In this paper, the authors focus on upstream transmission in TDMA-based IEEE 802.16j and propose two time slot assignment algorithms to decrease end-to-end transmission latency. One of the proposed algorithms assigns time slots considering the hop count from a gateway node, and the other takes the path from the relay node to the gateway node into account. In addition, a restriction in assigning time slots is introduced to reduce the delay at each relay node. The algorithms with the restriction assign later time slots considering the time slot order of links connecting a relay node. The performance of the proposed algorithms is evaluated through simulation experiments from the viewpoints of frame size and end-to-end transmission latency, and it is confirmed that the proposed algorithms achieve small transmission latency regardless of packet generation rate in the network, and decrease the transmission latency by up to 70% compared with the existing algorithm.

In this paper, we derive a set of discrete time difference equations that models the spreading process of computer worms such as Code-Red and Slammer, which uses a common strategy called “random scanning” to spread through the Internet. We show that the derived set of discrete time difference equations has an exact relationship with the Kermack and McKendrick susceptible-infectious-removed (SIR) model, which is known as a standard continuous time model for worm spreading.

Most of the IP mobility management schemes based on the IETF's MIPv6 may not be suitable for delay-sensitive vehicular applications since there will be frequent service disruptions as the moving vehicles frequently change their points of wireless network attachment. This paper presents a fast IP mobility management scheme for vehicular networks where multiple wireless network interfaces are used to perform fast handovers without handover latency or packet loss. In order to do this, the IETF standard HMIPv6 has been extended, where multiple simultaneous tunnels between the HMIPv6 mobility anchor point (MAP) and the mobile gateway are dynamically constructed. We have designed the architecture for a mobile gateway for supporting multiple tunnels, the structure of the extension MAP (E-MAP), and the signaling procedure to achieve fast IP handover in vehicular networks. Both mathematical analysis and simulation have been done for performance evaluation. The results show that the proposed scheme is superior to HMIPv6 and MIPv6 with regard to handover latency and packet loss as the vehicle moves between different wireless network cells at high speed.

Electrical performances of gate-all-around (GAA) tunneling field-effect transistors (TFETs) based on a silicon germanium (Si1-xGex) layer have been investigated in terms of subthreshold swing (SS), on/off current ratio, on-state current (Ion). Cut-off frequency (fT) and maximum oscillation frequency (fmax) were demonstrated from small-signal parameters such as effective gate resistance (Rg), gate-drain capacitance (Cgd), and transconductance (gm). According to the technology computer-aided design (TCAD) simulation results, the current drivability, fT, and fmax of GAA TFETs based on Si1-xGex layer were higher than those of GAA TFETs based on silicon. The simulated devices had 60 nm channel length and 10 nm channel radius. A GAA TFET with x = 0.4 had maximum Ion of 51.4 µA/µm, maximum fT of 72 GHz, and maximum fmax of 610 GHz. Additionally, improvements of performance at the presented device with PNPN junctions were demonstrated in terms of Ion, SS, fT, and fmax. When the device was designed with x = 0.4 and n+ layer width (Wn) = 6 nm, it shows Ion of 271 µA/µm, fT of 245 GHz, and fmax of 1.49 THz at an operating bias (VGS = VDS = 1.0 V).

In this letter, we propose a novel resource allocation scheme to enhance downlink system performance for orthogonal frequency division multiple access (OFDMA) and time division duplex (TDD) based femtocell networks. In the proposed scheme, the macro base station (mBS) and femto base stations (fBSs) service macro user equipments (mUEs) and femto user equipments (fUEs) in inner and outer zones in different periods to reduce interference substantially. Simulations show the proposed scheme outperforms femtocell networks with fractional frequency reuse (FFR) systems in terms of the system capacity and outage probability for mUEs and fUEs.

Spatial Multiplexing with precoding provides an opportunity to enhance the capacity and reliability of multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. However, precoder selection may require knowledeg of all subcarriers, which may cause a large amount of feedback if not properly designed. In addition, if the maximum-likelihood (ML) detector is employed, the conventional precoder selection that maximizes the minimum stream SNR is not optimal in terms of the error probability. In this paper, we propose to reduce the feedback overhead by introducing a ML clustering concept in selecting the optimal precoder for ML detector. Numerical results show that the proposed precoder selection based on the ML clustering provides enhanced performance for ML receiver compared with conventional interpolation and clustering algorithms.

