Showing papers by "NEC published in 2012"

Semiconductor device and manufacturing method thereof

Abstract: There is provided a low-cost semiconductor device that commercial and quality-assured (inspected) chip size packages can be stacked and has a small co-planarity value and a high mounting reliability. A semiconductor device in which a flexible circuit substrate is adhered to at least a part of a lateral side of a semiconductor package, and the flexible circuit substrate, which is on a side facing solder balls of the semiconductor package, is folded at a region inside of an edge of the semiconductor package (FIG. 1).

Less is more: trading a little bandwidth for ultra-low latency in the data center

Abstract: Traditional measures of network goodness--goodput, quality of service, fairness--are expressed in terms of bandwidth. Network latency has rarely been a primary concern because delivering the highest level of bandwidth essentially entails driving up latency--at the mean and, especially, at the tail. Recently, however, there has been renewed interest in latency as a primary metric for mainstream applications. In this paper, we present the HULL (High-bandwidth Ultra-Low Latency) architecture to balance two seemingly contradictory goals: near baseline fabric latency and high bandwidth utilization. HULL leaves 'bandwidth headroom' using Phantom Queues that deliver congestion signals before network links are fully utilized and queues form at switches. By capping utilization at less than link capacity, we leave room for latency sensitive traffic to avoid buffering and the associated large delays. At the same time, we use DCTCP, a recently proposed congestion control algorithm, to adaptively respond to congestion and to mitigate the bandwidth penalties which arise from operating in a bufferless fashion. HULL further employs packet pacing to counter burstiness caused by Interrupt Coalescing and Large Send Offloading. Our implementation and simulation results show that by sacrificing a small amount (e.g., 10%) of bandwidth, HULL can dramatically reduce average and tail latencies in the data center.

Design and Characterization of Miniaturized Patch Antennas Loaded With Complementary Split-Ring Resonators

Abstract: An investigation into the design of compact patch antennas loaded with complementary split-ring resonators (CSRRs) and reactive impedance surface (RIS) is presented in this study. The CSRR is incorporated on the patch as a shunt LC resonator providing a low resonance frequency and the RIS is realized using the two-dimensional metallic patches printed on a metal-grounded substrate. Both the meta-resonator (CSRR) and the meta-surface (RIS) are able to miniaturize the antenna size. By changing the configuration of the CSRRs, multi-band operation with varied polarization states can be obtained. An equivalent circuit has been developed for the CSRR-loaded patch antennas to illustrate their working principles. Six antennas with different features are designed and compared, including a circularly-polarized antenna, which validate their versatility for practical applications. These antennas are fabricated and tested. The measured results are in good agreement with the simulation.

TWINE: A Lightweight Block Cipher for Multiple Platforms ⋆

Abstract: This paper presents a 64-bit lightweight block cipher TWINE supporting 80 and 128- bit keys. TWINE realizes quite small hardware implementation similar to the previous lightweight block cipher proposals, yet enables efficient software implementations on various platforms, from micro-controller to high-end CPU. This characteristic is obtained by the use of generalized Feistel structure combined with an improved block shuffle, introduced at FSE 2010. Keywords: lightweight block cipher, generalized Feistel structure, block shuffle

Spin-current-driven thermoelectric coating

Abstract: Energy harvesting technologies, which generate electricity from environmental energy, have been attracting great interest because of their potential to power ubiquitously deployed sensor networks and mobile electronics. Of these technologies, thermoelectric (TE) conversion is a particularly promising candidate, because it can directly generate electricity from the thermal energy that is available in various places. Here we show a novel TE concept based on the spin Seebeck effect, called 'spin-thermoelectric (STE) coating', which is characterized by a simple film structure, convenient scaling capability, and easy fabrication. The STE coating, with a 60-nm-thick bismuth-substituted yttrium iron garnet (Bi:YIG) film, is applied by means of a highly efficient process on a non-magnetic substrate. Notably, spin-current-driven TE conversion is successfully demonstrated under a temperature gradient perpendicular to such an ultrathin STE-coating layer (amounting to only 0.01% of the total sample thickness). We also show that the STE coating is applicable even on glass surfaces with amorphous structures. Such a versatile implementation of the TE function may pave the way for novel applications making full use of omnipresent heat.

