Carnegie Mellon
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I am
on the job market in Spring 2009. ¡@ Member of Advanced Multimedia Processing Lab (AMP) ¡@ |
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I am a Ph.D. candidate in the Department of Electrical and Computer Engineering (ECE) at Carnegie Mellon University under advisement of Professor Tsuhan Chen and Professor Peter Steenkiste. Before starting my PhD studies, I was with ASUSTeK Computer Inc, Taiwan. At the time, I participated in design and development of ASUS's broadband communication, information appliance and voice over IP products. Earlier on, I was an alumnus of the Communication and Multimedia Lab in the Department of Computer Science and Information Engineering Department (CSIE) at National Taiwan University (NTU) where I was a member of the Network Group under Professor Jau-Hsiung Huang's advisement. I received my B.S. degree in Information Management (IM) and M.S. degree in Computer Science and Information Engineering (CSIE) at National Taiwan University. ¡@ |
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My research interests lie across the areas of wireless networking, video streaming, and mobile computing, particularly in the design, development, evaluation, and measurement of such systems. I aim to better understand the behavior of existing networks, and use this knowledge to build more powerful networking systems. I have worked on many interesting projects at CMU:
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Time-based adaptive retry (TAR) is a link-layer retransmission strategy for delay-sensitive applications such as video. TAR dynamically determines whether to send or discard a packet based on its associated retransmission deadline rather than adopting a static retry limit over all packets. By properly assigning retransmission deadlines, TAR can also offer unequal error protection over different types of video frames. TAR has been implemented on commodity hardware and widely evaluated in many real world scenarios. We have also integrated TAR into PRO to equip relays with time awareness. The hybrid solution can push the performance envelope further.
Forward Error Correction (FEC) coding and Automatic Repeat reQuest (ARQ) are two commonly used techniques to tackle packet erasures in wireless video streaming. To preserve flexibility while reducing end-to-end latency, Hybird ARQ (HARQ) has been proposed as an alternative that combines the advantages of FEC and ARQ. This work presents Cooperative Hybrid ARQ (CHARQ) that can further boost wireless video streaming quality. CHARQ takes advantage of the fact that, in the wireless environment, broadcast is free (from the sender¡¦s point of view) and that errors are location dependent so an intermediate proxy that overhears the source¡¦s transmission may transmit on behalf of the source to increase throughput efficiency.
Location-aware computing enables automatic tailoring of information and services based on the current location of a mobile user. We have designed and implemented CMUseum, a system that enables location-based video streaming applications, as well as other add-on services on top of the purposed infrastructure. Our novel design incorporates an 802.15.4 Zigbee sensor network for collecting location information and an 802.11 Wi-Fi network for streaming video contents. This framework is largely event-driven in order to support the real-time nature of the video streaming services it handles. We have demonstrated the viability of this system through implementing a working system in a museum tour guide scenario. Watch the following video to get an idea of this work!
The source code (based on Madwifi-0.9.3.1) can be downloaded here.
Earlier on, I was working on H.323 multimedia conferencing systems. We designed and implemented an H.323 compliant video phone prototype with support of an novel media synchronization scheme and an effective task management technique. I have also worked on the development of H.263+ and error resilience features of MPEG-4. ¡@ |
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Conference Papers:
Demos/Posters:
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PRO
(Protocol for Retransmitting Opportunistically) is a
link-layer protocol that allows overhearing nodes to
function as relays that retransmit on behalf of the source
after they learn about a failed transmission. Relays with
stronger connectivity to the destination have a higher
chance of delivering the packet than the source does,
thereby resulting in a more efficient use of the channel.
PRO has four main features. First, channel reciprocity
coupled with a run-time calibration process is used to
estimate the instantaneous link quality to the destination.
Second, a local qualification process filters out poor
relays early. Third, a distributed relay selection algorithm
chooses the best set of eligible relays among all qualified
relays and prioritizes them. Lastly, 802.11e Enhanced
Distributed Channel Access (EDCA) is leveraged to make sure
high priority relays transmit with high probability. PRO is
designed to coexist with legacy 802.11 stations. We have
implemented PRO in the driver of a commodity wireless card.
Our extensive evaluation both on a controlled testbed and in
the real world shows that PRO boosts throughput in various
wireless environments, particularly in contended channels,
under fading, or with user mobility. The following video shows a demo of PRO.
Detailed description and more information
can be found
Developing
and evaluating wireless protocols is challenging
because it requires flexible network interface hardware,
which is not readily available. To this end, we developed
FlexMAC, a wireless protocol development and evaluation
platform based on commodity hardware. FlexMAC targets
CSMA wireless protocols and allows customization of
functions
such as backoff, retransmission, and packet timing. FlexMAC is a useful
tool for conducting 802.11-style protocol research. The following video shows a demo that compares
the performance between a software (developed using FlexM) and a hardware 802.11 MAC.
More details of FlexMAC can be found 
M. Lu
,P. Steenkiste, and T. Chen "Design, Implementation and
Evaluation of an Efficient Opportunistic Retransmission
Protocol," 
amylu
AT cmu DOT edu¡@