Seminar Fall 2008

September 12, 2008 - Sangeeta Bhattacharya

Lorincz, K., Chen, B., Waterman, J., Werner-Allen, G., and Welsh, M.

2008. Resource aware programming in the Pixie OS. In Proceedings of the 6th ACM Conference on Embedded Network Sensor Systems (Raleigh, NC, USA, November 05 - 07, 2008). SenSys '08. ACM, New York, NY,

211-224. DOI= http://doi.acm.org/10.1145/1460412.1460434

September 19, 2008 - Greg Hackmann

A Measurement Study of Vehicular Internet Access Using In Situ Wi-Fi Networks.
Vladimir Bychkovsky, Bret Hull, Allen K. Miu, Hari Balakrishnan, Samuel Madden.
MobiCom 2006.

Links: Paper Slides

September 26, 2008 - Yong Fu

Paper:

Gong Chen, Wenbo He, Jie Liu, Suman Nath, Leonidas Rigas, Lin Xiao, and Feng Zhao, "Energy-Aware Server Provisioning and Load Dispatching for Connection-Intensive Internet Services" NSDI 2008, San Francisco, CA, April 2008.

Abstract:

Energy consumption in hosting Internet services is becoming a pressing issue as these services scale up. Dynamic server provisioning techniques are effective in turning off unnecessary servers to save energy. Such techniques, mostly studied for request-response services, face challenges in the context of connection servers that host a large number of long-lived TCP connections. In this paper, we characterize unique properties, performance, and power models of connection servers, based on a real data trace collected from the deployed Windows Live Messenger. Using the models, we design server provisioning and load dispatching algorithms and study subtle interactions between them. We show that our algorithms can save a significant amount of energy without sacrificing user experiences.

Links: Paper Slides

October 3, 2008 - Vincent Guo

Paper:

A Measurement Study of Interference Modeling and Scheduling in Low Power Wireless Networks. Ritesh Maheshwari (Stony Brook University, US); Shweta Jain (Staccato Communications, US); Samir Das (Stony Brook University, US). SenSys'08.

Abstract:

Accurate interference models are important for use in transmission scheduling algorithms in wireless networks. In this work, we perform extensive modeling and experimentation on two 20-node TelosB motes testbeds { one indoor and the otheroutdoor { to compare a suite of interference models for their modeling accuracies. We ¯rst empirically build and validate the physical interference model via a packet reception rate vs. SINR relationship using a measurement driven method. We then similarly instantiate other simpler models,such as hop-based, range-based, prot-

ocol model,etc. The modeling accuracies are then evaluated on the two testbeds using transmission scheduling exper- iments. We observe that while the physicalinterference model is the most accurate, it is still far from perfect, providing a 90-percentile error about 20-25% (and 80 percentile error 7-12%),depending on the scenario. The accura- cy of the other models is worse and scenario-speci¯c. The second best model trails the physical model by roughly 12-18 percentile points for similar accuracy targets. Somewhat similar throughput performance di®erential between models is also observed when used with greedy scheduling algorithms. Carrying on further, we look closely into the the two incarnations of the physical model {`thresholded'(conservative, but typically considered in literature) and `graded' (more realistic). We show via solving the one shot scheduling problem, that the graded version can improve `expected throughput' over the thresholded version by scheduling imperfect links.

Links: Paper, Slides (open document format)

October 10, 2008 - Chengjie Wu

Paper:

Hui, J. W. and Culler, D. E. 2008. IP is dead, long live IP for wireless sensor networks. In Proceedings of the 6th ACM Conference on Embedded Network Sensor Systems (Raleigh, NC, USA, November 05 - 07, 2008). SenSys '08. ACM, New York, NY, 15-28. DOI= http://doi.acm.org/10.1145/1460412.1460415

Abstract:

A decade ago as wireless sensor network research took off many researchers in the field denounced the use of IP as inadequate and in contradiction to the needs of wireless sensor networking. Since then the field has matured, standard links have emerged, and IP has evolved. In this paper, we present the design of a complete IPv6-based network architecture for wireless sensor networks. We validate the architecture with a production-quality implementation that incorporates many techniques pioneered in the sensor network community, including duty-cycled link protocols, header compression, hop-by-hop forwarding, and efficient routing with effective link estimation. In addition to providing interoperability with existing IP devices, this implementation was able to achieve an average duty-cycle of 0.65%, average per-hop latency of 62ms, and a data reception rate of 99.98% over a period of 4 weeks in a real-world home-monitoring application where each node generates one application packet per minute. Our results outperform existing systems that do not adhere to any particular standard or architecture. In light of this demonstration of full IPv6 capability, we review the central arguments that led the field away from IP. We believe that the presence of an architecture, specifically an IPv6-based one, provides a strong foundation for wireless sensor networks going forward.

Links: Paper

October 17, 2008 - N/A

Fall Break

October 24, 2008 - Justin Luner

Paper:

Dutta, P. and Culler, D. 2008. Practical asynchronous neighbor discovery and rendezvous for mobile sensing applications. In Proceedings of the 6th ACM Conference on Embedded Network Sensor Systems (Raleigh, NC, USA, November 05 - 07, 2008). SenSys '08. ACM, New York, NY, 71-84. DOI= http://doi.acm.org/10.1145/1460412.1460420

Abstract:

We present Disco, an asynchronous neighbor discovery and rendezvous protocol that allows two or more nodes to operate their radios at low duty cycles (e.g. 1%) and yet still discover and communicate with one another during infrequent, opportunistic encounters without requiring any prior synchronization information. The key challenge is to operate the radio at a low duty cycle but still ensure that discovery is fast, reliable, and predictable over a range of operating conditions. Disco nodes pick a pair of prime numbers such that the sum of their reciprocals is equal to the desired radio duty cycle. Each node increments a local counter with a globallyfixed period. If a node's local counter value is divisible by either of its primes, then the node turns on its radio for one period. This protocol ensures that two nodes will have some overlapping radio on-time within a bounded number of periods, even if nodes independently set their own duty cycle. Once a neighbor is discovered, and its wakeup schedule known, rendezvous is just a matter of being awake during the neighbor's next wakeup period,for synchronous rendezvous, or during an overlapping wake period, for asynchronous rendezvous.

Links: Paper

October 31, 2008 - Octav Chipara

Paper:

G. Zhou, J. Liu, C. Wan, M. Yarvis, and J. Stankovic, BodyQoS: Adaptive and Radio-Agnostic QoS for Body Sensor Networks, Infocom, April 2008.

Abstract:

As wireless devices and sensors are increasingly

deployed on people, researchers have begun to focus on wireless body-area networks. Applications of wireless body sensor networks include healthcare, entertainment, and personal assistance, in which sensors collect physiological and activity data from people and their environments. In these body sensor networks, quality of service is needed to provide reliable data communication over prioritized data streams. This paper proposes BodyQoS, the first running QoS system demonstrated on an emulated body sensor network. BodyQoS adopts an asymmetric architecture, in which most processing is done on a resource rich aggregator, minimizing the load on resource limited sensor nodes. A virtual MAC is developed in BodyQoS to make it radio-agnostic, allowing a BodyQoS to schedule wireless resources without knowing the implementation details of the underlying MAC protocols. Another unique property of BodyQoS is its ability to provide adaptive resource scheduling. When the effective bandwidth of the channel degrades due to RF interference or body fading effect, BodyQoS adaptively schedules remaining bandwidth to meet QoS requirements. We have implemented BodyQoS in NesC on top of TinyOS, and evaluated its performance on MicaZ devices. Our system performance study shows that BodyQoS delivers significantly improved performance over conventional

solutions in combating channel impairment.