The reduction in the gate length of the current devices to 65 nm causes their I-V characteristics to depart from the traditional MOSFETs. As a result, manufacturing of new efficient devices in nanoscale is inevitable. The fundamental properties of the metallic and semi-conducting carbon Nanotubes (CNTs) make them alternatives to the conventional silicon-based devices. In this paper an ultra high-speed and energy-efficient full adder is proposed, using Carbon Nanotube Field Effect Transistor (CNFET) in nanoscale. Extensive simulation results using HSPICE are reported to show that the proposed adder consumes lower power, and is faster compared to the previous adders.

In this paper, we propose a novel path tracking control algorithm for an underactuated autonomous underwater vehicle (AUV). The underactuated AUV is controlled by the thrust force and the yaw torque: no sway thruster is used. To deal with this underactuated AUV problem in the path tracking, we introduce an approach angle which makes the AUV converge to the reference path. To design the path tracking controller, we obtain the vehicle's error dynamics in the body-fixed frame, and then design the path tracking controller based on the dynamic surface control (DSC) method. The proposed controller only needs the information of the position and the heading angle of the reference path. Some simulation results demonstrate the effectiveness of the proposed controller.

In remote control, efficient compression or representation of control signals is essential to send them through rate-limited channels. For this purpose, we propose an approach of sparse control signal representation using the compressive sampling technique. The problem of obtaining sparse representation is formulated by cardinality-constrained 2 optimization of the control performance, which is reducible to 1-2 optimization. The low rate random sampling employed in the proposed method based on the compressive sampling, in addition to the fact that the 1-2 optimization can be effectively solved by a fast iteration method, enables us to generate the sparse control signal with reduced computational complexity, which is preferable in remote control systems where computation delays seriously degrade the performance. We give a theoretical result for control performance analysis based on the notion of restricted isometry property (RIP). An example is shown to illustrate the effectiveness of the proposed approach via numerical experiments.

Users recently find their interests by checking the contents published or mentioned by their immediate neighbors in social networking services. We propose semantics-based link navigation; links guide the active user to potential neighbors who may provide new interests. Our method first creates a graph that has users as nodes and shared interests as links. Then it divides the graph by link pruning to extract practical numbers, that the active user can navigate, of interest-sharing groups, i.e. communities of interests (COIs). It then attaches a different semantic tag to the link to each representative user, which best reflects the interests of COIs that they are included in, and to the link to each immediate neighbor of the active user. It finally calculates link attractiveness by analyzing the semantic tags on links. The active user can select the link to access by checking the semantic tags and link attractiveness. User interests extracted from large scale actual blog-entries are used to confirm the efficiency of our proposal. Results show that navigation based on link attractiveness and representative users allows the user to find new interests much more accurately than is otherwise possible.

Requirements changes frequently occur at any time of a software development process, and their management is a crucial issue to develop software of high quality. Meanwhile, goal-oriented analysis techniques are being put into practice to elicit requirements. In this situation, the change management of goal graphs and its support are necessary. This paper presents a technique related to the change management of goal graphs, realizing impact analysis on a goal graph when its modifications occur. Our impact analysis detects conflicts that arise when a new goal is added, and investigates the achievability of the other goals when an existing goal is deleted. We have implemented a supporting tool for automating the analysis. Two case studies suggested the efficiency of the proposed approach.

A Fourier domain optical coherence tomography system for obtaining a two-dimensional image is constructed. Imaging characteristics of the OCT system in a transverse direction are experimentally investigated. Angle dependence of reflection intensity from a smooth surface is clearly observed and analyzed with consideration of spatial mode coupling to a fiber.

This paper introduces a unified method of spectrum sensing for all existing analog television (TV) signals including NTSC, PAL and SECAM. We propose a correlation based method (CBM) with a single reference signal for sensing any analog TV signals. In addition we also propose an improved energy detection method. The CBM approach has been implemented in a hardware prototype specially designed for participating in Singapore TV white space (WS) test trial conducted by Infocomm Development Authority (IDA) of the Singapore government. Analytical and simulation results of the CBM method will be presented in the paper, as well as hardware testing results for sensing various analog TV signals. Both AWGN and fading channels will be considered. It is shown that the theoretical results closely match with those from simulations. Sensing performance of the hardware prototype will also be presented in fading environment by using a fading simulator. We present performance of the proposed techniques in terms of probability of false alarm, probability of detection, sensing time etc. We also present a comparative study of the various techniques.

