Mobisys 2005:The Third Gy Application and the Value of Net- Uitous I/O, Which Turns Any Surface International Conference on Worked S&R in Such Applications

He talked about a tele-epistemolo- Rashid also gave examples of ubiq- MobiSys 2005:The Third gy application and the value of net- uitous I/O, which turns any surface International Conference on worked S&R in such applications. into an interactive computing sur- Mobile Systems, Applications, He argued that almost all of the face, and of streaming intelligence, and Services S&R applications fall into the area such as skyserver.sdss.org and of control theory models and that skyquery.net, which allow scien- these models need to be applied Seattle, WA tists to do data mining against a and validated. He strongly argued June 5–8, 2005 large number of databases and has the need for real-time S&R bench- resulted in the discovery of new as- Summarizer shepherd: Maria R. Ebling marks, simulation, evaluation, met- tronomical phenomena. Tristan Henderson of Dartmouth College rics, emulation, autonomous opera- Rashid believes the goal of ubiqui- conducted a study of the conference tion, determinism in operation, and tous computing should be to bridge WLAN during the conference. Questions handling failure situations. the gap between the rich and the regarding the study can be directed to A fundamental question was raised poor. More than three billion peo- him at [email protected]. by the audience on whether we ple pay a poverty premium for were reproducing control theory basic goods and services. They work. The panel responded that, to KEYNOTE ADDRESS have little access to important some extent, S&R systems are al- Summarized by Himanshu Raj amenities and make decisions af- ready in the field (e.g., home con- fecting their livelihood (e.g., when trol systems). However, these sys- Technology’s Future: A Crisis in to plant crops) based on incom- tems do not scale up. They also Confidence? plete information. Even in the de- believe that existing control theory Rick Rashid, Microsoft Research veloped world, people with in- is being applied. Questions were Rick Rashid addressed the growing comes below $35,000 have a 70% raised about event management. unrest among the CS community chance of not having good online The panel talked about event han- about the future of the IT industry access. Wiring to every home in the dling, event bus architecture, and and opportunities for research. He whole world is not realistic. Rashid standards for handling events. then outlined certain trends emerg- described the Mesh Networking The panel discussed standards in ing from ubiquitous and pervasive Project, which is applying wireless depth and agreed that standards domains and suggested that we are networking technology and mesh should focus on accessing informa- actually just getting started on re- networks to form a cooperative net- tion and representing the data to search that will impact society at its work to cover the last hop. These abstractions provided by the sen- core. networks must be autonomic, in sors. As for what would enable that they should be self-managing, A terabyte of storage can hold every self-healing, and inexpensive. S&R to succeed, the panel felt that conversation you take part in for the entire community has a role to Other projects looking at this prob- your entire life. It can hold one pic- lem include the TIER project at play. Academia can contribute to ture for every minute of your life. It application, methodology, and met- Berkeley (http://tier.cs.berkeley can hold a year of everything you .edu/) and the Digital Gangetic rics for evaluation. In fact, the NSF can see, in full-motion video. The has a $40 million program in this Plains project at IIT Kanpur SenseCam project at Microsoft Re- (http://www.iitk.ac.in/mladgp/). area. Business can also contribute, search is examining what you could especially focusing on the ROI do with a terabyte of personal stor- In conclusion, there are ample op- question. age. They have devised a wearable portunities for reinvigorating CS data and image recorder. The de- research. The emphasis must be on vice contains a camera and numer- access to information rather than ous sensors (e.g., accelerometer, mere access to devices. passive IR, light level, temperature, During the Q&A session, Ramón images, etc.). Image capture is trig- Cáceres (IBM Research) asked gered by sensing some interesting about how to sustain technology change in environment (e.g., light- change in rural areas. Rashid re- ing levels). They are hoping to sponded that you must find the apply this technology to patients economic value behind the tech- with moderate memory impair- nology and that, unless the person ment and as an aid for caregivers of providing the information access patients with severe memory loss. points (such as Internet kiosks) It can also be used for self-reflec- makes money, he will not keep pro- tion. viding the service. Mandayam

64 ;LO GIN: V OL. 30, NO. 5 Raghunath, also of IBM Research, lenges. RealityFlythrough uses phones. Mosmondor pointed out followed up by asking how to get “motion” as a substitute for an that the server of LiveMail spent rural areas started. Rashid respond- infinite number of cameras; it uses 98% of the time on parameter adap- ed that there have been a number dynamic path estimation with tation yet only 2% of the time on of approaches. One that worked smoothened transition between storage and retrieval. in parts of India and Bangladesh scenes; and it uses dynamic archiv- Mosmondor answered questions was a bank that supports micro- ing of high-quality images from dif- regarding the relative importance of loans. Tapan Parikh (University of ferent locations to reduce the den- bandwidth and processing capabili- Washington) pointed out that the sity of camera deployment and the ty, the necessity of 3D rather than positive effects we foresee from amount of image data that needs to 2D face presentation, and the rela- technology have to do with the ap- be delivered. He concluded the talk tion of LiveMail to other efforts. plications that emerge from those with a discussion of their evalua- Mosmondor stressed that LiveMail technologies. Rashid agreed that tion. Overall, they found the num- does not require high bandwidth so this was true and then discussed ber of live cameras to be the bottle- much as high processing capability, whether this would cause the field neck, not the total number of such that the server could be of computer science to lose its cameras. dropped out of the architecture if identity. He pointed out that this After the talk, McCurdy discussed the client (e.g., cell phone or PDA) style of research can bring risks with the audience issues such as is fast enough. from a career and from a funding how to fetch archival images, how MediaAlert—A Broadcast Video perspective, but he also pointed out to deal with outdated images, the that about 50% of the basic re- Monitoring and Alerting System for impact of GPS precision on system Mobile Users search investment made by Mi- performance, and the network crosoft goes toward projects that challenges posed by the possible Bin Wei, Bernard Renger, Yih-Farn funding agencies are not (yet) com- use of omnidirectional cameras. Chen, Rittwik Jana, Huale Huang, Lee fortable with. He expressed hope Begeja, David Gibbon, Zhu Liu, and Be- that funding agencies would even- More information is available at hzad Shahraray, AT&T Labs—Research tually view these cross-disciplinary http://peanutgallery.homeip.net/ drupal/taxonomy/term/1. Bin Wei presented MediaAlert, a projects as legitimate research system for delivering TV news ac- areas. LiveMail: Personalized Avatars for cording to the interests of users. Mobile Entertainment Wei discussed the techniques em- APPLICATIONS ON THE GO Miran Mosmondor, Ericsson Nikola ployed in MediaAlert: processing Tesla; Tomislav Kosutic, KATE-KOM; media and extracting descriptive Summarized by Hongwei Zhang Igor S. Pandzic, Zagreb University abstractions of the media, and con- A Systems Architecture for Ubiquitous Miran Mosmondor presented Live- tent repurposing to disseminate Video Mail, a prototype system for com- media to devices with distinct pro- Neil J. McCurdy and William G. municating personalized images tocols and capabilities. He stressed Griswold, University of California, between mobile devices such as cell the importance of aligning unsyn- San Diego phones. He briefly introduced the chronized images and captions and the scalability of the system to sup- Neil McCurdy presented the archi- concepts and techniques of 3D port a large number of users and tecture of their ubiquitous video modeling, face animation, and 3D devices. system, RealityFlythrough, which graphics on mobile platforms, then enables users to visually explore a described the client-server architec- Wei walked through a scenario remote area in real time. McCurdy ture of LiveMail. The client enables where a user created an identity started by discussing the potential the user to customize the charac- and topics of interest, and Medi- applications of the system, which teristics of face animation, and the aAlert then analyzed and delivered include disaster response, remote server acts as the relay between the related images to the user. Wei also monitoring, remote navigation, and sender and the receiver. Mosmon- pointed out that media processing virtual shopping. dor stressed the importance of per- takes longer than dissemination forming face animation using and noted the importance of deal- McCurdy introduced the technical parameter adaptation, instead of ing with false positives in alert. challenges: the low density of cam- transmitting raw face images: by era deployment, the continuous David Kotz asked whether the transmitting the parameters instead movement of both the object and user’s location is used in the selec- of images, LiveMail only requires a the camera, and the need for reli- tion of content. Wei replied that it bandwidth of 0.3Kbps, which is able, live, and real-time data deliv- is and that the news content itself is available even in resource resource- ery. He then elaborated on how he location-dependent, because differ- constrained devices such as cell dealt with these technical chal- ent news channels provide different

;LOGIN: OCTOBER 2005 CONFERENCE SUMMARIES 65 content. Mark Corner asked simulate a lost key by impersonat- knows this is true, since he’s not whether closed captioning was im- ing one device and telling the other Alice, so he and Alice can agree portant to this system. Wei replied device that it has forgotten its key. that the bit is 1. If Alice instead had that closed captioning is very im- This action causes the two devices said, “I’m Bob,” Bob would know portant to the existing system and to run the full pairing process the that this is false, so they would that this is an area that will evolve. next time they communicate, thus both agree on the bit being 0. Eve Tristan Henderson asked whether opening the devices to the attack. hears these messages, but does not they had done any usability testing. Shaked suspects that custom hard- know who was the source and Wei said that they had only used ware would be required, because it therefore cannot determine the val- the system within their own team may be necessary to spoof the Blue- ues of the bits. and that more usability testing was tooth ID and because the timing of The challenge is to construct an en- necessary. Andre Hesse asked what the attack is critical. vironment where Eve cannot deter- happens once the user has received Shaked concluded the talk by sug- mine the source of a message. In the maximum number of alerts for gesting possible countermeasures this talk, Castelluccia discussed the day and then something really to this attack. One consequence of three approaches Eve could take to important happens. Wei clarified the re-pairing attack is that the user discover the source of a message. that the maximum number of alerts is asked to re-enter the PIN. Users She could use timing information, per day is for the scheduled alerts should be wary of such requests. signal power, or frequency. He then and that the system sends the most Users should also enter their PINs described ways that Alice and Bob relevant clips first. Real-time alerts as infrequently as possible to re- could protect against each of these cover emergency events and are not duce the risk of an attacker eaves- techniques, one of which required subject to the maximum. dropping on the pairing process. physically “shaking them up.” He also suggests that the hardware Someone suggested that an attacker SHAKE ’EM, BUT DON’T CRACK ’EM manufacturers use the 128-bit PINs could intentionally create a colli- that are allowed in the standard to Summarized by Neil McCurdy sion when Alice sends a message to make the brute-force attack less Bob, so Alice and Bob would not Cracking the Bluetooth PIN likely to succeed. Even when using agree. Castelluccia pointed out Yaniv Shaked and Avishai Wool, Tel Aviv a 128-bit PIN, though, a denial of that this would not work, since University service attack could still be per- 802.11 is reliable: Alice would ex- formed by constantly running the This paper describes the implemen- pect an ACK from Bob. Another re-pairing attack. tation of an attack on the Bluetooth questioner wondered whether cam- security mechanism and received Shake Them Up! A Movement-Based eras could be used to record the po- considerable press coverage prior Pairing Protocol for CPU-Constrained sitions of the devices as they were to MobiSys. Devices being shaken. The question was mostly asked in jest, but Castelluc- Shaked presented results which Claude Castelluccia, INRIA, France and cia pointed out that, even if such an show that a four-digit PIN (the PIN University of California, Irvine; Pars attack were feasible, the devices size on many commodity devices) Mutaf, INRIA, France could be obscured from view while can be cracked in less than 0.3 sec. This talk complemented the Blue- being shaken. on an old Pentium III 450MHz tooth cracking talk. Claude Castel- computer, and in 0.06 sec. on a luccia showed how secure authen- Pentium IV 3GHz HT computer. tication between sensor devices MOBILE SERVICES Because the attack uses brute force, could be performed across a clear Summarized by Mike Blackstock the time to crack larger PINs in- channel without using a PIN and Reincarnating PCs with Portable creases by a factor of 10 for each without using anything as CPU- SoulPads additional digit used in the PIN. intensive as a public key. Other The second contribution of this goals were: no preconfiguration, no Ramón Cáceres, Casey Carter, Chandra paper is the re-pairing attack, extra cost, no special equipment, Narayanaswami, and Mandayam which forces two Bluetooth devices and protection from denial of serv- Raghunath, IBM T.J. Watson Research to rerun the pairing process that ice attacks. Center had just been described. Because The strategy assumes that an eaves- Awarded Best Paper! devices usually store the link keys dropper cannot tell the source of a Mandayam Raghunath presented indefinitely, the first attack only message (source anonymity). As- SoulPad, a new approach to solving works during the short interval suming you have two devices, Alice the problem of providing a person- when devices first connect to each and Bob, Alice can send a message al and customized computing envi- other. However, an attacker can to Bob that says, “I’m Alice.” Bob ronment anywhere. When users

