel Reed-Solomon decoder to reduce hardware complexity. The proposed architecture has been designed and implemented with 90-nm CMOS technology. Synthesis results show that the proposed 16-channel Reed-Solomon-based forward error correction architecture requires 417,600 gates and can operate at 640 MHz to achieve a throughput of 240 Gb/s. The proposed architecture can be readily applied to Reed-Solomon-based forward error correction devices for next-generation short-reach optical communications.

It is well known that satellite communications systems are effective and essential communication infrastructure for disaster relief. NICT sent researchers to Tsunami stricken area in March right after the Great East Japan Earthquake and provided broadband satellite communications link to support rescue activities. Through this experience, we learned many kinds of requirements of communications for such purposes. In this paper, we list up the requirements and report what kind of satellite communications technologies are needed, and research and development issues.

Constructing APN or 4-differentially uniform permutations achieving all the necessary criteria is an open problem, and the research on it progresses slowly. In ACISP 2011, Carlet put forth an idea for constructing differentially uniform permutations using extension fields, which was illustrated with a construction of a 4-differentially uniform (n,n)-permutation. The permutation has optimum algebraic degree and very good nonlinearity. However, it was proved to be a permutation only for n odd. In this note, we investigate further the construction of differentially uniform permutations using extension fields, and construct a 4-differentially uniform (n,n)-permutation for any n. These permutations also have optimum algebraic degree and very good nonlinearity. Moreover, we consider a more general type of construction, and illustrate it with an example of a 4-differentially uniform (n,n)-permutation with good cryptographic properties.

Multicarrier communications including orthogonal frequency-division multiplexing (OFDM) is a technique which has been adopted for various wireless applications. However, a major drawback to the widespread acceptance of OFDM is the high peak-to-mean envelope power ratio (PMEPR) of uncoded OFDM signals. Finding methods for construction of sequences with low PMEPR is an active research area. In this paper, by employing some new shortened and extended Golay complementary pairs as the seeds, we enlarge the family size of near-complementary sequences given by Yu and Gong. We also show that the new set of sequences we obtained is just a reversal of the original set. Numerical results show that the enlarged family size is almost twice of the original one. Besides, the Hamming distances of the binary near-complementary sequences are also analyzed.

We introduce an efficient fully simulatable construction of oblivious transfer based on the McEliece assumptions in the common reference string model. This is the first efficient fully simulatable oblivious protocol based on coding assumptions. Moreover, being based on the McEliece assumptions, the proposed protocol is a good candidate for the post-quantum scenario.

Without recourse to the Shannon-Nyquist sampling theorem, a novel information sampling (IS) concept is proposed for ultra-wideband (UWB) communications. To implement IS, a random pre-coding system architecture is designed and system performance is studied. Simulation results from one of UWB channel models show that the proposed system is effective to detect UWB signals with a low-sampling-rate analog-to-digital converter (ADC) at the receiver. Moreover, it can operate in a regime of heavy inter-symbol interference (ISI).

For effective use of the frequency band, carrier superposing (common band) technique has been introduced to satellite communication systems. On the other hand, satellite's TWTA (Traveling Wave Tube Amplifier) should be operated near its saturation level for power efficiency. However, the TWTA nonlinearity characteristics around that level causes interference in carrier superposing systems. Therefore in this paper, a post-compensation technique for TWTA nonlinear distortion is introduced and verified for practical use in a carrier superposed Point to Point satellite communication system which adopts interference canceller. Simulation results show that it is possible to reduce the bit error rate degradation over the entire range, especially at nonlinear operating point.

An instrument that can efficiently measure individual competency of IT applications (ICITA) is presented. It allows an organization to develop and manage the IT application capability of individuals working in an enterprise IT environment. The measurement items are generated from the definition and major components of individual competency of IT applications. The reliability and validity of the instrument construct are verified by factor and correlation analysis. A 15-item instrument is proposed to efficiently measure individual competency of IT applications and the instrument will contribute to the improved ICITA of human resources working in an enterprise IT environment.

In block transmissions, inter-block interference (IBI) due to delayed waves exceeding a cyclic prefix severely limits the performance. To suppress IBI in downlink MC-CDMA systems, this paper proposes a novel channel shortening method using a time-domain equalizer. The proposed method minimizes a cost function related to equalizer output autocorrelations without the transmission of training symbols. We prove that the method can shorten a channel and suppress IBI completely. Simulation results show that the proposed method can significantly suppress IBI using relatively less number of received blocks than a conventional method when the number of users is moderate.

The mode-matching applications to scattering from circular and annular apertures in a thick perfectly conducting plane are reviewed. The Hankel and Weber transforms are utilized to solve the boundary-value problems of circular and annular apertures. Simple electrostatic problems are presented to illustrate the mode-matching method in terms of the Hankel and Weber transforms. Various types of Weber transform are discussed with boundary-value problems. Electromagnetic radiation and scattering from circular and annular aperture geometries are summarized. The utility of the mode-matching method in circular and annular aperture scattering is emphasized.

The research on body-centric wireless communications (BCWCs) is becoming very hot because of numerous applications, especially the application of E-health systems. Therefore, a small multi-band and low-profile planar inverted-F antenna (PIFA) with tuning function is presented for BCWCs in this paper. In order to achieve multi-band operation, there are two branches in the antenna: the longer branch low frequency band (950–956 MHz), and the shorter branch with a varactor diode embedded for high frequency bands. By supplying different DC voltages, the capacitance of the varactor diode varies, so the resonant frequency can be tuned without changing the dimension of the antenna. While the bias is set at 6 V and 14 V, WiMAX and ISM bands can be covered, respectively. From the radiation patterns, at 950 MHz, the proposed antenna is suitable for on-body communications, and in WiMAX and ISM bands, they are suitable for both on-body and off-body communications.

