Jingpu Shi
Department of Electrical and Computer Engineering, Rice University
6100 Main Street, MS-366, Houston, TX 77005
Phone: 713-348-3776, Email: jingpu@rice.edu
OBJECTIVE
To obtain a position in wireless networking.
EDUCATION
Rice University, Houston, TX
PhD Graduate Student, Electrical and Computer Engineering
08/2004-Present
The Ohio State University, Columbus, OH
MS, Electrical Engineering
08/2004
University of Electronic Science and Technology, China
BS, Electrical Engineering
07/1996
TEACHING EXPERIENCE
Held office hours, advised students and occasionally gave lectures for course:
ELEC 437, Introduction to Communication Networks
COMP 429, Introduction to Computer Networks
ELEC 537, Communication Networks
ELEC 438, Wireless Networking for Under-Resourced Urban Communities
Fall 2005
Spring 06
Fall 2006
Spring 2007
RESEARCH EXPERIENCE
Research Assistant
08/2004-Present
Rice University, Houston, TX， Department of Electrical and Computer Engineering
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Investigated starvation in operational urban mesh networks.
Modeled synchronized contention in CSMA multi-hop networks.
Designed a multi-channel MAC protocol to address starvation in multi-hop networks.
Analyzed and modeled medium access in CSMA multi-hop wireless networks.
PUBLICATIONS
1.
J. Shi, T. Salonidis and E. Knightly, "Modeling Fairness And Clock Drifts Under
Synchronized CSMA Contention," to be submitted.
2.
J. Shi, O. Gurewitz, V. Mancuso, J. Camp and E. Knightly "Starvation in operational
urban mesh networks: origins and solutions ", submitted to SIGCOMM 2007.
3.
J. Shi, T. Salonidis and E. Knightly, "Starvation Mitigation Through Multi-Channel
Coordination in CSMA-based Wireless Networks," in Proceedings of ACM
MobiHoc'06, Florence, Italy, May 2006 (acceptance rate 10%).
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4.
M. Garetto, J. Shi and E. Knightly, "Modeling Media Access in Embedded Two-Flow
Topologies of Multi-hop Wireless Networks," in Proceedings of ACM MobiCom'05,
Cologne, Germany, August 2005 (acceptance rate 10%).
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SKILLS
NS-2 network simulator, C, C++, AWK, TCL, MATLAB, Unix, Linux, Windows.
SERVICES, SCHOLARSHIPS AND AWARDS
Rice University
- Rice University Fellowship
2004-2005
The Ohio State University
- Outstanding Graduate Student Award (one of the three recipients)
- President of Cultural Ambassadors Association
- Voting member of Academic Misconduct Committee
- Engineering school representative in Research and Graduate Council
- Department representative at Council of Graduate Students
- University Fellowship
RESEARCH PROJECTS
Rice University, Houston, TX
Department of Electrical and Computer Engineering
2003
2003
2003
2003
2002
2001-2002
08/2004-Present
Countering starvation in operational urban networks
Tree-structured mesh networks that employ IEEE 802.11 lead to acute unfairness or
starvation, even for flows under end-to-end congestion control. Namely, mesh nodes closer
to the wired gateway receive significantly higher throughput than mesh nodes farther away.
I first present measurements obtained in a Houston urban network to show severe
throughput imbalance among TCP flows. To address this problem, I identify a simple
scenario as the critical building block for understanding and predicting the unfairness
behavior observed by TCP flows traveling over a mesh network. I propose a discrete time
Markov chain model to investigate the interaction between end-to-end congestion control
and the MAC congestion window. The model reveals the key role of the last hop in
controlling the stationary distribution of the system. Consequently I develop a simple
contention window policy to allow fair gateway bandwidth sharing between the mesh
nodes. I finally implement this policy in hardware and validate its effectiveness through
on-site deployment.
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Model and Fairness properties in synchronized CSMA wireless networks
A broad class of CSMA protocols use synchronized contention in which nodes periodically
contend at intervals of fixed duration. While synchronized CSMA contention has not been
proposed to improve fairness, in this project I show that it has the potential to address the
severe throughput imbalances that plague asynchronous CSMA protocols such as IEEE
802.11 DCF. However, its fairness properties have never been analyzed. I introduce an
analytical model that directly quantifies the interplay and impact of the main performance
factors: imperfect clock synchronization, contention window size, carrier sense, topology
properties and usage of guard time. This model reveals conditions on protocol parameters
under which the throughput of certain flows can exponentially decrease with clock drift. In
addition, it enables solutions that can offset such problems in a predictable manner.