66 ;LO GIN: V OL. 30, NO. 5 move locations, they want to sus- execute applications on a server DeltaCast: Efficient File Reconciliation pend their work and then start up over the Internet. The bandwidth in Wireless Broadcast Systems again exactly where they left off. over the Internet is often limited to Julian Chesterfield, University of In the SoulPad solution, the PC a T1 (1.5Mbps) and latency is high, Cambridge; Pablo Rodriguez, (body) is separated from the ses- leading to poor response to desktop Microsoft Research sion state and bits (soul). SoulPad interaction. In a manner similar to uses a pocket-sized USB drive that cyber-foraging, Slingshot replicates Julian Chesterfield presented the can be plugged into any PC to state from the remote (home) com- DeltaCast system, which very effi- allow users to resume their person- puting environment to a VM run- ciently reconciles two versions of a alized computing environment. ning on one or more surrogates. Be- file between a server and any num- The key enablers for SoulPad are cause Slingshot only replicates the ber of clients with any version of a fast, small, high-capacity USB 2.0 state, users can fall back to their file using a pure radio broadcast drives from mass market media home server in the event of surro- system. DeltaCast uses a hierarchi- players, auto-configuring OSes gate failure. Once a replica is in- cal hashing scheme, combined with such as Knoppix, and mature virtu- stantiated on one or more surro- decomposable hashes and erasure alization technologies. gates, a proxy broadcasts user coding for high efficiency. Delta- Cast was compared with file down- Although the virtual machine and interaction to all replicas and the home server. The applications test- load, flat hash, hierarchical hash swap space use an encrypted file schemes using Web pages, and bi- system, SoulPad is still currently ed are the VNC desktop and speech recognition, though Su only dis- nary data such as software up- vulnerable to hardware and BIOS grades. From this evaluation, it was attacks. To address reliability, the cussed the VNC application in her presentation. determined that the number of hi- system supports network backups, erarchy levels could be dynamic though local backup is also possi- The system was evaluated to show depending on the data type. Com- ble. To deal with hardware diversi- that once the state was transferred, pared to hierarchical and single- ty, the system needs to keep many taking 27 minutes, the interaction layer hash systems, the time re- drivers up to date. Some older sys- performance was 2.6 times faster. quired to get the data required to tems cannot boot from a USB don- Using a microdrive to store volatile update a file on a client is also gle, so a small boot CD could be re- state and chunk hashes sped things much lower for Web pages. The quired. up considerably, requiring only 6 amount of data downloaded is the Raghunath was asked whether minutes: about 3 minutes to trans- same as in hierarchical hash there are other issues that need to fer state, another 3 to replay the schemes and less than in single- be addressed to put SoulPads to logs. Overall the system improves layer hashing. DeltaCast trades off use. One issue is that certain appli- performance for low-latency appli- decoding time, but the overall cations check the hardware and as- cations and hides surrogate failures penalty is low. This system can be sume that they are pirated when by using replicas and broadcasting applied to not only broadcast radio they have been moved to a new PC. the interactions. networks but also IP multicast, There are also legal issues that need Ramón Cáceres asked if the system overlay networks, and content dis- to be addressed. relied on the applications running tribution networks. Further information is available at in a deterministic manner; for ex- One attendee asked why the au- http://www.research.ibm.com/ ample, could a Slingshot applica- thors did not consider the use of WearableComputing/SoulPad/ tion maintain communications Turbocodes or other well-known soulpad.html. from the outside world? Su re- hash algorithms. Apparently these sponded that determinism is re- hashes do not require the system to Slingshot: Deploying Stateful Services quired and that outside communi- in Wireless Hotspots solve linear equations, but use iter- cation is not yet supported. ative algorithms, so they should be Ya-Yunn Su and Jason Flinn, University Another member of the audience faster. Chesterfield answered that of Michigan asked whether requiring VMware they used a hash that was already Ya-Yunn Su presented the Slingshot on all surrogates might perhaps be available to them and understand system, which alleviates the bottle- too strong an assumption. Su re- that perhaps their system may not neck associated with the back-haul sponded that they do assume that be optimal in this area. Maria connection to hotspots by replicat- the surrogate is already running Ebling asked whether the carousel ing application state to surrogate VMware, but suggested that per- size of hashes or data on a given computers closer to wireless access haps VMware itself could be trans- channel was fixed. Chesterfield an- points. She presented the scenario ferred first in the future. swered that any number of erasure where a user brings a Pocket PC codes can be generated and any of into a coffee shop and uses VNC to

;LOGIN: OCTOBER 2005 CONFERENCE SUMMARIES 67 these blocks/codes is useful in re- ary talk on the technological and their role in improving the robust- generating data and hash codes. societal implications of the devel- ness of systems (i.e., punishing ac- opment of mobile pervasive sys- tions that are not allowed, such as POSTERS AND DEMONSTRATIONS tems, with an emphasis on the ro- spam, viruses, etc). But Spector bustness of these systems. also pointed out the challenges of Summarized by Denitsa Tilkidjieva Spector first described the trend of InfoP: privacy, storage for massive This session hosted 24 displays of mobile systems. On one hand, the data, digital signatures and CAs, researchers’ work in the field of ever-growing modality, decreasing and law enforcement across inter- mobile systems, applications, and form factor, declining cost, and ex- national boundaries. services. A wide range of applica- ploding connectivity have been Spector discussed the importance tions were on display. We highlight pushing the development of mobile of the “science of design” in in- just three of these here: systems. On the other hand, med- creasing system robustness. Besides The pre-hospital patient care sys- ical informatics and security appli- the traditional time and space com- tem (Hashmi et al.) consisted of a cations are calling for mobile sys- plexity, Spector specifically noted number of pulse sensors, attached tems. For instance, the market for the need to manage the complexity to patients’ fingers to monitor vital health care is about $1.5 trillion per of usage (i.e., user interface). To signs. It is most useful when multi- year, which