Showing papers presented at "International Conference on Mobile Systems, Applications, and Services in 2007"

MyExperience: a system for in situ tracing and capturing of user feedback on mobile phones

Abstract: This paper presents MyExperience, a system for capturing both objective and subjective in situ data on mobile computing activities. MyExperience combines the following two techniques: 1) passive logging of device usage, user context, and environmental sensor readings, and 2) active context-triggered user experience sampling to collect in situ, subjective user feedback. MyExperience currently runs on mobile phones and supports logging of more than 140 event types, including: 1) device usage such as communication, application usage, and media capture, 2) user context such as calendar appointments, and 3) environmental sensing such as Bluetooth and GPS. In addition, user experience sampling can be targeted to moments of interest by triggering off sensor readings. We present several case studies of field deployments on people's personal phones to demonstrate how MyExperience can be used effectively to understand how people use and experience mobile technology.

Context-for-wireless: context-sensitive energy-efficient wireless data transfer

Abstract: Ubiquitous connectivity on mobile devices will enable numerous new applications in healthcare and multimedia. We set out to check how close we are towards ubiquitous connectivity in our daily life. The findings from our recent field-collected data from an urban university population show that while network availability is decent, the energy cost of network interfaces poses a great challenge. Based on our findings, we propose to leverage the complementary strength of Wi-Fi and cellular networks by choosing wireless interfaces for data transfers based on network condition estimation. We show that an ideal selection policy can more than double the battery lifetime of a commercial mobile phone, and the improvement varies with data transfer patterns and Wi-Fi availability.We formulate the selection of wireless interfaces as a statistical decision problem. The key to attaining the potential battery improvement is to accurately estimate Wi-Fi network conditions without powering up its network interface. We explore the use of different context information, including time, history, cellular network conditions, and device motion, for this purpose. We consequently devise algorithms that can effectively learn from context information and estimate the probability distribution of Wi-Fi network conditions. Simulations based on field-collected traces show that our algorithms can improve the average battery lifetime of a commercial mobile phone for a three-channel electrocardiogram (ECG) reporting application by 39%, very close to the theoretical upper bound of 42%. Finally, our field validation of our most simple algorithm demonstrates a 35% improvement in battery lifetime.

Surface street traffic estimation

Abstract: In this paper, we propose a simple yet effective method of identifying traffic conditions on surface streets given location traces collected from on-road vehicles---this requires only GPS location data, plus infrequent low-bandwidth cellular updates. Unlike other systems, which simply display vehicle speeds on the road, our system characterizes unique traffic patterns on each road segment and identifies unusual traffic states on a segment-by-segment basis. We developed and evaluated the system by applying it to two sets of location traces. Evaluation results show that higher than 90% accuracy in characterization can be achieved after ten or more traversals are collected on a given road segment. We also show that traffic patterns on a road are very consistent over time, provided that the underlying road conditions do not change. This allows us to use a longer history in identifying traffic conditions with higher accuracy.

Vehicular opportunistic communication under the microscope

Abstract: We consider the problem of providing vehicular Internet access using roadside 802.11 access points. We build on previous work in this area [18, 8, 5, 11] with an extensive experimental analysis of protocol operation at a level of detail not previously explored. We report on data gathered with four capture devices from nearly 50 experimental runs conducted with vehicles on a rural highway. Our three primary contributions are: (1) We experimentally demonstrate that, on average, current protocols only achieve 50% of the overall throughput possible in this scenario. In particular, even with a streamlined connection setup procedure that does not use DHCP, high losses early in a vehicular connection are responsible for the loss of nearly 25% of overall throughput, 15% of the time. (2) We quantify the effects of ten problems caused by the mechanics of existing protocols that are responsible for this throughput loss; and (3) We recommend best practices for using vehicular opportunistic connections. Moreover, we show that overall throughput could be significantly improved if environmental information was made available to the 802.11 MAC and to TCP. The central messagein this paper is that wireless conditions in the vicinity of a roadside access point are predictable, and by exploiting this information, vehicular opportunistic access can be greatly improved.

