Applicability of Cavity Modeling Technique to Analyze Complex Waveguide Structures Involving Cavity Cross Couplings

Wireless Personal Communications - In this paper, we propose modulation and coding scheme level drop scheme for LTE evolved multimedia broadcast/multicast service (eMBMS) by transmitting additional...     

Min-max timing analysis and an application to asynchronous circuits

Modern high-performance asynchronous circuits depend on timing constraints for correct operation, so timing analyzers are essential asynchronous design tools. In this paper we present a 13-valued abstract waveform algebra and a polynomial-time min-max timing simulation algorithm for use in efficient, approximate timing analysis of asynchronous circuits with bounded component delays. Unlike several previous approaches, our algorithm computes separate propagation delay bounds from each circuit input to each internal gate. This is useful for analyzing asynchronous circuits, where the relative transition times of the inputs may not be known a priori, unlike synchronous circuits. We also describe an efficient reconvergent fanout analysis technique that helps in increasing the accuracy of simulation. We have applied our algorithm to build an efficient timing analysis tool for extended burst-mode circuits (a class of timing-dependent asynchronous circuits) implemented in the 30 design style. Our tool analyzes gate-level 30 circuits assuming bounded component delays and determines safe timing constraints for correct operation. Although our results represent conservative approximations to the true timing requirements in the worst case, experiments indicate that our technique is efficient and fairly accurate in practice     

Cloud Liquid Water Content and Cloud Attenuation Studies with Radiosonde Data at a Tropical Location

The profile of cloud liquid water density and the total liquid water content (LWC) are obtained from the radiosonde data using the Salonen model at Kolkata, India, a tropical location. The cumulative distribution LWC shows a departure from the ITU-R model at this location, exhibiting a significantly enhanced occurrence during the monsoon months. The cloud attenuation, derived by integrating the profile of specific attenuation obtained from the radiosonde data, is related to LWC at different frequencies in the range 10-100 GHz. A comparison indicates that the cloud attenuation at frequencies below 50 GHz is somewhat overestimated by the ITU-R model generated values and significantly underestimated by the ITU-R model at frequencies above 70 GHz at the present location.     

A Combined Circuit-Electromagnetic-Fluidic Computational Methodology for Force Prediction in Lab-on-Chip Environments

This paper focuses on a computational method for the simulation of the motion and manipulation of bio-particles using dielectrophoretic and micro-fluidic forces. The presented method uses surface integral equations for modeling both electromagnetic (EM) and fluidic domains. A coupled circuit-EM methodology is used to model electrical excitations. A steady Stokes flow is assumed for computing the fluidic traction forces. The resulting simulator accurately predicts the fields and forces on arbitrarily-shaped three dimensional particles representing bio-species. The presented methodology is amenable to acceleration with state of the art oct-tree-based fast matrix-vector schemes for rapid linear time iterative solution. This integrated computational approach leads to a pathway for rapid simulation of coupled circuit-EM-fluidic systems for Lab-on-chip (LoC) manipulation of biological species, which provides medical device designers the capability to augment control of bio-species, and explore new system designs     

On the effectiveness of movement prediction to reduce energy consumption in wireless communication

Node movement can be exploited to reduce the energy consumption of wireless network communication. The strategy consists in delaying communication until a mobile node moves close to its target peer node within an application- imposed deadline. We evaluate the performance of various heuristics that, based on the movement history of the mobile node, estimate an optimal time (in the sense of least energy use) of communication subject to the delay constraint. We evaluate the impact of the node movement model, length of movement history maintained, allowable delay, single hop versus multiple hop communication, and size of data transfer on the energy consumption. We also present measurement results on an iPAQ pocket PC that quantity energy consumption in executing the prediction algorithms. Our results show that, with relatively simple and, hence, efficient prediction heuristics, energy savings in communication can significantly outweigh the energy expenses in executing the prediction algorithms. Moreover, it is possible to achieve robust system performance across diverse node movement models.     

Optimization of SIP Session Setup Delay for VoIP in 3G Wireless Networks

Wireless networks beyond 2G aim at supporting real-time applications such as VoIP. Before a user can start a VoIP session, the end-user terminal has to establish the session using signaling protocols such as H.323 and session initiation protocol (SIP) in order to negotiate media parameters. The time interval to perform the session setup is called the session setup time. It can be affected by the quality of the wireless link, measured in terms of frame error rate (FER), which can result in retransmissions of packets lost and can lengthen the session setup time. Therefore, such protocols should have a session setup time optimized against loss. One way to do so is by choosing the appropriate retransmission timer and the underlying protocols. In this paper, we focus on SIP session setup delay and propose optimizing it using an adaptive retransmission timer. We also evaluate SIP session setup performances with various underlying protocols (transport control protocol (TCP), user datagram protocol (UDP), radio link protocols (RLPs)) as a function of the FER. For 19.2 Kbps channel, the SIP session setup time can be up to 6.12s with UDP and 7s with TCP when the FER is up to 10 percent. The use of RLP (1, 2, 3) and RLP (1, 1, 1, 1, 1, 1) puts the session setup time down to 3.4s under UDP and 4s under TCP for the same FER and the same channel bandwidth. We also compare SIP and H.323 performances using an adaptive retransmission timer: SIP outperforms H.323, especially for a FER higher than 2 percent.     

Performance evaluation of particle filter resampling techniques for improved estimation of misalignment and trajectory deviation

Delivery of airborne precision guided vehicles to pre-designated targets has assumed much importance in recent times. Transfer alignment is concerned with estimation of misalignment with respect to the airborne platform. During first few seconds of the post ejection phase, the trajectory deviates from intended one. Estimation of this deviation in trajectory can also be mapped to the transfer alignment problem. Large misalignment angle makes the system nonlinear while usage of mother measurements in each iteration makes it time varying. Particle filter variants can be designed to improve the quality of estimates but the time complexity increases. This work explores different resampling techniques to find a way to decrease the average time to complete an iteration. This allows more room for parallel execution with a residual evolutionary particle filter that does away with resampling by evolving through several system dynamics, thereby performing better when the knowledge of system dynamics is poor. It is observed that when the two filters are run together, the estimation accuracy improves considerably. The scheme is particularly useful in the time critical post ejection phase.     

High-performance E-mode AlGaN/GaN HEMTs

Enhancement-mode AlGaN/GaN high electron-mobility transistors have been fabricated with a gate length of 160 nm. The use of gate recess combined with a fluorine-based surface treatment under the gate produced devices with a threshold voltage of +0.1 V. The combination of very high transconductance (> 400 mS/mm) and low gate leakage allows unprecedented output current levels in excess of 1.2 A/mm. The small signal performance of these enhancement-mode devices shows a record current cutoff frequency (f/sub T/) of 85 GHz and a power gain cutoff frequency (f/sub max/) of 150 GHz.