is about as large as the this end, he argued that we should ple patients are in need of atten- whole IT industry. Nevertheless, in pay attention to the meaning and tion, because it can allow quick de- most scenarios of mobile pervasive measurement of robustness and of cisions at critical moments. systems, we are envisioning amal- design methodologies. He also em- gams of components. The systems phasized the importance of simple The inHand system for ubiquitous are usually so complex that we can- yet flexible architectures, as well as personalized interactive content not prove their correctness. In self-healing and self-optimization. (Bhatti et al.) was shown in both a many cases, it is also impossible to Finally, he suggested that the tech- poster and a demonstration. The anticipate what may go wrong in a nical community should work with researchers demonstrated the in- system. the wider society to address a Hand device and how it can be broader range of robustness issues. used to gather user-customizable Given the complexity of pervasive information about movies, events, systems, Spector argued that one and the like. key challenge of designing these SPEEDY WI RELESS systems is to guarantee their ro- If you try to cook a turkey, a duck, Summarized by Xiaoqiao (George) Meng bustness, e.g., ease of use, evolu- and a chicken all in one, you will tion, QoS, reliability, security, and Improving TCP Performance over get a Turducken. Sorber and his fitness to purpose. Wireless Networks with Collaborative colleagues borrowed this name for Multi-Homed Mobile Hosts their system for hierarchical power After discussing the challenges management, consisting of a lap- posed by mobile pervasive systems, Kyu-Han Kim and Kang G. Shin, Uni- top, a stripped-down PDA, and a Spector analyzed why existing versity of Michigan mote. The device always chooses techniques and architectures do not Kyu-Han Kim pointed out that the platform that performed the satisfy the need for robustness. To wireless networks have capacity given task at the lowest energy cost, demonstrate design for robustness, limitations. In practice, a group of thus extending the lifetime of the Spector described a hierarchical ar- nearby hosts may constitute a mo- device up to 10 times. chitecture based on a common bile collaborative community trusted computing base, a secure Photos of the posters and demon- (MC2) where hosts share band- hypervisor, and trusted virtual do- strations can be found at width and content. In such a com- mains. Spector stressed the impor- http://www.mtholyoke.edu/ munity, each host is multi-homed tance of adopting a top-down ap- ~dntilkid/mobisys. and data is multiplexed to improve proach and the development of utilization. Accordingly, it is impor- trustworthy capabilities (e.g., attes- tant to allow TCP to achieve high PLENARY SESSION tation, privacy services, and au- utilization of the aggregate band- Summarized by Hongwei Zhang thentication). width over multiple interfaces, but this presents several challenges, Staying Off the Hot Seat with Cool Mo- In particular, Spector stressed the from requiring exact link-state in- bile Systems concept of “information prove- nance (InfoP),” by which the origin formation, to coping with dynamic Alfred Spector, IBM Software of information can be identified wireless links, to handling out-of- Alfred Spector, chief technology of- with proof. InfoP can provide the order packet delivery, to controlling ficer at IBM Software, gave a vision- basis for law enforcement to play congestion.

68 ;LO GIN: V OL. 30, NO. 5 To cope with these challenges, Kim lenges, from coping with limited by limiting how much data each introduced PRISM, Proxy-based In- bandwidth, to dealing with applica- host can send. The proposed solu- verse Multiplexer. PRISM consists tions having dissimilar needs, to tion is called Overlay MAC Layer of adaptive scheduling, intelligent dealing with dissimilar network (OML). OML uses readily available, acknowledgment controlling, net- channels with varying QoSes. inexpensive hardware, and can work-assisted fast recovery, and Horde middleware provides a num- evolve to meet diverse application IMUX at the proxy’s network layer. ber of services, the most novel of scenarios/requirements. Rao then PRISM architecture has an adaptive which is QoS modulation. With described how to implement OML. scheduler (ADAS) to achieve cheap QoS modulations, applications He summarized the results of their and adaptive fair-scheduling. express stream QoS sensitivities, evaluation on both a six-node test- PRISM has been implemented in where the QoS is multi-dimension- bed (based on Click from MIT) and Linux kernel 2.4.20 and netfilter. al. When an application sends data, a Qualnet network simulator. They PRISM-IMUX is a filter at a net- it receives some utility from the found that the disparity between work layer. The authors also de- consumption of its data at another one-hop and four-hop flows was re- vised a testbed, by which they host. Applications express QoS duced but that the throughput on found that PRISM delivers 95% of “objectives” which define QoS con- the one-hop flows was also greatly the aggregated bandwidth. In a set- straints on streams. In summary, reduced. ting with three heterogeneous mo- the goal for Horde is to build a flex- Himanshu Raj asked whether pro- bile nodes, PRISM achieved more ible network striping middleware viding fairness reduced the overall bandwidth than vanilla TCP. for WWANs. throughput. Rao explained that this David Kotz asked how members of David Kotz asked how many appli- approach actually increases the the community find one another. cations the authors have examined throughput, though it is not shown Kim answered that they can use the and how many more they plan to in the graph because the graph service location protocol to find ex- explore. Qureshi expressed con- does not account for starved flows. isting collaborative communities, cern that the interface may be too Ramón Cáceres pointed out that but that forming communities and rich, in that you may be able to ex- with an asymmetric link, one node dealing with membership dynamics press more than is necessary. They would never be in the active list, is an area for future work. are building the telemedicine appli- but Rao clarified that a node in the Horde: Separating Network Striping cation to gain more experience middle can piggyback information Policy from Mechanism with the system. about the other node so that it will be added to the active list. Richard Asfandyar Qureshi and John Guttag, An Overlay MAC Layer for 802.11 Paine encouraged Rao to propose MIT Computer Science and AI Laborato- Networks some of these changes to 802.11 ry Ananth Rao and Ion Stoica, University because, although 802.11n address- Asfandyar Qureshi presented of California, Berkeley es some of these issues, it would be Horde, a middleware mechanism Multi-hop wireless networks are useful to address the other ques- that allows multi-stream applica- being considered for last-mile tions as well. Brian Noble asked tions to communicate over multi- broadband connectivity. However, what happens if one of the nodes ple channels with widely varying such networks are subject to issues gets greedy, and Rao explained that latency and bandwidth. The au- of fairness. This work addresses they currently assume that the box thors were motivated to build this issue; specifically, the authors is tamper-proof. Horde in order to support mobile show how to prevent starvation of telemedicine, specifically