As one innovative research that heavily depends on the network virtualization for its realization and deployment on an Internet-scale, we propose an approach to utilize user resources in information-centric network (ICN). We try to fully benefit from the in-network cache that is one attractive feature of ICN by expanding the in-network cache indirectly based on the user resources. To achieve this, in this paper, we focus on how to encourage users to contribute their resources in ICN. Through simulations, we examine a feasibility of our approach and an effect of user participation on the content distribution performance in ICN. We also briefly discuss how the network virtualization technique can be utilized for our research in terms of its evaluation and deployment.

This paper presents a high-efficiency boost converter with voltage clamp function. It clarifies how to design the inductance of the coupled inductor used in the converter, and derives characteristic equations that associate the fluctuation in the input voltage with the output ripple current. For this converter, a theoretical analysis, simulation and experimentation (prototype output: 98 V, 13 A) are performed. As a result, the converter is achieved high efficiency (Maximum efficiency: 98.1%) in the rated output condition, indicating that the voltage stress on the switching power semiconductors can be mitigated by using the voltage clamp function. And it is verified that the snubber circuit can be eliminated in the switching power semiconductors. In addition, the theoretical output ripple current characteristics are corresponded well with simulation and experimental results, and the validity of the design method is proved.

Due to universal frequency reuse, cell edge users in HSDPA suffer from serious inter-cell interference (ICI). In this letter we present a coordinated scheme for HSDPA which can mitigate ICI by interference avoidance in spatial domain. A system level simulation shows that our scheme can effectively improve the performance of the cell edge users.

In this letter, we propose a non-cooperative limited feedback precoding and subchannel selection scheme for non-reciprocal multiple-input multiple-output (MIMO) interference channels. At each iteration of the proposed scheme, each user updates its precoder selection for each subchannel and then chooses the predetermined number of subchannels in a distributed and non-cooperative way. We present simulation results to verify the performance of the proposed scheme.

NTRU is a public key cryptosystem based on hard problems over lattices. In this paper, we present efficient methods for convolution product computation which is a dominant operation of NTRU. The new methods are based on the observation that repeating patterns in coefficients of an NTRU polynomial can be used for the construction of look-up tables, which is a similar approach to the sliding window methods for exponentiation. We provide efficient convolution algorithms to implement this idea, and we make a comprehensive analysis of the complexity of the new algorithms. We also give software implementations over a Pentium IV CPU, a MICAz mote, and a CUDA-based GPGPU platform. According to our analyses and experimental results, the new algorithms speed up the NTRU encryption and decryption operations by up to 41%.

The broadcast scheduling problem (BSP) in wireless ad-hoc networks is a well-known NP-complete combinatorial optimization problem. The BSP aims at finding a transmission schedule whose time slots are collision free in a wireless ad-hoc network with time-division multiple access (TDMA). The transmission schedule is optimized for minimizing the frame length of the node transmissions and maximizing the utilization of the shared channel. Recently, many metaheuristics can optimally solve smaller problem instances of the BSP. However, for complex problem instances, the computation of metaheuristics can be quite time and memory consuming. In this work, we propose a greedy genetic algorithm for solving the BSP with a large number of nodes. We present three heuristic genetic operators, including a greedy crossover and two greedy mutation operators, to optimize both objectives of the BSP. These heuristic genetic operators can generate good solutions. Our experiments use both benchmark data sets and randomly generated problem instances. The experimental results show that our genetic algorithm is effective in solving the BSP problem instances of large-scale networks with 2,500 nodes.

Recently, some cryptographic primitives have been described that are based on the supposed hardness of finding an isogeny between two supersingular elliptic curves. As a part of such a primitive, Charles et al. proposed an algorithm for computing sequences of 2-isogenies. However, their method involves several redundant computations. We construct simple algorithms without such redundancy, based on very compact descriptions of the 2-isogenies. For that, we use some observations on 2-torsion points.