Starvation Mitigation Through Multi-channel Coordination in CSMA-based Wireless
Networks
Existing multi-channel protocols have been demonstrated to significantly increase
aggregate throughput compared to single-channel protocols. However, I show that despite
such improvements in aggregate throughput, existing protocols can lead to flow starvation
in a multi-hop network. In this project, I devise Asynchronous Multi-channel Coordination
Protocol (AMCP), a distributed medium access protocol that not only increases aggregate
throughput, but, more importantly, addresses the fundamental coordination problems that
lead to starvation. I analytically derive and experimentally validate an approximate lower
bound on the throughput of any flow in an arbitrary topology. I also demonstrate that
AMCP can deliver significantly higher per-flow throughput than both IEEE 802.11 and
existing multi-channel solutions.
Modeling Media Access in Embedded Two-Flow Topologies of Multi-hop Wireless
Networks
I decompose a multi-hop wireless network into embedded subgraphs, each consisting of
four nodes and two flow pairs. I identify all twelve possible topologies that arise according
to whether the different nodes are in radio range of each other. I show that under both a
random spatial distribution of nodes and random waypoint mobility with shortest-path
routing, a critical and highly probable scenario is a class in which the channel state shared
by the two flows is not only incomplete (i.e., the graph is not fully connected), but there is
also asymmetry in the state between the two flows. I develop an accurate analytical model
validated by simulations to characterize the long-term unfairness that naturally arises when
CSMA with two or four-way handshake is employed as a random access protocol.
Moreover, we show that another key class of topologies consists of incomplete but
symmetric shared state. I show that in this case, the system achieves long-term fairness, yet
endures significant durations in which one flow dominates channel access with many
repeated transmissions before relinquishing the channel.
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SIMULATIONS AND IMPLEMENTATIONS
Rice University, Houston, TX
Department of Electrical and Computer Engineering
08/2004-Present
Synchronized CSMA (S-CSMA)
S-CSMA is a single-channel synchronized CSMA protocol in which time is partitioned
into fixed-duration cycles. In a perfectly synchronized system, each node begins each cycle
at the same time instant. Each cycle consists of a contention phase followed by a data
transmission phase. At the beginning of each cycle, each node senses the medium and
waits while it is busy. The data transmission phase may consist of one or more data-link
frames and their corresponding acknowledgments provided that all transmission (data and
acknowledgment) is completed by the end of the cycle.
I implemented S-CSMA using ns-2 (ns-2.28) simulator with CMU wireless extensions. I
wrote scripts and evaluated its fairness properties in various experiments under both
perfect and imperfect synchronization.
Asynchronous Multi-channel Coordination Protocol (AMCP)
AMCP is a MAC protocol that utilizes multiple channels to increase per-flow throughput.
It uses a dedicated control channel on which nodes contend to reserve data channels by
exchanging RTS/CTS packets according to 802.11 DCF. All channels are orthogonal with
respect to each other. Each node has a single transceiver, hence it can either transmit or
listen, but not both. Also it can listen to or transmit on one channel at a time. To execute
AMCP, each node maintains a local channel status table.
I implemented AMCP using ns-2 (ns-2.28) simulator with CMU wireless extensions. I
developed scripts and evaluated AMCP in both single-hop and multi-hop topologies.
Multi-band Opportunistic Auto Rate (MOAR)
Multi-band Opportunistic Auto Rate (MOAR) is an opportunistic media access protocol for
multi-rate IEEE 802.11. Building on the IEEE 802.11 MAC protocol, MOAR uses an
optimal band skipping rule to find the best band for transmission every time a node pair
gains access to the medium.
I implemented this protocol to systematically investigated its performance in various
network settings. I utilized Opportunistic Auto Rate (OAR) as a starting point. The NS
extensions include Rice Networks Group (RNG) implementation of OAR for ns-2.1b7. The
implementation of Ricean Fading Model is based on CMU additions to NS to handle
Ricean and Rayleigh fading. All simulation results are presented in the following paper:
A. Sabharwal, A. Khoshnevis and E. Knightly, Opportunistic Spectral Usage: Bounds and
a Multi-band CSMA/CA Protocol, to appear in ACM Transactions on Networking, 2007.
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REFERENCES
Professor Edward W. Knightly
Department of Electrical and Computer Engineering
Rice University
6100 Main Street, MS 380
Houston, TX 77005-1892
(713) 348-5748
knightly@ece.rice.edu
Professor Ashutosh Sabharwal
Department of Electrical and Computer Engineering
Rice University
6100 Main Street, MS 380
Houston, TX 77005-1892
(713) 348-5057
ashu@ece.rice.edu
Professor David B. Johnson
Department of Computer Science
Rice University
6100 Main Street, MS 132
Houston, TX 77005-1892
(713) 348-3063
dbj@cs.rice.edu
Dr. Omer Gurewitz
Department of Electrical and Computer Engineering
Rice University
6100 Main Street, MS 380
Houston, TX 77005-1892
(713) 348-2359
gurewitz@ece.rice.edu
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