an appli- flows without changing the hard- OPERATING SYSTEMS FOR cation that allows doctors to exam- ware. SENSOR NETWORKS ine patients in transit to the ER. This application requires the trans- Ananth Rao first described a starva- Summarized by David Johnson tion problem with 802.11 MAC mission of unidirectional video, bi- Design and Implementation of a that they identified by using a test- directional audio, and low-rate Single-System Image Operating bed with six nodes. They found physiological data streams in real System for Ad Hoc Networks time from a moving ambulance. that the cause of this problem was Hongzhou Liu, Tom Roeder, Kevin This system requires high through- interference and asymmetric carrier Walsh, Rimon Barr, and Emin Gün Sirer, put, low latency, and the ability to sense. Rao pointed out that existing Cornell University deal with vehicular motion in an solutions to this problem (e.g., con- urban area. tention-based MACs and TDMA) Hongzhou Liu presented Magnet- require hardware modifications but OS, a distributed operating system Network striping in a WWAN envi- that the starvation problem can designed for use in ad hoc net- ronment presents substantial chal- also be solved above the MAC layer works. Liu observed that ad hoc

;LOGIN: OCTOBER 2005 CONFERENCE SUMMARIES 69 network applications are extremely SOS: A Dynamic Operating System for costs were 400 times as much as for difficult to program, even today. Sensor Nodes SOS, because updates to TinyOS re- MagnetOS responds to this prob- Chih-Chieh Han, Ram Kumar, Roy Shea, quire the replacement of the entire lem by combining all network Eddie Kohler, and Mani Srivastava, system binary. Kumar observed that nodes into a single, event-based University of California, Los Angeles the important metric to observe virtual machine; this abstraction when comparing update energy eases application development and Ram Kumar presented SOS, an op- costs is the frequency of updates. erating system designed for use in increases network lifetime. In Mag- Himanshu Raj asked what impact netOS, synchronous and asynchro- sensor network applications. Be- cause sensor networks often mani- one module can have on another nous events signal code execution and whether they can crash one an- by triggering event handlers. A stat- fest in long-term deployments, in- dividual nodes must be flexible to other. Kumar responded that the ic partitioning approach converts architecture provides no form of application class files into event respond to remotely controlled changes. SOS is a modular, applica- memory protection and that a wild handlers. Migration of event han- pointer could corrupt the data dlers provides improved energy ef- tion-independent operating system that supports dynamic reprogram- space of another module. Unfortu- ficiency and saving of computation nately, there is no hardware support if loss of power is imminent. Mag- ming via module updates and re- placements. In contrast, TinyOS, to correct this problem. Bhanu netOS provides several migration Pisupati asked about the program- algorithms that are designed to the de facto sensor network operating system, produces a static binary ming model. Kumar responded that minimize communication energy it is described in more detail in the overhead. composed of both system and application-level functionality and paper, but that all modules are im- Liu presented results from evaluat- must be recompiled and replaced plemented as message handlers and ing MagnetOS with an application on each node to effect an upgrade. listen on a particular port for mes- called SenseNet, in which there are Another similar system, Maté, pro- sages intended for them. Jason a number of fixed sensors and mo- vides a virtual machine that can Flinn found the idea of safety bile data processing components. execute small code fragments dis- checks fairly interesting, but asked They compared a number of algo- tributed through the network. Ap- for clarification about how this re- rithms, three that required no com- plication-level upgrades are possi- ally works. Kumar responded that munication overhead and two that ble, but interpreter upgrades must static checks would require analyz- did. The TopoCenter(1) algorithm, fall back on the TinyOS update sys- ing the entire source code and which moves objects using one- tem. SOS consists of a static kernel, would not solve the problem. He hop neighborhood knowledge from which provides an abstraction of clarified that the base stations each communicating partner, in- the hardware, and is installed on all maintain some information about creased system lifetime by a factor nodes. Dynamically linked mod- the kind of modules present on the of 2.5. ules communicate with various nodes and do some analysis at load Ahmad Al-Hammouri asked why kernel services and device drivers time before sending a module. they did not use aglets, since aglets as necessary. Modules can register provide a clean environment for functions with the kernel, and po- LOCATION (HERE) mobile agents. Liu explained that tential callers may subscribe to pro- Summarized by Neil McCurdy the major complaint about mobile vided functions. The kernel pro- agents is security, because they can vides priority scheduling, dynamic A Relative Positioning System for Co- execute any code on any node. memory and intra-module message Located Mobile Devices Doug Terry added that MagnetOS is passing, as well as safety features. Mike Hazas, Christian Kray, Hans using a different model; they are Kumar discussed the results of an Gellersen, Henoc Agbota, and Gerd Ko- breaking their code onto different evaluation comparing TinyOS, rtuem, Lancaster University, U.K.; Al- machines. Terry then asked SOS, and Maté. All ran Surge-like bert Krohn, University of Karlsruhe, whether they thought they would applications (Surge is a well-known Germany need multiple algorithms and adapt multi-hop data-gathering applica- Mike Hazas introduced Relate, a between them dynamically or tion for TinyOS). They found that compelling approach to determin- whether one would be sufficient. CPU activity was on average 1% ing fine-grained relative locations Liu responded that they currently higher in SOS than in TinyOS. En- and orientations between proxi- require the programmer to pick one ergy usage during code updates in mate devices. It uses ultrasound and that their experience to date SOS was an order of magnitude peer-to-peer sensing, giving the suggests that the two Topo algo- larger than in Maté, because Maté user relative location accuracy in rithms perform well throughout must update only a small chunk of the 10cm range and eliminating the the range. bytecode. However, TinyOS update need for the infrastructure-based

