Error analysis of the multilevel fast multipole algorithm is studied for electromagnetic scattering problems. We propose novel error prediction and control methods and verify that the computational error for scattering problems with over one million unknowns can be precisely controlled under desired digits of accuracy. Optimum selection of truncation numbers to minimize computational error also will be discussed.

In the scattering problem of periodic gratings, at a low grazing limit of incidence, the incident plane wave is completely cancelled by the reflected wave, and the total wave field vanishes and physically becomes a dark shadow. This problem has received much interest recently. Nakayama et al. have proposed “the shadow theory”. The theory was first applied to the diffraction by perfectly conductive gratings as an example, where a new description and a physical mean at a low grazing limit of incidence for the gratings have been discussed. In this paper, the shadow theory is applied to the analyses of multilayered dielectric periodic gratings, and is shown to be valid on the basis of the behavior of electromagnetic waves through the matrix eigenvalue problem. Then, the representation of field distributions is demonstrated for the cases that the eigenvalues degenerate in the middle regions of multilayered gratings in addition to at a low grazing limit of incidence and some numerical examples are given.

Evaluation of addition coefficients introduced by the addition theorems for vector spherical harmonics is one of the most intractable problems in electromagnetic scattering by multi-sphere systems. The derivation of the analytical expressions for the addition coefficients is lengthy and complex while the computation of the addition coefficients is annoyingly time-consuming even with the reasonably fast computers available nowadays. This paper presents an efficient algorithm for calculating addition coefficients which is based on the recursive relations of scalar addition coefficients. Numerical results from the formulation derived in this paper agree with those of previous published results but the algorithm proposed here reduces the computational time considerably. This paper also discusses the strengths and limitations of other formulations and numerical techniques found in the literature.

In this paper, we shall describe a basic fuzzy-estimation theory based on the concept of set-valued operators, suitable for available operation of extremely complicated large-scale network systems. Fundamental conditions for availability of system behaviors of such network systems are clarified in a form of β-level fixed point theorem for system of fuzzy-set-valued operators. Here, the proof of this theorem is accomplished by the concept of Hausdorff's ball measure of non-compactness introduced into the Banach space.

We introduce a novel method to optimize field decomposition for a mode matching technique. Using our method, expanded mode numbers can be minimized to achieve the desired digits of computational accuracy.

Recently, numerous service discovery protocols have been introduced in the open literature. Unfortunately, many of them did not consider security issues, and for those that did, many security and privacy problems still remain. One important issue is to protect the privacy of a service provider while enabling an end-user to search an alternative service using multiple keywords. To deal with this issue, the existing protocols assumed that a directory server should be trusted or owned by each service provider. However, an adversary may compromise the directory server due to its openness property. In this paper, we suggest an efficient verification of service subscribers to resolve this issue and analyze its performance and security. Using this method, we propose an efficient and secure service discovery protocol protecting the privacy of a service provider while providing multiple keywords search to an end-user. Also, we provide performance and security analysis of our protocol.

Pairings on elliptic curves over finite fields are crucial for constructing various cryptographic schemes. The ηT pairing on supersingular curves over GF(3n) is particularly popular since it is efficiently implementable. Taking into account the Menezes-Okamoto-Vanstone attack, the discrete logarithm problem (DLP) in GF(36n) becomes a concern for the security of cryptosystems using ηT pairings in this case. In 2006, Joux and Lercier proposed a new variant of the function field sieve in the medium prime case, named JL06-FFS. We have, however, not yet found any practical implementations on JL06-FFS over GF(36n). Therefore, we first fulfill such an implementation and we successfully set a new record for solving the DLP in GF(36n), the DLP in GF(36·71) of 676-bit size. In addition, we also compare JL06-FFS and an earlier version, named JL02-FFS, with practical experiments. Our results confirm that the former is several times faster than the latter under certain conditions.

Constructing a secure and efficient key wrapping scheme is demanding, and the scheme based on a universal hash function and an elementary encryption mode like ECB and CBC modes is potential for a practical use. However, at SAC 2009, Gennaro and Halevi showed that a key wrapping scheme using a universal hash function and ECB mode (a HtECB scheme) is broken, and the security of a scheme based on a universal hash function and CBC mode (a HtCBC scheme) has been left as an open problem. In this paper, we first generalize classical notions of universal and uniform hash functions, and propose a total of four new notions of the keyed hash function. We then prove that HtECB and HtCBC schemes are secure key wrapping schemes if the universal hash function satisfies uniformity and our notions, where the result on the HtCBC scheme gives a partial answer to the open problem. Then we discuss a basic problem of identifying relations between various notions of a keyed hash function, and point out that a monic polynomial hash function satisfies all the new notions.