The susceptibility of a static random access memory (SRAM) core against static and dynamic variation of power supply voltage is evaluated, by using on-chip diagnosis structures of memory built-in self testing (MBIST) and on-chip voltage waveform monitoring (OCM). The SRAM core of interest in this paper is a synthesizable version applicable to general systems-on-a-chip (SoC) design, and fabricated in a 90 nm CMOS technology. RF power injection to power supply networks is quantified by OCM. The number of resultant erroneous bits as well as their distribution in the cell array is given by MBIST. The frequency-dependent sensitivity reflects the highly capacitive nature of densely integrated SRAM cells.

In this paper, a high-throughput debloking filter is presented for H.264/AVC standard, catering video applications with 4 K2 K (40962304) ultra-definition resolution. In order to strengthen the parallelism without simply increasing the area, we propose a luma-chroma parallel method. Meanwhile, this work reduces the number of processing cycles, the amount of external memory traffic and the working frequency, by using triple four-stage pipeline filters and a luma-chroma interlaced sequence. Furthermore, it eliminates most unnecessary off-chip memory bandwidth with a highly reusable memory scheme, and adopts a “slide window” buffer scheme. As a result, our design can support 4 K2 K at 30 fps applications at the working frequency of only 70.8 MHz.

Tomlinson-Harashima precoding (THP) is considered to be a prominent precoding scheme due to its ability to efficiently cancel out the known interference at the transmitter side. Therefore, the information rates achieved by THP are superior to those achieved by conventional linear precoding schemes. In this paper, new lower bounds on the achievable information rates for the regularized THP scheme are derived. Analytical results show that the lower bounds derived in this paper are tighter than the original lower bounds particularly for the low SNR range, while all lower bounds converge to as SNR ∞.

This paper discusses a wireless control system for cooperative motion of multiple machines, and clarifies the influence of packet losses on the system behavior. We focus on the synchronization of the motion of the machines, and using the nature of wireless, we propose a new wireless control scheme for maintaining the synchronization performance under packet loss conditions. In the proposed scheme, each controlled object (plant) utilizes control information destined for all plants, and the main controller also utilizes state information of all plants. The additional information of the other controller-plant pairs is used to compensate lost information. As an example of the controlled plants, rotary inverted pendulums, which move synchronously with wireless connections in their control-feedback loops, are considered. Numerical examples confirm the superiority of the proposed scheme from the view-point of the synchronization of the motion of the plants.

This paper proposes a sub-ps resolution TDC utilizing a differential pulse-shrinking buffer ring. This scheme uses two differentially-operated pulse-shrinking inverters and the TDC resolution is finely controlled by the transistor size ratio between them. The proposed TDC realizes 9 bit, 580 fs resolution in a 0.18 µm CMOS technology with 0.04 mm2 area, and achieves DNL and INL of +0.8/-0.8LSB and +4.3/-4.0LSB, respectively, without linearity calibration. A power dissipation at 1.5 MS/s ranges from 10.8 to 12.6 mW depending on the input time intervals.

This paper proposes an adaptive bandwidth control scheme for the private wireless networks. Carrier sense multiple access with collision avoidance (CSMA/CA), which is commonly used within the private networks, is not efficient in terms of spectral efficiency due to its strict collision avoidance process. In order to relax the collision avoidance rule, this paper employs dynamic spectrum control (DSC), in which a certain number of discrete spectra having the higher channel gain is selected in a selfish manner with each link allowing a partial band interference. Such interference may be suppressed by the equalizer at the receiver. Aiming at optimal selection of the bandwidth for the selfish DSC according to channel realizations, in the sense of throughput maximization, this paper proposes a channel capacity maximization-based BAR control scheme. Computer simulations validate that the proposed scheme achieves high throughput efficiency.

The Viterbi algorithm is widely used for decoding of the convolutional codes. The trace-back method is preferable to the register exchange method because of lower power consumption especially for convolutional codes with many states. A drawback of the conventional trace-back is that it generally requires long latency to obtain the decoded data. In this paper, a method of the trace-back with source states instead of decision bits is proposed which reduces the number of memory accesses. The dedicated memory is also presented which supports the proposed trace-back method. The reduced memory accesses result in smaller power consumption and a shorer decode latency than the conventional method.