Jogesh K. Muppala (梅伯樂)

Exploiting Proximity in Unstructured Peer-to-Peer Networks (New)

Abstract: Peer-to-peer (P2P) networks have long being used for file-sharing among the connected nodes in the Internet. Recently, the popular BitTorrent tool has permitted the exchange of large sized files by dividing it into fragments, and enabling the peers to exchange the fragments amongst themselves through the overlay network. The popularity of BitTorrent has prompted several researchers to study the performance of various aspects of the protocols used in BitTorrent and suggest improvements. The BitTorrent overlay is set up without due consideration of the topology of the underlying network and the locations of the peers. This mismatch often leads to ineffective utilization of network resources. In this proposal, we explore the use of proximity both in the construction of the overlay network, and the efficient exchange of the file fragments, mainly aimed at reducing the download time for the peers and at the same time reducing the resource usage (esp. link bandwidth) in the underlying network. We focus on the use of location proximity among peers in a BitTorrent overlay in order to improve its performance.

Cooperative Management of Data and Quality of Service  in Variable Topology Networks (Completed)

Abstract: Computer networks are commonly used nowadays to transfer data. For many current applications, including multimedia applications, the quality of service (QoS) such as delay time of data transfer is important. Much work has been done on QoS guarantees on traditional fixed topology networks. In this work, we propose to exploit the use of cooperation among the network nodes to manage data and QoS issues in order to improve performance in two types of newer networks whose topologies are not fixed. These are peer-to-peer networks and ad-hoc wireless networks. Peer-to-peer networks make use of any computers in the network, including home PCs, that are willing to participate instead of servers for data transfer to reduce cost. These nodes may come and go at any time. The target users are home users, but some companies are beginning to take advantage of this service as well. Ad-hoc networks are wireless networks in which there are no dedicated transceivers for routing data. The mobile devices assume the role of routers as well. The main advantage is ease of setting up the network. But, mobile devices can move, making routing and management issues more complicated. The target users include small offices and the military. We believe that simple cooperative schemes will allow these networks to perform more effectively without introducing too much overhead. So far, there is little work along this direction in the literature. We plan to use the most prominent applications for each type of network to illustrate the practicality of our schemes.

Publications:

  • W. Tu, J. K. Muppala and H. Zhuge, Distributed End Host Multicast Algorithms for The Knowledge Grid, Concurrency and Computation: Practice and Experience, 2007, to appear.
  • L. Zhang, J. K. Muppala and W. Tu, Exploiting Proximity in Cooperative Download of Large Files in Peer-to-Peer Networks, The Second International Workshop on P2P Systems and Applications (P2PSA 2007), Mauritius, May 2007.
  • L. Zhang, J. K. Muppala and S. T. Chanson, Integrated Location Management and Location-Aided Routing System for Mobile Ad-Hoc Networks, Journal of Parallel and Distributed Computing,Vol. 66, No. 3, 2006, pp 367-378.
  • L. Zhang, J. K. Muppala and S. T. Chanson, Provisioning Virtual Private Networks in the Hose Model with Delay Requirements, 2005 Int. Conference on Parallel Processing (ICPP 2005), Oslo, Norway, Jun. 2005, pp. 211-218.

 

Control-Theoretic Approaches to Power Management in Embedded Processors

Abstract: Embedded systems often operate in environments quite different from traditional computers with many operational constraints. These systems are often implemented with CPUs operating at low speed, with limited memory and often non-existent secondary storage, and with severe power and communication constraints. With the ubiquity of the Internet, many of these embedded systems are becoming network enabled. Power awareness and power management is a major consideration for these systems.

Our focus in this research project is on the power management for embedded processors. Existing approaches to power management are based on the classic dynamic voltage scaling (DVS) approaches which has been widely studied in the literature. Most of these a are based on heuristics, with an incomplete understanding of the system dynamics. The use of formal techniques for power management based on a control-theoretic framework has not received significant attention in the literature. We aim to design novel power management techniques that are based on a control-theoretic framework for expressing the power constraints. We believe that this formal approach would yield a better power management approach than is currently available, and can easily handle a wide range of system operation dynamics.

