This letter presents delayed perturbation bounds (DPBs) for receding horizon controls (RHCs) of continuous-time systems. The proposed DPBs are obtained easily by solving convex problems represented by linear matrix inequalities (LMIs). We show, by numerical examples, that the RHCs have larger DPBs than conventional linear quadratic regulators (LQRs).

A 3D micromagnetic model is established to analyze the dynamics of single-pole-type (SPT) heads, in which a main pole and a soft underlayer (SUL) are included. It is found that, in an SPT head whose write pole thickness Lm and pole width W are 40 nm each, the throat height should be no greater than the pole tip width to avoid high remnant field at the static state. The influences of the head's parameters and the damping constant on switching time of SPT head are analyzed respectively. The crystalline anisotropy field of SUL is also proved to have great effect on the switching characteristics: a high anisotropy field along the cross-track direction could stabilize the magnetic moments in SUL and greatly shorten the switching time.

Reconstruction of real-world scenes from a set of multiple images is a topic in computer vision and 3D computer graphics with many interesting applications. Attempts have been made to real-time reconstruction on PC cluster systems. While these provide enough performance, they are expensive and less flexible. Approaches that use a GPU hardware-acceleration on single workstations achieve real-time framerates for novel-view synthesis, but do not provide an explicit volumetric representation. This work shows our efforts in developing a GPU hardware-accelerated framework for providing a photo-consistent reconstruction of a dynamic 3D scene. High performance is achieved by employing a shape from silhouette technique in advance. Since the entire processing is done on a single PC, the framework can be applied in mobile environments, enabling a wide range of further applications. We explain our approach using programmable vertex and fragment processors and compare it to highly optimized CPU implementations. We show that the new approach can outperform the latter by more than one magnitude and give an outlook for interesting future enhancements.

Recently, space-time block codes (STBCs) obtained from coordinate interleaved orthogonal designs (CIODs) have attracted considerable attention, due to the advantages of full-diversity transmission and single-symbol decodability. In this letter, we design a novel STBC from CIOD for two transmit antennas. The proposed code guarantees full-diversity and full-rate along with low peak-to-minimum power ratio (PMPR). Furthermore, in contrast to the existing Alamouti code, the performance of the proposed code is not degraded even in severely time-selective fading channels.

Test compression / decompression using variable-length coding is an efficient method for reducing the test application cost, i.e., test application time and the size of the storage of an LSI tester. However, some coding techniques impose slow test application, and consequently a large test application time is required despite the high compression. In this paper, we clarify the fact that test application time depends on the compression ratio and the length of codewords and then propose a new Huffman-based coding method for achieving small test application time in a given test environment. The proposed coding method adjusts both of the compression ratio and the minimum length of the codewords to the test environment. Experimental results show that the proposed method can achieve small test application time while keeping high compression ratio.

Various trajectories of design, arising from the new methodology of analog network design, are analyzed. Several major criteria suggested for optimal selection of initial approximation to the design process permit the minimization of computer time. The initial approximation point is selected with regard to the previously revealed effect of acceleration of the design process. The concept of separatrix is defined making it possible to determine the optimal position of the initial approximation. The numerical results obtained for passive and active networks prove the possibility of optimal choice of the initial point in design process.

Future optical code division multiple access (CDMA) networks should be designed for multirate and fully integrated multimedia services. In the conventional schemes, multilength optical orthogonal codes (OOCs) are designed to support multirate systems, while variable-weight OOCs are designed to support differentiated quality of service (QoS) for multimedia applications. In this paper, a novel class of optical signature codes; multiple-length variable-weight optical orthogonal codes (MLVW-OOC) is proposed for supporting multirate and integrated multimedia services in optical CDMA networks. The proposed MLVW-OOC has features that are easy to construct variable-weight codes and expanded to multiple-length codes. A construction method for designing MLVW-OOCs up to three levels of codes is discussed. The designed MLVW-OOCs can support differentiated requirements on data rates and QoS for several types of services in the networks. A code analysis for obtaining the value of cross-correlation constraints or multiple access interference (MAI) computation for several levels of codes is also suggested. The cross-correlation constraints of the proposed codes are better than the conventional codes such as multilength OOCs. Finally, the bit error probability performance of the two-level MLVW-OOC is evaluated analytically. The results show that the proposed MLVW-OOC can provide differentiated bit error probability performances for several combinations of data rates and QoS.