SmartSiren: virus detection and alert for smartphones

Abstract: Smartphones have recently become increasingly popular because they provide "all-in-one" convenience by integrating traditional mobile phones with handheld computing devices. However, the flexibility of running third-party softwares also leaves the smartphones open to malicious viruses. In fact, hundreds of smartphone viruses have emerged in the past two years, which can quickly spread through various means such as SMS/MMS, Bluetooth and traditional IP-based applications. Our own implementations of two proof-of-concept viruses on Windows Mobile have confirmed the vulnerability of this popular smartphone platform.In this paper, we present SmartSiren, a collaborative virusdetection and alert system for smartphones. In order to detect viruses, SmartSiren collects the communication activity information from the smartphones, and performs joint analysis to detect both single-device and system-wide abnormal behaviors. We use a proxy-based architecture to offload the processing burden from resource-constrained smartphones and simplify the collaboration among smartphones. When a potential virus is detected, the proxy quarantines the out-break by sending targeted alerts to those immediately threatened smartphones. We have demonstrated the feasibility of SmartSiren through implementations on a Dopod 577w smartphone, and evaluated its effectiveness using simulations driven by 3-week SMS traces from a national cellular carrier. Our results show that SmartSiren can effectively prevent wide-area virus outbreaks with affordable overhead.

Wireless wakeups revisited: energy management for voip over wi-fi smartphones

Abstract: IP based telephony is rapidly gaining acceptance over traditional means of voice communication. Wireless LANs are also becoming ubiquitous due to their inherent ease of deployment and decreasing costs. In enterpriseWi-Fi environments, VoIP is a compelling application for devices such as smart phones with multiple wireless interfaces. However, the high energy consumption of Wi-Fi interfaces, especially when a device is idle,presents a significant barrier to the widespread adoption of VoIP over Wi-Fi.To address this issue, we present Cell2Notify, a practical and deployable energy management architecture that leverages the cellular radio on a smart phone to implement wakeup for the high-energy consumption Wi-Fi radio. We present detailed measurements of energy consumption on smart phone devices, and we show that Cell2Notify, can extend the battery lifetime of VoIPover Wi-Fi enabled smart phones by a factor of 1.7 to 6.4.

Preserving location privacy in wireless lans

Abstract: The broadcast and tetherless nature of wireless networks and the widespread deployment of Wi-Fi hotspots makes it easy to remotely locate a user by observing her wireless signals. Location is private information and can be used by malicious individuals for blackmail, stalking, and other privacy violations. In this paper, we analyze the problem of location privacy in wireless networks and present a protocol for improving location privacy. Our basic approach is to obfuscate several types of privacy-compromising information revealed by a mobile node, including sender identity, time of transmission, and signal strength. Our design is driven by real-system implementation and field experiments along with analysis and simulations. Our system allows users to choose the level of privacy they desire, thereby increasing the performance of less private users (while not sacrificing private users' privacy at the same time). We evaluated our system based on real-life mobility data and wireless LAN coverage. Our results show that a user of our system can be indistinguishable from a thousand users in the same coverage area.

MobiSteer: using steerable beam directional antenna for vehicular network access

Abstract: In this work, we investigate the use of directional antennas and beam steering techniques to improve performance of 802.11 links in the context of communication between amoving vehicle and roadside APs. To this end, we develop a framework called MobiSteer that provides practical approaches to perform beam steering. MobiSteer can operate in two modes - cached mode - where it uses prior radiosurvey data collected during "idle" drives, and online mode, where it uses probing. The goal is to select the best AP and beam combination at each point along the drive given the available information, so that the throughput can be maximized. For the cached mode, an optimal algorithm for AP and beam selection is developed that factors in all overheads.We provide extensive experimental results using a commercially available eight element phased-array antenna. In the experiments, we use controlled scenarios with our own APs, in two different multipath environments, as well as in situ scenarios, where we use APs already deployed in an urban region - to demonstrate the performance advantage of using MobiSteer over using an equivalent omni-directional antenna. We show that MobiSteer improves the connectivity duration as well as PHY-layer data rate due to better SNR provisioning. In particular, MobiSteer improves the throughput in the controlled experiments by a factor of 2 - 4. In in situ experiments, it improves the connectivity duration by more than a factor of 2 and average SNR by about 15 dB.

