Performance Evaluation of Optical Multicast Protection Approaches for Combined Node and Link Failure Recovery

Up to now, most research on optical multicast protection has been focused on link failure recovery, due to its predominance. Nevertheless, the impact of node failures is more severe, although they are less frequent. In a network, it might be less cost effective to implement dedicated protection approaches for separate link failure recovery and node failure recovery. A combined node and link failure recovery approach is more cost-effective and very crucial to network survivability. Hence, in this paper, we provide a detailed performance evaluation of several types of optical multicast protection approaches for 100% combined node and link failure recovery. The optical multicast protection approaches considered in this paper include the node-and-link protecting ${p}$-cycle based approach, the tree-protecting ${p}$ -cycle based approach and the optimal path pair based approach. Among them, the node-and-link protecting ${p}$-cycle based approach is newly proposed in this paper, which is a novel multicast application of previously reported ordinary ${p}$-cycle approach. Simulation results show that the integer linear programming based spare capacity optimization of node-and-link protecting ${p}$-cycle algorithm achieves the best capacity efficiency, for static traffic. For dynamic traffic, the efficiency-score based heuristic algorithm of node-and-link protecting ${p}$-cycle outperforms the other heuristic algorithms.      

An Analytical Method to Extract the Physical Parameters of a Solar Cell From Four Points on the Illuminated $J{-}V$ Curve

For a variety of solar cells, it is shown that the single exponential $J{-}V$ model parameters, namely—ideality factor $eta$ , parasitic series resistance $R_{s}$, parasitic shunt resistance $R_{rm sh}$, dark current $J_{0}$, and photogenerated current $J_{rm ph}$ can be extracted simultaneously from just four simple measurements of the bias points corresponding to $V_{rm oc}$, $sim!hbox{0.6}V_{rm oc}$, $J_{rm sc}$, and $sim! hbox{0.6}J_{rm sc}$ on the illuminated $J{-}V$ curve, using closed-form expressions. The extraction method avoids the measurements of the peak power point and any $dJ/dV$ (i.e., slope). The method is based on the power law $J{-}V$ model proposed recently by us.      

2 MHz AO $Q$ -switched ${rm TEM}_{00}$ Grazing Incidence Laser With 3 at.% Neodymium Doped Nd:YVO$_{4}$

We present a detailed experimental and theoretical study of the ultrahigh repetition rate AO $Q$ -switched ${rm TEM}_{00}$ grazing incidence laser. Up to 2.1 MHz $Q$-switching with ${rm TEM}_{00}$ output of 8.6 W and 2.2 MHz $Q$ -switching with multimode output of 10 W were achieved by using an acousto-optics $Q$ -switched grazing-incidence laser with optimum grazing-incidence angle and cavity configuration. The crystal was 3 at.% neodymium doped Nd:YVO$_{4}$ slab. The pulse duration at 2 MHz repetition rate was about 31 ns. The instabilities of pulse energy at 2 MHz repetition rate were less than ${pm}6.7hbox{%}$ with ${rm TEM}_{00}$ operation and ${pm}3.3hbox{%}$ with multimode operation respectively. The modeling of high repetition rate $Q$-switched operation is presented based on the rate equation, and with the solution of the modeling, higher pump power, smaller section area of laser mode, and larger stimulated emission cross section of the gain medium are beneficial to the $Q$-switched operation with ultrahigh repetition rate, which is in consistent with the experimental results.      

An FIR-Embedded Noise Filtering Method for $Delta Sigma$ Fractional-N PLL Clock Generators

This paper describes a noise filtering method for $Delta Sigma$ fractional- $N$ PLL clock generators to reduce out-of-band phase noise and improve short-term jitter performance. Use of a low-cost ring VCO mandates a wideband PLL design and complicates filtering out high-frequency quantization noise from the $Delta Sigma$ modulator. A hybrid finite impulse response (FIR) filtering technique based on a semidigital approach enables low-OSR $Delta Sigma$ modulation with robust quantization noise reduction despite circuit mismatch and nonlinearity. A prototype 1-GHz $Delta Sigma$ fractional-$N$ PLL is implemented in 0.18 $muhbox{m}$ CMOS. Experimental results show that the proposed semidigital method effectively suppresses the out-of-band quantization noise, resulting in nearly 30% reduction in short-term jitter.      

