This paper presents a method of synthesizing covariance matrix elements of array input signal for high resolution 2-D Direction-Of-Arrival (DOA) estimation via antenna (sensor) switching. Antenna array generally has the same number of array elements and receiver modules which often leads large receiver hardware cost. Two of the authors have already studied a way of antenna switching to reduce receiver cost, but it can be applied only for periodic incident signals like sinusoid. In this paper, we propose two simple methods of DOA estimation from sparse data by synthesizing covariance matrix elements of array input signal via antenna switching, which can also be applied to DOA estimation of antiperiodic incident signals. Performance of the proposed approach is evaluated in detail through some computer simulation.

In this paper, Hermite polynomial representation is proposed as an alternative way to represent finite fields of characteristic two. We show that multiplication in Hermite polynomial representation can be achieved with subquadratic space complexity. This representation enables us to find binomial or trinomial irreducible polynomials which allows us faster modular reduction over binary fields when there is no desirable such low weight irreducible polynomial in other representations. We then show that the product of two elements in Hermite polynomial representation can be performed as Toeplitz matrix-vector product. This representation is very interesting for NIST recommended binary field GF(2571) since there is no ONB for the corresponding extension. This representation can be used to obtain more efficient finite field arithmetic.

Based on sample-pair refinement and local optimization, this paper proposes a high-accuracy and quick matting algorithm. First, in order to gather foreground/background samples effectively, we shoot rays in hybrid (gradient and uniform) directions. This strategy utilizes the prior knowledge to adjust the directions for effective searching. Second, we refine sample-pairs of pixels by taking into account neighbors'. Both high confidence sample-pairs and usable foreground/background components are utilized and thus more accurate and smoother matting results are achieved. Third, to reduce the computational cost of sample-pair selection in coarse matting, this paper proposes an adaptive sample clustering approach. Most redundant samples are eliminated adaptively, where the computational cost decreases significantly. Finally, we convert fine matting into a de-noising problem, which is optimized by minimizing the observation and state errors iteratively and locally. This leads to less space and time complexity compared with global optimization. Experiments demonstrate that we outperform other state-of-the-art methods in local matting both on accuracy and efficiency.

We propose a current mode sense amplifier that uses a current-mirror to increase the bitline sensing current, which dominates the sensing speed. A comparison of the sensing delay shows that the proposed sense amplifier can provide about 12.6∼15.4% improvement depending on different bitline loads in sensing speed over original WTA scheme.

In this paper, for an odd prime p such that p≡3 mod 4, odd n, and d=(pn+1)/(pk+1)+(pn-1)/2 with k|n, the value distribution of the exponential sum S(a,b) is calculated as a and b run through $mathbb{F}_{p^n}$. The sequence family $mathcal{G}$ in which each sequence has the period of N=pn-1 is also constructed. The family size of $mathcal{G}$ is pn and the correlation magnitude is roughly upper bounded by $(p^k+1)sqrt{N}/2$. The weight distribution of the relevant cyclic code C over $mathbb{F}_p$ with the length N and the dimension ${ m dim}_{mathbb{F}_p}mathcal{C}=2n$ is also derived.

This paper introduces two schemes to put the decoding of the convolutional network code (CNC) into practice, which are named the Intermittent Packet Transmission Scheme (IPTS) and the Redundancy Packet Transmission Scheme (RPTS). According to the decoding formula of the sink nodes, we can see that, at the time k+δ in order to decode the source packet generated at time k, the sink node should know all the source packets generated before k-1. This is impractical. The two schemes we devised make it unnecessary. A construction algorithm is also given about the RPTS networks. For the two schemes, we analyze the strengths and weaknesses and point out their implemented condition.

The authors have developed a mechanism that applies real vibration to electrical contacts by hammering oscillation in the vertical direction similar to that in real cases, and they have studied the effects of micro-oscillation on the contacts using the mechanism. It is shown that the performance of the hammering oscillation mechanism (HOM) for measuring acceleration and force is superior to that of other methods in terms of the stability of data. Using the mechanism, much simpler and more practical protocols are proposed for evaluating acceleration, force, and mass using only the measured acceleration. It is also indicated that the relationship between the inertial force generated by the hammering oscillation mechanism and the frictional force in electrical devices attached on a board is related to one of the causes of the degradation of electrical contacts under the effect of external micro-oscillation.

The conventional hybrid STBC schemes can achieve less BER performance for STBC detection schemes than conventional STBC schemes since SM symbols interfere with STBC symbols. Therefore, this letter proposes the improved scheme for hybrid STBC systems. STBC and SM schemes are combined for the hybrid space-time block code system. Our approach effectively obtains both diversity gain and spectral efficiency gain. The proposed scheme offers improved BER performance since it uses iterative detection. Moreover, it increases the data rate effectively with a little performance loss.