\textnormal{\textsc{TWINE}}: A Lightweight Block Cipher for Multiple Platforms

Abstract: This paper presents a 64-bit lightweight block cipher \(\textnormal{\textsc{TWINE}}\) supporting 80 and 128-bit keys. \(\textnormal{\textsc{TWINE}}\) realizes quite small hardware implementation similar to the previous lightweight block cipher proposals, yet enables efficient software implementations on various CPUs, from micro-controllers to high-end CPUs. This characteristic is obtained by the use of generalized Feistel combined with an improved block shuffle, introduced at FSE 2010.

Electric-field control of magnetic domain-wall velocity in ultrathin cobalt with perpendicular magnetization

Abstract: The manipulation of domain walls in magnetic materials is attracting interest because of its potential use in memory devices. Chiba et al. demonstrate that the velocity of domain walls in perpendicularly magnetized films can be changed by more than an order of magnitude by applying an electric field.

Terabit Optical Access Networks Based on WDM-OFDMA-PON

Abstract: Next-generation optical access networks are envisioned to evolve into a converged, high-speed, multiservice platform supporting residential, business, mobile backhaul, and special purpose applications. Moreover, bandwidth demand projections suggest that terabit aggregate capacity may need to be reached in such next-generation passive optical networks (PON). To satisfy these requirements while leveraging the large investments made in existing fiber plants, a wavelength division multiplexed (WDM)-based long-reach PON architecture combined with a multiple access technology that features a passive last-mile split, large per-λ speeds, and statistical bandwidth multiplexing can be exploited. In this paper, the first terabit PON based on hybrid WDM orthogonal frequency division multiple access (OFDMA) technology is proposed and experimentally verified. To enable high-speed, long-reach transmission with simplified optical network unit (ONU)-side digital signal processing, multiband OFDMA with ONU-side sub-band selectivity is proposed. Design challenges and tradeoffs between analog and digital domain sub-band combining and selection are also discussed. Finally, the experimental setup and results of the first 1.2 Tb/s (1 Tb/s after overhead) symmetric WDM-OFDMA-PON over 90 km straight single-mode fiber and 1:32 passive split, featuring multiband OFDMA, digitally selective ONUs, and a coherent-receiver OLT are presented and analyzed. By supporting up to 800 ONUs with 1.25/10 Gb/s guaranteed/peak rates and exhibiting a record rate-distance product achieved in long-reach PON, the demonstrated architecture may be viewed as promising for future converged terabit optical metro/access.

Electrical control of Curie temperature in cobalt using an ionic liquid film

Abstract: The electric field effect on magnetization properties and Curie temperature of Co ultra-thin films has been investigated. An electric field is applied to a Co film by using an electric double layer (EDL) formed in a polymer film containing an ionic liquid. The change in the Curie temperature is ∼100 K by applying the gate voltage of ±2 V, suggesting that the observed large modifications of magnetization properties are attributed to the significant change in the Curie temperature, which is induced by a large amount of carrier density control due to the formation of the EDL.

Operations management apparatus, operations management system, data processing method, and operations management program

Abstract: An operations management apparatus which acquires performance information for each of a plurality of performance items from a plurality of controlled units and manages operation of the controlled units includes a correlation model generation unit which derives a correlation function between a first element and a second element of the performance information, generates a correlation model between the first element and the second element based on the correlation function, and obtains the correlation model for each element pair of the performance information, and a model searching unit which searches for the correlation model for each element between an input element and an output element among elements of the performance information in series, and predicts a value of the output element from a value of the input element based on the searched correlation model.

Path control method for multihop wireless network

Abstract: A multihop wireless network includes a plurality of wireless nodes. Each wireless node calculates a metric value indicating a quantity of providing a guideline for selecting a superordinate destination node with each candidate for the superordinate destination node when carrying out a multihop wireless communication with a specific wireless node based on peripheral node information about node information received from the peripheral wireless nodes and determines the superordinate destination node based on the calculated metric value. The network system selects a superordinate wireless node as a target wireless node expected to change the number of the wireless nodes existing in a subordinate hierarchy, and intentionally changes a value of the node information sent from the target wireless node to the peripheral wireless nodes.

