Browsing by Author "Du, Shu"

Now showing 1 - 5 of 5
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    An Architecture for Distributed Wavelet Analysis and Processing in Sensor Networks
    (2006-04-01) Wagner, Raymond; Baraniuk, Richard G.; Du, Shu; Johnson, David B.; Cohen, Albert
    Distributed wavelet processing within sensor networks holds promise for reducing communication energy and wireless bandwidth usage at sensor nodes. Local collaboration among nodes de-correlates measurements, yielding a sparser data set with significant values at far fewer nodes. Sparsity can then be leveraged for subsequent processing such as measurement compression, de-noising, and query routing. A number of factors complicate realizing such a transform in real-world deployments, including irregular spatial placement of nodes and a potentially prohibitive energy cost associated with calculating the transform in-network. In this paper, we address these concerns head-on; our contributions are fourfold. First, we propose a simple interpolatory wavelet transform for irregular sampling grids. Second, using ns-2 simulations of network traffic generated by the transform, we establish for a variety of network configurations break-even points in network size beyond which multiscale data processing provides energy savings. Distributed lossy compression of network measurements provides a representative application for this study. Third, we develop a new protocol for extracting approximations given only a vague notion of source statistics and analyze its energy savings over a more intuitive but naive approach. Finally, we extend the 2-dimensional (2-D) spatial irregular grid transform to a 3-D spatio-temporal transform, demonstrating the substantial gain of distributed 3-D compression over repeated 2-D compression.
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    Design and Performance of PRAN: A System for Physical Implementation ofAd Hoc Network Routing Protocols
    (2005-02-28) Du, Shu; Johnson, David B.; PalChaudhuri, Santashil; Saha, Amit Kumar; To, Khoa
    Simulation and physical implementation are both valuable tools in evaluating ad hoc network routing protocols, but neither alone is sufficient. In this paper, we present the design and performance of PRAN, a new system for implementation of ad hoc network routing protocols that merges these two types of evaluation tools. PRAN (Physical Realization of Ad Hoc Networks) allows existing simulation models of ad hoc network routing protocols to be used—without modification—to create a physical implementation of the same protocol. We have evaluated the simplicity and portability of our approach across multiple protocols and multiple operating systems through example implementations in PRAN of the DSR and AODV routing protocols in FreeBSD and Linux using the existing, unmodified ns-2 simulation models. We illustrate the ability of the resulting protocol implementations to handle real, demanding applications by describing a demonstration with this DSR implementation transmitting real-time video over a multi hop mobile ad hoc network; the demonstration features mobile robots being remotely operated based on the video stream transmitted over the network. We also present a detailed performance evaluation of PRAN to show the feasibility of our architecture.
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    Routing in large-scale ad hoc networks based on a self-organizing coordinate system
    (2004) Du, Shu; Johnson, David B.
    In this thesis, I present the design and evaluation of new techniques to solve the routing problem in large-scale city-wide wireless ad hoc networks. With an upsurge of wireless technologies, many routing protocols have been proposed for wireless ad hoc networks, but none of them have been proven capable of handling the tasks in a large-scale network that is composed of thousands of nodes. We propose a new routing scheme that is a hybrid of the current proactive and reactive routing mechanisms. This scheme uses proactive beaconing messages to build a virtual hierarchical coordinate system in an ad hoc network and thereafter uses reactive routing maintenance techniques to bypass the stale information between beacons. I implemented this new hybrid scheme in the network simulator ns-2. The simulation results show that it performs well in a large-scale ad hoc network of one thousand of nodes with low overhead.
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    Self-Organizing Hierarchical Routing for Scalable Ad Hoc Networking
    (2005-02-08) Druschel, Peter; Du, Shu; Johnson, David B.; Khan, Muhammed; PalChaudhuri, Santashil; Post, Ansley; Riedi, Rudolf H.; Saha, Amit
    As wireless devices become more pervasive, mobile ad hoc networks are becoming increasingly important, motivating the development of highly scalable ad hoc networking techniques. In this paper, we present the design and evaluation of a novel protocol for scalable routing in ad hoc networks, as part of the Safari project. Safari leverages and integrates research in both ad hoc networking and peer-to-peer networking. We develop a probabilistic, elf-organizing network hierarchy formation protocol that recursively forms the nodes of the ad hoc network into an adaptive, proximity-based hierarchy of cells. We develop a hybrid routing protocol that uses this hierarchy, with reactive and proactive routing, to scale to large number of nodes. The mapping of unique node identifiers to hierarchical addresses is done using a distributed hash table that leverages the hierarchical network structure. We evaluate this design through analysis and simulations, under increasing network size, increasing fraction of mobile nodes, and increasing offered traffic load. Our analysis is well matched by our simulations, and our results demonstrate the protocol's scalability.
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    Using routing information to improve MAC performance in multi-hop wireless networks
    (2008) Du, Shu; Johnson, David B.
    As wireless communication technology becomes increasingly available, multi-hop wireless networks such as wireless sensor networks and wireless mesh networks are receiving substantial attention from both academic and industrial efforts. However, traditional contention-based wireless MAC protocols such as IEEE 802.11 DCF are designed for single-hop wireless networks and do not perform well in multi-hop scenarios due to inefficiency in their medium reservation mechanisms. In this thesis, a new general mechanism, utilizing a new Pioneer (PION) scheduling frame, is introduced to improve the efficiency in wireless medium reservation for multi-hop wireless networks. With the help of limited routing information at the MAC layer, this new mechanism enables multiple stations along a delivery path to cooperate. In particular, the PION control frame can travel across multiple hops and make medium reservations along the route for the upcoming data frame transmissions. This cooperation across multiple hops at the MAC layer can therefore greatly improve the medium reservation efficiency. This thesis introduces the PION mechanism and illustrates its use through application in two different types of MAC protocols. First, in the energy-constrained sensor network environment, I develop a new a duty-cycle based MAC protocol, called RMAC. Comparing against S-MAC, a classic duty-cycle MAC protocol, RMAC shows significant performance improvement in both packet delivery latency and network throughput, with even better energy efficiency. Second, the new PION mechanism is then applied to the general case of multi-hop wireless networks in the design of a MAC protocol called EMAC. Simulation results under various scenarios and traffic loads have shown the potential of EMAC over IEEE 802.11, including throughput improvement and decrease in packet relaying time.