Simplifying cyber foraging for mobile devices

Abstract: Cyber foraging is the transient and opportunistic use of compute servers bymobile devices. The short market life of such devices makes rapid modification of applications for remote execution an important problem. We describe a solution that combines a "little language" for cyber foraging with an adaptive runtime system. We report results from a user study showing that even novice developers are able to successfully modify large, unfamiliar applications in just a few hours. We also show that the quality of novice-modified and expert-modified applications are comparable in most cases.

COMBINE: leveraging the power of wireless peers through collaborative downloading

Abstract: Mobile devices are increasingly equipped with multiple network interfaces: Wireless Local Area Network (WLAN) interfaces for local connectivity and Wireless Wide Area Network (WWAN) interfaces for wide-area connectivity. The WWAN typically provides much wider coverage but much lower speeds than the WLAN. To address this dichotomy, we present COMBINE, a system for collaborative downloading wherein devices that are within WLAN range pool together their WWAN links, significantly increasing the effective speed available to them.COMBINE makes a number of novel contributions overprior work in this area, including: (a) a framework of incentives for collaboration that addresses several practical issues including the unification of monetary and energy costs, and on-the-fly estimation of the energy cost of communication in a system in operation; (b) a protocol for collaborative group formation and workload distribution that is energy efficient and adaptive to fluctuations in network conditions; and (c) an application-level striping procedure that eases deployment by avoiding the need for special-purpose proxies in the infrastructure. We present experimental results based on the prototype we have implemented that showen couraging speeds-ups with COMBINE.

SmokeScreen: flexible privacy controls for presence-sharing

Abstract: Presence-sharing is an emerging platform for mobile applications, but presence-privacy remains a challenge. Privacy controls must be flexible enough to allow sharing between both trusted social relations and untrusted strangers. In this paper, we present a system called SmokeScreen that provides flexible and power-efficient mechanisms for privacy management.Broadcasting clique signals, which can only be interpreted by other trusted users, enables sharing between social relations; broadcasting opaque identifiers (OIDs), which can only be resolved to an identity by a trusted broker, enables sharing between strangers. Computing these messages is power-efficient since they can be pre-computed with acceptable storage costs.In evaluating these mechanisms we first analyzed traces from an actual presence-sharing application. Four months of traces provide evidence of anonymous snooping, even among trusted users. We have also implemented our mechanisms on two devices and found the power demands of clique signals and OIDs to be reasonable. A mobile phone running our software can operate for several days on a single charge.

Shooter localization and weapon classification with soldier-wearable networked sensors

Abstract: The paper presents a wireless sensor network-based mobilecountersniper system. A sensor node consists of a helmetmountedmicrophone array, a COTS MICAz mote for internodecommunication and a custom sensorboard that implementsthe acoustic detection and Time of Arrival (ToA) estimationalgorithms on an FPGA. A 3-axis compass providesself orientation and Bluetooth is used for communicationwith the soldier's PDA running the data fusion and the userinterface. The heterogeneous sensor fusion algorithm canwork with data from a single sensor or it can fuse ToA orAngle of Arrival (AoA) observations of muzzle blasts andballistic shockwaves from multiple sensors. The system estimatesthe trajectory, the range, the caliber and the weapontype. The paper presents the system design and the resultsfrom an independent evaluation at the US Army AberdeenTest Center. The system performance is characterized by 1-degree trajectory precision and over 95% caliber estimationaccuracy for all shots, and close to 100% weapon estimationaccuracy for 4 out of 6 guns tested.