This paper deals with a characteristic of the so-called effective boundary condition for a plane wave scattering from periodic surfaces with perfect conductivity. The perturbation solution with all orders is explicitly given under the effective boundary condition. It is newly found that such a perturbation solution satisfies the optical theorem under the exact boundary condition. A comparison between such a perturbation solution and a reference solution for the exact boundary condition by other methods is performed. Then, the validity of such a perturbation solution is concretely discussed.

This article presents a differential fault analysis (DFA) technique using round addition for a generalized Feistel network (GFN) including CLEFIA and RC6. Here the term “round addition” means that the round operation executes twice using the same round key. The proposed DFA needs bypassing of an operation to count the number of rounds such as increment or decrement. To verify the feasibility of our proposal, we implement several operations, including increment and decrement, on a microcontroller and experimentally confirm the operation bypassing. The proposed round addition technique works effectively for the generalized Feistel network with a partial whitening operation after the last round. In the case of a 128-bit CLEFIA, we show a procedure to reconstruct the round keys or a secret key using one correct ciphertext and two faulty ciphertexts. Our DFA also works for DES and RC6.

The cooperative orthogonal frequency-division multiplexing (OFDM) relaying system is widely regarded as a key design for future broadband mobile cellular systems. This paper focuses on channel estimation in such a system that uses amplify-and-forward (AF) as the relaying strategy. In the cooperative AF relaying, the destination requires the individual (disintegrated) channel state information (CSI) of the source-relay (S-R) and relay-destination (R-D) links for optimum combination of the signals received from source and relay. Traditionally, the disintegrated CSIs are obtained with two channel estimators: one at the relay and the other at the destination. That is, the CSI of the S-R link is estimated at relay and passed to destination, and the CSI of the R-D link is estimated at destination with the help of pilot symbols transmitted by relay. In this paper, a new disintegrated channel estimator is proposed; based on an expectation-maximization (EM) algorithm, the disintegrated CSIs can be estimated solely by the estimator at destination. Therefore, the new method requires neither signaling overhead for passing the CSI of the S-R link to destination nor pilot symbols for the estimation of the R-D link. Computer simulations show that the proposed estimator works well under the signal-to-noise ratios of interest.

To improve Last-Level Cache (LLC) management, numerous approaches have been proposed requiring additional hardware budget and increased overhead. A number of these approaches even change the organization of the existing cache design. In this letter, we propose Adaptive Insertion and Promotion (AIP) policies based on Least Recently Used (LRU) replacement. AIP dynamically inserts a missed line in the middle of the cache list and promotes a reused line several steps left, realizing the combination of LRU and LFU policies deliberately under a single unified scheme. As a result, it benefits workloads with high locality as well as with many frequently reused lines. Most importantly, AIP requires no additional hardware other than a typical LRU list, thus it can be easily integrated into the existing hardware with minimal changes. Other issues around LLC such as scans, thrashing and dead lines are all explored in our study. Experimental results on the gem5 simulator with SPEC CUP2006 benchmarks indicate that AIP outperforms LRU replacement policy by an average of 5.8% on the misses per thousand instructions metric.

This paper describes a simulation platform for use in the quantitative assessment of different respiratory motion correction techniques in Coronary MR angiography (CMRA). The simulator incorporates acquisition of motion parameters from heart motion tracking and applies it to a deformable heart model. To simulate respiratory motion, a high-resolution 3-D coronary heart reference image is deformed using the estimated linear transformation from a series of volunteer coronal scout scans. The deformed and motion-affected 3-D coronary images are used to generate segmented k-space data to represent MR data acquisition affected by respiratory motion. The acquired k-space data are then corrected using different respiratory motion correction methods and converted back to image data. The resulting images are quantitatively compared with each other using image-quality measures. Simulation experiment results are validated by acquiring CMRA scans using the correction methods used in the simulation.