This proposes a scalable QoS control scheme, called Elephant Flow Control Scheme (EFCS) for high-speed large-capacity networks; it controls congestion and provides appropriate bandwidth to normal users' flows by controlling just the elephant flows. EFCS introduces a sampling packet threshold and drops packets considering flow size. EFCS also adopts a compensation parameter to control elephant flows to an appropriate level. Numerical results show that the sampling threshold increases control accuracy by 20% while reducing the amount of memory needed for packet sampling by 60% amount of memory by packet sampling; the elephant flows are controlled as intended by the compensation parameter. As a result, EFCS provides sufficient bandwidth to normal TCP flows in a scalable manner.

The traffic with asymmetry between uplink and downlink has recently been getting remarkable on mobile communication systems providing multimedia communication services. In the future mobile communications, the accommodation of asymmetric traffic is essential to realize efficient multimedia mobile communication systems. This paper discusses asymmetric traffic accommodation in CDMA/FDD cellular packet communication systems and proposes its efficient scheme using an adaptive cell sizing technique. In the proposed scheme, each base station autonomously controls its coverage area so that almost the same communication quality can be achieved across the service area under the asymmetric traffic conditions. We present some numerical examples to demonstrate the effectiveness of the proposed scheme by using computer simulation. The simulation results show that, under asymmetric traffic conditions, the proposed scheme can provide fair communication quality across the service area in both links and can improve total transmission capacity in the uplink.

This paper discusses the behavior of the second-order modes (Hankel singular values) of linear continuous-time systems under typical frequency transformations, such as lowpass-lowpass, lowpass-highpass, lowpass-bandpass, and lowpass-bandstop transformations. Our main result establishes the fact that the second-order modes are invariant under any of these typical frequency transformations. This means that any transformed system that is generated from a prototype system has the same second-order modes as those of the prototype system. We achieve the derivation of this result by describing the state-space equations and the controllability/observability Gramians of transformed systems.

LDCs system with finite-rate error-free feedback is proposed in this letter. The optimal transmission codeword is selected at the receiver and the codeword index is sent to the transmitter. A simple random search algorithm is introduced for codebook generation. Moreover, the max-min singular value criterion is adopted for codeword selection. Simulation results showed that, with only 3-4 feedback bits, the low-complexity Zero-Forcing receiver can approach the Maximum-Likelihood (ML) performance.

The frequency hopping (FH) based ultra-wideband (UWB) communication system divides its available frequency spectrum into several sub-bands, which leads to inherent disparities between carrier frequencies of each sub-band. Since the propagation loss is proportional to the square of the transmission frequency, the propagation loss on the sub-band having the highest carrier frequency is much larger than that on the sub-band having the lowest carrier frequency, resulting in disparities between received signal powers on each sub-band, which in turn leads to a bit error rate (BER) degradation in the FH UWB system. In this paper we propose an adaptive receiver for FH based UWB communications, where the integration time is adaptively adjusted relative to the hopping carrier frequency, which reduces the disparity between the received signal energies on each sub-band. Such compensation for lower received powers on sub-bands having higher carrier frequency leads to an improvement on the total average BER of the entire FH UWB communication system. We analyze the performance of the proposed reception scheme in Nakagami fading channels, and it is shown that the performance gain provided by the proposed receiver is more significant as the Nakagami fading index m increases (i.e., better channel conditions).

We study the problem of optimizing admission control policies in mobile multimedia cellular networks when predictive information regarding movement is available and we evaluate the gains that can be achieved by making such predictive information available to the admission controller. We consider a general class of prediction agents which forecast the number of future handovers and we evaluate the impact on performance of aspects like: whether the prediction refers to incoming and/or outgoing handovers, inaccurate predictions, the anticipation of the prediction and the way that predictions referred to different service classes are aggregated. For the optimization process we propose a novel Reinforcement Learning approach based on the concept of afterstates. The proposed approach, when compared with conventional Reinforcement Learning, yields better solutions and with higher precision. Besides it tackles more efficiently the curse of dimensionality inherent to multimedia scenarios. Numerical results show that the performance gains measured are higher when more specific information is provided about the handover time instants, i.e. when the anticipation time is deterministic instead of stochastic. It is also shown that the utilization of the network is maintained at very high values, even when the highest improvements are observed. We also compare an optimal policy obtained deploying our approach with a previously proposed heuristic prediction scheme, showing that plenty of room for technological innovation exists.

An 8.8-GS/s 6-bit CMOS analog-to-digital converter (ADC) chip was implemented by time-interleaving eight 1.1-GS/s 6-bit flash ADCs with a 0.18-µm CMOS process. Eight uniformly-spaced 1.1 GHz clocks with 50% duty cycle for the eight flash ADCs were generated by a clock generator, which consists of a phase-locked-loop, digital phase adjusters and digital duty cycle correctors. The input bandwidth of ADC with the ENOB larger than 5.0 bits was measured to be 1.2 GHz. The chip area and power consumption were 2.24 mm2 and 1.6 W, respectively.