In this paper, we propose a novel layered scalable- multiple description coding (LS-MDC) which offers the benefits of both scalable video coding and multiple description coding for robust video transmission over packet lossy networks. In the proposed LS-MDC method, multiple descriptions including base layer, enhancement layers, and their corresponding FEC parity data are allocated into two network paths of a path diversity system. Unlike the conventional approaches, the source base/enhancement data and their own parities in the proposed method are not transmitted together but are transferred over different paths. Therefore, the effect of burst packet losses can be effectively reduced for the descriptions. Furthermore, in order to minimize the overall distortion for the LS-MDC system and exploit the benefits of path diversity, we also propose an optimal rate allocation scheme that can adaptively control the transmission rate as well as the channel coding rate for media senders. Experiments show that the proposed method provides much better peak signal-to-noise ratio (PSNR) than conventional MDC techniques.

The authors previously conducted the observation of microstructures and three-dimensional SEM on fretting wear phenomena at tin-plated contacts. In this study, we report the fretting characteristics of dissimilar metal contacts by studying the relation between the contact resistance behaviors and micro structural changes of gold and tin-plated fretting contacts, through surface SEM observations and cross sectional SEM and AES analysis.

In this paper, for an odd prime p, new quaternary sequences of even period 2p with ideal autocorrelation property are constructed using the binary Legendre sequences of period p. For the new quaternary sequences, two properties which are considered as the major characteristics of pseudo-random sequences are derived. Firstly, the autocorrelation distribution of the proposed quaternary sequences is derived and it is shown that the autocorrelation values of the proposed quaternary sequences are optimal. For both p≡1 mod 4 and p≡3 mod 4, we can construct optimal quaternary sequences while only for p≡3 mod 4, the binary Legendre sequences can satisfy ideal autocorrelation property. Secondly, the linear complexity of the proposed quaternary sequences is also derived by counting non-zero coefficients of the discrete Fourier transform over the finite field Fq which is the splitting field of x2p-1. It is shown that the linear complexity of the quaternary sequences is larger than or equal to p or (3p+1)/2 for p≡1 mod 4 or p≡3 mod 4, respectively.

Current network elements consume 10-20% of the total power in data centers. Today's network elements are not energy-proportional and consume a constant amount of energy regardless of the amount of traffic. Thus, turning off unused network switches is the most efficient way of reducing the energy consumption of data center networks. This paper presents Honeyguide, an energy optimizer for data center networks that not only turns off inactive switches but also increases the number of inactive switches for better energy-efficiency. To this end, Honeyguide combines two techniques: 1) virtual machine (VM) and traffic consolidation, and 2) a slight extension to the existing tree-based topologies. Honeyguide has the following advantages. The VM consolidation, which is gracefully combined with traffic consolidation, can handle severe requirements on fault tolerance. It can be introduced into existing data centers without replacing the already-deployed tree-based topologies. Our simulation results demonstrate that Honeyguide can reduce the energy consumption of network elements better than the conventional VM migration schemes, and the savings are up to 7.8% in a fat tree with k=12.

To enhance the throughput while satisfying the quality of service (QoS) requirements of wireless local area networks (WLANs), this paper proposes a distributed coordination function-based (DCF-based) medium access control (MAC) protocol that realizes centralized radio resource management (RRM) for a basic service set. In the proposed protocol, an access point (AP) acts as a master to organize the associated stations and attempts to reserve the radio resource in a conventional DCF-manner. Once the radio resource is successfully reserved, the AP controls the access of each station by an orthogonal frequency division multiple access (OFDMA) scheme. Because the AP assigns radio resources to the stations through the opportunistic two-dimensional scheduling based on the QoS requirements and the channel condition of each station, the transmission opportunities can be granted to the appropriate stations. In order to reduce the signaling overhead caused by centralized RRM, the proposed protocol introduces a station-grouping scheme which groups the associated stations into clusters. Moreover, this paper proposes a heuristic resource allocation algorithm designed for the DCF-based MAC protocol. Numerical results confirm that the proposed protocol enhances the throughput of WLANs while satisfying the QoS requirements with high probability.

A method to estimate sound source orientation in a reverberant room using a microphone array is proposed. We extend the conventional modeling of a room transfer function based on the image method in order to take into account the directivity of a sound source. With this extension, a transfer function between a sound source and a listener (or a microphone) is described by the superposition of transfer functions from each image source to the listener multiplied by the source directivity; thus, the sound source orientation can be estimated by analyzing how the image sources are distributed (power distribution of image sources) from observed signals. We applied eigenvalue analysis to the spatial correlation matrix of the microphone array observation to obtain the power distribution of image sources. Bsed on the assumption that the spatial correlation matrix for each set of source position and orientation is known a priori, the variation of the eigenspace can be modeled. By comparing the eigenspace of observed signals and that of pre-learned models, we estimated the sound source orientation. Through experiments using seven microphones, the sound source orientation was estimated with high accuracy by increasing the reverberation time of a room.

