In this paper, introducing a stochastic hill-climbing dynamics into an optimal competitive Hopfield network model (OCHOM), we propose a new algorithm that permits temporary energy increases, which helps the OCHOM escape from local minima. In graph theory, a clique is a completely connected subgraph and the maximum clique problem (MCP) is to find a clique of maximum size of a graph. The MCP is a classic optimization problem in computer science and in graph theory with many real-world applications, and is also known to be NP-complete. Recently, Galan-Marin et al. proposed the OCHOM for the MCP. It can guarantee convergence to a global/local minimum of energy function, and performs better than other competitive neural approaches. However, the OCHOM has no mechanism to escape from local minima. The proposed algorithm introduces stochastic hill-climbing dynamics which helps the OCHOM escape from local minima, and it is applied to the MCP. A number of instances have been simulated to verify the proposed algorithm.

We have proposed and theoretically verified a 2R (reshaping and regeneration) limiter circuit using continuous wave (CW) holding beam for cross-gain modulation (XGM) wavelength converter, through simulation. The gain clamping effect of semiconductor optical amplifier (SOA), which is caused by CW holding beam injected into SOA, was used to obtain the accurate optical gain and phase conditions for SOA's in 2R limiter circuit. XGM wavelength converter with the proposed 2R limiter circuit provides higher extinction ratio (ER) as well as more enhanced operation speed than any other wavelength converter. Our numerical results show that after the wavelength-converted signal from XGM wavelength converter passed the 2R limiter circuit, it was re-inverted with the improved ER of 30 dB at 5 Gb/s. In case of high-speed operation, great enhancement to decrease power penalty of about 12 dB was shown at 10 Gb/s.

We have integrated a phase change random access memory (PRAM), completely based on 0.24 µm-CMOS technologies using nitrogen doped GeSbTe films. The Ge2Sb2Te5 (GST) thin films are well known to play a critical role in writing current of PRAM. Through device simulation, we found that high-resistive GST is indispensable to minimize the writing current of PRAM. For the first time, we found the resistivity of GST film can be controlled with nitrogen doping. Doping nitrogen to GST film successfully reduced writing current. A 0.24 µm PRAM using N-doped GST films were demonstrated with writing pulse of 0.8 mA-50 ns for RESET and 0.4 mA-100 ns for SET. Also, the cell endurance has been enhanced with grain growth suppression effect of dopant nitrogen. Endurance performance of fully integrated PRAM using N-doped GST shows no fail bit up to 2E9 cycles. Allowing 1% failures, extrapolation to 85 indicates retention time of 2 years. All the results show that PRAM is one of the most promising candidates in the market for the next generation memories.

In this study, a fourth-order cumulants based iterative algorithm for blind channel equalization is introduced, which is robust with respect to the existence of heavy Gaussian noise in a channel and does not require the minimum phase characteristic of the channel. The transmitted signals at the receiver are over-sampled to ensure the channel described by a full-column rank matrix. It changes a single-input/single-output (SISO) finite-impulse response (FIR) channel to a single-input/multi-output (SIMO) channel. Based on the properties of the fourth-order cumulants of the over-sampled channel inputs, the iterative algorithm is derived to estimate the deconvolution matrix which makes the overall transfer matrix transparent, i.e., it can be reduced to the identity matrix by simple reordering and scaling. In simulation studies, both a closed-form and a stochastic version of the proposed algorithm are tested with three-ray multi-path channels, and their performances are compared with the methods based on conventional second-order statistics and higher-order statistics (HOS) as well. Relatively good results with fast convergence speed are achieved, even when the transmitted symbols are significantly corrupted with Gaussian noise.

In mobile cellular networks it is crucial to be able to use the available radio spectrum as efficiently as possible while providing a certain level of Quality of Service (QoS) for the users. Emergence of miscellaneous services has dramatically increased the complexity of this problem by creating a heterogeneous traffic environment. In this paper an efficient resource allocation scheme between two real-time services with different bandwidth requirements has been proposed for cellular networks with multimedia offered traffic and highly mobile users, which combines classical intera-cell resource borrowing concept with a novel inter-cell resource-sharing scheme between diverse classes of traffic. By assuming the heterogeneous offered traffic to be a combination of audio and video traffic types, through extensive simulations it will be shown that HCBA-UCB is capable of significantly improving audio teletraffic performance of the system while preserving fairness in service provision, i.e. without imposing additional expenses upon video QoS performance.

