This work proposes an exponential computation with low-computational complexity and applies this technique to the expectation-maximization (EM) algorithm for Gaussian mixture model (GMM). For certain machine-learning techniques, such as the EM algorithm for the GMM, fast and low-cost implementations are preferred over high precision ones. Since the exponential function is frequently used in machine-learning algorithms, this work proposes reducing computational complexity by transforming the function into powers of two and introducing a look-up table. Moreover, to improve efficiency the look-up table is scaled. To verify the validity of the proposed technique, this work obtains simulation results for the EM algorithm used for parameter estimation and evaluates the performances of the results in terms of the mean absolute error and computational time. This work compares our proposed method against the Taylor expansion and the exp( ) function in a standard C library, and shows that the computational time of the EM algorithm is reduced while maintaining comparable precision in the estimation results.

A gate-all-around tunneling field-effect transistor (GAA TFET) with local high-k gate-dielectric and tunneling-boost n-layer based on silicon is demonstrated by two dimensional (2D) device simulation. Application of local high-k gate-dielectric and n-layer leads to reduce the tunneling barrier width between source and intrinsic channel regions. Thus, it can boost the on-current (Ion) characteristics of TFETs. For optimal design of the proposed device, a tendency of device characteristics has been analyzed in terms of the high-k dielectric length (Lhigh-k) for the fixed n-layer length (Ln-layer). The simulation results have been analyzed in terms of on- and off-current (Ion and Ioff), subthreshold swing (SS), and RF performances.

The wideband noise controlling performance of the delayless subband adaptive filtering technique is affected by the group delay and in-band aliasing distortion of analysis filter banks. A method of recursive second-order cone programming is proposed to design the uniform DFT modulated analysis filter banks, with a small in-band aliasing error and low group delay. Simulation results show that the noise controlling performance is improved with small residual noise power spectra, a high noise attenuation level and fast convergence rate.

In this letter, we present an efficient method for high quality surface reconstruction from simulation data of smoothed particles hydrodynamics (SPH). For computational efficiency, instead of computing scalar field in overall particle sets, we only construct scalar field around fluid surfaces. Furthermore, an adaptive scalar field model is proposed, which adaptively adjusts the smoothing length of ellipsoidal kernel by a constraint-correction rule. Then the isosurfaces are extracted from the scalar field data. The proposed method can not only effectively preserve fluid details, such as splashes, droplets and surface wave phenomena, but also save computational costs. The experimental results show that our method can reconstruct the realistic fluid surfaces with different particle sets.

Training one-class support vector machines (one-class SVMs) involves solving a quadratic programming (QP) problem. By increasing the number of training samples, solving this QP problem becomes intractable. In this paper, we describe a modified Pegasos algorithm for fast training of one-class SVMs. We show that this algorithm is much faster than the standard one-class SVM without loss of performance in the case of linear kernel.

A predictive spatio-temporal interval join finds all pairs of moving objects satisfying a join condition on future time interval and space. In this paper, we propose a method called PTJoin. PTJoin partitions the inner index into small sub-trees and performs the join process for each sub-tree to reduce the number of disk page accesses for each window search. Furthermore, to reduce the number of pages accessed by consecutive window searches, we partition the index so that overlapping index pages do not belong to the same partition. Our experiments show that PTJoin reduces the number of page accesses by up to an order of magnitude compared to Interval_STJoin [9], which is the state-of-the-art solution, when the buffer size is small.

Searching for the shortest paths from a query point to several target points on a road network is an essential operation for several types of queries in location-based services. This search can be performed using Dijkstra's algorithm. Although the A* algorithm is faster than Dijkstra's algorithm for finding the shortest path from a query point to a target point, the A* algorithm is not so fast to find all paths between each point and the query point when several target points are given. In this case, the search areas on road network overlap for each search, and the total number of operations at each node is increased, especially when the number of query points increases. In the present paper, we propose the single-source multi-target A* (SSMTA*) algorithm, which is a multi-target version of the A* algorithm. The SSMTA* algorithm guarantees at most one operation for each road network node, and the searched area on road network is smaller than that of Dijkstra's algorithm. Deng et al. proposed the LBC approach with the same objective. However, several heaps are used to manage the search area on the road network and the contents in each heap must always be kept the same in their method. This operation requires much processing time. Since the proposed method uses only one heap, such content synchronization is not necessary. The present paper demonstrates through empirical evaluations that the proposed method outperforms other similar methods.

