Fast Array Multichannel 2D-RLS Based OFDM Channel Estimator

In this paper a Fast Array Multichannel Two-Dimensional Recursive Least Square (FAM 2D-RLS) adaptive filter is proposed for estimating an OFDM channel in frequency domain. This filter makes use of the shift structure of the input data vector. Thus the computational cost of the classical RLS filter which is O(M ²) is reduced to O(M) for each iteration where M is the order of the filter. In order to ensure numerical stability in finite precision, we make use of array-based methods for implementing FAM 2D-RLS. The adaptive filters illustrated in the standard literature consist of a weight vector and desired data as a scalar. But in our scenario of OFDM channel estimation the weight is a matrix while the desired data are a vector. Hence the algorithm for the matrix form of FAM-2D RLS and its steady state equations are derived. Numerical stability, steady state and convergence performance are verified using MATLAB simulations.     

Single event crosstalk prediction in nanometer technologies

As CMOS technology continues to scale down, circuits become increasingly more sensitive to transient pulses caused by single event (SE) particles. On the other hand, coupling effects among interconnects can cause single event transients to contaminate electronically unrelated circuit paths which may increase the SE susceptibility of CMOS circuits. The coupling effects among interconnects need to be considered in single event hardening, modeling and analysis of CMOS logic gates due to technology scaling effects that increase both SE vulnerability and crosstalk effects. This work, for the first time, proposes an SE crosstalk noise estimation method for use in design automation tools. The proposed method uses an accurate 4-π model for interconnect and correctly models the effect of non-switching aggressors as well as aggressor tree branches noting the resistive shielding effect. The SE crosstalk noise expressions derived show very good results in comparison to HSPICE results. Results show that average error for noise peak is about 5.2% while allowing for very fast analysis in comparison to HSPICE.     

Analytical modeling of high performance single-walled carbon nanotube field-effect-transistor

We present a novel analytical modeling of a zigzag single-walled semiconducting carbon nanotube field effect transistor (CNFET) by incorporating quasi-one-dimensional (Q1D) top-of-a-potential barrier approach. By implementing multimode carrier transport, we explore and compare the performance of a low- (360 cm²/Vs) and high-mobility (7200 cm²/Vs) CNFET model with experimental data from nanotube and 45 nm MOSFET, respectively, as well as existing compact models. Mobility and carrier concentration models are also developed to obtain a good matching with physical data. For a high mobility CNFET, we found that a maximum of 120 μA is obtained. In addition to this, a CNT-based inverter is also developed by constructing n-type and p-type CNFET in ORCAD’s analog behavioral model (ABM). A gain of as high as 5.2 is forecasted for an inverter of 80 nm CNFET.     

A 2.488–11.2 Gb/s SerDes in 40 nm low-leakage CMOS with multi-protocol compatibility for FPGA applications

This paper presents the design and Silicon verification of a 2.488–11.2 Gbps multi-standard SerDes transceiver in a 40 nm low-leakage CMOS process. The paper explores the architectural and circuit techniques used to meet the stringent requirements of the high-speed SerDes and to mitigate the performance impact of the low-leakage process. A system modeling approach is described, which is used for optimizing the architectural trade-offs. The transceiver makes use of a low-jitter LC phase locked loop to enable high-reliability system design. The design has 420 fs RJ_rms and consumes 30.1 mW/Gbps at 11.2 Gbps.     

Timing and Carrier Frequency Offset Estimation Using Selective Extended Cyclic Prefix for Correlation Sequence for OFDM Systems

In this paper a novel technique for timing and carrier frequency offset (CFO) estimation for orthogonal frequency division multiplexing (OFDM) systems is presented. This technique is a modification of extended cyclic prefix for correlation sequence (ECPCS) based technique, called as selective extended cyclic prefix for correlation sequence (SECPCS) based technique. In cyclic prefix (CP) based technique, magnitude of timing metric near the exact starting point of CP is quite similar which causes problem in timing estimation. SECPCS is utilized in order to increase the difference between magnitudes of timing metric at the exact starting point of time of CP and its adjacent timing instants. In SECPCS technique, first of all correlation length of CP is extended using available CP samples and then those sequences which enlarge the difference in the magnitude of timing metric is selected. In the proposed technique the difference between magnitude of timing metric at exact starting point and its adjacent timing instants is significantly large compared to the previous techniques. The performance of different techniques is evaluated in terms of mean square error (MSE) in estimation of timing and CFO estimate. Further signal-to-interference-plus-noise ratio (SINR) loss of different techniques in different channel conditions is also estimated. From the simulation results it is observed that under different channel conditions, performance of the proposed SECPCS based technique is significantly better than previous techniques.     