$S$ - and $C$ -Band Ultra-Compact Phase Shifters Based on All-Pass Networks

Ultra-compact phase shifters are presented. The proposed phase-shifting circuits utilize the lumped element all-pass networks. The transition frequency of the all-pass network, which determines the size of the circuit, is set to be much higher than the operating frequency. This results in a significantly small chip size of the phase shifter. To verify this methodology, 5-bit phase shifters have been fabricated in the $S$ - and $C$ -band. The $S$ -band phase shifter, with a chip size of 1.87 mm $,times,$0.87 mm (1.63 mm $^{2}$), has achieved an insertion loss of ${hbox{6.1 dB}} pm {hbox{0.6 dB}}$ and rms phase-shift error of less than 2.8$^{circ}$ in 10% bandwidth. The $C$ -band phase shifter, with a chip size of 1.72 mm $,times,$0.81 mm (1.37 mm $^{2}$), has demonstrated an insertion loss of 5.7 dB $pm$ 0.8 dB and rms phase-shift error of less than 2.3 $^{circ}$ in 10% bandwidth.      

A 125–1250 MHz Process-Independent Adaptive Bandwidth Spread Spectrum Clock Generator With Digital Controlled Self-Calibration

A process-independent adaptive bandwidth spread-spectrum clock generator (SSCG) with digitally controlled self-calibration techniques is proposed. By adaptively calibrating the VCO gain ($K_v$) and charge-pump (CP) current over C ($I_{CP}/C$), the SSCG can realize not only adaptive bandwidth but also process independence at each operating frequency. The innovative point is the adaptive bandwidth control using $K_v$ and $I_{CP}/C$ calibration. This control enabled a test chip to keep a sharp triangular SSC profile while operating over a wide frequency range (125 to 1250 $~$MHz). The variations of VCO gain and CP current are reduced to one third those of the conventional architecture. At 1250 $~$Mbps (625$~$MHz) the reduction of spectrum peak amplitude is 18.6$~$dB which is 2.3$~$dB better than the reduction obtained without calibration.      

Design of a Beam Switching/Steering Butler Matrix for Phased Array System

A compact broadband 8-way Butler matrix integrated with tunable phase shifters is proposed to provide full beam switching/steering capability. The newly designed multilayer stripline Butler matrix exhibits an average insertion loss of 1.1 dB with amplitude variation less than $pm$2.2 dB and an average phase imbalance of less than 20.7$^{circ}$ from 1.6 GHz to 2.8 GHz. The circuit size is only $160times 100 {rm mm}^{2}$, which corresponds to an 85% size reduction compared with a comparable conventional microstrip 8-way Butler matrix. The stripline tunable phase shifter is designed based on the asymmetric reflection-type configuration, where a Chebyshev matching network is utilized to convert the port impedance from 50 $Omega$ to 25 $Omega$ so that a phase tuning range in excess of 120$^{circ}$ can be obtained from 1.6 GHz to 2.8 GHz. To demonstrate the beam switching/steering functionality, the proposed tunable Butler matrix is applied to a 1 $times$ 8 antenna array system. The measured radiation patterns show that the beam can be fully steered within a spatial range of 108 $^{circ}$.      