In this letter, a timing synchronization scheme is proposed for cooperative WBAN which can be utilized in wireless medical telemetry systems. The approach efficiently exploits the cyclic structure of a presented preamble in order to effectively separate the superposition of cooperative signals. Then, each timing-offset and each channel parameter are estimated in the separated signal. The proposed scheme effectively recovers the original data based on the timing-offset estimates and the channel estimates. The simulation results reveal the excellent performance of the suggested method in terms of MSE and PER.

In this paper, we study how to automatically classify mathematical expressions written in MathML (Mathematical Markup Language). It is an essential preprocess to resolve analysis problems originated from multi-meaning mathematical symbols. We first define twelve equation classes based on chapter information of mathematics textbooks and then conduct various experiments. Experimental results show an accuracy of 94.75%, by employing the feature combination of tags, operators, strings, and “identifier & operator” bigram.

Computational Fluid Dynamics (CFD) is used as a common design tool in the aerospace industry. UPACS, a package for CFD, is convenient for users, since a customized simulator can be built just by selecting desired functions. The problem is its computation speed, which is difficult to enhance by using the clusters due to its complex memory access patterns. As an economical solution, accelerators using FPGAs are hopeful candidate. However, the total scale of UPACS is too large to be implemented on small numbers of FPGAs. For cost efficient implementation, partial reconfiguration which dynamically loads only required functions is proposed in this paper. Here, the MUSCL scheme, which is used frequently in UPACS, is selected as a target. Partial reconfiguration is applied to the flux limiter functions (FLF) in MUSCL. Four FLFs are implemented for Turbulence MUSCL (TMUSCL) and eight FLFs are for Convection MUSCL (CMUSCL). All FLFs are developed independently and separated from the top MUSCL module. At start-up, only required FLFs are selected and deployed in the system without interfering the other modules. This implementation has successfully reduced the resource utilization by 44% to 63%. Total power consumption also reduced by 33%. Configuration speed is improved by 34-times faster as compared to full reconfiguration method. All implemented functions achieved at least 17 times speed-up performance compared with the software implementation.

We propose a methodology of loop design optimization for fourth-order fractional-N phase locked loop (PLL) frequency synthesizers featuring a short settling time of 5 µsec for applications in an active RFID (radio frequency identification) and automobile smart-key systems. To establish the optimized design flow, equations presenting the relationship between the specification and PLL loop parameters in terms of settling time, loop bandwidth, phase margin, and phase noise are summarized. The proposed design flow overcomes the settling time inaccuracy in conventional second-order approximation methods by obtaining the accurate relationship between settling time and loop bandwidth with the MATLAB Control System Toolbox for the fourth-order PLLs. The proposed flow also features the worst-case design by taking account of the process, voltage, and temperature (PVT) variations in loop filter components, and considers the tradeoff between phase noise and area. The three-step optimization process consists of 1) the derivation of the accurate relationship between the settling time and loop bandwidth for various PVT conditions, 2) the derivation of phase noise and area as functions of area-dominant filter capacitance, and 3) the derivation of all PLL loop components values. The optimized design result is compared with circuit simulations using an actually designed fourth-order fractional-N PLL in a 1.8 V 0.18 µm CMOS technology. The error between the design and simulation for the setting time is reduced from 0.63 µsec in the second-order approximation to 0.23 µsec in the fourth-order optimization that proves the validity of the proposed method for the high-speed settling operations.

The convergence behavior of turbo APPM (TAPPM) decoding is analyzed by using a three-dimensional extrinsic information transfer (EXIT) chart and the decoding trajectory. The signal-to-noise ratio (SNR) threshold, below which iterative decoding fails to converge, is predicted by using the 3-D EXIT chart analysis. Bit error rate performances of TAPPM schemes validate the EXIT-chart-based SNR threshold predictions. Outer constituent codes of TAPPM are chosen to show the lowest SNR threshold with the aid of EXIT chart analysis.

In our previous research, to achieve unequal error protection (UEP), we proposed a scheme which encodes the data by randomly switching between several codes which use different signal constellations and showed the effectiveness in AWGN channels. In this letter, we propose our UEP system using MMSE-FDE for fast and selective fading by using the fact that importance levels are changed every few symbols, i.e., every block, in the proposed system. We confirmed the improvement in BER performance and the effectiveness of adaptive equalization for the proposed system in fading channels. Moreover, in fading channels we confirmed the validity of the theoretical tradeoff shown in static conditions.

Mining and explaining relationships between concepts are challenging tasks in the field of knowledge search. We propose a new approach for the tasks using disjoint paths formed by links in Wikipedia. Disjoint paths are easy to understand and do not contain redundant information. To achieve this approach, we propose a naive method, as well as a generalized flow based method, and a technique for mining more disjoint paths using the generalized flow based method. We also apply the approach to classification of relationships. Our experiments reveal that the generalized flow based method can mine many disjoint paths important for understanding a relationship, and the classification is effective for explaining relationships.

To meet the demand for light sources for on-chip optical interconnections, we demonstrate the continuous-wave (CW) operation of photonic-crystal (PhC) nanocavity lasers at up to 89.8 by using InP buried heterostructures (BH). The wavelength of a PhC laser can be precisely designed over a wide range exceeding 100 nm by controlling the lattice constant of the PhC. The dynamic responses of the PhC laser are also demonstrated with a 3-dB bandwidth of over 7.0 GHz at 66.2. These results reveal the laser's availability for application to wavelength division multiplexed (WDM) optical interconnection on CMOS chips. We discuss the total bandwidths of future on-chip optical interconnections, and report the capabilities of PhC lasers.