Network entity, communication device, mobile communication device and method thereof

Abstract: A communication system is described in which a mobile communication device receives MDT configuration requests from a base station or radio network controller to initiate an MDT measurement session for obtaining measurement data and location related data for identifying a location to which said measurement data relates. The mobile communication device checks a user consent indicator in memory and only provides the location related data if the user consent indicator indicates that a user of the mobile communication device consents to the provision the location related data.

Computer system, and communication method

Abstract: In a computer system according to the present invention, by using an ARP response packet in which a MAC address of a physical server is set as a transmission source MAC address, the MAC address of the physical server corresponding to a target VIP address included in an ARP request packet from a terminal device, a controller executes a proxy response to the ARP request packet to notify the terminal device of the MAC address of the physical server which is the access destination of the terminal device. In addition, the controller sets a flow entry to the switch, the flow entry regulating that a reception packet, which is transmitted from the terminal device and in which the MAC address is set as a destination MAC address, is made to be forwarded to a communication route to the physical server. Accordingly, a server which is an access destination of a terminal device can be arbitrarily set while increase of costs is suppressed in a high-speed network environment.

A 25.6 W 13.56 MHz wireless power transfer system with a 94% efficiency GaN Class-E power amplifier

Abstract: In this work, we propose the design and implementation of a 13.56 MHz GaN Class-E power amplifier, which takes into account transistor parasitic effects. The design uses the parasitic capacitance of the transistor to replace the charging capacitance, simplifying the circuit structure and obtaining a 93.6% efficiency at output power of 26.8 W. In addition, a wireless power transfer system using the proposed Class-E amplifier is demonstrated, achieving a 73.4% system efficiency when the power delivered to the load is 25.6 W.

High-Speed Quantum Key Distribution System for 1-Mbps Real-Time Key Generation

Abstract: A high-speed quantum key distribution (QKD) system has been developed with the goal of a 1-Mbps final secure key generation rate under 10-dB transmission loss, which corresponds to 50 km of standard single mode fiber. For the purpose of speeding-up all processes in QKD sequence, we apply a wavelength-division-multiplexing (WDM) technique using the colorless interferometric technique and a key distillation hardware (HW) engine. We establish a novel WDM scheme, sharing interferometers and their temperature regulators over multiple channels, which enables us to increase the number of channels with a small impact on system cost and size. To generate a secure key while satisfying both high speed and high security, we develop a key distillation HW engine which enables us to execute key distillation with 1-Mbit code length in real time. We have experimentally evaluated the performance of the developed system through installed fiber. By operating three wavelength channels, a new, world leading key generation rate of greater than 200 kbps over a 14.5-dB transmission loss has been achieved.

A 3.14 um 2 4T-2MTJ-cell fully parallel TCAM based on nonvolatile logic-in-memory architecture

Abstract: A four-MOS-transistor/two-MTJ-device (4T-2MTJ) cell circuit is proposed and fabricated for a standby-power-free and a high-density fully parallel nonvolatile TCAM. By optimally merging a nonvolatile storage function and a comparison logic function into a TCAM cell circuit with a nonvolatile logic-in-memory structure, the transistor counts required in the cell circuit become minimized. As a result, the cell size becomes 3.14um2 under a 90-nm CMOS and a 100-nm MTJ technologies, which achieves 60% and 86% of area reduction in comparison with that of a 12T-SRAM-based and a 16T-SRAM-based TCAM cell circuit, respectively.

High-speed wavelength-division multiplexing quantum key distribution system

Abstract: A high-speed quantum key distribution system was developed with the wavelength-division multiplexing (WDM) technique and dedicated key distillation hardware engines. Two interferometers for encoding and decoding are shared over eight wavelengths to reduce the system’s size, cost, and control complexity. The key distillation engines can process a huge amount of data from the WDM channels by using a 1 Mbit block in real time. We demonstrated a three-channel WDM system that simultaneously uses avalanche photodiodes and superconducting single-photon detectors. We achieved 12 h continuous key generation with a secure key rate of 208 kilobits per second through a 45 km field fiber with 14.5 dB loss.