Links: Paper

November 7, 2008 - Sangeeta Bhattacharya

Paper:

Shah, R. C., Nachman, L., and Wan, C. 2008. On the performance of Bluetooth and IEEE 802.15.4 radios in a body area network. In Proceedings of the ICST 3rd international Conference on Body Area Networks (Tempe, Arizona, March 13 - 17, 2008). ICST (Institute for Computer Sciences Social-Informatics and Telecommunications Engineering), ICST, Brussels, Belgium, 1-9.

Abstract:

The last few years have seen the emergence of many applications such as wellness, chronic disease management and assisted living that require pervasive sensing of people and the environment. Many of these applications require on-body sensing of various parameters including heart-rate, caloric burn, activity, temperature, etc. Low power wireless technologies are a key enabler for these applications, as it allows distributed sensing and aggregation without the cost of wiring the individual. Bluetooth is a well established low power wireless technology and has the advantage of being integrated into many handheld devices today whereas IEEE 802.15.4 has gained momentum in wireless sensor networks over the last few years due to its low power and cost. The performance of these radios in the context of WSN applications has been explored and published in numerous papers. However there hasn't been a lot of work exploring the effect of the human body on the performance of these radios. We have designed and conducted experiments on multiple people to measure the effect of the human body on the performance of Bluetooth and IEEE 802.15.4. We have explored different activities (sitting, standing and walking) as well as many sensor locations (ear, chest, waist, knee and ankle). Finally we explored the co-existence of both of these radios. In this paper, we present the results of these experiments and provide a detailed analysis of the suitability of these radios for body area networks.

Links: Paper

November 14, 2008 - Greg Hackmann

NAWMS: Nonintrusive Autonomous Water Monitoring System.
Younghun Kim, Thomas Schmid, Zainul M. Charbiwala, Jonathan Friedman, Mani B. Srivastava.
SenSys '08.

Links: Paper Slides

November 21, 2008 - Yong Fu

Paper:

Padala, P., Shin, K. G., Zhu, X., Uysal, M., Wang, Z., Singhal, S., Merchant, A., and Salem, K. 2007. Adaptive control of virtualized resources in utility computing environments. In Proceedings of the 2nd ACM Sigops/Eurosys European Conference on Computer Systems 2007 (Lisbon, Portugal, March 21 - 23, 2007). EuroSys '07. ACM, New York, NY, 289-302. DOI= http://doi.acm.org/10.1145/1272996.1273026

Abstract:

Data centers are often under-utilized due to over-provisioning as well as time-varying resource demands of typical enterprise applications. One approach to increase resource utilization is to consolidate applications in a shared infrastructure using virtualization. Meeting application-level quality of service (QoS) goals becomes a challenge in a consolidated environment as application resource needs differ. Furthermore, for multi-tier applications, the amount of resources needed to achieve their QoS goals might be different at each tier and may also depend on availability of resources in other tiers. In this paper, we develop an adaptive resource control system that dynamically adjusts the resource shares to individual tiers in order to meet application-level QoS goals while achieving high resource utilization in the data center. Our control system is developed using classical control theory, and we used a black-box system modeling approach to overcome the absence of first principle models for complex enterprise applications and systems. To evaluate our controllers, we built a testbed simulating a virtual data center using Xen virtual machines. We experimented with two multi-tier applications in this virtual data center: a two-tier implementation of RUBiS, an online auction site, and a two-tier Java implementation of TPC-W. Our results indicate that the proposed control system is able to maintain high resource utilization and meets QoS goals in spite of varying resource demands from the applications.

Links: Paper, Slides

November 28, 2008 - N/A

Thanksgiving

December 5, 2008 - Vincent Guo

The  Beta  Factor:  Measuring  Wireless  Link  Burstiness. Kannan Srinivasan (Stanford University, US); 
Maria Kazandjieva; Saatvik Agarwal; Philip Levis (Stanford, US). SenSys'08.

links:paper

December 19, 2008 - Chengjie Wu

Passive diagnosis for wireless sensor networks.
Kebin Liu, Mo Li, Yunhao Liu, Minglu Li, Zhongwen Guo, Feng Hong.
SenSys 2008.

Links: [Paper]

Winter Break