This paper proposes a bandwidth allocation algorithm and a demand accommodation algorithm guaranteeing utility max-min fairness under bandwidth constraints. We prove that the proposed algorithms can fairly split network resources among connections and achieve call admission control considering the fairness among different types of applications. We then formulate three different network design problems to maximize the total utility of all customers, the number of users accommodated in the network, and the average utility of the customers accommodated in the network. To solve the problems, we extend the conventional network design algorithms considering utility max-min fair share, and numerically evaluate and compare their performance. Finally, we summarize the best algorithms to design the utility max-min fair share networks considering the operation policy of network providers.

In this letter, we show the effects of the chip waveform selection on the detection performance of the energy detector in DS/SS communications. Three chip waveforms such as rectangular, half-sine and raised-cosine are examined as the DS/SS chip waveform. It is demonstrated that the partial-band detection can enhance the detection performance of the energy detector approximately 50-70% compared with the full-band detection. When the chip rate is identical, the raised-cosine waveform shows lower detection probability due to its wider spreading bandwidth. However, when the spreading bandwidth is identical, the rectangular waveform shows lower detection probability due to its lower partial-band energy factor.

An empirical formula of resonant frequency of bow-tie microstrip antennas is presented, which is based on the cavity model of microstrip patch antennas. A procedure to design a bow-tie antenna using genetic algorithm (GA) in which we take the formula as a fitness function is also given. An optimized bow-tie antenna by genetic algorithm was constructed and measured. Numerical and experimental results are used to validate the formula and GA. The results are in good agreement.

A novel method is presented to the symbolic computation of Noise Figure (NF) of transistor circuits. Several computationally efficient macromodels of BJTs and MOSFETs by using nullors, are introduced. To demonstrate the suitability of the proposed method, the fully-symbolic expression of NF of a CMOS current-mirror is computed, and the total output noise-voltage is compared with HSPICE simulations. The calculated NF and the simulated noise are in good agreement. Finally, the method is extended to compute NF of a CMOS translinear circuit biased in weak inversion.

A Power on Reset signal generation circuit referencing threshold voltage without standby current consumption has been proposed. The POR signal is generated when supply voltage is larger than the sum of threshold voltages of N- and P-MOSFET.

In this article we propose a new framework to support QoS and 4G enabled mobility management. The key feature of this framework is twofold; the Policy based Handover control, and the adaptive handover mechanisms. On one hand, the adaptive handover mechanism will allow the selection of different handover schemes based on the user service level specification in order to differentiate the handover quality provided for the required service level, thus optimizing the network resources usage and providing the agreed service level to users. On the other hand, the proposed handover control mechanism considers resource availability and other constraints during the handover decision in order to provide support for QoS aware mobility on the contrary of the classical naïve mobility management that considers only signal strength fading. This decision mechanism will provide mainly the interaction between the mobility and QoS management frameworks but also a 4G handover control. In addition, the QoS aware handover will provide the knowledge necessary to achieve a proactive handover's procedures control.

Noise generation systems are used to generate noise signals with specified characteristics. In recent study, noise generation system using DCT outperforms the conventional noise generation system when a noise model requires complicated PSD(Power Spectral Density) specifications. In this paper, low area and low power structures of non-DCT block in DCT-based noise generation system are proposed. Simulation results show that the low area structure results in area reduction by 61-64% and the low power structure achieves power reduction by 88-89% except DCT blocks.

A cryogenic Whispering Gallery sapphire resonator oscillator has been investigated using a 4 K pulse-tube cryocooler. The turnover temperature of the chosen mode in the sapphire crystal was 9.17 K with an unloaded Q-factor of 7108. The prototype sapphire-loaded cavity oscillator was designed to oscillate at 9.195 GHz. A fractional frequency stability of 210-13 was measured at integration times of 10 s.

This paper presents the design of an automatic surveillance system to monitor the dangerous non-frontal gazes of the car driver. To track the driver's eyes, we propose a novel filter to locate the "between-eye", which is the middle point between the two eyes, to help the fast locating of eyes. We also propose a specially designed criterion function named mean ratio function to accurately locate the positions of eyes. To analyze the gazes of the driver, a multilayer perceptron neural network is trained to examine whether the driver is losing the proper gaze or not. By incorporating the neural network output with some well-designed alarm-issuing rules, the system performs the monitoring task for single dedicated driver and multiple different drivers with a satisfied performance in our experiments.