The Linking Open Data (LOD) cloud is a collection of linked Resource Description Framework (RDF) data with over 31 billion RDF triples. Accessing linked data is a challenging task because each data set in the LOD cloud has a specific ontology schema, and familiarity with the ontology schema used is required in order to query various linked data sets. However, manually checking each data set is time-consuming, especially when many data sets from various domains are used. This difficulty can be overcome without user interaction by using an automatic method that integrates different ontology schema. In this paper, we propose a Mid-Ontology learning approach that can automatically construct a simple ontology, linking related ontology predicates (class or property) in different data sets. Our Mid-Ontology learning approach consists of three main phases: data collection, predicate grouping, and Mid-Ontology construction. Experiments show that our Mid-Ontology learning approach successfully integrates diverse ontology schema with a high quality, and effectively retrieves related information with the constructed Mid-Ontology.

This paper identifies a ripple effect problem (REP) that spreads interference to neighbors and proposes a novel channel localization mechanism to decrease the REP in a Wi-Fi system. The proposed mechanism has less blocking probability when compared to a random channel allocation mechanism and also has increased channel reusability. The proposed mechanism in simulation yields less channels BEm as the number of users and Tused increase.

Network topology significantly affects network cost, path length, link load distribution, and reliability, so we need to consider multiple criteria with different units simultaneously when designing a network's topology. The analytic hierarchy process (AHP) is a technique of balancing multiple criteria in order to reach a rational decision. Using AHP, we can reflect the relative importance of each criterion on the evaluation result; therefore, we have applied it to network topology evaluation in past research. When evaluating network topologies using AHP, we need to construct the set of topology candidates prior to the evaluation. However, the time required to construct this set greatly increases as the network size grows. In this paper, we propose applying a binary partition approach for constructing a topology candidate set with dramatically reduced calculation time. To reduce the calculation time, we introduce an upper limit for the total link length. Although the results of AHP are affected by introducing the upper limit of the total link length, we show that desirable topologies are still selected in AHP.

In this paper, we study four simple but fundamental cooperative protocols operating in the decode-and-forward (DF) fashion. Intuitively, finding an appropriate relay for such protocols may greatly improve the outage performance in practice. To this end, we investigate the issue of relay selection in this paper. Specifically, using the asymptotic outage probability, we define and derive the cooperative gain (CG) which quantitatively evaluates the superiority of cooperation over direct transmission. To simplify the process of relay selection, we derive the cooperative region (CR) where a relay is necessarily invoked to aid the communication from source to destination. With the aid of CG and CR, we propose our relay selection algorithm requiring the geographical information rather than the instantaneous channel state information (CSI), and predict the optimal relay locations. In addition, two diversity bounds are also prepared and compared. Finally, both simulations and numerical results are provided on the asymptotic outage probability, CG and CR.

In this letter, we point out that key substitution attacks should be taken into account for multisignature schemes, which implies that the existing security notions for multisignature schemes are not sufficient. As an example, we show that the multisignature scheme proposed by Boldyreva at PKC'03 is susceptible to key substitution attacks.

A novel conjugate unitary ESPRIT (CU-ESPRIT) algorithm for the joint direction of departure (DOD), and direction of arrival (DOA), estimation in a bistatic MIMO radar is proposed. A new virtual array is formed by using the properties of noncircular signals, and the properties of the centro-Hermitian matrix are employed to convert the complex-valued data matrix into a real-valued data matrix. Then the real-valued rotational invariance properties of the new virtual array are determined to estimate DODs and DOAs, which are paired automatically. The proposed method provides better angle estimation performance and detects more targets owing to double number of MIMO virtual array elements. Simulation results are presented to verify the effectiveness of the proposed algorithm.

In this paper we propose MR-MAC, a new multiple reservation MAC protocol for asynchronous duty cycling wireless sensor networks. In MR-MAC, the receiver transmits a collection packet to the senders when it wakes up that asks for the number of packets each sender wants to send. Then each sender replies to the receiver according to the scheduled sequence with a short report packet. After getting the number of packets from each sender, the receiver assigns multiple batch transmission (MBT) for the senders and begins to initiate the transmissions. The senders then transmit packets to the receiver in a batch style as scheduled so that packets can be delivered to the receiver as fast as possible. Experiments on a Tmote-sky testbed show that our protocol outperforms other protocols in diverse performance metrics such as throughput, latency and energy efficiency.