In wireless networks, how to provide reliable data transfer is an important and challenging issue due to channel fading and interference. Several approaches, e.g., Automatic Repeat reQuest (ARQ), Hybrid ARQ (HARQ) and Network Coding (NC), are used to enhance reliability of transmission in wireless networks. However, we note that these schemes implement the data recovery process for mixed unicast and multicast (MUM) communications by simply separating the process into two phases, unicast and multicast phase. This is inefficient and expensive. In this paper, we propose an efficient retransmission scheme with network coding for MUM transmission, aiming at improving bandwidth utilization. UMNC searches for coding opportunities from both unicast and multicast flows, which offer the potential benefit of improved recovery in the event of packet loss. We theoretically prove that UMNC can effectively reduce the total number of retransmissions and thus improve bandwidth efficiency, compared with existing schemes.

As a consequence of recent developments in communications, the parameters of communication signals, such as the modulation parameter values, are becoming unstable because of time-varying SNR under electromagnetic conditions. In general, it is difficult to classify target signals that have time-varying parameters using traditional signal recognition methods. To overcome this problem, this study proposes a novel recognition method that works well even for such time-dependent communication signals. This method is mainly composed of feature extraction and classification processes. In the feature extraction stage, we adopt Shannon entropy and index entropy to obtain the stable features of modulated signals. In the classification stage, the interval gray relation theory is employed as suitable for signals with time-varying parameter spaces. The advantage of our method is that it can deal with time-varying SNR situations, which cannot be handled by existing methods. The results from numerical simulation show that the proposed feature extraction algorithm, based on entropy characteristics in time-varying SNR situations,offers accurate clustering performance, and the classifier, based on interval gray relation theory, can achieve a recognition rate of up to 82.9%, even when the SNR varies from -10 to -6 dB.

Most of scientists except computer scientists do not want to make efforts for performance tuning with rewriting their MPI applications. In addition, the number of processing elements which can be used by them is increasing year by year. On large-scale parallel systems, the number of accumulated messages on a message buffer tends to increase in some of their applications. Since searching message queue in MPI is time-consuming, system side scalable acceleration is needed for those systems. In this paper, a support function named LHS (Limited-length Head Separation) is proposed. Its performance in searching message buffer and hardware cost are evaluated. LHS accelerates searching message buffer by means of switching location to store limited-length heads of messages. It uses the effects such as increasing hit rate of cache on host with partial off-loading to hardware. Searching speed of message buffer when the order of message reception is different from the receiver's expectation is accelerated 14.3 times with LHS on FPGA-based network interface card (NIC) named DIMMnet-2. This absolute performance is 38.5 times higher than that of IBM BlueGene/P although the frequency is 8.5times slower than BlueGene/P. LHS has higher scalability than ALPU in the performance per frequency. Since these results are obtained with partially on loaded linear searching on old Pentium®4, performance gap will increase using state of art CPU. Therefore, LHS is more suitable for larger parallel systems. The discussions for adopting proposed method to state of art processors and systems are also presented.

We have studied photo-induced effects in a p-type transistor based on a [1]benzothieno[3,2-b]benzothiophene (BTBT) derivative. Repetition of blue light irradiation and electrical characterization under dark reveals that its threshold voltage gradually shifts in the positive direction as the cumulative exposure time increases. This shift is slowly reversed when the transistor is stored under dark. The onset voltage defined as the gate bias at which the sub-threshold current exceeds a certain level behaves in a similar manner. Mobility remains more or less the same during this exposure period and the storage period. Time evolution of the threshold voltage shift is fit by a model assuming two charged meta-stable states decaying independently. A set of parameters consists of a decay constant for each state and the ratio of the two states. A single parameter set reproduces the positive shift during the exposure period and the negative shift during the storage period. Time evolution of the onset voltage is reproduced by the same parameter set. We have also studied photo-induced effects in two types of n-type transistors where either a pure solution of a perylene derivative or a solution mixed with an insulating polymer is used for printing each semiconductor layer. A similar behavior is observed for these transistors: blue light irradiation under a negative gate bias shifts the threshold and the onset voltages in the negative direction and these shifts are reversed under dark. The two-component model reproduces the behavior of these voltage shifts and the parameter set is slightly different among the two transistors made from different semiconductor solutions. The onset voltage shift is well correlated to the threshold voltage shift for the three types of organic transistors studied here. The onset voltage is more sensitive to illumination than the threshold voltage and its sensitivity differs among transistors.

This paper presents a new scalable method to considerably reduce the rollback propagation effect of the conventional optimistic message logging by utilizing positive features of reliable FIFO group communication links. To satisfy this goal, the proposed method forces group members to replicate different receive sequence numbers (RSNs), which they assigned for each identical message to their group respectively, into their volatile memories. As the degree of redundancy of RSNs increases, the possibility of local recovery for each crashed process may significantly be higher. Experimental results show that our method can outperform the previous one in terms of the rollback distance of non-faulty processes with a little normal time overhead.