70 ;LO GIN: V OL. 30, NO. 5 location support that is typically WALRUS: Wireless Acoustic Location mation in the packets. David Kotz needed for such fine-grained accu- with Room-Level Resolution Using Ul- commented that one of the unique racy. The Relate team created their trasound characteristics of this work was own hardware—a USB dongle that Gaetano Borriello, University of Wash- that they were using existing de- has three ultrasound transmitters ington and Intel Research; Alan Liu, vices. He then asked why they de- and sensors. Time of flight of the Tony Offer, and Christopher Palistrant, cided to move toward custom hard- ultrasound signal determines the University of Washington; Richard ware. Borriello replied that one range, and the signal strength, as Sharp, Intel Research Cambridge, UK thing to consider is how much op- recorded by each of the three sen- timization each device could have. sors, determines the angle of ar- Gaetano Borriello presented a sys- Robert Hall asked whether they rival. tem that provides room-level gran- had considered the health implica- ularity by using a combination of To evaluate the system, Hazas de- tions of ultrasound. Borriello said wireless and ultrasound. Borriello that they are not boosting the scribed an experiment in which five began by explaining the impor- laptops were placed at various posi- speaker output and that one of the tance of room-level localization to reasons to move toward custom tions on a 2.4 x 1.6m surface. One usability. The goals of the system hundred iterations of this experi- hardware was to move further away included low deployment cost, low from the audible range. Another ment were performed, with half of support cost, and a system that was them ensuring that the dongles had member of the audience asked incrementally useful and deploy- whether they had considered plac- line-of-sight to one another. With able. The system should also ap- good line-of-sight, one can expect ing microphones in the room to proach 100% accuracy while main- measure the volume levels and then roughly 9 cm, 33° accuracy. With taining privacy. limited line of sight, one can expect including those volume levels in approximately 11cm, 48° accuracy. Borriello described WALRUS as the WiFi packets so that clients Hazas closed by discussing some of being inspired by lightning and would know what volume to ex- the issues with this approach. First, thunder, with WiFi (through an ac- pect. Borriello responded that they he posited that hardware that is cess point broadcast of informa- had walked around the room and better equipped to do signal pro- tion) acting as the lightning and ul- measured the volume levels, but cessing may be able to get the accu- trasound (through commodity they found that this was not impor- racy to as low as 2 or 3cm. He also speakers) acting as the thunder. tant because their detection algo- pointed out that there is a limit to Clients receiving the WiFi packet rithm relied on a relative measure the number of devices that can be keep the packet only if they also of strength. handled, since only one device can detect the sound. The system was tested in two environments under communicate at a time. WORK-IN-PROGRESS many different conditions (music REPORTS (WIPS) The Relate system was demonstrat- playing, conversations ongoing, ed on Monday night, and Hazas keys jangling, doors slammed, Summarized by Ya-Yunn Su was asked how his system differed etc.), and the system proved largely CAM: Architecture for Automating from Cricket. Relate dongles have immune to extraneous noise. Bor- three transducers, are optimized for Paper-Based Processes in the riello concluded by discussing Developing World co-planar calculations, and can cal- some of the limitations in the exist- culate the angle of arrival to deter- ing implementation and presenting Tapan Parikh, University of Washington mine the orientation of the devices. a vision of future prototypes that Tapan Parikh said that in develop- The Relate system also does not re- might one day be located in a store ing countries paper-based processes quire any calibration. near you: a wristwatch receiving are inefficient, but cell phone pene- One questioner pointed out that lo- device, with light bulb and air tration is growing, and most cell cation accuracy is more important freshener transmitting devices. phones have built-in cameras. He as the devices get closer to one an- Lin Zhong asked whether they had proposed using such mobile other. For example, 10cm accuracy considered listening to the ultra- phones to digitize manual, paper- may not be adequate when the de- sound signal first and then the driven processes. A user could take vices are only 2cm apart. Hazas WiFi. Borriello responded that this a picture of a paper document, agreed. There was also a question approach might be perfectly rea- transfer the data to a remote ma- about whether the signal process- sonable, but that they haven’t tried chine, and propagate it to the ap- ing could be done in software. it. Ed Nightingale asked whether propriate recipient. The receiver Hazas did not see any reason why they had considered rooms that could then print the document. not. were changing. Borriello responded http://www.cs.washington.edu/ that you could put arbitrary infor- homes/tapan

;LOGIN: OCTOBER 2005 CONFERENCE SUMMARIES 71 Smart Attire–The Digital Diary from syslog data, extracts mobility located at http://www.guide Tarek Abdelzaher, University of Virginia characteristics from the user’s path, .lancs.ac.uk/. and extracts speed/duration/pause Invisible Agents The author proposed building sen- to generate the mobility model. sors into clothing to record user ac- Nobuo Kawaguchi and Negishi Yuuya, tivity. The smart attire includes ac- Emulab Unleashed! Into the WiFi and Nagoya University Mobile Wireless Dimensions celerometers, magnetometers, and Nobuo Kawaguchi pointed out that temperature, sound, light, and GPS David Johnson, University of Utah in a world with many computers sensors. Possible applications are David Johnson presented Emulab, a (PC, laptop, PDAs, etc.) and smart personal digital diaries, and med- network emulation testbed. Due to appliances (music players, TiVo), ical monitors. The prototype sys- the complex nature of wireless net- we do not have a good interface to tem is a winter jacket with five works, simulation is not enough in control and aggregate the interfaces motes and a GPS tracking device. testing and validating new research of all the devices. They built invisi- The motes on the jacket record ac- ideas. A real testbed like Emulab ble agents to solve this problem. tivities and upload the data when would be a better way. Emulab has The example is a conference room near an access station using added three wireless testbeds in- with a projector, multiple monitors, 802.15.4. One example shows that cluding a building-scale WiFi test- ceiling lights, and similar equip- the author can infer the user’s activ- bed, a fixed sensor net, and a mo- ment. They can combine brightness ity (e.g., typing, walking) from the bile WiFi network. The WiFi with a human sensor to control the data collected by accelerometers. testbed enables remote hardware ceiling light, or a human sensor to Another example shows the user’s reset functionality, since it is diffi- activate the projector. On each of path or stillness by data from the cult to find the real location and re- the target devices, they run a VNC GPS device. The user may use data boot the machine manually. There server. The master device connects mining techniques to understand are also fully programmable motes to all the target devices. personal life patterns (e.g., Is my and mobile robots with a tracking social life declining?) and query the A Social Networking Web Site for the system accurate to 1cm. Emulab Research Community history to keep track of health or fi- can be remotely accessed and al- nancial activities (e.g., When is the lows multiple users. It provides a James Scott and Richard Sharp, Intel last time I visited my dentist?). The realistic and repeatable wireless en- Cambridge prototype system shows that power vironment. Future work includes James Scott said that the popula- management is important for smart automated rechargeable stations tion of researchers is huge and attire. and power monitoring. More growing. There