A Design and Implementation of OpenFlow Controller Handling IP Multicast with Fast Tree Switching

Abstract: We present a design of an OpenFlow controller handling IP multicast and a method to switch a multicast tree to the other with little packet loss. Reducing packet loss during reconstruction of multicast tree triggered by a failure has been an important problem to make multicast communications more reliable. One approach for this problem is to use redundant trees for multicast trees, but algorithms to compute redundant trees require centralized computation therefore cannot be used in IP network. We used OpenFlow, which has features of centralized control and programmability, to realize redundant multicast trees in the network. In this paper, we present a design of an OpenFlow controller supporting IP multicast and a method to set up multiple multicast trees of one multicast group in the network for fast tree switching. To avoid delivering duplicate packets to the receivers, we assign an ID to each tree, embed it into multicast packets, and select the tree to deliver multicast packets in the sender switch by rewriting the packet header. We showed little packet loss when switching the multicast tree triggered by the failure using implementation of the OpenFlow controller by the evaluation experiment.

Communication system, method, and apparatus

Abstract: A core network includes a plurality of nodes that serve as nodes managing mobility of a terminal and that are different with regards to service functions that nodes provide to the terminal. Based on subscriber information and terminal information, a node to be connected to the terminal is selected on the core network side, depending on a service characteristic utilized by the terminal or on a type of the terminal and the terminal is connected to the selected node.

Terminal, control device, communication method, communication system, communication module, program, and information processing device

Abstract: A terminal communicating with a network including a forwarding device(s) for forwarding a packet and a control device for controlling the forwarding device(s) in accordance with a request from the forwarding device, includes: a communication unit that receives a processing rule indicating that a packet for communicating with a first destination is changed so as to communicate with a second destination, from the control device; a storage unit that stores the received processing rule, and a processing unit that in a case of communicating with the network, changes a destination of a packet in accordance with a processing rule that corresponds to the packet by referring to the processing rule stored in the storage unit.

Database encryption system, method, and program

Abstract: A user apparatus connected to database apparatus via network comprises: unit that manages key information in order to encrypt and decrypt; storage unit that stores security configuration information of data and/or metadata; application response unit that determines whether or not encryption is necessary for database operation command, and if encryption is necessary, selects encryption algorithm corresponding to data and/or metadata, performs encryption, and transmits result to database control unit to cause database control unit to execute database operation, if encryption is not necessary, transmits database operation command to database control unit to cause database control unit to execute database operation, and receives processing result transmitted by database control unit, and if decryption or conversion of data and/or metadata of processing result is necessary, performs necessary decryption or conversion, and returns response to database operation command; and security configuration unit that configures security information of data stored in database.

Term synonym acquisition method and term synonym acquisition apparatus

Abstract: A term synonym acquisition apparatus includes: a first generating unit which generates a context vector of an input term in an original language and a context vector of each synonym candidate in the original language; a second generating unit which generates a context vector of an auxiliary term in an auxiliary language that is different from the original language, where the auxiliary term specifies a sense of the input term; a combining unit which generates a combined context vector based on the context vector of the input term and the context vector of the auxiliary term; and a ranking unit which compares the combined context vector with the context vector of each synonym candidate to generate ranked synonym candidates in the original language.

Machine learning predictive modelling high-level synthesis design space exploration

Abstract: A machine learning-based predictive model design space exploration (DSE) method for high-level synthesis (HLS) is presented The method creates a predictive model for a training set until a given error threshold is reached and then continues with the exploration using the predictive model avoiding time-consuming synthesis and simulations of new configurations Results show that the authors' method is on average 192 times faster than a genetic-algorithm DSE method generating comparable results, whereas it achieves better results when constraining the DSE runtime When compared with a previously developed simulated annealer (SA)-based method, the proposed method is on average 209 faster, although again achieving comparable results

Spectroscopy of low-frequency noise and its temperature dependence in a superconducting qubit

Abstract: We report a direct measurement of the low-frequency noise spectrum in a superconducting flux qubit. Our method uses the noise sensitivity of a free-induction Ramsey interference experiment, comprising free evolution in the presence of noise for a fixed period of time followed by single-shot qubit-state measurement. Repeating this procedure enables Fourier-transform noise spectroscopy with access to frequencies up to the achievable repetition rate, a regime relevant to dephasing in ensemble-averaged time-domain measurements such as Ramsey interferometry. Rotating the qubit's quantization axis allows us to measure two types of noise: effective flux noise and effective critical-current or charge noise. For both noise sources, we observe that the very same 1/f-type power laws measured at considerably higher frequencies (0.2-20 MHz) are consistent with the noise in the 0.01-100-Hz range measured here. We find no evidence of temperature dependence of the noises over 65-200 mK, and also no evidence of time-domain correlations between the two noises. These methods and results are pertinent to the dephasing of all superconducting qubits. © 2012 American Physical Society.