Separated Unicast/Multicast Splitter-and-Delivery Switch and Its Use in Multicasting-Capable Optical Cross-Connect

We propose a novel separated unicast/multicast splitter-and-delivery (SUM-SaD) switch for mixed unicast and multicast traffic. Only multicast connections undergo extra splitting loss but are compensated by incorporated optical amplifiers. A typical multicasting-capable optical cross-connect is constructed by using the proposed SUM-SaDs. Theoretically, we prove that it is strictly nonblocking for both unicast and multicast connections if $d=N/2$, where $N$ and $d$ are the dimension of SUM-SaD and the number of SaD input ports, respectively. Therefore, $d$ means the maximum accommodated trees in the SUM-SaD. To save cost, $d$ can be less than $N/2$ , and the throughput performance is investigated by simulation. The results show that the throughput is improved when $d$ increases. In the experiment, we construct a 4 $times$ 4 SUM-SaD prototype and measure the bit-error rate (BER) of unicast connection, multicast connection with or without optical amplifier. There is no clear BER difference between them for the small dimensional SUM-SaD switch.      

On the Mean Residual Life Function of Coherent Systems

We consider a coherent structure consisting of $n$ components having the property that if it is known that at most $r$ components $(r≪n)$ have failed, the system is still operating with probability 1. Some examples of the systems having this property are $(n-k+1)$-out-of- $n$, some parallel-series, and some series-parallel structures. Depending on the structure, and the number of active components of the coherent systems at time $t$ , the mean residual life function of the system is studied, by several authors. This paper investigates more properties of the mean residual life function of the coherent systems sharing the described property. We will show that, when the components of the system have increasing failure rate, the mean residual life function of the system is decreasing in time. Several examples, and illustrative graphs are also provided.      

Virus Spread in Networks

The influence of the network characteristics on the virus spread is analyzed in a new—the $N$ -intertwined Markov chain—model, whose only approximation lies in the application of mean field theory. The mean field approximation is quantified in detail. The $N$ -intertwined model has been compared with the exact $2^{N}$-state Markov model and with previously proposed “homogeneous” or “local” models. The sharp epidemic threshold $tau_{c}$ , which is a consequence of mean field theory, is rigorously shown to be equal to $tau_{c}=1/(lambda_{max}(A))$ , where $lambda_{max}(A)$ is the largest eigenvalue—the spectral radius—of the adjacency matrix $A$ . A continued fraction expansion of the steady-state infection probability at node $j$ is presented as well as several upper bounds.      

$hbox{TiN/ZrO}_{2}$/Ti/Al Metal–Insulator–Metal Capacitors With Subnanometer CET Using ALD-Deposited $hbox{ZrO}_{2}$ for DRAM Applications

We provide the first report of the structural and electrical properties of $hbox{TiN/ZrO}_{2}$/Ti/Al metal–insulator–metal capacitor structures, where the $hbox{ZrO}_{2}$ thin film (7–8 nm) is deposited by ALD using the new zirconium precursor ZrD-04, also known as Bis(methylcyclopentadienyl) methoxymethyl. Measured capacitance–voltage ($C$– $V$) and current–voltage ( $I$–$V$) characteristics are reported for premetallization rapid thermal annealing (RTP) in $hbox{N}_{2}$ for 60 s at 400 $^{circ}hbox{C}$, 500 $^{circ}hbox{C}$, or 600 $^{ circ}hbox{C}$. For the RTP at 400 $^{circ}hbox{C}$ , we find very low leakage current densities on the order of nanoamperes per square centimeter at a gate voltage of 1 V and low capacitance equivalent thickness values of $sim$ 0.9 nm at a gate voltage of 0 V. The dielectric constant of $ hbox{ZrO}_{2}$ is 31 $pm$ 2 after RTP treatment at 400 $^{circ}hbox{C}$.      

Linear Systems, Sparse Solutions, and Sudoku

In this paper, we show that Sudoku puzzles can be formulated and solved as a sparse linear system of equations. We begin by showing that the Sudoku ruleset can be expressed as an underdetermined linear system: ${mmb{Ax}}={mmb b}$, where ${mmb A}$ is of size $mtimes n$ and $n>m$. We then prove that the Sudoku solution is the sparsest solution of ${mmb{Ax}}={mmb b}$, which can be obtained by $l_{0}$ norm minimization, i.e. $minlimits_{mmb x}Vert{mmb x}Vert_{0}$ s.t. ${mmb{Ax}}={mmb b}$. Instead of this minimization problem, inspired by the sparse representation literature, we solve the much simpler linear programming problem of minimizing the $l_{1}$ norm of ${mmb x}$, i.e. $minlimits_{mmb x}Vert{mmb x}Vert_{1}$ s.t. ${mmb{Ax}}={mmb b}$, and show numerically that this approach solves representative Sudoku puzzles.      

