1. ALARM-NET: W IRELESS S ENSOR N ETWORKS FOR A SSISTED -L IVING AND R ESIDENTIAL M ONITORING Presented by, Swathi Krishna Kilari A. Wood, G. Virone, T. Doan, Q. Cao, L. Selavo, Y. Wu, L. Fang, Z. He, S. Lin, J. Stankovic Department of Computer Science University of Virginia

2. C ONTENTS Abstract Introduction Related Work ALARM-NET Architecture Query Management Circadian Activity Rhythms Dynamic Context-Aware Privacy Network and Data Security Context-Aware Power Management Data Association Implementation Hardware and Sensors Software System Evaluation and Performance Conclusion

3. A BSTRACT ALARM-NET, a wireless sensor network integrates environmental and physiological sensors in a scalable, heterogeneous architecture. A query protocol allows real-time collection and processing of sensor data by user interfaces and back-end analysis programs. One such program determines circadian activity rhythms of residents, feeding activity information back into the sensor network to aid context- aware power management, dynamic privacy policies, and data association. Communication is secured end-to-end to protect sensitive medical and operational information.

4. I NTRODUCTION The ALARM-NET system has been implemented as a network of MICAz sensors, stargate gateways, iPAQ PDAs, and PCs. Software components include: Tiny OS query processor and security modules for motes; AlarmGate, an embedded Java application for managing power, privacy, security, queries, and client connections; Java resident monitoring and sensor data querying applications for PDAs and PCs; a circadian activity rhythm analysis program.

5. E XAMPLE : A SSISTED L IVING D EPLOYMENT Person Person w/Body Network Backbone node Sensor node Fig: Assisted-living deployment example, showing connections among sensors, body networks, and back- bone nodes.

6. R ELATED W ORK Researchers at Intel Research Seattle and the University of Washington have built a prototype system that can infer a person's activities of daily living. University of Rochester is building The Smart Medical Home, which is a five-room house. Georgia Tech built an Aware Home as a prototype for an intelligent space. Massachusetts Institute of Technology (MIT) and TIAX, LLC are working on the PlaceLab initiative [8], which is a part of the House n project. Researchers at Harvard have developed a suite of wireless sensors and software called CodeBlue for a range of medical applications. University of Washington's Assisted Cognition project incorporates novel computer systems enhancing the quality of life of people suffering from Alzheimer's Disease and similar cognitive disorders.

7. ALARM-NET A RCHITECTURE ALARM-NET integrates heterogeneous devices in a common architecture, spanning wearable body networks, emplaced wireless sensors, and IP-network elements. Components: Body Networks Emplaced Sensors AlarmGate Back-end User Interfaces

8. C ONTD. In−Network Interfaces: SeeMote Mobile Body Networks: Pulse, SpO2, ECG, Accelerometer Emplaced Sensor Network: Temperature, Dust, Motion, Light PDA Alarm Gate IP Network PC User Interfaces DatabaseAnalysis Back-End Fig: ALARM-NET architecture components and logical topology

9. Q UERY M ANAGEMENT Real-time data queries are an important functionality in ALARM-NET, enabling user interaction with the running system and automatic data collection. Queries are identified by tuples, and request a certain type of sensor data about a subject. For a single-shot query, the sensor samples the requested data and returns a single report to the originator, completing the transaction. Periodic queries are issued with a given sample period. A separately specified report period allows multiple samples to be collected and aggregated into a single report using various lightweight aggregation functions. For integration with power management, queries are given a priority.

10. C ONTD. Software Components run on the AlarmGate and on motes. The properly translated and authorized query is sent to the sensor(s) in the WSN, where it is parsed by a Query Processor. Queries are originated by the system or by users. Single, stop, and reissue commands are designed to be as small as possible, for maximum efficiency.

11. C ONTD. Query Processor Query Query ParserData Cache Report Data Ready Query Processor Query Query Parser Data Cache Report Data Ready Sampler Filter Reporter Aggregator Sensor Sampler create config start stop destroy dataReady flush EventSensorPollableSensor eventDetected SplitPhaseSensor getData Motion Heartbeat Get data dataReady Sensor Driver ECG Pulse Photo Shim SpO2 Dust Temp Shim Weight Voltage Shim Accel Shim Figure 3. Query processing stack on sensor devices. The Query Processor parses queries, and starts the Sampler, which reads data from the sensor drivers on schedule, generating data that ows up the processing chain toward the Query Processor for reporting. Light RSSI

12. C IRCADIAN A CTIVITY R HYTHMS CAR supports context-aware protocols based on these activities for dynamic alarm-driven privacy and smart heterogeneous power management. CAR supports a GUI, which displays various information related to the activity analysis.

13. C ONTD. Fig: Circadian Activity Rhythms analysis GUI. Average time spent in every room per hour is graphed on the left side. Sums of daily deviations from the user's norm are on the right, showing a learning period after initial deployment.

14. D YNAMIC C ONTEXT -A WARE P RIVACY A privacy protection framework is implemented which is dynamically adjustable to users' context. The main component of the privacy framework is the Privacy Manager module. Context, identified by the tuple, is the result of domain expert analysis. The Privacy Manager resides in the AlarmGate application and has three main functional components: the Context Manager, the Request Authorizer, and the Auditor

15. C ONTD. Fig: Privacy-related components in ALARM-NET Back− end Data base Privacy Manager Context Update Access Request Access Decision Audit Request Context Manager Authorizer Request Auditor Context Object Role/Use r Object Policy object Audit Trail

16. N ETWORK AND D ATA S ECURITY Security of medical records and data is a vital part of ALARM-NET. Access to an AlarmGate by user interfaces is limited to legitimate users of the system. After a client connects and authenticates, communication between it and the AlarmGate on the IP network is encrypted whenever sensor data is reported. Messages sent and received to/from the WSN by the AlarmGate must also be secured, using message authentication codes (MACs) and encryption when necessary.