Sensitivity Analysis of Server Virtualized System Availability

Abstract: Server virtualization is a technology used in many enterprise systems to reduce operation and acquisition costs, and increase the availability of their critical services. Virtualized systems may be even more complex than traditional nonvirtualized systems; thus, the quantitative assessment of system availability is even more difficult. In this paper, we propose a sensitivity analysis approach to find the parameters that deserve more attention for improving the availability of systems. Our analysis is based on Markov reward models, and suggests that host failure rate is the most important parameter when the measure of interest is the system mean time to failure. For capacity oriented availability, the failure rate of applications was found to be another major concern. The results of both analyses were cross-validated by varying each parameter in isolation, and checking the corresponding change in the measure of interest. A cost-based optimization method helps to highlight the parameter that should have higher priority in system enhancement.

Factorized Asymptotic Bayesian Inference for Mixture Modeling

Abstract: This paper proposes a novel Bayesian approximation inference method for mixture modeling. Our key idea is to factorize marginal log-likelihood using a variational distribution over latent variables. An asymptotic approximation, a factorized information criterion (FIC), is obtained by applying the Laplace method to each of the factorized components. In order to evaluate FIC, we propose factorized asymptotic Bayesian inference (FAB), which maximizes an asymptotically-consistent lower bound of FIC. FIC and FAB have several desirable properties: 1) asymptotic consistency with the marginal log-likelihood, 2) automatic component selection on the basis of an intrinsic shrinkage mechanism, and 3) parameter identifiability in mixture modeling. Experimental results show that FAB outperforms state-of-the-art VB methods.

Method of manufacturing semiconductor device

Abstract: A trench gate type power transistor of high performance is provided. A trench gate as a gate electrode is formed in a super junction structure comprising a drain layer and an epitaxial layer. In this case, the gate electrode is formed in such a manner that an upper surface of the epitaxial layer becomes higher than that of a channel layer formed over the drain layer. Then, an insulating film is formed over each of the channel layer and the epitaxial layer and thereafter a part of the insulating film is removed to form side wall spacers over side walls of the epitaxial layer. Subsequently, with the side wall spacers as masks, a part of the channel layer and that of the drain layer are removed to form a trench for a trench gate.

Breaking and Repairing GCM Security Proofs

Abstract: In this paper, we study the security proofs of GCM Galois/Counter Mode of Operation. We first point out that a lemma, which is related to the upper bound on the probability of a counter collision, is invalid. Both the original privacy and authenticity proofs by the designers are based on the lemma. We further show that the observation can be translated into a distinguishing attack that invalidates the main part of the privacy proof. It turns out that the original security proofs of GCM contain a flaw, and hence the claimed security bounds are not justified. A very natural question is then whether the proofs can be repaired. We give an affirmative answer to the question by presenting new security bounds, both for privacy and authenticity. As a result, although the security bounds are larger than what were previously claimed, GCM maintains its provable security. We also show that, when the nonce length is restricted to 96 bits, GCM has better security bounds than a general case of variable length nonces.

Distributed storage system and distributed storage method

Abstract: A distributed storage system of the present invention includes a plurality of data nodes coupled via a network and respectively including data storage units. At least two of the data nodes hold in the respective data storage units thereof replicas of a plurality of types of data structures that are logically identical but are physically different between the data nodes.

Content delivery system, controller and content delivery method

Abstract: In delivering contents over a mobile network, network congestion is to be avoided. From a cache server that temporarily retains at least part of a plural number of contents stored in a storage apparatus, a controller receives an access frequency to the contents and a load state of the cache server. The controller also receives, from a packet forwarding apparatus, information of a terminal being or not being in a service area. The controller decides that a content an access frequency to which is higher than a predetermined threshold value will be allocated to two or more of the plural number of the cache servers predetermined. The controller also decides that at least part of the other contents will be allocated to the plural number of the cache servers using at least one out of the access frequency, the load state, the information of a terminal being or not being in a service area and topology information of the mobile network. The controller instructs the cache servers to retain the contents depending on the decided allocation.