This paper proposes novel robust speech F0 estimation using Summation Residual Harmonics (SRH) based on TV-CAR (Time-Varying Complex AR) analysis. The SRH-based F0 estimation was proposed by A. Alwan, in which the criterion is calculated from LP residual signals. The criterion is summation of residual spectrum value for harmonics. In this paper, we propose SRH-based F0 estimation based on the TV-CAR analysis, in which the criterion is calculated from the complex AR residual. Since complex AR residual provides higher resolution of spectrum, it can be considered that the criterion is effective for F0 estimation. The experimental results demonstrate that the proposed method performs better than conventional methods; weighted auto-correlation and YIN.

A new method for predominant melody extraction from polyphonic music signals based on harmonic structure is proposed. The proposed method first extracts a set of fundamental frequency candidates by analyzing the distance between spectral peaks. Then, the predominant fundamental frequency is selected by pitch tracking according to the harmonic strength of the selected candidates. Finally, the method runs pitch smoothing on a large temporal scale for eliminating pitch doubling error, and conducts voicing frame detection. The proposed method shows the best overall performance for ADC 2004 DB in the MIREX 2011 audio melody extraction task.

A new theoretical formulation based on BIBO (Bounded Input Bounded Output) operators is proposed for a general feedback amplifier circuit. Several fundamental theorems are derived in this letter. The main theorem provides a basis for a realization of an inverse of a feedback-branch linear or nonlinear BIBO operator satisfying the associative law.

Nature-inspired devices and architectures are attracting considerable attention for various purposes, including the development of novel computing techniques based on spatiotemporal dynamics, exploiting stochastic processes for computing, and reducing energy dissipation. This paper demonstrates that networks of optical energy transfers between quantum nanostructures mediated by optical near-field interactions occurring at scales far below the wavelength of light could be utilized for solving a constraint satisfaction problem (CSP), the satisfiability problem (SAT), and a decision making problem. The optical energy transfer from smaller quantum dots to larger ones, which is a quantum stochastic process, depends on the existence of resonant energy levels between the quantum dots or a state-filling effect occurring at the larger quantum dots. Such a spatiotemporal mechanism yields different evolutions of energy transfer patterns in multi-quantum-dot systems. We numerically demonstrate that networks of optical energy transfers can be used for solution searching and decision making. We consider that such an approach paves the way to a novel physical informatics in which both coherent and dissipative processes are exploited, with low energy consumption.

This paper investigates space and polarization multiplexing for multichannel transmission in a 120-GHz band wireless link system. The 120-GHz-band wireless equipment employs Cassegrain antennas with a gain of about 49dBi and cross-polar discrimination of 23dB. When each of two 120-GHz wireless links transmits a 10-Gbit/s data signal in the same direction over a distance of 800m, a bit error rate (BER) of below 10-12 is obtained when the receivers are set 30m apart. When forward error correction and polarization multiplexing are used for each wireless link, we can set two wireless links within 1m of each other and obtain a BER below 10-12. Moreover, we have experimentally shown that the rain attenuation of V- and H-polarization 120-GHz-band signal is almost the same.

With the approval of IEEE 1901 standard for power line communications (PLC) and the recent Internet-enable home appliances like the IPTV having access to a content-on-demand service through the Internet as AcTVila in Japan, there is no doubt that PLC has taken a great step forward to emerge as the preeminent in-home-network technology. However, existing schemes developed so far have not considered the PLC network connected to an unstable Internet environment (i.e. more realistic situation). In this paper, we investigate the communication performance from the end-user's perspective in networks with large and variable round-trip time (RTT) and with the existence of cross-traffic. Then, we address the problem of unfair bandwidth allocation when multiple and different types of flows coexist and propose a TCP rate control considering the difference in terms of end-to-end delay to solve it. We validate our methodology through simulations, and show that it effectively deals with the throughput unfairness problem under critical communication environment, where multiple flows with different RTTs share the PLC and cross-traffic exists on the path of the Internet.

The underlaying architecture of Device-to-device (D2D) communication supports direct communication between users by reusing the radio resources of the LTE-A system. Despite the co-channel interference between the conventional cellular user equipment (CUE) and the D2D communication user equipment (DUE), LTE-A system can improve the combined data rate of CUEs and DUEs through effective transmit power control and resource allocation schemes. In this paper, we propose a novel mechanism, which combines the resource allocation scheme with the transmit power control scheme to maximize the overall data rate (defined as the sum-rate in the paper). We perform system-level simulations to determine the effectiveness of the proposed mechanism in terms of increasing the sum-rate. The simulation result shows that the proposed mechanism can improve the sum-rate in an underlaying LTE-A system that supports D2D communication.

A microwave mammography setup for clinical testing was developed and used to successfully carry out an initial clinical test. The equipment is based on multistatic ultra wideband (UWB) radar, which features a multistatic microwave imaging via space time (MS-MIST) algorithm for high resolution and a conformal array with an aspirator for fixing the breast in place. In this paper, an outline of the equipment, a numerical simulation, and clinical test results are presented.