17. C ONTD. IP Network Security involves connections to the Alarm-Gate from potentially any Internet host. Secure Remote Password (SRP) Protocol is used to authenticate clients to the AlarmGate. The server and client agree a priori on a modulus and generator. The back-end database stores the tuple, where the salt is generated randomly when the user is enrolled, and the verifier is derived from his password.

18. C ONTD. WSN Security is provided by SecureComm, a link-layer security suite we developed for MICAz and Telos motes. Security−Aware Application AMStandard SecureComm CC2420RadioC CC2420SecurityC KeyStore ReceiveMsg[] ReceiveMsg BareSendMsg SendMsg Fig: SecureComm component wiring

19. C ONTD. Internal Security functions in the AlarmGate application include key management and auditing. AlarmGate shares a key with each sensor device that is a direct neighbor. Incoming secure messages from either network require a lookup to find the appropriate key in the KeyStore, followed by decryption and/or MAC verification. Outgoing messages also require a key lookup, followed by MAC computation and/or encryption if indicated

20. C ONTEXT -A WARE P OWER M ANAGEMENT ALARM-NET supports a heterogeneous power situation where some nodes are plugged into the wall and others operate on batteries. To satisfy all these power management requirements, a Context-aware and Open Power Management (COPM) module for ALARM-NET is designed. The COPM module uses four functional components: Sensor Drivers Context Management Circadian Activity Rhythm (CAR) and User Interface

21. C ONTD. Fig: Power Management components in ALARMNET CARUser Interface Context Aware Power Management Activity Pattern Context Policy Commands Sensor Drivers Commands Detection

22. D ATA A SSOCIATION In ALARM-NET, a data association program is implemented that uses low cost, heterogeneous, ubiquitous sensors. ALARM-NET uses Dempster-Shafer evidential theory which is a probability-based data fusion classification algorithm.

23. I MPLEMENTATION Hardware and Sensors: MICAz by Crossbow and Telos Sky by MoteIV as the base for the sensor nodes. Users can access ALARM-NET through desktop computers over the Internet or iPAQ PDA or LCD- enabled mote devices wirelessly. To detect motion we modified the commercially available wireless motion sensor HawkEye MS13A for X-10 networks. A dust sensor module for MICAz motes is built. SeeMote is designed and implemented, an LCD module that serves as a user interface device attachable to the MICAz motes.

24. C ONTD. Software : a) Sensor device software stack b) AlarmGate software stack. c) Back-end analysis and storage. Query processor Power Manag er Sampler Secure Comm Sensor Driver Routing Sensor HW Network Query Manager Privacy Manager Power Manager Database Interface Secure Comm Audit Log Authenti cation Phoenix Source Routing Client Manager Sensor Network IP Network Circadian Activity Rhythm Analysis Data Associati on D at ab as e (a) Sensor device software stack (b) AlarmGate software stack. (c) Back-end analysis and storage

25. S YSTEM E VALUATION AND P ERFORMANCE Integration and Back-End Analysis Fig: Simulated Residence

26. C ONTD. Privacy-Aware Queries A wearable pulse rate sensor to the resident and an environmental temperature sensor to the living room are added. A user of the system, a technician, connects to the AlarmGate and issues a single query for the environmental temperature of the resident's unit. The simulated resident then moved around the living space in a manner different from the behavior profile learned.

27. C ONTD. Context-Aware Power Management For this analysis, we classified certain combinations of sensors that can be used in ALARM-NET to define the following four typical power modes: Environment Sense (ES): A mote in ES enables the light, temperature and acoustic sensing components, as well as the radio to send the sensing report. Body Sense (BS): A mote in BS is typically involved in a body network. It should enable the accelerometer to report the resident's movement and the radio. Standby: A mote in Standby has the Radio on and ready to receive or transmit data, but all the sensors are turned off. Sleep: When the mote is in the sleep mode, the radio and all the sensors are turned off.

28. C ONTD. Some basic context policies are: Policy 1: For M-motes, keep the motion sensor on and the radio off until a motion interrupt turns it on. Policy 2: When the resident is sleeping, all the E- motes and the B-mote switch to the Sleep mode. Policy 3: When the resident is awake, the B-mote should stay in the BS mode, the E-motes in the room where the resident is staying switch to the ES mode, and all other E-motes go to Standby mode.

29. C ONTD. (a) Power Measurement with disabled components Components Supply Current All enabled 45.0 mA Temp disabled 44.9 Light disabled 44.9 Accel disabled 44.4 Magnet disabled 35.1 Acoustic disabled 44.0 Radio disabled 19.2 (b) Power Measurement in different power modes Power Modes Supply Current ES 33.9mA BS 33.4mA Standby 32.8mA Sleep 6.2mA (c) Power Measurement of motion sensor Motion Sensor Supply Current All components enabled 32.5mA Motion sensor disabled 32.5mA Radio disabled 7.1mA

30. C ONTD. Embedded Code Details Java code for the PDA and stargate easily fit within their memory constraints. Code sizes given are the sizes of the class files, including the JDBC connector, crypto library, and PhoenixSource and its dependences. Application Lines Code Size Data Size SensorMote 7224 23158 2031 SensorMote-alone 7224 13334 1638 AlarmGate 7429 1342241 -- PDA Query Issuer 8210 340950 --

31. C ONCLUSION ALARM-NET, a wireless sensor network designed for long-term health monitoring in the assisted living and residential environments. A central design goal was to adapt the operation of the system, including power management and privacy policy enforcement. To associate data with the proper individual, we use sensor data and Dempster-Shafer evidential theory. For protection of medical information IP and WSN communication is secured with SRP and SecureComm.