are many types of Extracting a Mobility Model from information can be found at relationships between researchers Network Traces http://www.emulab.net. (e.g., as co-authors, work col- Minkyong Kim, Dartmouth College Content Management for Mobile and leagues, conference attendees), but Pervasive Experiences communities that overlap might Researchers need a realistic mobili- also be isolated (e.g., SIGMOBILE, ty model to simulate the effective- Nigel Davies, Lancaster University Pervasive/UbiComp, SIGCOMM). ness of new algorithms on wireless Nigel Davies emphasized the im- One useful feature of a social net- networks. There are two ways to portance of content in a working Web site would be an easy generate network traces: syslog and ubicom/pervasive computing envi- home-page generator containing GPS. Syslog data collected on ac- ronment based on experience in basic information (e.g., bio, publi- cess points contains client events, GUIDE deployment. Their solution cations, photos). To prevent spam- including time and action. It has was to assign many students to ming, the Web site could be semi- the advantage of availability of work on content and the user inter- exclusive or could follow Gmail’s large data sets, but it is often hard face. Other projects, such as Can invitation-based model. The Web to estimate a user’s location from an You See Me Now? (http://www site would encourage people to reg- AP location, perhaps due to the de- .canyouseemenow.co.uk) and ister and verify their information. vice not being associated to the Equator (http://www.equator.ac.uk/) closest AP or perhaps because of Crawdad—A Community Resource for reached similar conclusions. In the Archiving Wireless Data at Dartmouth some device-specific implementa- e-Campus project, content can tion. An alternative is GPS. Unfor- come from users, be automatically David Kotz, Dartmouth College tunately, there is no GPS data set generated, etc. The challenge is David Kotz pointed out that there publicly available, and it does not how to manage multimedia content is little real wireless network traffic work indoors. To address these lim- in future mobile and ubiquitous available for researchers. They initi- itations, Kim extracts the user’s computing environments. More in- ated Crawdad as a facility for stor- path from time and AP location formation on the GUIDE project is ing data sets collected from real

72 ;LO GIN: V OL. 30, NO. 5 wireless networks. They already tion technologies are GPS and Robert Harle asked what the test had a campuswide wireless infra- WiFi. GPS devices are not accurate environments were like. Youssef in- structure for collecting traces. The and have limited coverage. WiFi dicated that it was a typical CS de- challenges include developing a can only be used on limited de- partment with offline measure- common data format, importing vices. Based on calculations from ments taken at night and used existing data, and anonymizing GSM tower signal strengths, the during the day to capture environ- data. They hope to coordinate with cell phone can provide accuracy ment variations in a typical deploy- other communities to develop net- within 30cm outdoors and 4m ac- ment. Mark Corner asked how the work trace formats and tools. The curacy with a 1m grid. They plan to new dynamic power control feature tools and data can also be used in make the trace publicly available. would affect location determina- course projects. More information tion using the new WLAN systems. is available at http://crawdad.cs LOCATION (THERE) Youssef thought that their ongoing .dartmouth.edu/. work in automatically generating Summarized by Mike Blackstock Secure Mobile Architecture the radio maps based on environ- The Horus WLAN Location ment changes may be effective in Richard Paine, Boeing Technology Determination System dealing with this problem. Richard Paine proposed a secure Moustafa Youssef and Ashok Agrawala, Deploying and Evaluating a Location- mobile architecture that can cryp- University of Maryland Aware System tographically identify each packet. They can support mobility by Moustafa Youssef presented the R.K. Harle and A. Hopper, University of transparently changing the address Horus system used to determine in- Cambridge, U.K. for the user and application. This door locations to an accuracy of Robert Harle presented their expe- framework improves their enter- less than 2m by using existing rience with deploying and using prise network by reducing opera- wireless LAN infrastructure. Horus, the Active Bat system at Cam- tional cost and complexity. They like other WLAN-based locating bridge. The Bat system is accurate use four techniques to achieve their systems, uses APs as reference to 3 to 5cm in three dimensions. goal: points and the observed signal The data on which this study is strength to these APs to estimate 1. PKI: Public key infrastructure. based was collected over a period distance via triangulation. Howev- Each client uses his/her badge for of more than two years from a de- er, when indoors, the observed sig- client authentication. ployment that covers about 500 nal strength readers can differ by square meters in their new build- 2. HIP: Host mobility protocol. 15dBm for a given distance. Like ing. Communications are based on Radar, Horus uses a radio map to Harle found that the killer applica- IPSec, therefore each host is identi- characterize the area to counter tion for this type of system was al- fied by a security parameter index these effects. Unlike Radar, howev- lowing companies to learn more (SPI) rather than IP. Each host is er, Horus is a probabilistic system about how office building space is further identified by a host identity rather than deterministic. tag (HIT), which is SHA-1 of the used, to encourage people to work The goals of this system were high public key. more effectively. Surveys showed accuracy, low computational re- that privacy was not an issue, but 3. NDS: Network directory servic- quirements, energy efficiency, and that result may not extend beyond es. The client goes through an iden- scalability (both in number of users small communities such as theirs. tification process before using and in the area covered). The A more meaningful study of such LDAP. Horus techniques accounted for a systems would require deployment 4. LENS: Location-enabled net- 25% reduction in the average dis- in a corporate office or perhaps a work services: see http://www tance error. The Horus system is hospital where there is more over- .opengroup.org/bookstore/catalog/ shown to have higher accuracy on lap in working hours and collabo- select.tpl?text=secure+mobile+ average than Radar by more than ration is more common. 82% and better than 27% for the architecture. James Scott thought it was interest- probabilistic system, and is more GSM War Drive ing that the corporate space usage computationally efficient by an was the best application rather than Mike Chen, Intel Seattle order of magnitude. The authors an application that benefited end then applied the Horus ideas in Mike Chen presented their goal of users. Harle indicated that in fact Radar and showed that these ideas providing a playground for location- one company expected to get a re- could reduce Radar’s average dis- based services. Cell phones are the turn on their investment in one tance error by more than 58% and location devices people already year of data collection, without decrease the worst-case error by carry every day. Some current loca- using any of the software that could more than 78%.