The effects of fluorine implantation on flicker noise and reliability of NMOSFET and PMOSFETs were concurrently investigated. The flicker noise of an NMOSFET was decreased about 66% by fluorine implantation, and that of a PMOSET was decreased about 76%. As indicated by the results, fluorine implantation is one of the methods that can be used to improve the noise characteristics of MOSFET devices. However, hot-carrier degradation was enhanced by fluorine implantation in NMOSFETs, which can be related to the difference of molecular binding within the gate oxide. On the contrary, in case of PMOSFETs, NBTI life time was increased by fluorine implantation. Therefore, concurrent investigation of hot-carrier and NBTI reliability and flicker noise is necessary in developing MOSFETs for analog/digital mixed signal applications.

Developing a complex network accelerator like an IPsec processor is a great challenge. To this end, we propose a Network Virtual Platform ( NetVP ) that consists of one or more virtual host (vHOST) modules and virtual local area network (vLAN) modules to support electronic system level (ESL) top-down design flow as well as provide the on-line verification throughout the entire development process. The on-line verification capability of NetVP enables the designed target to communicate with a real network for system validation. For ESL top-down design flow, we also propose untimed and timed interfaces to support hardware/software co-simulation. In addition, the NetVP can be used in conjunction with any ESL development platform through the untimed/timed interface. System development that uses this NetVP is efficient and flexible since it allows the designer to explore design spaces such as the network bandwidth and system architecture easily. The NetVP can also be applied to the development of other kinds of network accelerators.

Detailed tracking is required for many vision applications. A visual feature-based constraint underlies most conventional motion estimation methods. For example, optical flow methods assume that the brightness of each pixel is constant in two consecutive frames. However, it is difficult to realize accurate extraction and tracking using only visual feature information, because viewpoint changes and inconsistent illumination cause the visual features of some regions of objects to appear different in consecutive frames. A structure-based constraint of objects is also necessary for tracking. In the proposed method, both visual feature matching and structure matching are formulated as a linear assignment problem and then integrated.

A smart meter, a component of smart grid systems, has low computational capability. This is in contrast to data collection units (DCUs) and meter data management servers (MDMSs). In this study, we propose a lightweight signature scheme and an authentication and report protocol that can reduce computational overhead and facilitate efficient operation of these three components in smart grid systems. The proposed signature scheme, called the linear map digital signature scheme (LMDSS), uses properties of linear maps and matrix operations; hence, it has low computational requirements. The proposed protocol is a delegation-based authentication protocol that uses an intermediate node, DCU. Using the proposed protocol, authentication of a DCU can be completed by a hash function. To evaluate the performance of the scheme and protocol, we implemented signature schemes, ours and others, and simulated the proposed protocol to obtain analytical results. We also proved that the scheme is secure by using a random oracle and analyzing the security of the protocol based on possible attack scenarios.

Design of acoustic modem becomes increasingly important in underwater sensor networks' development. This paper presents the design of a reconfigurable acoustic modem, by defining modulation and demodulation as reconfigurable modules, the proposed modem changes its modulation scheme and data rate to provide reliable and energy efficient communication. The digital system, responsible for signal processing and control, is implemented on Xilinx Virtex5 FPGA. Hardware and software co-verification shows that the modem works correctly and can self-configure to BFSK and BPSK mode. Partial reconfiguration design method improves flexibility of algorithm design, and slice, LUT, register, DSP, RAMB are saved by 17%, 25%, 22%, 25%, 25% respectively.

This letter proposes an analog active noise control (ANC) circuit with an all-pass filter (APF). To improve performance of the previously reported analog ANC circuit, we inserted an APF to the circuit in order to fit phases of a noise and an electrical signal in the circuit. As a result, we confirmed improvement of the noise canceling effect of the analog ANC circuit.