A total-field/scattered-field (TF/SF) boundary for the constrained interpolation profile (CIP) method is proposed for multi-dimensional electromagnetic problems. Incident fields are added to or subtracted from update equations in order to satisfy advection equations into which Maxwell's equations are reduced by means of the directional splitting. Modified incident fields are introduced to take into account electromagnetic fields after advection. The developed TF/SF boundary is examined numerically, and the results show that it operates with good performance. Finally, we apply the proposed TF/SF boundary to a scattering problem, and it can be solved successfully.

This paper presents a restoration method using several degraded observed images obtained through a technique known as microscanning. It is shown that microscanning provides sufficient spatial information for image restoration with minimal information about the original image and without knowing the interference function that causes degradation.

Asymptotic expansions of the amplitudes of the direct and scattered waves in a waveguide system with an imperfection core are derived for large core number and the partial cancellation of the direct wave by the scattered wave is shown in detail. The total power of light in the cross section of a waveguide system is analytically derived and it is shown that the total power of the sum of the direct and scattered waves decreases from that of the direct wave because of the cancellation, the difference of the total power transfers to the localized wave and the total power of light is conserved.

In Long-Term Evolution (LTE)-Advanced, an important goal in addition to achieving high-speed, high-capacity communications is throughput enhancement for cell-edge users. One solution is to relay radio transmissions between an eNode B and user equipment (UE). Relays are expected to extend the coverage to the cell boundary and coverage hole areas, and are expected to reduce network costs. It was agreed that in Release 10 LTE, a Layer-3 (L3) relay, which achieves self-backhauling of radio signals between an eNode B and a UE in Layer 3 should be standardized. Meanwhile, a Layer-1 (L1) relay, which amplifies and forwards received radio frequency signals, has already found widespread use in second-generation and third-generation mobile communication systems. This paper investigates the downlink system level performance for L3 and L1 relays with orthogonal frequency division multiple access (OFDMA) in LTE-Advanced. Various practical factors are taken into account in the evaluations such as the processing delay and upper bound of the amplifier gain of the L1 relay, capacity limitation of the backhaul channels, and empty buffer status at the L3 relay. We also propose and investigate a downlink backhaul link (radio link between the eNode B and L3 relay node) scheduling method for the in-band half-duplex L3 relay. In the proposed scheduling method, radio resources from an eNode B to an L3 relay node and macro UE are multiplexed in the same backhaul subframe considering the number of relay UEs and macro UEs, and the channel quality of the backhaul link to the L3 relay and the access link to the macro UE. Based on system-level simulations, we clarify the system impact of several conditions for the relay such as the number of relay nodes and the number of backhaul (radio link between eNode B and L3 relay) subframes, the distance between the eNode B and relay, and show the throughput performance gain of the L3 relay compared to the L1 relay. We also clarify that the cell-edge UE throughput performance is increased by approximately 10% by applying the proposed scheduling method due to more efficient and fair resource allocation to the L3 relay and macro UEs.

A finite buffer shared by multiple packet queues is considered. Partitioning the buffer to maximize total throughput is formulated as a resource allocation problem, the solution is shown to be achieved by a greedy incremental algorithm in polynomial time. The optimal buffer allocation strategy is applied to different models for a wireless downlink. First, a set of parallel M/M/1/mi queues, corresponding to a downlink with orthogonal channels is considered. It is verified that at high load, optimal buffer partitioning can boost the throughput significantly with respect to complete sharing of the buffer. Next, the problem of optimal combined buffer allocation and channel assignment problems are shown to be separable in an outage scenario. Motivated by this observation, buffer allocation is considered in a system where users need to be multiplexed and scheduled based on channel state. It is observed that under finite buffers in the high load regime, scheduling simply with respect to channel state with a simply partitioned buffer achieves comparable throughput to combined channel and queue-aware scheduling.

In this paper, we propose an iterative minimum mean square error detection with interference cancellation (MMSED-IC) for frequency-domain filtered single carrier (SC)-frequency-division multiple-access (FDMA) uplink transmission. The use of a square-root Nyquist transmit filter reduces the peak-to-average power ratio (PAPR) while increases the frequency-diversity gain. However, if carrier-frequency separation among multiple-access users is kept the same as the one used for the case of roll-off factor α=0 (i.e., brick-wall filter), then the adjacent users' spectra will overlap and multi-user interference (MUI) occurs. The proposed MMSED-IC can sufficiently suppress the MUI from adjacent users while achieving the maximum frequency-diversity gain. We apply the proposed MMSED-IC to a packet access using filtered SC-FDMA, multi-input multi-output (MIMO) multiplexing, and hybrid automatic repeat request (HARQ). It is shown by computer simulation that filtered SC-FDMA with α=1 can achieve higher throughput than orthogonal frequency division multiple access (OFDMA).