In real-time systems, deadline misses of the tasks cause a degradation in the quality of their results. To improve the quality, we have to allocate CPU utilization for each task adaptively. Recently, Buttazzo et al. address a feedback scheduling algorithm, which dynamically adjusts task periods based on the current workloads by applying a linear elastic task model. In their model, the utilization allocated to each task is treated as the length of a linear spring and its flexibility is described by a constant elastic coefficient. In this paper, we first consider a nonlinear elastic task model, where the elastic coefficient depends on the utilization allocated to the task. We propose a simple iterative method for calculating the desired allocated resource and derive a sufficient condition for the convergence of the method. Next, we apply the nonlinear elastic model to an adaptive fair sharing controller. Finally, we show the effectiveness of the proposed method by computer simulation.

We have numerically evaluated the filtering characteristics of two vertically coupled microring resonator filters. In this evaluation we used the finite-difference time-domain method as the numerical analysis method. The structure we designed allows only a specific wavelength to pass. The filtering characteristics of this structure can be altered by changing the layout of the microring resonator. By using this structure the interval between peak wavelengths at a specific wavelength in the output spectrum can be increased. Specifically, the interval between peak wavelengths can be increased from 20 nm to 40 nm at wavelengths near 1.46 µm.

We propose a service differentiation scheme for optical burst switching (OBS) with the scheduling algorithm Horizon. In the proposed scheme, in addition to the latest horizon used in the conventional Horizon, we introduce the second latest horizon and use them for reservation preemption. Burst priority order is perfectly guaranteed according to the burst class information informed by its control packet if the arrival time of the burst is later than the second latest horizon and earlier than the latest horizon. Since the extra offset time is no longer needed for service differentiation, the burst blocking probability and the data latency will be reduced. We assume a multi-hop network with ring topology where bursts traverse five intermediate nodes, and evaluate the performance in terms of the end-to-end and hop-by-hop burst blocking probabilities. Simulation results show that the proposed scheme can achieve service differentiation with smaller blocking probability than the extra-offset-time-based scheme with Horizon. Furthermore, we show that the proposed scheme preserves service differentiation even in multi-hop environments.

Conventional clock and data recovery (CDR) using a phase locked loop (PLL) suffers from problems such as long lock time, low frequency acquisition and harmonic locking. Consequently, a CDR system using a time to digital converter (TDC) is proposed. The CDR consists of simple arithmetic calculation and a TDC, allowing a fully digital realization. In addition, utilizing a TDC also allows the CDR to have a very wide frequency acquisition range. However, deterministic jitter is caused with each sample, because the system's sampling time period is changing slightly at each data edge. The proposed system does not minimize jitter, but it tolerates small jitter. Therefore, the system offers a faster lock time and a smaller sampling error. This proposed system has been verified on system level in a Verilog-A environment. The proposed method achieves faster locking within just a few data bits. The peak to peak jitter of the recovered clock is 60 ps and the RMS jitter of the recovered clock is 30 ps, assuming that the TDC resolution is 10 ps. In applications where a small jitter error can be tolerated, the proposed CDR offers the advantage of fast locking time and a small sampling error.

In this Letter, we propose a least mean square (LMS) with adaptive step-size (AS) algorithm for adaptive blind carrier frequency offset (CFO) estimation in the orthogonal frequency division multiplexing system. In conjunction with the closed-loop estimate structure, the proposed algorithm eliminates the inter-carrier interference caused by time varying CFO. To improve the convergence performance of the fixed step-size LMS estimator, the regular AS LMS algorithm offers faster convergence speed and more accuracy to the CFO estimate. Several computer simulation examples are presented for illustrating the effectiveness of the proposed algorithm.

A novel structure of a resonator type guided-wave electro-optic intensity modulator is introduced that uses a higher-order harmonic resonant electrode of coupled microstrip lines combined with polarization-reversed structure. The light modulation cancellation caused by the light transit-time effect in the resonant electrode, which is longer than the wavelength of the standing wave, is compensated for to enhance modulation efficiency. The modulator for 26 GHz operation was designed and fabricated with a LiTaO3 substrate. The modulation electrode is 9.03 mm long for seventh order harmonic resonance by RF signal. The workability of the modulator was confirmed by experiments with 1.3 µm wavelength light.