This paper presents an M-channel (M=2n (n ∈ N)) integer discrete cosine transforms (IntDCTs) based on fast Hartley transform (FHT) for lossy-to-lossless image coding which has image quality scalability from lossy data to lossless data. Many IntDCTs with lifting structures have already been presented to achieve lossy-to-lossless image coding. Recently, an IntDCT based on direct-lifting of DCT/IDCT, which means direct use of DCT and inverse DCT (IDCT) to lifting blocks, has been proposed. Although the IntDCT shows more efficient coding performance than any conventional IntDCT, it entails many computational costs due to an extra information that is a key point to realize its direct-lifting structure. On the other hand, the almost conventional IntDCTs without an extra information cannot be easily expanded to a larger size than the standard size M=8, or the conventional IntDCT should be improved for efficient coding performance even if it realizes an arbitrary size. The proposed IntDCT does not need any extra information, can be applied to size M=2n for arbitrary n, and shows better coding performance than the conventional IntDCTs without any extra information by applying the direct-lifting to the pre- and post-processing block of DCT. Moreover, the proposed IntDCT is implemented with a half of the computational cost of the IntDCT based on direct-lifting of DCT/IDCT even though it shows the best coding performance.

In this paper we establish a secure communication model where eavesdropper and intended receiver have multiple antennas. We use cooperation and jamming to achieve physical layer security. First, we study how to allocate power between the information bearing signal and the jamming signal. Second, based on this model, we also jointly optimize both the information bearing signal weights and the jamming signal weights to improve physical layer security. The optimal power allocation and the weights are obtained via an iteration algorithm to maximize the secrecy rate. Comparing with equal power allocation and some other different methods, it shows that using cooperative relaying and jamming can significantly improve the physical layer security from the simulation results.

Three dimensional integration using Through-Silicon Vias (TSVs) offers short inter-layer interconnects and higher packing density. In order to take advantage of these attributes, a novel hybrid 3D NoC-Bus architecture is proposed in the paper. For vertical link, a Fake Token Bus architecture is elaborated, which utilizes the bandwidth efficiently by updating token synchronously. Based on this bus architecture, a methodology of hybrid 3D NoC-Bus design is introduced. The network hybridizes with the bus in vertical link and distributes long links of the full connected network into different layers, which achieves a network with a diameter of only 3 hops and limited radix. In addition, a congestion-aware routing algorithm applied to the hybrid network is proposed. The algorithm routes packets in horizontal firstly when the bus is busy, which balances the communication and reduces the possibility of congestion. Experimental results show that our network can achieve a 34.4% reduction in latency and a 43% reduction in power consumption under uniform random traffic and a 36.9% reduction in latency and a 48% reduction in power consumption under hotspot traffic over regular 3D mesh implementations on average.

In Long-Term Evolution (LTE)-Advanced, heterogeneous networks where femtocells and picocells are overlaid onto macrocells are being extensively discussed in addition to traditional well-planned macrocell deployment to improve further the system throughput. In heterogeneous networks, cell range expansion (CRE), which is a technique for expanding the cell radius of picocells by biasing the handover criteria, e.g., the downlink received signal power, is applied so that the UEs will more frequently select the picocells. This paper investigates a fractional transmission power control (TPC) method suitable for the heterogeneous networks that employ CRE in the LTE-Advanced uplink and evaluates the cell-edge user throughput and cell throughput performance. Simulation results (2-8 picocells and 25 (30) UEs are located within one macrocell with a uniform (cluster) distribution, the difference in transmission power between the macro and picocells is 16 dB, and the Typical Urban and Pedestrian-A channel models are employed) show that almost the same cell-edge user throughput is obtained by setting an appropriate difference in the target received signal power between the macro and picocells according to the CRE offset value.

As a flexible and cost-efficient scalable Internet access network, we studied architectures, protocols, and design optimizations of the Wireless Internet-access Mesh NETwork (WIMNET). WIMNET is composed of multiple access points (APs) connected through multihop wireless communications on IEEE 802.11 standards. The increasing popularity of real-time applications such as IP-phones and IP-TV means that they should be supported in WIMNET. However, the contention resolution mechanism using a random backoff-time in the CSMA/CA protocol of 802.11 standards is not sufficient for handling real-time traffic in multihop wireless communications. In this paper, we propose a Fixed Backoff-time Switching (FBS) method for the CSMA/CA protocol to improve the real-time traffic performance in WIMNET by giving the necessary activation chances to each link. We implement our proposal on the QualNet simulator, and verify its effectiveness through simulations on three network topologies with four scenarios.