Reliability of Combined $k{hbox{-out-of-}}n$ and Consecutive $k_{c}{hbox{-out-of-}}n$ Systems of Markov Dependent Components

A combined $k{hbox{-out-of-}}n$ :$F(G)$ & consecutive $k_{c}{hbox{-out-of-}}n{hbox{:}}F(G)$ system fails (functions) iff at least $k$ components fail (function), or at least $k_{c}$ consecutive components fail (function). These models involve two common failure criteria, and can be used in various situations depending on the actual failure criteria involving consecutive components, or all components. Explicit formulas for the reliabilities of these systems are obtained for Markov dependent components using the distribution theory of runs. Some numerical results are also presented.      

Delta-Sigma Modulation for Direct Digital Frequency Synthesis

This paper compares different $DeltaSigma$ modulation techniques for direct digital frequency synthesis (DDS). $DeltaSigma$ modulators such as MASH, feedforward, feedback, and error feedback have been implemented in both the phase and frequency domains in a CMOS DDS prototype IC fabricated in a 0.35-$mu$m CMOS technology with core area of $1.7times 2.1 {hbox {mm}}^{2}$ and total current consumption of 75 mA. Measured DDS performance demonstrates that the frequency domain $DeltaSigma$ modulation technique achieves better output spectrum purity than the phase domain method. Moreover, a programmable feedforward $DeltaSigma$ modulator is proposed to achieve different in-band and out-band noise shaping effects for DDS applications.      

180$^{circ}$ and 90$^{circ}$ Phase Shifting Networks With an Octave Bandwidth and Small Phase Errors

A new phase shifting network for both 180 $^{circ}$ and 90 $^{circ}$ phase shift with small phase errors over an octave bandwidth is presented. The theoretical bandwidth is 67% for the 180$^{circ}$ phase bit and 86% for the 90$^{circ}$ phase bit when phase errors are $pm 2^{circ}$. The proposed topology consists of a bandpass filter (BPF) branch, consisting of a LC resonator and two shunt quarter-wavelength transmission lines (TLs), and a reference TL. A theoretical analysis is provided and scalable parameters are listed for both phase bits. To test the theory, phase shifting networks from 1 GHz to 3 GHz were designed. The measured phase errors of the 180$^{circ}$ and the 90$^{circ}$ phase bit are $pm 3.5^{circ}$ and $pm 2.5^{circ}$ over a bandwidth of 73% and 102% while the return losses are better than 18 dB and 12 dB, respectively.      

Performance Improvement of N-Type $hbox{TiO}_{x}$ Active-Channel TFTs Grown by Low-Temperature Plasma-Enhanced ALD

We report on performance improvement of $n$-type oxide–semiconductor thin-film transistors (TFTs) based on $hbox{TiO}_{x}$ active channels grown at 250 $^{circ}hbox{C}$ by plasma-enhanced atomic layer deposition. TFTs with as-grown $hbox{TiO}_{x}$ films exhibited the saturation mobility $(mu_{rm sat})$ as high as 3.2 $hbox{cm}^{2}/hbox{V}cdothbox{s}$ but suffered from the low on–off ratio $(I_{rm ON}/I_{rm OFF})$ of $hbox{2.0} times hbox{10}^{2}$. $hbox{N}_{2}hbox{O}$ plasma treatment was then attempted to improve $I_{rm ON}/I_{rm OFF}$. Upon treatment, the $hbox{TiO}_{x}$ TFTs exhibited $I_{rm ON}/I_{rm OFF}$ of $hbox{4.7} times hbox{10}^{5}$ and $mu_{rm sat}$ of 1.64 $hbox{cm}^{2}/hbox{V}cdothbox{s}$, showing a much improved performance balance and, thus, demonstrating their potentials for a wide variety of applications such as backplane technology in active-matrix displays and radio-frequency identification tags.      