;LOGIN: OCTOBER 2005 CONFERENCE SUMMARIES 73 benefit the end user. Further, they land (a less dense suburb where MORE POWER TO YOU were not interested in deploying homes are 15 to 20 feet apart)— end-user applications until they and compared their location esti- Summarized by Ram Kumar Rengaswamy had reaped that ROI. Minkyong mates with GPS readings. Energy Efficiency of Handheld Kim asked whether providing more They then applied three different Computer Interfaces: Limits, information to the end user regard- algorithms. Their baseline tests Characterization, and Practice ing the accuracy of a location read- found that the specific algorithm Lin Zhong and Niraj K. Jha, Princeton ing would increase system trust. used did not matter much, though University Harle indicated that they experi- fingerprints performed poorly with mented with a five-bar system Lin Zhong noted that the role of only one AP. Interestingly, errors the user interface has often been ig- ranking and found it useful, but were higher in the more dense that this ranking system did not nored in the design of energy-effi- downtown area, probably owing to cient systems. The speed of the help this issue significantly. Guan- the fact that many APs are higher ling Chen asked whether the high human interaction is significantly up and not contributing to making lower than the speed of the com- accuracy of the Bat system was nec- measurements more accurate. They essary for the applications in this puter. The computer ends up concluded that it is possible to get spending significant time waiting deployment. Harle indicated that acceptable accuracy of 13–20m in although it was not needed for this for user inputs. The energy con- high-density areas, and around sumed by the computer in these type of application, there are class- 40m in lower-density areas, with es of applications, such as those idle periods can be eliminated about 30 to 60 minutes of calibra- through better system design. that use position clicking and tion for the neighborhood. pointing, that require it. He agreed Zhong and Jha compared two that the most important thing is David Kotz asked about the data forms of user input, speech and highly accurate room-level granu- corresponding to Figure 4, where handwriting, using energy efficien- larity. the Y axis is labeled “% of Time”; cy as the metric. Energy efficiency Cheng clarified that it actually rep- is a combination of the speed of the Accuracy Characterization for resents “% of records.” Another Metropolitan-Scale WiFi Localization input and its power efficiency. The member of the audience was asked experiments showed that speech is Yu-Chung Cheng, Intel Research Seattle whether the urban results were af- more energy efficient than hand- and University of California, San Diego; fected by the GPS noise in urban writing. Zhong also designed a Yatin Chawathe and Anthony LaMarca, canyons. Cheng said that they wireless wrist-watch to be used as a Intel Research Seattle; John Krumm, Mi- countered this possible effect by low-power, low-cost cache device. crosoft Research checking that readings were corre- The cache device is a slave to the While an intern at Intel Research, lated by three GPS units and only main computer. It collects user Yu-Chung Cheng and his col- using those that were consistent. input while the main computer is leagues worked to characterize the David Kotz then asked whether it put to sleep. This results in system- accuracy of the Place Lab WLAN would be possible to improve accu- level power savings. racy with the indoor Horus tech- location determination systems for The results evoked a lot of interest use outdoors. Unlike GPS, their niques. Youssef and Cheng discussed this possibility offline. from the audience. Brian Noble system works in urban canyons and raised an interesting point about indoor environments, and it relies Youssef later reported that they concluded that the Horus tech- the usage scenarios of the input on more ubiquitous technology techniques. Listening and writing (check out the density map for niques would be useful when there is more information available for are concurrent operations while Manhattan at http://www.wigle speaking and listening are not. .net). Unlike other WLAN systems, the localization algorithm. For example, when the number of APs Hence, from a holistic viewpoint, it their system requires less configu- might be more energy efficient to ration time (1km2 area/1 hour) per scan increases, Horus techniques can give a significant advan- listen and write than to listen and using war driving. Although it is speak. consequently less accurate tage. However, where you have just (13–40m), this is not an issue for one AP per scan, there is not applications such as a location- enough information to notice a dif- based Web search. ference between the techniques. For their experiment they gathered The traces and source code for this data in three neighborhoods— paper are available at http://www downtown Seattle, an urban resi- .placelab.org/. dential area, and an area in Kirk-

74 ;LO GIN: V OL. 30, NO. 5 Turducken: Hierarchical Power Management for Mobile Devices Jacob Sorber, Nilanjan Banerjee, and Mark D. Corner, University of Massachusetts; Sami Rollins, Mount Holyoke College Jacob Sorber explained that the main principle of hierarchical power management is to pick the most energy-efficient component of the system for a task. The challenge is in partitioning a given task into a set of subtasks and assigning each to the most efficient component. Such an approach automatically maximizes system lifetime. It is de- sirable to have minimum user in- tervention in such a system. The authors developed the Tur- ducken system for hierarchical power management in laptops. Turducken consists of a laptop attached to a PDA and a mote sensor node. The role of the mote is to maintain clock synchronization with a time server. The laptop and the PDA derive their clock from the mote upon their wakeup. The PDA is responsible for caching Web pages and waking up the laptop to display the pages once they are fully loaded. The user interacts di- rectly with the laptop. The laptop responds to user queries (e.g., email retrieval). Turducken significantly lowers average power consumption compared to convention- al systems. The audience provided some very interesting comments and sugges- tions. The power supply design of such a system was discussed. It was concluded that it would be most energy efficient to have separate batteries for each system component. Usage of the lower-tier components during the transition interval of a high-tier device from one state to another was considered.

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