Reproducing consistent wireless protocol performance across environments

Full scale experimentation with wireless networks in deployment environments is difficult. Therefore a common validation technique is to test a prototype network in a convenient environment prior to deployment. In this paper, we consider the problem of obtaining comparable protocol performance when the test and deployment environments differ in RF propagation environment and/or inter-node spacing. To achieve comparable protocol behavior in the two settings, we propose the concept of “link usage spectrum”. Based on the hypothesis that the link usage spectrum is a gross predictor for network performance, we show how to replicate in the test setting the link usage spectrum of the protocol that is expected in the deployment setting. We show our technique for achieving comparable protocol behavior via experiments and simulations in multiple indoor and outdoor propagation environments. The link usage spectrum is protocol specific; we illustrate for a family of protocols how the link usage spectrum is calculated analytically, from the protocol metric for choosing forwarding links in the network, and how power scaling can be used to match the link usage spectrum across networks.     

Statistical DOE-ILP based power-performance-process (P3) optimization of nano-CMOS SRAM

As technology continues to scale, maintaining important figures of merit of Static Random Access Memories (SRAMs), such as power dissipation and an acceptable Static Noise Margin (SNM), becomes increasingly challenging. In this paper, we address SRAM instability and power (leakage) dissipation in scaled-down technologies by presenting a novel design flow for simultaneous power minimization, performance maximization and process variation tolerance (P3) optimization of nano-CMOS circuits. The 45 and 32 nm technology node standard 6-Transistor (6T) and 8T SRAM cells are used as example circuits for demonstration of the effectiveness of the flow. Thereafter, the SRAM cell is subjected to a dual threshold voltage (dual-V_Th) assignment based on a novel statistical Design of Experiments-Integer Linear Programming (DOE-ILP) approach. Experimental results show 61% leakage power reduction and 13% increase in the read SNM. In addition, process variation analysis of the optimized cell is conducted considering the variability effect in twelve device parameters. To the best of the authors' knowledge, this is the first study which makes use of statistical DOE-ILP for optimization of conflicting targets of stability and power in the presence of process variations in SRAMs.     

一种Ka波段混合集成的单平衡混频器

本文介绍了一种由正交E面折叠魔T与鳍线混合集成的Ka波段单平衡混频器的研制概况,混频器使用国产W121封装的带状引线混频二极管。介质基片采用国产的仿RT-Duroid5880,经测试该混频器的最小单边带噪声为5.7dB(不包括前中噪声),射频与本振的隔离度均优于20dB,整体尺寸为32×19×14(mm)。     

Signal through-the-silicon via planning and pin assignment for thermal and wire length optimization in 3D ICs

Signal through-the-silicon via (STS-via) planning plays an important role in multi-layer nets which need vertical interconnection between different device layers. Moreover, STS-via can also dissipate heat, which is a much more serious problem in 3D ICs than in 2D ICs. Since the through-the-silicon via is large and can only be inserted into whitespace of the device layer, planning STS-via for thermal optimization may affect the interconnection wire length. Therefore, in order to make STS-via planning more flexible, we integrated STS-via with pin assignment. In this paper, we use min-cost maximum flow algorithm for STS-via planning and pin assignment simultaneously. Experimental results show that our approach can reduce both temperature and wire length effectively with short runtime.     

Electronically tunable high-input impedance voltage-mode universal biquadratic filter based on simple CMOS OTAs

This paper describes a new electronically tunable three inputs and single output voltage-mode universal biquadratic filter based on simple CMOS operational transconductance amplifiers (OTAs) and grounded capacitors. The proposed configuration provides lowpass, highpass, bandpass, bandstop and allpass voltage responses at a high impedance input terminal, which enable easy cascadability. Additionally, the circuit parameters ω_o${\omega }_o$ and Q   can be set orthogonally by adjusting the transconductances and grounded capacitors. The filter also offers an independent electronic control of parameters ω_o${\omega }_o$ by adjusting the transconductance through the bias current/voltage of the OTA. For realizing all the filter responses, no critical component matching condition is required, and all the incremental parameter sensitivities are low. PSPICE simulation results are performed to confirm the theoretical analysis.     

Neighbor discovery in wireless networks with sectored antennas

Directional antennas offer many potential advantages for wireless networks such as increased network capacity, extended transmission range and reduced energy consumption. Exploiting these advantages requires new protocols and mechanisms at various communication layers to intelligently control the directional antenna system. With directional antennas, many trivial mechanisms, such as neighbor discovery, become challenging since communicating parties must agree on where and when to point their directional beams to communicate.In this paper, we propose a fully directional neighbor discovery protocol called Sectored-Antenna Neighbor Discovery (SAND) protocol. SAND is designed for sectored-antennas, a low-cost and simple realization of directional antennas, that utilize multiple limited beamwidth antennas. Unlike many proposed directional neighbor discovery protocols, SAND depends neither on omnidirectional antennas nor on time synchronization. SAND performs neighbor discovery in a serialized fashion allowing individual nodes to discover all potential neighbors within a predetermined time. SAND guarantees the discovery of the best sector combination at both ends of a link, resulting in more robust and higher quality links between nodes. Finally, SAND reliably gathers the neighborhood information in a centralized location, if needed, to be used by centralized networking protocols. The effectiveness of SAND has been assessed via simulation studies and real hardware implementation.     

Characterizing pairwise contact patterns in human contact networks

We use a counting process representation of the pairwise contact process to analyze pairwise contact patterns. Studying two real-world traces, we find that the pairwise contact patterns have three characteristics. First, human contact patterns are influenced by daily and weekly cycles of activity. Second short time intervals with intensive contact event (bursts) are separated by long periods with few contact events. Third, the pairwise contact process exhibits long range dependence. We introduce a Markov modulated Poisson process (MMPP) as a flexible model for pairwise contact process exhibiting both regular structure and irregular bursts of activity. Using standard statistical techniques, we demonstrate that the proposed model is consistent with the empirical data. Our work has significant implication for mobility modeling and performance analysis in human contact networks.     

Development, implementation, and testing of fault detection strategies on the National Wind Technology Center’s controls advanced research turbines

The National Renewable Energy Laboratory’s National Wind Technology Center dedicates two 600 kW turbines for advanced control systems research. A fault detection system for both turbines has been developed, analyzed, and improved across years of experiments to protect the turbines as each new controller is tested. Analysis of field data and ongoing fault detection strategy improvements have resulted in a system of sensors, fault definitions, and detection strategies that have thus far been effective at protecting the turbines. In this paper, we document this fault detection system and provide field data illustrating its operation while detecting a range of failures. In some cases, we discuss the refinement process over time as fault detection strategies were improved. The purpose of this article is to share field experience obtained during the development and field testing of the existing fault detection system, and to offer a possible baseline for comparison with more advanced turbine fault detection controllers.     

Multiphase sinusoidal oscillators using second generation current conveyors

A voltage-mode Multiphase Sinusoidal Oscillator realized using Second Generation Current Conveyors and only grounded passive elements is introduced in this paper. The proposed topology is suitable for realizing oscillators with both odd and even number of phases without modifying the core of the topology. Only non-inverting Current Conveyors are required for the construction of the oscillator's topology and this is a benefit from the discrete component implementation point of view. The behavior of the proposed topology has been evaluated, through experimental results, in the cases of three and six-phase oscillators.