In this letter, we analyze blocking probabilities for prioritized multi-classes in optical burst switching (OBS) networks. The blocking probability of each traffic class can be analytically evaluated by means of class aggregation and iteration method. The analytic results are validated with results garnered from simulation tests.

From the bifurcation viewpoint, this study examines a boost PFC converter with average-current-mode control. The boost PFC converter is considered to be a nonlinear circuit because of its use of a multiplier and its large duty cycle variation for input current control. However, most previous studies have implemented linear analysis, which ignores the effects of nonlinearity. Therefore, those studies were unable to detect instability phenomena. Nonlinearity produces bifurcations and chaos when circuit parameters change. The classical PFC design is based on a stable periodic orbit that has desired characteristics. This paper describes the main bifurcations that this orbit may undergo when the parameters of the circuit change. In addition, the instability regions in the PFC converter are delimited. That fact is of practical interest for the design process. Moreover, a prototype PFC circuit is introduced to examine these instability phenomena experimentally. Then, a special numerical program is developed. Bifurcation maps are provided based on this numerical study. They give a comprehensive outstanding for stability conditions and identify stable regions in the parameter space. Moreover, these maps indicate PFC converter dynamics, power factors, and regulation. Finally, numerical analyses and experimentation show good agreement.

In this paper, we propose the Synchronized Mobile Multicast (SMM) scheme for the real-time multimedia service to achieve three most important characteristics that the traditional Home Subscription (HS) and Remote Subscription (RS) mobile schemes cannot support. First, the SMM scheme supports the scalable one-to-many and many-to-many synchronized multimedia multicast on mobile IP networks to achieves seamless playback of continuous media streams even when both the mobile sender and receivers handoff simultaneously. Second, it analyzes the minimal buffer requirements of the mobile sender, the core router, the foreign agents and the mobile receivers in the multicast tree and formulates the initial playback delay within a handoff Guarantee Region (GR). Further, combined with the fine granularity scalability (FGS) encoding approach in the MPEG-4 standard, the SMM scheme achieves superior multimedia QoS guarantees and unlimited numbers of handoffs of the mobile sender and receivers only at the cost of degraded video quality for a short period after handoff with minimal extra bandwidth.

Using daily infection data for Hong Kong we explore the validity of a variety of models of disease propagation when applied to the SARS epidemic. Surrogate data methods show that simple random models are insufficient and that the standard epidemic susceptible-infected-removed model does not fully account for the underlying variability in the observed data. As an alternative, we consider a more complex small world network model and show that such a structure can be applied to reliably produce simulations quantitative similar to the true data. The small world network model not only captures the apparently random fluctuation in the reported data, but can also reproduce mini-outbreaks such as those caused by so-called "super-spreaders" and in the Hong Kong housing estate of Amoy Gardens.

This paper deals with an on-line identification method based on a radial basis function (RBF) network model for continuous-time nonlinear systems. The nonlinear term of the objective system is represented by the RBF network. In order to track the time-varying system parameters and nonlinear term, the recursive least-squares (RLS) method is combined in a bootstrap manner with the genetic algorithm (GA). The centers of the RBF are coded into binary bit strings and searched by the GA, while the system parameters of the linear terms and the weighting parameters of the RBF are updated by the RLS method. Numerical experiments are carried out to demonstrate the effectiveness of the proposed method.

In this paper, we propose a set of broadcast streaming protocols designed for unidirectional radio channels. Considering the limited size and implementation overhead on a mobile terminal, the proposed protocol set is almost compliant with the current mobile streaming protocols, i.e. 3GPP PSS (Packet-switched Streaming Service), except for that the proposed protocols are designed to work on a unidirectional downlink channel. This protocol set enables flexible layout rendering by SMIL (Synchronized Multimedia Integration Language) in combination with SDP (Session Description Protocol), and reliable and synchronized static media (including still image and text) delivery by RTP (Real-time Transport Protocol) carousel. We present the prototype of this protocol set and measure its performance of video quality and waiting time for video presentation through a W-CDMA radio channel emulator and header compression nodes. From the experimental results, we show 1) trade-off between video quality and waiting time, 2) advantage and disadvantage of header compression, 3) effectiveness of synchronized transmission of SDP, SMIL, and I-frames of video objects, and 4) reliability of RTP-carousel. This protocol set is applicable to 3G MBMS (Multimedia Broadcast/Multicast Service) streaming service.