Undergraduate Papers

Guobin Shen, Changxi Zheng, Wei Pu and Shipeng Li
Distributed Segment Tree: A Unified Architecture to Support Range Query and Cover Query.
Technical Report MSR-TR-2007-30, 2007

Paper (PDF)
Changxi Zheng, Guobin Shen, Shipeng Li, and Scott Shenker
Distributed Segment Tree: Support of Range Query and Cover Query over DHT.
The 5th International Workshop on Peer-to-Peer Systems (IPTPS) Santa Barbara, US, February 2006

Paper (PDF) Abstract Bibtex
Range query, which is defined as to find all the keys in a certain range over the underlying P2P network, has received a lot of research attentions recently. However, cover query, which is to find all the ranges currently in the system that cover a given key, is rarely touched. In this paper, we first identify that cover query is a highly desired functionality by some popular P2P applications, and then propose distributed segment tree (DST), a layered DHT structure that incorporates the concept of segment tree. Due to the intrinsic capability of segment tree in maintaining the sturcture of ranges, DST is shown to be very efficient for supporting both range query and cover query in a uniform way. It also possesses excellent parallelizability in query operations and can achieve O(1) complexity for moderate query ranges. To balance the load among DHT nodes, we design a downward load stripping mechanism that controls tradeoffs between load and performance. We implemented DST on publicly available OpenDHT service and performed extensive real experiments. All the results and comparisons demonstrate the effectiveness of DST for several important metrics.
@inproceedings{Zheng06DST,
    author      = {Changxi Zheng and Guobin Shen and Shipeng Li and Scott Shenker},
    title       = {Distributed segment tree: Support of range query and cover query over dht},
    booktitle   = {In proceedings of the 5th International Workshop on 
                   Peer-to-Peer Systems (IPTPS 06)},
    year        = {2006}
}
Ke Liang, Zaoyang Gong, Changxi Zheng, and Guobin Shen
MOVIF: A Lower Power Consumption Live Video Multicasting Framework over Ad-hoc Networks with Terminal Collaboration.
International Symposium on Intelligent Signal Processing and Communication Systems (ISPACS), Hong Kong, December 2005

Paper (PDF) Abstract
Live video multicasting over wireless ad hoc networks is a tough problem due to the restricted computational ability of the mobile devices and non-predictive networks status. In this paper, we propose MoViF, a lower power consumption multicasting framework for live video multicasting over ad-hoc networks. The proposed MoViF adopts distributed video coding (DVC) scheme and, as a result, enjoys all the beneļ¬ts of DVC such as lightweight encoder and built-in error resilient capability. Moreover, MoViF manages to apply an elegant strategy to minimize the overall power consumption for all the receivers while improving their decoding quality by dynamically assign the tasks of aid information extraction to some intermediate powerful nodes in the multicast tree. Simulation results demonstrate that the optimal strategy can lower down the overall power consumption comparing to the random strategy.
Changxi Zheng, Guobin Shen, and Shipeng Li
Distributed Prefetching Scheme for Random Seek Support in Peer-to-Peer Streaming Applications.
Workshop on Advances in Peer-to-Peer Multimedia Streaming, ACM Multimedia 2005, Singapore, November 2005

Paper (PDF) Abstract Bibtex
Through analysis of large volume of user behavior logs during playing multimedia streaming, we extract a user viewing pattern. The pattern indicates that random seek is a pervasive phenomenon, contrary to the common assumptions that users would watch a video session sequentially and passively in most works on peer-to-peer streaming. We propose to use efficient prefetching to facilitate the random seek functionality. Because of the statistical nature of the user viewing pattern and the ignorance of the users to the content, we argue that the pattern should be used as a guidance to the random seek. Based on the pattern, we set up an analogy between the optimization problem of minimizing the seeking distance and the optimal scalar quantization problem. We then propose an optimal prefetching scheduling algorithm based on the optimal scalar quantization theory. We further propose a hierarchical prefetching scheme to carry out the prefetching more effectively. Real user viewing logs are used to drive the simulations which demonstrate that the proposed prefetching scheduling algorithm and the hierarchical prefetching scheme can improve the seeking performance significantly.
@inproceedings{zheng2005distributed,
  title={Distributed prefetching scheme for random seek support in peer-to-peer 
         streaming applications},
  author={Zheng, Changxi and Shen, Guobin and Li, Shipeng},
  booktitle={Proceedings of the ACM workshop on Advances in peer-to-peer multimedia streaming},
  pages={29--38},
  year={2005},
}
Changxi Zheng, Guobin Shen, and Shipeng Li
Segment Tree Based Control Plane Protocol for Peer-to-Peer On-Demand Streaming Service Discovery.
Proc. of Visual Communication and Image Processing (VCIP), Beijing, China, July 2005

Paper (PDF) Abstract Bibtex
As the intense academic interest in video streaming over peer-to-peer(P2P) network, more and more streaming protocols have been proposed to address different problems on this field, such as QoS, load balancing, transmission reliability, bandwidth efficiency, etc. However, to the best of our knowledge, an important component of any practical P2P streaming system, the streaming service discovery, is rarely granted particular considerations, which is to discover potential peers from which a newcomer could receive the requested stream. In this paper, we are inspired from a special data structure, named Segment Tree(ST), and propose a protocol to address this problem specifically. Furthermore, we fully decouple the control plane and data plane on video streaming, and hence provide more flexibilities in designing protocols on both of them.
@inproceedings{Zheng05VCIP,
    author      = {Changxi Zheng and Guobin Shen and Shipeng Li},
    title       = {Segment Tree Based Control Plane Protocol for Peer-to-Peer 
                   On-Demand Streaming Service Discovery},
    booktitle   = {In proceedings of Visual Communication and Image Processing (VCIP)},
    year        = {2006}
}
Changxi Zheng, Guobin Shen, Shipeng Li and Qianni Deng
Joint Sender/Receiver Optimization Algorithm for Multi-Path Video Streaming Using High Rate Erasure Resilient Code.
Proc. of IEEE International Conference on Multimedia and Expo (ICME), Amsterdam, Netherlands, July 2005

Paper (PDF) Abstract Bibtex
In this paper we present a joint sender/receiver optimization algorithm and a seamless rate adjustment protocol to reduce the total number of packets over different paths in a streaming framework with a variety of constraints such as target throughput, dynamic packet loss ratio, and available bandwidths. We exploit the high rate erasure resilient code for the ease of packet loss adaption and seamless rate adjustment. The proposed algorithm and adjustment protocol can be applied at an arbitrary scale. Simulation results demonstrate that the overall traffic is significantly reduced with the proposed algorithm and protocol.
@inproceedings{Zheng05ICME,
    author      = {Changxi Zheng and Guobin Shen and Shipeng Li and Qianni Deng},
    title       = {Joint Sender/Receiver Optimization Algorithm for Multi-Path Video Streaming 
                   Using High Rate Erasure Resilient Code},
    booktitle   = {IEEE International Conference on Multimedia and Expo (ICME)}, 
    month       = July,
    year        = {2005}
}