43537984
A performance analysis of a discrete-time queueing system with server interruption for modeling wireless ATM multiplexer
In this paper, we study the effect of channel errors on wireless ATM. The salient characteristic of the wireless channel is that it is time varying. This variability is modeled by a Markov chain with two states corresponding to high and low error states, respectively. The channel is modeled as being synchronous with the basic time unit being the slot. The transitions from high to low error states, and vice versa occur at the slot boundaries. It is assumed that no transmission over the channel is possible during the high-error state.The information source feeding into the channel is modeled as the superposition of independent sources. Each source is controlled by a two-state Markov chain which operates in synchronism with, but statistically independent of the channel. In the source Off state, no data is emitted while, in the On state, the source generates a random number of packets in a slot each of which fits into a channel slot.It is assumed that the traffic generated by all the sources will form a single global queue which will be served by the two-state Markov channel. A discrete-time queuing analysis derives the probability generating function (PGF) of the queue length under the assumption of an infinite buffer. From the PGF, we determine mean queue length and mean delay. Finally, numerical results are presented to demonstrate the effect of wireless channel error characteristics on performance.
21113650
A Discrete-Time Queuing Analysis of the Wireless ATM Multiplexing System
In this paper we analyze a wireless channel model which is subject to service interruption either because the channel is not available or the server is serving to the other users. The wireless channel is modeled by a Markov chain with two states corresponding to high and low error states, respectively. It is assumed that the channel is slotted in time and no transmission is possible during the high-error state. The traffic generated by a mobile user is modeled as the superposition of independent two states On-Off Markov sources, which are statistically independent of the server. A source generates packets only during an On state each of which fits to a channel slot. A discrete-time queuing analysis derives the probability generating function (PGF) of the queue length under the assumption of an infinite buffer. From the PGF, mean queue length, mean delay and approximate finite buffer overflow probabilities are calculated.
2980184
Supporting Scalable and Distributed Data Subsetting and Aggregation in Large-Scale Seismic Data Analysis
The ability to query and process very large, terabyte-scale datasets has become a key step in many scientific and engineering applications. In this paper, we describe the application of two middleware frameworks in an integrated fashion to provide a scalable and efficient system for execution of seismic data analysis on large datasets in a distributed environment. We investigate different strategies for efficient querying of large datasets and parallel implementations of a seismic image reconstruction algorithm. Our results on a state-of-the-art mass storage system coupled with a high-end compute cluster show that our implementation is scalable and can achieve about 2.9 Gigabytes per second data processing rate – about 70% of the maximum 4.2GB/s application-level raw I/O bandwidth of the storage platform.
4974735
Deep submicron CMOS integrated circuit reliability simulation with SPICE
The purpose of the paper is to introduce a new failure rate-based methodology for reliability simulation of deep submicron CMOS integrated circuits. Firstly, two of the state-of-the-art MOSFET degradation models are reviewed. They have been developed into reliability simulation tools and commercialized in industry for many years, however, their inherent limitations of characterizing circuit lifetime, including tedious processes for extracting device degradation parameters and model fitting parameters, impeded their wide applications in the product's front-end design process. Secondly, a set of accelerated lifetime models for the most important intrinsic silicon degradation mechanisms are proposed. These lifetime models correlate a device's electrical operating parameters to its mean time to failure (MTTF) in simple forms. Finally, a new failure rate-based SPICE reliability simulation methodology is developed, in which MTTF and failure in time (FIT) are the primary reliability parameters to be characterized. The power of this new reliability simulation method, due to its simplicity, makes it an important design-for-reliability tool for electronic product developers.
15260068
Motion-compensating long-term memory prediction
Motion-compensating long-term memory prediction extends the spatial displacement utilized in block-based hybrid video coding by a variable time delay permitting the use of more frames than the previously decoded one for motion compensation. The long-term memory covers the decoded frames of some seconds at encoder and decoder. We investigate the influence of memory size in our motion compensation scheme and analyze the trade-off between the bit-rates spent for motion compensated prediction and residual coding. Simulation results are obtained by integrating long-term memory prediction into an H.263 codec. PSNR improvements up to 2 dB for the Foreman sequence and 1.5 dB for the Mother-Daughter sequence are demonstrated in comparison to the TMN-2.0 H.263 coder.
6515511
Evolvable view environment (EVE): non-equivalent view maintenance under schema changes
Supporting independent ISs and integrating them in distributed data warehouses (materialized views) is becoming more important with the growth of the WWW. However, views defined over autonomous ISs are susceptible to schema changes. In the <italic>EVE</italic> project we are developing techniques to support the maintenance of data warehouses defined over distributed <italic>dynamic</italic> ISs [5, 6, 7]. The <italic>EVE</italic> system is the first to allow views to survive <italic>schema changes</italic> of their underlying ISs while also adapting to changing data in those sources. <italic>EVE</italic> achieves this is two steps: applying view query rewriting algorithms that exploit information about alternative ISs and the information they contain, and incrementally adapting the view extent to the view definition changes. Those processes are referred to as <italic>view synchronization</italic> and <italic>view adaption</italic>, respectively. They increase the survivability of materialized views in changing environments and reduce the necessity of human interaction in system maintenance.
39876273
A Dependable Micro-Electronic Peptide Synthesizer Using Electrode Data
The research in the area of microelectronic fluidic devices for biomedical applications is rapidly growing. As faults in these devices can have serious personal implications, a system is presented which includes fault tolerance with respect to the synthesized biomaterials (peptides). It can employ presence and purity detection of peptide droplets via current (charge) tests of control electrodes or impedance (phase) measurements using direct sensing electrodes near the peptide collector area. The commercial multielectrode array performs better in pure and impure detection of peptides in impedance and phase. Our two-electrode X-MEF case shows slightly poorer results. In both cases the phase is the best choice for contents detection. If there are presence or purity problems, the location is marked, and repeated peptide synthesis at another collector site is initiated.