¡@ Amy Mei-Hsuan Lu

Carnegie Mellon   

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Bio

I am currently with Microsoft Corporate. Prior to MSFT, I also worked with Conviva Inc. shortly. I earned my PhD degree in the Department of Electrical and Computer Engineering (ECE) at Carnegie Mellon University in Aug. 2009, 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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Research

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:

  •  Link-layer Opportunistic Retransmission Protocol (PRO)

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 here.

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  • Link-layer Time-based Adaptive Retransmission (TAR)

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.

  • Cooperative Hybrid ARQ (CHARQ)

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.

  • CMUsuem

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!

  • FlexMAC

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 here.

 

The source code (based on Madwifi-0.9.3.1) can be downloaded here.

  • Multimedia Video Conferencing System

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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Publications
Journal Papers :
  • M. Lu, P. Steenkiste, and T. Chen, "Opportunistic Retransmission in Wireless LANs,"  submitted to IEEE Transactions on Mobile Computing.
  • M. Lu, P. Steenkiste, and T. Chen, "Robust Wireless Video Streaming Using Hybrid Spatial/Temporal Retransmission,"  IEEE Journal on Selected Areas in Communications, Special Issue on Wireless Video Transmission, Vol. 28, No. 3, April 2010.
  • M. Lu, P. Steenkiste, and T. Chen, "A Time-based Adaptive Retry Strategy for Video Streaming in 802.11 WLANs ," Wireless Communications and Mobile Computing, Special Issue on Video Communications for 4G Wireless Systems, submitted June 2006, revised Sept 2006, published Fec. 2007.  

Conference Papers:

  • M. Lu ,P. Steenkiste, and T. Chen "Design, Implementation and Evaluation of an Efficient Opportunistic Retransmission Protocol," accepted by ACM MobiCom 2009, Beijing China, Sept. 2009. (acceptance rate: 10%)
  • M. Lu, P. Steenkiste, and T. Chen, "CHARQ: Cooperative Hybrid ARQ for Wireless Video Streaming," IEEE International Conference on Multimedia and Expo (ICME 2009), July 2009.
  • M. Lu, Y. Chiu, and T. Chen, "Learning-based Relay Selection for Opportunistic Routing," IEEE International Conference on Multimedia and Expo (ICME 2009), July 2009.
  • M. Lu, P. Steenkiste, and T. Chen, "Using Commodity Hardware Platform to Develop and Evaluate CSMA Protocols," accepted by The Third ACM International Workshop on Wireless Network Testbeds, Experimental Evaluation and Characterization (WiNTECH 2008) in conjunction with ACM MobiCom 2008. slides
  • G. Judd, X. Wang, M. Lu, and P. Steenkiste, "Using Physical Layer Emulation to Optimize and Evaluate Mobile and Wireless Systems," 5th Annual International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services (Mobiquitous 2008), Dublin, Ireland, July 2008.
  • M. Lu, P. Steenkiste, and T. Chen, "Video Transmission over Wireless Multihop Networks Using Opportunistic Routing,"  Packet Video Workshop (PV2007), Nov. 2007. poster
  • M. Lu, P. Steenkiste, and T. Chen, "Time-aware Opportunistic Relay for Video Streaming over WLANs,"  IEEE International Conference on Multimedia and Expo (ICME 2007), July 2007.
  • M. Lu and T. Chen, "CMUseum: A Location-aware Adaptive Retry Strategy for Video Streaming in 802.11 WLANs," IEEE International Conference on Multimedia and Expo (ICME), July 2006. 
  • M. Lu, P. Steenkiste, and T. Chen, "Video Streaming over 802.11 WLANs with Content-aware Adaptive Retry,"  IEEE International Conference on Multimedia and Expo (ICME), July 2005.  poster
  • T. Chen, M. Lu, J. Huang, "Design and Implementation of an H.323 Multimedia Conference System" Proceedings of 1999 Workshop on Distributed System Technologies & Applications, Tainan, Taiwan,  May 1999. 

  • T. Chen, M. Lu, J. Huang, "Real-time Multimedia Synchronization on H.323 Multimedia Conference System", Proceedings of 1999 Multimedia Technology and Application Symposium, Kaohsiung, Taiwan, March 1999.

Demos/Posters:

  • K. Borries, X. Wang, M. Lu, G. Nychis, D. Stancil, and P. Steenkiste, ¡¨Repeatable and Fully Controlled Wireless and Mobile Experiments,¡¨ ACM MobiCom, Demo, Sept. 2008.
  • M. Lu, P. Steenkiste, and T. Chen, ¡¨FlexMAC: A Wireless Protocol Development and Evaluation Platform Based On Commodity Hardware,¡¨ ACM MobiCom/WiNTECH, Demo, Sept. 2008.

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Contact

amylu AT cmu DOT edu
t. +1 (412) 268-7114
f. +1 (412) 268-2860

Porter Hall B42
Department of Electrical and Computer Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
U.S.A.

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©2009 March Amy, Mei-Hsuan Lu