Fault Tolerant
Sensor Network Routing for
Patient Monitoring
Shanshan Jiang, Annarita Giani,
Allen Yang, Yuan Xue, and
Ruzena Bajcsy
Vanderbilt University
University of California at Berkeley
TRUST Autumn 2008 Conference
November 11th, 2008
Outline
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Motivation
System and Network Architecture
System Prototype and Implementation
Network and Routing Model of the Backbone
Network
• Optimization-based Routing Restoration of the
Backbone Network
• Performance Evaluation
Fault Tolerant Sensor Network Routing for Patient Monitoring
Motivation
• Aging population
– According to the U.S. Census
Bureau, the number of people over
the age of 65 is expected to hit 70
million by 2030, having doubled
since 2000.
• Health care expenditures
– Health care expenditures in the
United States are projected to rise
to 15.9% of the GDP ($2.6 trillion)
by 2010.
– The cost of health care for the
nation’s aging population has
become a national concern.
Fault Tolerant Sensor Network Routing for Patient Monitoring
Motivation
• Wireless Sensor Networks
– Deploy wearable sensors on the bodies of patients in a residential setting
– Continuously monitor physiological signals (such as ECG, blood oxygen
levels) and other health related information (such as physical activity)
• Advantages
– Shift from a clinic-oriented, centralized healthcare system to a patientoriented, distributed healthcare system
– Reduce healthcare expenses through more efficient use of clinical
resources and earlier detection of medical conditions
• Challenges
– Performance, Reliability, Scalability, QoS, Privacy, Security …
– More prone to failures, caused by power exhaustion, software and
hardware faults, natural disasters, malicious attacks, and human errors etc.
Provide fault-tolerant wireless communication that can satisfy
both the performance and reliability requirements
Fault Tolerant Sensor Network Routing for Patient Monitoring
Outline
•
•
•
•
Motivation
System and Network Architecture
System Prototype and Implementation
Network and Routing Model of the Backbone
Network
• Optimization-based Routing Restoration of the
Backbone Network
• Performance Evaluation
Fault Tolerant Sensor Network Routing for Patient Monitoring
System and Network Architecture
Fault Tolerant Sensor Network Routing for Patient Monitoring
System and Network Architecture
Lower Tier: Body Sensor Network
Upper Tier: Multi-hop Wireless
Backbone Network
Fault Tolerant Sensor Network Routing for Patient Monitoring
Outline
•
•
•
•
Motivation
System and Network Architecture
System Prototype and Implementation
Network and Routing Model of the Backbone
Network
• Optimization-based Routing Restoration of the
Backbone Network
• Performance Evaluation
Fault Tolerant Sensor Network Routing for Patient Monitoring
System Prototype and Implementation
• Hardware Devices
• Software Design
Fault Tolerant Sensor Network Routing for Patient Monitoring
System Prototype Experiment
Fault Tolerant Sensor Network Routing for Patient Monitoring
Outline
•
•
•
•
Motivation
System and Network Architecture
System Prototype and Implementation
Network and Routing Model of the Backbone
Network
• Optimization-based Routing Restoration of the
Backbone Network
• Performance Evaluation
Fault Tolerant Sensor Network Routing for Patient Monitoring
Network Model of the Backbone Network
• Backbone Network Performs Sensor Data
Routing and Forwarding
• Network and Interference Model
– Topology: G=(V, E)
– All nodes have a uniform transmission range
and interference range
– Two edges interfere with each other if they
have two nodes within the interference range
of each other
Backbone Network
• Traffic Demand Model
– df is the traffic demand of flow f, which is an
aggregation amount of all the sensor data
received at the sender of flow f
• Be routed over multiple paths
• xf(e) denotes the amount of flow f’s traffic being
routed on link e
Fault Tolerant Sensor Network Routing for Patient Monitoring
Routing Model of the Backbone Network
• Metric for routing performance
– Minimum Flow Throughput Scaling Factor
• The minimum, over all flows, of the actual flow throughput being routed
divided by its throughput demand
amount of traffic received at the destination node rf
• Optimal Routing Formulation
wireless channel constraint
(necessary scheduling condition)
flow
conservation
conditions
Fault Tolerant Sensor Network Routing for Patient Monitoring
Outline
•
•
•
•
Motivation
System and Network Architecture
System Prototype and Implementation
Network and Routing Model of the Backbone
Network
• Optimization-based Routing Restoration of the
Backbone Network
• Performance Evaluation
Fault Tolerant Sensor Network Routing for Patient Monitoring
Optimization-based Routing Restoration
• Discover Alternate Paths Bypassing the Failed Nodes
• Reactive Restoration
– Not reserve any network resource
– Deal with failures only when they occur through network resource
reallocation
– Application
• Resource-limited System that allows performance degradation upon
failures
• Proactive Restoration
– Reserve additional resources a priori
– Provide certain performance assurance for the rerouted flows with
a shorter restoration time
– Application
• Life-critical System
• Admission Control
– Result in a lower network utilization before failure occurs
– Need to know the worst-case node failure situations
Fault Tolerant Sensor Network Routing for Patient Monitoring
Optimization-based Routing Restoration
• End-to-end Restoration
– The flows from the failed path will be diverted to a
number of paths from its source to the destination
– Failure information has to be propagated to the
source nodes of the disrupted flows
• Local Restoration
– Uses a set of bypaths to route around the failed
node locally
– The restoration is locally activated
Fault Tolerant Sensor Network Routing for Patient Monitoring
Increase
Network Performance after Restoration
– All flows will be rerouted in order to get an optimal
utilization of the network
– All flows have to be notified with the failure
information
Increase
Repairing Time During Restoration
• Global Restoration
Optimization-based Routing Restoration
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Global Restoration
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End-to-end Restoration: (1) Calculate Unaffected Flow Truncations (2) Optimal Flow
Augmentation Restoration Formulation
•
Local Restoration: (1) Calculate Bypass Flows (2) Optimal Bypass Restoration Formulation
Fault Tolerant Sensor Network Routing for Patient Monitoring
Outline
•
•
•
•
Motivation
System and Network Architecture
System Prototype and Implementation
Network and Routing Model of the Backbone
Network
• Optimization-based Routing Restoration of the
Backbone Network
• Performance Evaluation
Fault Tolerant Sensor Network Routing for Patient Monitoring
Performance Evaluation
Simulated Backbone Network
Fault Tolerant Sensor Network Routing for Patient Monitoring
Conclusion
• Three-Phase System Architecture
• Two-Tier Data Collection Network
• Routing Restoration of the Backbone Network
– Based on optimization theory and linear programming
approach
• Reserve network resource or not
– Proactive Restoration
– Reactive Restoration
• Restoration scale
– Global Restoration
– End-to-end Restoration
– Local Restoration
Fault Tolerant Sensor Network Routing for Patient Monitoring