Radio interferometric tracking of mobile wireless nodes

Abstract: Location-awareness is an important requirement for many mobile wireless applications today. When GPS is not applicable because of the required precision and/or the resource constraints on the hardware platform, radio interferometric ranging may offer an alternative. In this paper, we present a technique that enables the precise tracking of multiple wireless nodes simultaneously. It relies on multiple infrastructure nodes deployed at known locations measuring the position of tracked mobile nodes using radio interferometry. In addition to location information, the approach also provides node velocity estimates by measuring the Doppler shift of the interference signal. The performance of the technique is evaluated using a prototype implementation on mote-class wireless sensor nodes. Finally, a possible application scenario of dirty bomb detection in a football stadium is briefly described.

NodeMD: diagnosing node-level faults in remote wireless sensor systems

Abstract: Software failures in wireless sensor systems are notoriously difficult to debug. Resource constraints in wireless deployments substantially restrict visibility into the root causes of node-level system and application faults. At the same time, the high cost of deployment ofwireless sensor systems often far exceeds the cumulative cost of allother sensor hardware, so that software failures that completely disable a node are prohibitively expensive to repair in real worldapplications, e.g. by on-site visits to replace or reset nodes. We describe NodeMD, a deployment management system that successfully implements lightweight run-time detection, logging, and notificationof software faults on wireless mote-class devices. NodeMD introduces a debug mode that catches a failure before it completely disables a node and drops the node into a stable state that enables further diagnosis and correction, thus avoiding on-site redeployment. We analyze the performance of NodeMD on a real world application ofwireless sensor systems.

Accelerometer-based human abnormal movement detection in wireless sensor networks

Abstract: Wireless sensor networks have become increasingly common in everyday applications due to decreasing technology costs and improved product performance. An ideal application for wireless sensor networks is a biomedical patient monitoring tool. Wireless patient monitoring systems improve quality of life for the subject by granting them more freedom to continue their daily routine, which would not be feasible if wired monitoring equipment were used. This paper explores an application of wireless biomedical sensor networks, which attempts to monitor patients for a specific condition in a completely non-invasive, non-intrusive manner. This non-invasive technique uses an accelerometer to determine if a person's arm movement is similar to that of a person suffering from a seizure. The effectiveness of the presented algorithm has been verified on test subjects and showed rare occurrences of false positives.

Real-time deployment of multihop relays for range extension

Abstract: When the range of single-hop wireless communication is limited by distance or harsh radio propagation conditions, relays can be used to extend the communication range through multihop relaying. This paper targets the need in certain scenarios for rapid deployment of these relays when little or nothing is known in advance about a given environment and its propagation characteristics. Applications include first responders entering a large building during an emergency, search and rescue robots maneuvering a disaster sight, and coal miners working underground. The common element motivatingthis work is the need to maintain communications in an environment where single-hop communication is typically inadequate. This paper investigates the feasibility of the automated deployment of a multihop network. A deployment procedure is proposed that employs real-time link measurements and takes into account the physical layer characteristics of a mobile multipath fading environment and the radio in use. A prototype system is implemented based on 900 MHz TinyOS motes supporting low-speed data applications including text messaging, sensor data and RFID-assisted localization. Results of deployments in a hi-rise office building are presented.

PageTailor: reusable end-user customization for the mobile web

Abstract: Most pages on the Web are designed for the desktop environment and render poorly on the small screens available on handheld devices. We introduce Reusable End-User Customization (REUC), a technique that lets end users adapt the layout of Web pages by removing, resizing and moving page elements. REUC records the user's customizations and automatically reapplies them on subsequent visits to the same page or to other, similar pages, on the same Web site. We present PageTailor, a REUC prototype based on the Minimo Web browser that runs on Windows Mobile PDAs. We show that users can utilize PageTailor to adapt sophisticated Web sites, such as Amazon, BBC and MSN, for browsing on a PDA. Moreover, the customizations remain effective for up to a year, even as the content of pages is updated, and can be reused across similar pages, limiting the customization effort required to browse a site.

