11672412
Dealing with Node Mobility in Ad Hoc Wireless Network
A Mobile “Ad hoc” wireless NETwork (MANET) is a network established for a special, often extemporaneous service customized to applications. The ad hoc network is typically set up for a limited period of time, in an environment that may change from application to application. As a difference from the Internet where the TCP/IP protocol suite supports a vast range of applications, in the MANET the protocols are tuned to a specific customer and application (eg, send a video stream across the battlefield; find out if there is a fire in the forest; establish a videoconference among several teams engaged in a rescue effort, etc). The customers move and the environment may change dynamically and unpredictably. For the MANET to retain its efficiency, the ad hoc protocols at various layers may need to self-tune to adjust to environment, traffic and mission changes. From these properties emerges the vision of the MANET as an extremely flexible, malleable and yet robust and formidable network architecture. Indeed, an architecture that can be deployed to monitor the habits of birds in their natural habitat, and which, in other circumstances, can be organized to interconnect rescue crews after a Tsunami disaster, or yet can be structured to launch deadly attacks onto unsuspecting enemies.
8697404
Audio streaming over Bluetooth: an adaptive ARQ timeout approach
Streaming audio has become a popular form of media on the Internet. As wireless personal area network architectures (e.g. Bluetooth) are now targeted to support multimedia traffic, streaming audio over these technologies give rise to interesting applications. But, the variable nature of the wireless medium will not lend itself easily to supporting audio streaming. We focus on Bluetooth and propose, an enhancement to the Bluetooth link layer ARQ mechanism to compensate for channel degradation and to better support audio streaming. Specifically, our scheme adoptively sets the ARQ timeout value based on current channel measurements. We show through testbed experiments that the adaptive ARQ improves the streaming quality significantly compared to the "vanilla" link layer of Bluetooth, especially in noisy environments. Our proposed approach is simple to implement and can actually be extended to the link layer of any wireless technology.
1912999
Improving wireless link throughput via interleaved FEC
Wireless communication is inherently vulnerable to errors from the dynamic wireless environment. Link layer packets discarded due to these errors impose a serious limitation on the maximum achievable throughput in the wireless channel. To enhance the overall throughput of wireless communication, it is necessary to have a link layer transmission scheme that is robust to the errors intrinsic to the wireless channel. To this end, we present interleaved-forward error correction (I-FEC), a clever link layer coding scheme that protects link layer data against random and busty errors. We examine the level of data protection provided by I-FEC against other popular schemes. We also simulate I-FEC in Bluetooth, and compare the TCP throughput result with Bluetooth's integrated FEC coding feature. We show that I-FEC consistently and significantly outperforms other link layer coding schemes by providing an impressive amount of protection against heavy channel burst errors.
10161187
Accuracy of link capacity estimates using passive and active approaches with CapProbe
CapProbe is an inexpensive and accurate means to estimate capacity. CapProbe combines both dispersion and end-to-end delay to estimate the capacity of the narrowest link on a path. We evaluate in this paper the accuracy of CapProbe estimation, and its dependence on end systems speed, packet sizes, narrow link speeds, and other system parameters. We test kernel and user level implementations of CapProbe and find the kernel implementation to be much more accurate. We also evaluate through experiments the effect of probing packet size on the accuracy of CapProbe estimation. Finally, we explore the idea of a "passive CapProbe" within the context of a TCP flow. Passive here means that the dispersion and delay observed for the TCP flow data and ACK packets, without introducing any additional probing packets. We test active and passive versions of CapProbe with TCP. The active version is found to produce more accurate capacity estimates than the passive version.
4799274
XEM: managing the evolution of XML documents
As information on the World Wide Web continues to proliferate at an astounding rate, the Extensible Markup Language (XML) has been emerging as a standard format for data representation on the Web. In many applications, specific document type definitions (DTDs) are designed to enforce a semantically agreed-upon structure of the XML documents for management. However, both the data and the structure of XML documents tend to change over time for a multitude of reasons, including to correct design errors in the DTD, to allow expansion of the application scope over time, or to account for the merging of several businesses into one. However most of the current software tools that enable the use of XML do not provide explicit support for such data or schema changes. In this vein, we put forth the first solution framework, called XML Evolution Manager (XEM) to manage the evolution of XML. XEM provides a minimal yet complete taxonomy of basic change primitives. These primitives, classified as either data changes or schema changes, are consistency-preserving, i.e., for a data change, they ensure that the modified XML document conforms to its DTD both in structure and constraints; and for a schema change, they ensure that the new DTD is a valid DTD and all existing XML documents are transformed also to conform to the modified DTD. We prove the completeness of the taxonomy in terms of DTD transformation. To verify the feasibility of our XEM approach we have implemented a working prototype system using PSE Pro as our backend storage system.
