1 safirenet: next-generation networks for situational awareness nalini venkatasubramanian
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SAFIRENET: Next-Generation Networks for Situational Awareness
Nalini Venkatasubramanian
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Situational Awareness for Firefighters
Questions to be answered: Where are the firefighters? Are they doing well? Any danger?
Limited infrastructure access
High network deployment cost
Challenges
The Problem
Deliver contextual data sensed by firefighters to the incident commander
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Motivation Multitude of technologies
WiFi (infrastructure, ad-hoc), WSN, UWB, mesh networks, DTN, zigbee
SAFIRE Data needs Timeliness
immediate medical triage to a FF with significant CO exposure
Reliability accuracy levels needed for CO
monitoring
Limitations Resource Constraints
Video, imagery Transmission Power, Coverage,
Failures and Unpredictability Goal
Reliable delivery of data over unpredictable infrastructure
Sensors
Dead Reckoning(don’t send Irrelevant data)
Multiple networks
Information need
DA
TA
NE
ED
S
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Experiences with Existing Network Technologies…
Lessons Learned: Despite multitudes of technologies, rapidly deployable, self-configuring networks that provide end-to-end & continuous
connectivity are hard to create!!!
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Experiences in deploying WiFi Mesh
Commercial mesh routers not good enough
5X improvement with new antenna technology
Better signal coverage better building penetration
• Some Setup effort required
• Not always feasible
• Vulnerable to hardware failures
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SAFIRE Mote Sensor Deployment
IEEE 802.15.4 (zigbee)
Crossbow MIB510 Serial Gateway
Polar Heart Rate Module
Polar T31 Heart rate strap transmitter
Proprietary EMF transmission
To SAFIRE Server
IMU (5 degrees
of freedom)
Crossbow MDA 300CA Data Acquisition board on MICAz 2.4Ghz Mote
Heart Rate
Inertial positioning
Carbon monoxide
Temperature, humidity Carboxyhaemoglobin, light
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Experiences in deploying mote sensors and Zigbee networksCalibration is essential
Rout e updat e per iod
Re
lia
bil
ity
static
mobile
↑Density↑Reliability
↑Mobility↓Reliability Network convergence, gatewayavailability
↑Size↓Reliability
Frequency matters!!
Topology matters!!
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(Un) Reliability of Wi-Fi Networks
Ad-hoc 1hop > Ad-hoc 2 hops > Private AP >>> Public AP
• No background traffic• Controllable configuration
• Increased bandwidth share• Reduced
contentions/collisions
• Less interferences• Distributed
Beaconing
• Varying traffic load• Varying level of contentions and congestions• Varying inter-device distance
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Creating Reliable Networks for Onsite Communication…
Goal: Enabling Robust, Timely Data Transfer by combining technologies
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Approaches
Exploit multiple networks that together provide connectivity (Mobiquitous 2005, WCNC 2007, INFOCOM 2009)
WiFi mesh – direct connectivity to a mesh router MANETS – hop by hop connectivity to gateway nodes Zigbee adhoc – connect to WiFi backbone through gateway node
Exploit mobility when disconnected Store-and-forward networks (Delay Tolerant Networking)
mobile nodes ferry data to gateway node
Combine connected network clouds and disconnected networks
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Reliable Content Delivery in Connected Networks Two aspects: Data delivery, message awareness
RADCAST: Flash Broadcast in MANETS (Infocom 2009, Percom 2009) Concurrent dissemination of awareness and content
Data diffusion: based on a mix of push/pull (Pryer) Awareness assurance: network traversal using walkers (Peddler)
Problem: fast network traversal (NP-hard) Minimizing cover time, termination time and transmission overhead
AwarenessAssurance
Fragmentation
DataDiffusion
ReliableContent
Dissemination
Metadata
Content Data
{{
{concurrent
Walker
Walker
concurrent
Assures reception
Pull
Push
concurrent
GuidesRetrievesmissing
Spreads
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Supporting Varying Reliability Needs in Connected Networks
Reliability Level Reliability Needs Awareness
AssuranceData
DiffusionNetwork Size
Knowledge Cost
Max All reachable nodes receive the content √ √ Ignore High
Lower-Bounded
A specified number of nodes are guaranteed to
receive the content√ √ Exploit Medium
Best-EffortAs many nodes as possible
receive the content, no guarantee is required
√ × N/A Low
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Situational Awareness in a disconnected environment
Aggregatecontextual data
Incident Commander
Board
Forward bundlesupon device encounters
Forward bundlesupon gateway
encounters
Periodically sensing e.g., WiFi AP fingerprints, accelerometer readings, residue battery, snapshots, audio/video recording, etc.
Visualizing the task execution process spatially and temporally
Easy deployment of one or several mesh routers at the edge
of the area
A Store-Move-and-Forward (DTN) based approach
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The Store-and-Forward Data Transfer Problem
System Model
• Each device maintains a cache storing bundles from itself and others
• Devices exchange certain bundles in cache upon encounters
Goals
• High reliability• Low storage cost• Low transmission cost• Short latency
• How many copies should be generated for each bundle?Replication
• Which bundles should be forwarded upon device encounters, and in what order?Forwarding
• Which bundles should be removed to accommodate incoming bundles upon cache overflow?Purging
Sub-Problems
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Store-and-Forward Data Transfer: Solution Overview
Replication
ForwardingContext Sens-ing & Collection{
Purging
Components
Fixed Number of Distinct Copies
Location-Closeness Based
Aliveness-Signi-ficance Based
TaskScheduling
0-1Knapsack
Strategies Modeling
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Implementation on Mobile Devices
Applications
Middleware DTN-Based
Operating System SymbianMaemo
Emergency Situ-ational Awareness
RADcast
Flash Broadcast
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Note: Reliable networks ≠Reliable Data Collection Sensing Errors Occur
Visibility Readings vary Occlusions etc.
Spikes in SpCO readings due to FF movement
Read errors due to misaligned sensor strip
Reliability at application level is also needed needed
Sensor Calibration (MMCN08) Heart-rate, CO exposure
Exploitation of Semantics, prediction Exploit application tolerance to
errors
-1000 0 1000 2000 3000 40000
200
400
600
800
1000
1200
Light readings (HZ-FF2)
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Tim e [sec]
Lig
ht
lev
el
-500 0 500 1000 1500 2000 2500 3000 35000
500
1000
1500Light readings (HZ-FF1)
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Tim e [sec]
Light
level