Energy-efficient multi-hop medical sensor networking

Abstract: Wireless sensor networks represent a key technology enabler for enhanced health care and assisted living systems. Recent standardization eorts to ensure compatibility among sensor network systems sold by dierent vendors have produced the IEEE 802.15.4 standard, which specifies the MAC and physical layer behavior. This standard has certain draw-backs: it supports only single-hop communication; it does not mitigate the hidden terminal problem; and it does not coordinate node sleeping patterns. The IEEE 802.15.4 standard design philosophy assumes that higher layer mechanisms will take care of any added functionality. Building on IEEE 802.15.4, this paper proposes TImezone COordinated Sleep Scheduling (TICOSS), a mechanism inspired by MERLIN [2] that provides multi-hop support over 802.15.4 through the division of the network into timezones. TICOSS is cross-layer in nature, as it closely coordinates MAC and routing layer behavior. The main contributions of TICOSS are threefold: (1) it allows nodes to alternate periods of activity and periods of inactivity to save energy; (2) it mitigates packet collisions due to hidden terminals belonging to nearby star networks; (3) it provides shortest path routing for packets from a node to the closest gateway. Simulation experiments confirm that augmenting IEEE 802.15.4 networks with TICOSS doubles the operational lifetime for high trac scenarios. TICOSS has also been implemented on the Phillips AquisGrain modules for testing and eventual deployment in assisted living systems.

Context browsing with mobiles - when less is more

Abstract: Except for a handful of "mobile" Web sites, the Web is designed for browsing using personal computers with large screens capable of fully rendering the content of most Web pages. Browsing with handhelds, such as small-screen PDA's or cell phones, usually involves a lot of horizontal and vertical scrolling, thus making Web browsing time-consuming and strenuous. At the same time, one isoften only interested in a fragment of a Web page, which again may not fit on the limited-size screens of mobile devices, requiring more scrolling in both dimensions. In this paper, we address the problem of browsing fatigue during mobile Web access using geometric segmentation of Web pages and the notion of context. Our prototype system, CMo, reduces information overload by allowing its users to see the most relevant fragment of the page and then navigate between other fragments if necessary. On following a link, CMo captures the context of the link, employing a simple topic-boundary detection technique; then, it uses the context to identify relevant information in the next page with the help of a Support Vector Machine, a statistical machine-learning model. Our experiments show that the use of context can potentially save browsing time and improve the mobile browsing experience.

MobiUS: enable together-viewing video experience across two mobile devices

Abstract: We envision a new better-together mobile application paradigm where multiple mobile devices are placed in a close proximity and study a specific together-viewing video application in which a higher resolution video isplayed back across screens of two mobile devices placed side by side. This new scenario imposes real-time, synchronous decoding and rendering requirements which are difficult to achieve because of the intrinsic complexity of video andthe resource constraints such as processing power and battery life of mobile devices. We develop a novel efficient collaborative half-frame decoding schemeand design a tightly coupled collaborative system architecture that aggregates resources of both devices to achieve the task. We have implemented the system and conducted experimental evaluation. Results confirm that our proposed collaborative and resource aggregation techniques can achieve our vision of better-together mobile experiences.

Improving mobile database access over wide-area networks without degrading consistency

Abstract: We report on the design, implementation, and evaluation of a system called Cedar that enables mobile database access with good performance over low-bandwidth networks. This is accomplished without degrading consistency. Cedar exploits the disk storage and processing power of a mobile client to compensate for weak connectivity. Its central organizing principle is that even a stale client replica can be used to reduce data transmission volume from a database server. The reduction is achieved by using content addressable storage to discover and elide commonality between client and server results. This organizing principle allows Cedar to use an optimistic approach to solving the difficult problem of database replica control. For laptop-class clients, our experiments show that Cedar improves the throughput of read-write workloads by 39% to as much as 224% while reducing response time by 28% to as much as 79%.