A 10:1 Unequal Wilkinson Power Divider Using Coupled Lines With Two Shorts

A novel unequal Wilkinson power divider is presented. A coupled-line section with two shorts is proposed to realize the high characteristic impedance line, which cannot be implemented by conventional microstrip fabrication technique due to fabrication limitation. The proposed coupled-line structure is compatible with single layer integration and can be easily designed based on an even-odd mode analysis. As a design example, a 10:1 Wilkinson power divider at 2 GHz is fabricated and measured. The measured $-10~{rm dB}$ bandwidth of $S_{11}$ is about 16%, and the isolation $S_{32}$ is better than $-20~{rm dB}$ . The measured amplitude balance between output port 2 and port 3 is between $-10.20~{rm dB}$ and $-9.52~{rm dB}$, and the corresponding phase difference is between 0$^{circ}$ and 4.6$^{circ}$.      

Anisotropic Transient and Stationary Electron Velocity in Bulk Wurtzite GaN

The theoretical calculation of transient electron velocity overshoot in wurtzite $c$-axis GaN indicates a higher transient overshoot peak for transport in the basal plane ( $Gammahbox{-}M$ and $Gamma hbox{-}K$) than along the growth direction ($Gammahbox{-}A$ ). Characteristic rise times for the transient overshoot peak are found to be shorter for transport along the $c$-axis. Stationary electron velocity is significantly larger for transport oriented in the basal plane than along the $c$ -axis. No significant anisotropy is observed, however, in either the transient or steady-state electron velocity as a function of field orientation within the basal plane itself. The higher peak transient and stationary velocities in the basal plane are directly attributable to the anisotropy of the electronic dispersion, which exhibits lower effective mass along the $Gammahbox{-}M$ and $Gammahbox{-}K$ directions and greater nonparabolicity along the $Gammahbox{-}A$ direction.      

Integrated Quadrature Couplers and Their Application in Image-Reject Receivers

Several fully-integrated multi-stage lumped-element quadrature hybrids that enhance bandwidth, amplitude and phase accuracies, and robustness are presented, and a fully-integrated double-quadrature heterodyne receiver front-end that uses two-stage Lange/Lange couplers is described. The Lange/Lange cascade exploits the inherent wide bandwidth characteristic of the Lange hybrid and enables a robust design using a relatively low transformer coupling coefficient. The measured image-rejection ratio is $>$ 55 dB over a 200 MHz bandwidth centered around 5.25 $~$GHz without any tuning, trimming, or calibration; the front-end features 23.5 dB gain, $-$79 dBm sensitivity, 5.6 dB SSB NF, $-$7$~$ dBm IIP3, $-$18 dB $S_{11}$ and a 1 mm $times$ 2 mm die area in 0.18$ mu{hbox {m}}$ CMOS.      

Characterization and Modeling of RF-Performance $(f_{T})$ Fluctuation in MOSFETs

The fluctuation of RF performance (particularly for $f_{T}$ : cutoff frequency) in the transistors fabricated by 90-nm CMOS technology has been investigated. The modeling for $f_{T}$ fluctuation is well fitted with the measurement data within approximately 1% error. Low-$V_{t}$ transistors (fabricated by lower doping concentration in the channel) show higher $f_{T}$ fluctuation than normal transistors. Such a higher $f_{T}$ fluctuation results from $C_{rm gg}$ (total gate capacitance) variation rather than $g_{m}$ variation. More detailed analysis shows that $C_{rm gs} + C_{rm gb}$ (charges in the channel and the bulk) are predominant factors over $C_{rm gd}$ (charges in LDD/halo region) to determine $C_{rm gg}$ fluctuation.