18283115
Mining Maximal Frequently Changing Subtree Patterns from XML Documents
Due to the dynamic nature of online information, XML documents typically evolve over time. The change of the data values or structures of an XML document may exhibit some particular patterns. In this paper, we focus on the sequence of changes to the structures of an XML document to find out which subtrees in the XML structure frequently change together, which we call Frequently Changing Subtree Patterns (FCSP). In order to keep the discovered patterns more concise, we further define the problem of mining maximal FCSPs. An algorithm derived from the FP-growth is developed to mine the set of maximal FCSPs. Experiment results show that our algorithm is substantially faster than the naive algorithm and it scales well with respect to the size of the XML structure.
8891364
Supporting a Real-Time Distributed Intrusion Detection Application on GATES
Increasingly, a number of applications across computer sciences and other science and engineering disciplines rely on, or can potentially benefit from, analysis and monitoring of data streams. We view the problem of flexible and adaptive processing of distributed data streams as a grid computing problem. In our recent work, we have been developing a middleware, GATES (Grid-based AdapTive Execution on Streams), for enabling grid-based processing of distributed data streams. 
 
This paper reports an application study using the GATES middleware system. We focus on the problem of intrusion detection. We have created a distributed and self-adaptive real-time implementation of the algorithm proposed by Eskin using our middleware. The main observations from our experiments are as follows. First, our distributed implementation can achieve detection rates which are very close to the detection rate by a centralized algorithm. Second, our implementation is able to effectively adjust the adaptation parameters.
63481154
MobiMessenger: An Instant Messenger System Based on Mobile Ad-Hoc Network
Mobile ad-hoc network offers many new ways for CSCW resolution. So we develop an ad-hoc instant messenger, MobiMessenger, which will be used as a platform for our future research work on ad-hoc collaboration. In this paper, we present the design and implement of MobiMessenger, which is based on AODV algorithm, including the system architecture and implementation. Also present our future work on ad-hoc collaboration.
8972258
Designing oscillators in synthetic gene networks based on multi-scale dynamics
Multistability, oscillations, and switching exist at various levels of biological processes and organizations and have been investigated on the basis of many theoretical models, such as circadian oscillations with the period protein (PER) and the timeless protein (TIM) in Drosophila, and multistable dynamics regulated by transcriptional factors. Considerable experimental evidence suggests that cellular processes are intrinsically rhythmic or periodic. Various periodic oscillations with different time scales ranging from less than a second to more than a year, which may allow for living organisms to adapt their behaviors to a periodically varying environment, have also been observed experimentally. On the other hand, in synthetic gene networks, both toggle switch and repressilator have been theoretically proposed and further confirmed by experiments. All of these works stress the importance of feedback regulation of transcriptional factors, which is a key in giving rise to oscillatory or multistable dynamical behaviors exhibited by biological genetic systems. In addition, it should be noted that many periodic behaviors do not simply oscillate smoothly; rather, they change rapidly or jump at certain states. In gene expression systems, many different time scales characterize the gene regulatory processes. For instance, the transcription and translation processes generally evolve on a time scale that is much slower than that of phosphorylation, dimerization or binding reactions of transcription factors. In genetic networks, the time scale for expression of some genes is much slower than that of others, depending on the length of the genes. We aim to design robust periodic oscillators in synthetic gene-protein systems by simple nonlinear models and to analyze the basic mechanism of limit cycles with jumping behaviors or relaxation oscillations by exploiting multiple time-scale properties [1, 2]. We show that periodic oscillations are mainly generated by nonlinear feedback loops in gene regulatory systems and the jumping dynamics caused by time scale differences among biochemical reactions. Moreover, effects of time delay are also examined. We show that time delay generally enlarges the stability region of oscillations, thereby making the oscillations more sustainable despite parameter changes or noise [1, 2]. The dynamics of the proposed models is robust in terms of stability and period length to the parameter perturbations or environment variations. Although we mainly analyze some specific models, the mechanisms identified in this work are likely to apply to a variety of genetic regulatory systems. These simple models may actually act as basic building block in synthetic gene-protein networks, such as genetic oscillators or switches because the dynamics is robust for parameter perturbations or environment variations. Several examples are also provided to demonstrate implementation of synthetic oscillators by using genes of the /spl lambda/ phage bacteria.