We have identified two possible control-theoretic approaches, viz., model predictive control (MPC) and adaptive control based on the classical PID control approach. In this research we wish to evaluate and compare the two control-theoretic approaches with the traditional heuristic techniques used for processor power management. Our research is expected to yield insights into the power management. This will be a stepping stone for further expansion into a control theoretic approach for system-wide coordinated power management techniques that can be used for the various components of embedded systems.

Lecture PODcasting: Enhancing course materials through recorded MP3 audio of lectures for portable MP3 players (Completed) (website)

Abstract: In this project we will explore the feasibility, technical and pedagogical issues of supplementing course materials through recorded MP3 audio of lectures that students can download and listen (offline) on their portable MP3 players like Apple IPod. With the rapid technological progress made in digital audio capture, online delivery and portable equipment, it is now possible to easily capture the instructor’s audio live during the class and make it available for students to download and listen on their portable players at their convenience. We will consider the technical aspects of deploying a suitable and convenient infrastructure for faculty to manage the capture and uploading the lecture audio, the pedagogical aspects of how to enhance the audio with suitable (audio) cues for students to relate the audio to the printed lecture notes. We will survey both instructors and students to understand the appropriate means of facilitating this process.

Publications:

  • K. K. Chan and J. K. Muppala, ReCap: A Tool for Automated Capture and Generation of Synchronized Audio, PowerPoint and Digital Ink Presentation, IASTED International Conference on Computers and Advanced Technology in Education (CATE 2007), Beijing, China, Oct. 2007.
  • J. K. Muppala and K. K. Chan, Podcasting and Its Use in Enhancing Course Content, IASTED International Conference on Computers and Advanced Technology in Education (CATE 2007), Beijing, China, Oct. 2007.
  • J. K. Muppala and K. K. Chan, Emerging Web Technologies and Their Use in Enhancing Course Content: An Experience Report, APRU Distance Learning and the Internet 2006 Conference (APRU DLI 2006), Tokyo, Japan, Nov. 2006, to appear.

 

Internet Quality of Service Using a Control Theoretic Approach (Completed)

Abstract: Rapid development in telecommunication technologies and ever-growing network-user demands have made network congestion a critical problem in today’s Internet. Congestion not only leads to significant network-centric performance degradation such as low link utilization, but also damages the user-centric Quality-of-Service (QoS). In addition, the increasingly heterogeneous network environments plus varying and unpredictable traffic conditions suggests that any mechanism without adaptability hardly be able to deliver QoS requirements.


This project considers the issue of congestion control and two QoS issues brought up by congestion in various network infrastructures including wired networks and wireless LANs. The two QoS issues are: (i) bandwidth assurance in the Assured Forwarding (AF) service in Differentiated Services (DiffServ) wired networks; and (ii) application level fairness between downlink and uplink flows in an infrastructure WLAN using the DCF mode. This thesis explores using a control theoretic approach to analyze and design mechanisms for these problems based only on the local knowledge.
First we describe a generic controller structure and discuss its features. Then, we use it to design a stable queue-based adaptive AQM mechanism for the current Internet. We aim to alleviate two tradeoffs: (i) between fast transient response and stability, and (ii) between fast transient response and small steady state error. Stability analysis of the closed-loop nonlinear system is conducted, providing guidelines for designing the algorithm and selecting control parameters.


The current Internet is a best-effort network and most AQM schemes focus on providing QoS assurance from a network-centric standpoint. The DiffServ approach has been proposed as a scalable mechanism in order to provide QoS. However, the AF service in this approach fails providing bandwidth assurance under certain conditions. In this thesis, we instantiate the generic controller structure in the AF service framework and analyze the features of the existing ingress-based mechanisms for improving bandwidth assurance among AF flows. Based on the analysis, we propose a simple but robust controller for this problem. Extensive simulations are carried out to validate the analysis and demonstrate that the proposed mechanism outperforms the mechanisms proposed in the literature over a wide range of network dynamics.