In this letter, we propose two antenna grouping schemes for uplink Nx SC-FDMA MIMO systems, where the multiple component carriers can be divided into several groups which are handled by different antennas, thus the number of component carriers on each antenna will be reduced by the group method. As a result, the peak-to-average power ratio (PAPR) of each antenna has been reduced. To further enhance the performance, an interleaving method is proposed to achieve better diversity gain due to the channel varying in the spatial domain and the frequency domain during one turbo coded stream. Our simulation figures clearly demonstrate that in all examples, the proposed schemes are shown to be effective in improving the Block Error Rate (BLER) performance while reducing the PAPR.

Ridge optical waveguides (OWGs) of fluorinated polyimides were deposited on a quartz crystal microbalance (QCM), and a hybrid sensor employing the OWG spectroscopy and the QCM technique was prepared. A polyvinyl alcohol (PVA) film with CoCl2 was deposited on the OWG, and humidity sensing characteristics were investigated. White light was entered into the waveguide and the output light spectra was observed. The output light intensity markedly changed because of the chromism of CoCl2 by humidity sorption. During the output light measurement, the QCM frequency was monitored simultaneously. The humidity dependences of the QCM frequency and output light were also investigated in a range from 10% to 70%. Furthermore, the response to hydrofluoroether (HFE) was observed, and the change in the output light was hardly observed because CoCl2 does not exhibit chromism in HFE sorption.

It is well known that an nth-order real polynomial D(z)= is Schur stable if its coefficients satisfy the monotonic condition, i.e., dn > dn-1 > > d1 > d0 > 0. In this letter it is shown that even if the monotonic condition is violated by one coefficient (say dk), D(z) is still Schur stable if the deviation of dk from dk+1 or dk-1 is not too large. More precisely we derive upper bounds for the admissible deviations of dk from dk+1 or dk-1 to ensure the Schur stability of D(z). It is also shown that the results obtained in this letter always yield the larger stability range for dk than an existing result.

Traditional cellular networks suffer the so-called “cell-edge problem” in which the user throughput is deteriorated because of pathloss and inter-cell (co-channel) interference. Recently, Base Station Cooperation (BSC) was proposed as a solution to the cell-edge problem by alleviating the interference and improving diversity and multiplexing gains at the cell-edge. However, it has minimal impact on cell-inner users and increases the complexity of the network. Moreover, static clustering, which fixes the cooperating cells, suffers from inter-cluster interference at the cluster-edge. In this paper, dynamic fractional cooperation is proposed to realize dynamic clustering in a shared RRU network. In the proposed algorithm, base station cooperation is performed dynamically at cell edges for throughput improvement of users located in these areas. To realize such base station cooperation in large scale cellular networks, coordinated scheduling and distributed dynamic cooperation are introduced. The introduction of coordinated scheduling in BSC multi-user MIMO not only maximizes the performance of BSC for cell-edge users but also reduces computational complexity by performing simple single-cell MIMO for cell-inner users. Furthermore, the proposed dynamic clustering employing shared RRU network realizes efficient transmission at all cell edges by forming cooperative cells dynamically with minimal network complexity. Owing to the combinations of the proposed algorithms, dynamic fractional cooperation achieves high network performance at all areas in the cellular network. Simulation results show that the cell-average and the 5% cell-edge user throughput can be significantly increased in practical cellular network scenarios.

A two-dimensional shape is generally represented with line drawings or object contours in a digital image. Shapes can be divided into two types, namely ordered and unordered shapes. An ordered shape is an ordered set of points, while an unordered shape is an unordered set. As a result, each type typically uses different attributes to define the local descriptors involved in representing the local distributions of points sampled from the shape. Throughout this paper, we focus on unordered shapes. Since most local descriptors of unordered shapes are not scale-invariant, we usually make the shapes in an image data set the same size through scale normalization, before applying shape matching procedures. Shapes obtained through scale normalization are suitable for such descriptors if the original whole shapes are similar. However, they are not suitable if parts of each original shape are drawn using different scales. Thus, in this paper, we present a scale-invariant descriptor constructed by von Mises distributions to deal with such shapes. Since this descriptor has the merits of being both scale-invariant and a probability distribution, it does not require scale normalization and can employ an arbitrary measure of probability distributions in matching shape points. In experiments on shape matching and retrieval, we show the effectiveness of our descriptor, compared to several conventional descriptors.

This paper proposes a test scheduling method for stuck-at faults in a CHAIN interconnect, which is an asynchronous on-chip interconnect architecture, with scan ability. Special data transfer which is permitted only during test, is exploited to realize a more flexible test schedule than that of a conventional approach. Integer linear programming (ILP) models considering such special data transfer are developed according to the types of modules under test in a CHAIN interconnect. The obtained models are processed by using an ILP solver. This framework can not only obtain optimal test schedules but also easily introduce additional constraints such as a test power budget. Experimental results using benchmark circuits show that the proposed method can reduce test application time compared to that achieved by the conventional method.