A prefix-based approach for joint Doppler and channel estimation in underwater communication

Developing a reliable and robust underwater acoustic communication system is a difficult task due to the complicated nature of the underwater channel, non-stationary noise, and several other factors. Indeed, channel estimation or equalization presents numerous challenges in this non-stationary, highly Doppler, multipath environment; as a result, traditional equalizers and PLL-based methods have limited performance. Generally, communication over such time-varying channels is accomplished via packets that contain a prefix/preamble signal for training, a payload containing the actual data, and a silent period for proper alignment. The prefix signal must be designed properly because it is used to estimate the channel and determine the start of the packet. In this paper, we propose a new prefix signal based on the hyperbolic chirp signal, which has Doppler invariance properties. These properties enable the extraction of the entire packet even under severe multipath and Doppler. Our new proposed prefix signal can accurately and efficiently characterize an underwater channel by estimating the multipath delay, amplitude, and Doppler scales. Our new method has been validated through extensive simulations using various channel models for its robustness and effectiveness under various conditions. It has also been tested on a real-world channel.     

Acquisition of operations capability: A model and test across US and European firms

In this paper, a three-factor model of operations capability is presented which, unlike previous studies that view capability as an outcome, examines the drivers of capability acquisition. The model proposes that capability acquisition is a function of an organization's commitment to the principles of quality management, just-in-time practices, and effective new product development processes. Furthermore, the paper proposes that these underlying facets of capability acquisition are common across geographic boundaries. The model is tested using data drawn from US and European companies. Results not only provide support for the three-factor model, but also for the invariance of the model and its underlying components between US and European firms.     

Strengthening Mechanisms in Mechanically Milled Oxide-Dispersed Iron Powders

Nanocrystalline iron and oxide dispersion-strengthened (ODS) iron powders (Fe, Fe-Y₂O₃, and Fe-Y₂O₃-Ti) were prepared by mechanical milling for periods ranging from 1 to 40 hours. The as-milled powders were examined for changes in their particle sizes, crystallite sizes, hardness values, and phases present as a function of milling time. Both the particle and the crystallite sizes of all the three compositions decreased with milling time, while the hardness values of all the three powders increased with milling time because of the crystallite size refinement. At the same crystallite size, the hardness values of Fe-Y₂O₃ and Fe-Y₂O₃-Ti powders were higher than that of the Fe powders. Though, the presence of 40 nm Y₂O₃ could be established for 2-hour milling, such particles were not resolvable in 40-hour-milled powders. However, SAD patterns confirmed the presence of complex oxide dispersoids in the Fe-Y₂O₃ and Fe-Y₂O₃-Ti powders. The variation of hardness value with the crystallite size and as a function of the milling time can be rationalized on the basis of Hall–Petch crystallite size strengthening in combination with dispersion strengthening (in Fe-Y₂O₃- and Fe-Y₂O₃-Ti-milled powders) due to dispersoids. The observed double-positive slopes in the Hall–Petch relationship can be explained in terms of an increase in misorientation angle between the crystallites with increasing milling time due to the crystallite rotation driven by disclination dipoles.     

Chitosan-Based Thermosensitive Hydrogel Containing Liposomes for Sustained Delivery of Cytarabine

Sustained release thermosensitive solution containing cytarabine-loaded liposome delivery system offers the possibility of reduced dosing frequency and sustained drug action. Biodegradable and biocompatible chitosan-beta-glycerophosphate (C-GP) thermosensitive solution having the property to gel at body temperature and to maintain its physical integrity for longer period of time was used. The C-GP solution containing cytarabine-loaded liposomes (CGPCLL) was studied, and the results showed that the cytarabine liposomes were capable of high encapsulation efficiency (85.2?±?2.58%) with the mean diameter of 220?±?6.9 nm of extruded cytarabine-loaded liposome. Furthermore, transmission electron microscopy showed spherical-shaped liposomes after extrusion with smooth surface. In vitro studies of CGPCLL in PBS buffer showed that this system can sustain release of encapsulated drug for more than 60 h compared with drug-loaded liposomal suspension (upto 48 h). Pharmacokinetic studies of CGPCLL resulted in higher t_1/2 (28.86 h) and AUC 2526.88 μg/mL h compared with cytarabine-loaded liposomal suspension (CLLS) and C-GP containing free cytarabine (CGPFC) in rats. CGPCLL was capable of sustaining the cytarabine release for more than 60 h in vivo compared with CLLS and CGPFC which showed maximum amount of drug release within 42 and 10 h, respectively. Thus, these results showed that the CGPCLL gels at body temperature and can sustain the delivery of cytarabine effectively.