Multiple access relay systems with network coding provide spatial diversity with fewer transmissions. However, errors generated at the relay can propagate to the destination and the system performance can be severely degraded. Although many techniques have been proposed to resolve the error propagation, these techniques require some special operations at the relay or complicated reception schemes at the destination unless the global channel state information is available at the destination. This paper proposes a simple cooperative demodulation scheme for multiple access relay systems with network coding assuming that the relay simply forwards the decoded data and the destination has only the local channel state information.

In this paper, we propose a novel baseband (BB) phase shifter (PS) using a fixed-gain-amplifier (FGA) matrix. The proposed BB PS consists of 5 stages of a vector synthesis type FGA matrix with in-phase/quadrature-phase (I/Q) input/output interfaces. In order to achieve low gain variation between phase shift states, 3rd to 5th stages are designed to have a phase shift of +φi and -φi (i=3,4,5). To change between +φi and -φi phase shift states, two FGAs with DC bias in-phase/out-phase switches are used. The two FGAs have the same gain, therefore ideally no gain variation can be achieved. Using this configuration, phase shift error and gain variation caused by process mismatch and temperature variation can be reduced. Fabricated 5-bit BB PS has 3-dB bandwidth of 1.05GHz, root-mean-square (rms) phase errors lower than 2.2°, rms gain variations lower than 0.42dB. Power consumption of the PS core and output buffer are 4.9mW and 14.3mW, respectively. 1-dB compression output power is -12.5dBm. The fabricated PS shows that the total phase shift error and gain variation are within the required accuracy of a 5-bit PS with no requirement of calibration.

This paper introduces open-wire fault-resilient multiple-valued codes for reliable asynchronous point-to-point global communication links. In the proposed encoding, two communication modules assign complementary codewords that change between two valid states without an open-wire fault. Under an open-wire fault, at each module, the codewords don't reach to one of the two valid states and remains as “invalid” states. The detection of the invalid states makes it possible to stop sending wrong codewords caused by an open-wire fault. The detectability of the open-wire fault based on the proposed encoding is proven for m-of-n codes. The proposed code used in the multiple-valued asynchronous global communication link is capable of detecting a single open-wire fault with 3.08-times higher coding efficiency compared with a conventional multiple-valued code used in a triple-modular redundancy (TMR) link that detects an open-wire fault under the same dynamic range of logical values.

Many applications of wireless sensor networks (WSNs) require secure communication. The tree-based key management scheme, which is a symmetric key scheme, provides backward and forward secrecy. The sensor nodes in the communication group share a secret key for encrypting messages. When the sensor nodes are added to or evicted from the group, the group key has to be updated by sending rekeying messages. In this paper, we propose a method of key tree structure (KTS) generation by considering the addition and eviction ratio of sensor nodes to reduce the number of rekeying messages, which is influenced by the structure of the tree. For this, we define an extension of an existing tree structure such as a binary or ternary tree and generate KTS using an A* algorithm. To reduce the energy consumed by the message transmission, we also exploit genetic algorithm (GA) to build a secure communication group by considering the KTS. In the paper, we show the effectiveness of the proposed method compared with the existing structure via the simulation in terms of memory usage, the number of rekeying messages and energy consumption.

We experimentally investigate and analyze faults in optical fiber connections with refractive index matching material that have incorrectly cleaved fiber ends. We explain that incorrectly cleaved fiber ends, which are not ideal because they are uneven and not perpendicular to the fiber axis, are caused by defective optical fiber cleavers. We discover that the optical performance of field installable connections using incorrectly cleaved fiber ends might change greatly. We also infer that the significant change in insertion and return losses might be attributed to partially air-filled gaps by using scatter diagrams of measured insertion and return losses. Our experiment results reveal that the optical performance might deteriorate to more than 40dB in terms of insertion loss and less than 30dB in terms of return loss.

We have optimized and evaluated organic thin-film solar cell devices with a structure of graded junction. The graded junction consisting of donor and accepter materials was fabricated by varying the deposition rates of both materials with a continuous grading, using two evaporation sources of cupper phthalocyanine and fullerene as p- and n-type materials, respectively. By evaluating device characteristics, optimized device structure ITO/CuPc (10 nm)/graded layer (35 nm)/C60 (15 nm)/BCP (10 nm)/Ag (100 nm) with an efficiency of 1.36% was obtained. In the structure, short-circuit current density was the largest and existence of larger voltage dependence in current density was observed. In addition, we have measured temperature dependences of current density versus voltage characteristics in the graded organic solar cell under illumination. The carrier extraction was enhanced by changing voltage possibly due to the internal electric field of the graded junction.

The sub-channel is empty except each user's allocated sub-channel in an orthogonal frequency division multiple access (OFDMA) system. The scheme of cooperative communication using this empty sub-channel has been studied. But, because each user wastes the time slots in the cooperation phase, it is difficult to achieve the full rate. In this letter, a new cooperative communication scheme based on OFDMA is proposed to improve transmission rate in Rayleigh fading channel.