Triage: balancing energy and quality of service in a microserver

Abstract: The ease of deployment of battery-powered and mobile systems is pushing the network edge far from powered infrastructures. A primary challenge in building untethered systems is offering powerful aggregation points and gateways between heterogeneous end-points---a role traditionally played by powered servers. Microservers are battery-powered in-network nodes that play a number of roles: processing data fromclients, aggregating data, providing responses to queries, and actingas a network gateway. Providing QoS guarantees for theseservices can be extremely energy intensive. Since increasedenergy consumption translates to a shorter lifetime, there is a need for a new way to provide these QoS guarantees at minimal energy consumption.This paper presents Triage, a tiered hardware and softwarearchitecture for microservers. Triage extends the lifetime of a microserver by combining two independent, but connected platforms: a high-power platform that provides the capability to executecomplex tasks and a low-power platform that provides high responsiveness at low energy cost. The low-power platform acts similarto a medical triage unit, examining requests to find critical ones, and scheduling tasks to optimize the use of the high-powerplatform. The scheduling decision is based on evaluating each task's resource requirements using hardware-assisted profiling of execution time and energy usage. Using three microserver services, storage, network forwarding, and query processing, we show that Triage provides more than 300% increase in microserver lifetime over existing systems while providing probabilistic quality of service guarantees.

Experiences of designing and deploying intelligent sensor nodes to monitor hand-arm vibrations in the field

Abstract: The NEMO project is exploring the use of mobile sensor nodes toaugment physical work artefacts in order to ensure compliance with health and safety regulations. In this paper we present our experiences of designing and deploying the NEMO Hand Arm Vibration (HAV) monitoring system. Long term exposure to hand arm vibration can lead to serious health conditions and the NEMO HAV monitoring system offers an integrated architecture for capturing HAV exposure data in the field, providing feedback about exposure levels both in the field and as input to a back-end database. Our design allows health and safety regulations specified at the enterprise level to be embedded within the wireless sensor nodes allowing them to operate without any infrastructural support. The system has been the subject of a two week field trial that took place with the collaboration of a British construction and maintenance company. During the field trial, the NEMO HAV system was deployed to a roa dmaintenance patching gang and data were collected on HAV exposure caused by hydraulic drills. The paper reports on the results of the field trial and the lessons learned through the real deployment of the system.

Emulating mobile ad-hoc networks of hand-held devices: the OCTOPUS virtual environment

Abstract: Nowadays, Mobile Ad-hoc NETworks (manet are investigated and adopted in many application scenarios, such as emergency management. Unfortunately, testing and validating complex systems developed on top of manet is still a difficult and error-prone task, due to the scarce availability of virtual environments. In this paper, we present octopus a virtual emulation environment for manet in which designers and developers can create scenarios in large scale areas including obstacles, defining different movement models, and use real hand-held devices for deploying their software/applications.

Dali: a communication-centric data abstraction layer for energy-constrained devices in mobile sensor networks

Abstract: Communications in mobile and frequently-disconnected sensor networks are characterized by low-bandwidth radios, unreliable links, and disproportionately high energy costs compared to other system operations. Therefore, we must use as efficiently as possible any periods of connectivity that we have. For this reason, nodes in these networks need mechanisms that organize data to streamline search operations, local computation, and communications.This work proposes a Data Abstraction Layer (DALi), which is inserted between the application layer and the file system. DALi organizes data with networking in mind to facilitate the development of services for Data Search, Naming, and Reduction that combine to make communications more efficient. From the resulting two-tiered data hierarchy, we develop a multi-layer drill-down search structure that can locate data multiple orders of magnitude faster (and with much lower energy) than simpler data storage structures. Additionally, DALi conserves energy and bandwidth through a mechanism that acknowledges and removes specific data segments from a mobile sensor network. Finally, it seamlessly integrates in a lossless compression algorithm specifically designed for sensor networks to save additional energy.

A feature combination approach for the detection of early morning bathroom activities with wireless sensors

Abstract: In this paper we investigate the use of wearable accelerometers and wireless home sensors for the detection of early morning daily activities to assist people with cognitive impairments. In particular we focus on the detection of brushing, washing face and shaving activities by using a wireless accelerometer sensor attached to the right wrist of the subjects to collect the hand movement data. We extracted time and frequency domain features of the accelerometer data for activity recognition. In order to compare the efficiency of different frequency domain features, we used fast Fourier transform and autoregressive modeling. The extracted time and frequency domain features are input to an ensemble of Gaussian mixture models (GMM) which represent individual activities we focus on. Finally, they are post processed by a finite state machine for classification. We show promising experimental results from 7 subjects while completing washing face, shaving and brushing activities. The proposed system achieved 93.5%, 92.5% and 95.6% classification accuracy in the recognition of these three tasks respectively.