Design equations for satisfying off-nominal operating conditions of the class E amplifier with a nonlinear shunt capacitance for a grading coefficient of 0.5 and the duty cycle D=0.5 are derived. By exploiting the off-nominal class E operation, various amplifier parameters such as input voltage, operating frequency, output power, and load resistance can be set as design specifications. As a result of the analysis in this paper, the following extension of the usability of the class E amplifier was achieved. With rising up the dc supply voltage, the shunt capacitance which achieves the off-nominal operation can be increased. This means that a transistor with higher output capacitance can be used for ZVS operation. This also means that maximum operating frequency which achieves ZVS can be increased. An example of a design procedure of the class E amplifier is given. The theoretical results were verified with an experiment.

Break arcs are generated in a DC48V resistive circuit. The circuit current is varied from 1A to 6A. The contact resistance distribution on the anode surfaces eroded by break arcs is investigated. The following results are shown. When the current is 2A, 3A and 6A, the contact resistance at the center region of the anode surface is higher than that around the center region. The contact resistance around the center region decreases with the decrease of the circuit current. When the current is 1A, the contact resistance is very low at all positions on the contact surface. The lower contact resistance may be caused by the occurrence of the short arc that is extinguished in the metallic phase arc.

Information security has been seriously threatened by the differential power analysis (DPA). Delay-based dual-rail precharge logic (DDPL) is an effective solution to resist these attacks. However, conventional DDPL convertors have some shortcomings. In this paper, we propose improved convertor pairs based on dynamic logic and a sense amplifier (SA). Compared with the reference CMOS-to-DDPL convertor, our scheme could save 69% power consumption. As to the comparison of DDPL-to-CMOS convertor, the speed and power performances could be improved by 39% and 54%, respectively.

Orthogonal arrays have important applications in statistics and computer science, as well as in coding theory. In this letter, a new construction method of symmetric orthogonal arrays of strength t is proposed, which is a concatenation of two orthogonal partitions according to a latin square. As far as we know, this is a new construction of symmetric orthogonal arrays of strength t, where t is a given integer. Based on the different latin squares, we also study the enumeration problem of orthogonal partitions, and a lower bound on the count of orthogonal partitions is derived.

This paper proposes the use of on-chip monitor circuits to detect process shift and process spread for post-silicon diagnosis and model-hardware correlation. The amounts of shift and spread allow test engineers to decide the correct test strategy. Monitor structures suitable for detection of process shift and process spread are discussed. Test chips targeting a nominal process corner as well as 4 other corners of “slow-slow”, “fast-fast”, “slow-fast” and “fast-slow” are fabricated in a 65nm process. The monitor structures correctly detects the location of each chip in the process space. The outputs of the monitor structures are further analyzed and decomposed into the process variations in threshold voltage and gate length for model-hardware correlation. Path delay predictions match closely with the silicon values using the extracted parameter shifts. On-chip monitors capable of detecting process shift and process spread are helpful for performance prediction of digital and analog circuits, adaptive delay testing and post-silicon statistical analysis.

NAND Flash memories are widely used as data storages today. The memories are not intrinsically error free because they are affected by several physical disturbances. Technology scaling and introduction of multi-level cell (MLC) has improved data density, but it has made error effect more significant. Error control codes (ECC) are essential to improve reliability of NAND Flash memories. Efficiency of codes depends on error characteristic of systems, and codes are required to be designed to reflect this characteristic. In MLC Flash memories, errors tend to direct values to neighborhood. These errors are a class of M-ary asymmetric symbol error. Some codes which reflect the asymmetric property were proposed. They are designed to correct only 1 level shift errors because almost all of the errors in the memories are in such errors. But technology scaling, increase of program/erase (P/E) cycles, and MLC storing the large number of bits can cause multiple-level shift. This paper proposes single error control codes which can correct an error of more than 1 levels shift. Because the number of levels to be corrected is selectable, we can fit it into noise magnitude. Furthermore, it is possible to add error detecting function for error of the larger shift. Proposed codes are equivalent to a conventional integer codes, which can correct 1 level shift, on a certain parameter. Therefore, the codes are said to be generalization of conventional integer codes. Evaluation results show information lengths to respective check symbol lengths are larger than nonbinary Hamming codes and other M-ary asymmetric symbol error correcting codes.