Congestion control and fairness issues are not only prominent for the Internet infrastructure when wired backbones and centralized control entities are available, but are also essential for various applications that use wireless technologies for flexible data communication. Therefore, this dissertation extends the research methodologies and technologies for Internet congestion control and QoS problems to wireless LANs. We explore the feasibility of combining AQM schemes with the underlying MAC protocol design in WLANs to provide fairness for traffic flows traversing between wired and wireless domains.
 

Publications:

  • X. Chang and J. K. Muppala, The Effects of AQM on the Performance of Assured Forwarding Service, Computer Communications, to appear.
  • X. Chang and J. K. Muppala, A Stable Queue-based Adaptive Controller for Improving AQM Performance, Computer Networks, 2005, to appear.
  • X. Chang and J. K. Muppala, On Improving Bandwidth Assurance in AF-based DiffServ Networks Using a Control Theoretic Approach, Computer Networks, Vol. 49, No. 6, 2005, pp. 816-839.
  • X. Chang, X. Lin and J. K. Muppala, A Control-Theoretic Approach to Improving Fairness in DCF Based WLANs, Proc. 25th Int. Performance, Computing and Communications Conference (IPCCC 2006), Phoenix, AZ, USA, Apr. 2006, to appear.
  • X. Lin, X. Chang and J. K. Muppala, VQ-RED: An Efficient Virtual Queue Management Approach to Improve Fairness in Infrastructure WLAN, Fifth International IEEE Workshop on Wireless Local Networks (WLN 2005), Sydney, Australia, Nov. 2005, pp. 632-638.
  • X. Chang, X. Lin and J. K. Muppala, An Adaptive Queue Management Mechanism for Improving TCP Fairness in the Infrastructure WLAN, 16th Ann. Int. Symposium on Personal Indoor and Mobile Radio Communications (PIMRC 2005), Berlin, Germany, Sep. 2005, to appear.
  • X. Chang and J. K. Muppala, Applying Adaptive Virtual Queue to Improve the Performance of the Assured Forwarding Service, Proc. 2005 IEEE International Conference on Communications (ICC 2005), Seoul, South Korea, May 2005, pp. 100-104.
  • X. Chang and J. K. Muppala, The Effects of AQM on the Performance of Assured Forwarding Services, Proc. 24th Int. Performance, Computing and Communications Conference (IPCCC 2005), Phoenix, AZ, USA, Apr. 2005, pp. 321-328.
  • X. Chang and J. K. Muppala, An Integral Sliding Mode based AQM for Queue Length Stability, Proc. IEEE 2004 Global Telecommunications Conference (Globecom 2004), Dallas, TX, USA, Dec. 2004, pp. 1698-1702.
  • X. Chang, J. K. Muppala  and J.-T. Yu, A Robust Nonlinear PI controller for Improving AQM Performance, Proc. 2004 IEEE International Conference on Communications (ICC 2004), Paris, France, Jun. 20-24, 2004, pp. 2272-2276.
  • X. Chang and J. K. Muppala, A Robust Controller for Improving Performance in the AF-based Differentiated Services Network, Proc. 23rd Int. Performance, Computing and Communications Conference (IPCCC 2004), Phoenix, AZ, USA, Apr. 15-17, 2004, pp. 487-494.
  • X. Chang and J. K. Muppala, Adaptive Marking Threshold for Improving Bandwidth Assurance in a Differentiated Services Network, Proc. IEEE 2003 Global Telecommunications Conference (Globecom 2003), Vol. 6, San Francisco, CA, USA, Dec. 2003, pp. 3073 - 3077.
  • X. Chang, and J. K. Muppala, Adaptive Marking Threshold for Assured Forwarding Services, Proc. IEEE  International Conference on Computer Communications and Networks (ICCCN 2003), Dallas, TX, USA, Oct. 2003, pp. 325 - 330.