Toward highly-available WSNs for assisted living

Abstract: In response to the consistent increase of elder people living in their apartments, and the need for innovative non-obtrusive tools to connect elders to their caregivers, we started an initiative with the Institute of Gerontology at Wayne State University to explore the application of wireless sensor networks (WSNs) for the monitoring of elder people and the communication of potential emergency conditions to their remote caregivers. Motivated by the fact that sensor nodes are resource-constrained and error-prone on one hand, and mission urgency on the other hand, we argue that high availability is a vital requirement that viable WSNs for assisted living have to acquire. We propose the use of classical reliability theory techniques to tackle this issue in a systematic way. We develop analytical models of the WSN availability in terms of the availability of the underlying sensor nodes. These models help in planning for the required number of nodes and the way these nodes are scheduled ON and OFF Our preliminary results show that using node scheduling almost doubles the expected WSN total uptime.

Cell phones as a research platform

Abstract: Panel Summary Cell phones are clearly the dominant platform for mobile computing and communication. Therefore, they are increasingly being used by the research community. Yet, building research prototypes using cellphones can be non-trivial. This panel brings together researchers who have successfully used cellphones in their work. They will address why they chose to work with cellphones and their experiences, both positive and negative. They will also offer their of prognostications of future trends, and open research problems that ought to be addressed by the Mobisys community.

Proceedings of the 1st international MobiSys workshop on Mobile opportunistic networking

Abstract: Welcome to the first edition of the Workshop on Mobile Opportunistic Networking, MobiOpp 2007. The workshop is co-located with ACM MobiSys 2007 and is sponsored by ACM SIGMOBILE. Opportunistic networking is one of the most exciting evolutions of the Mobile Ad hoc Networking (MANET) paradigm, in which the assumption of complete paths between data senders and receivers is released. Opportunistic networks enable users' communication in disconnected environments, in which islands of connected devices appear, disappear, and reconfigure dynamically. Opportunistic networks thus encompass the scope of delay or disruption tolerant networks (DTN), and are very suitable to accommodate the pervasive networking view, in which a huge number of devices carried by users and embedded in the environment communicate wirelessly without requiring any pre-existing infrastructure. The response to the Call for Papers shows that MobiOpp has been particularly well received by researchers working in the field of opportunistic Networks. Specifically, we received thirty-five submissions, addressing topics related to all fields of opportunistic networks. Out of them, the Program Committee selected ten regular papers for presentation in the workshop sessions. In addition, four papers have been selected as short contributions, and will be presented in the Work-in-Progress session. These figures and the quality of the received papers, show that MobiOpp is already seen as a premiere forum for presenting and discussing ideas and results in all the fields of opportunistic networking. The MobiOpp program also includes a Keynote Speech by Prof. Gaetano Borriello of the University of Washington, and a panel.

A resource optimized physical movement monitoring scheme for environmental and on-body sensor networks

Abstract: Perhaps the most significant challenge in design of on-body sensors is the wearability concern. This concern requires that the size of the nodes (sensors, processing units and batteries) is minimized. Therefore, the computation and communication executed in on-body nodes must be moderated significantly. In this paper, we propose a collaborative signal processing scheme for physical movement monitoring that utilizes on-body and environmental sensors. The environmental sensor nodes perform the bulk of the signal processing and provide feedback to the on-body sensor nodes. This is due to the fact that the environmental sensor nodes have access to more powerful processing units and an unlimited energy supply. The feedback simplifies the signal processing on the on-body nodes significantly. We achieve this by performing a hierarchical classification and introducing a probabilistic measure on likelihood of possible classes for the final level of classification on on-body sensor nodes. The experimental results show the effectiveness of our method. On average the classification accuracy is reduced by 3% while the computational complexity can be scaled down by one order of magnitude compared to a global and comprehensive classification scheme.