1. University of Colorado at Boulder
Sensor Data Collection through a Delay-Tolerant MANET of Small Unmanned Aircraft
Daniel Henkel
University of Colorado at Boulder
Adhoc ’06, Stockholm, May 3-4, 2006
A Reliable Data Collection System Using Unmanned Aircraft

2. Outline AUGNet & Sensor Data Collection Problem Data Delivery
Controlled Mobility
Conclusion

3. AUGNet
Group 1
16cm
Group 2
241cm
Ad hoc UAV Ground Network

4. Sensor Data Collection
SMS-3
Gateway-2
CDMA
Sensor-1
SMS-1
Sensor-2
SMS-2
Gateway-1
Sensor-3
Have sensors all on left side
Highlight ferrying to the right side SMS locations
Sparsely distributed sensors
Limited radio range, power
Multiple monitoring stations

5. Collection Tasks Data Delivery Controlled Mobility
SMS-3
Gateway-2
CDMA
Sensor-1
SMS-1
Sensor-2
SMS-2
Gateway-1
Sensor-3
Have sensors all on left side
Highlight ferrying to the right side SMS locations
Data Delivery
Sensor event delivery (multicast)
SMS to sensor control (uni-cast)
Controlled Mobility

6. Outline Sensor Data Collection Problem Data Delivery
Controlled Mobility
Conclusion

7. Data Collection Problems
SMS-3
Change graph MN in all nodes
Multicasting of event messages to all SMS
Intermittent connectivity on any link
Service discovery of GW, SMS

8. Event Multicasting Staged delivery (custody transfer)
Network 1
Network 2
Network 3
MANET
SMS
Gateway
ISR
Terminus
SMS
Gateway
SMS
Staged delivery (custody transfer)
Multiplication of messages in each stage
NAPT

9. Reliable Packet Forwarding
TX stage
RX stage
put in send buffer
Event packet
seconds to minutes
TCP
ACK packet
delete from send buffer
Special cases need to be addressed
What if packet/ACK gets lost?
What if duplicates arrive?
What if seq# wraps around & long delayed packet?
Modified UDP, no TCP, no RUDP
Sequence numbers, RX: seq# hash table
ACK & Timeout-based reliability

10. Service Discovery Multiple GW, SMS; in & out of coverage
Heartbeat and GW advertisements

11. Click Modular Router

12. Implementation/Performance
Soekris SBC, embedded Gentoo Linux
Atheros miniPCI, Madwifi-ng driver
RTT 40ms, 15hrs sustained operation

13. Backhaul CDMA phone with USB data cable
close-up of soekris board, cdma phone, base station
CDMA phone with USB data cable

14. Outline Sensor Data Collection Problem Data Delivery
Controlled Mobility
Conclusion

15. So What? Intermittent networking shown …given eventual connectivity
How do we guarantee eventual connectivity?
Solution: Controlled Mobility

16. Ferrying Store, Carry, Forward network
Data physically carried to destination by special ferry nodes
Prior work: Zhang/Ammar – Path planning for ferries; TSP; theory
controlled movement
Missing are…
Network latency in milliseconds
Relatively high data rates
End-to-End paths at all times
Connectivity throughout data transfer
Bi-directional communication
Send Buffer
Ferry Buffer
Receiver

17. Ferrying Models
Conveyor-belt Model
Chain-Relay Model

18. Chain-Relay Ferrying Model1 2 3 B
Ferries hand-off data to each other
No ferry flies whole distance A-B

19. Performance Results Metrics: throughput, packet delay
Which model is better?
Fast ferries
Conveyor Belt Model
High data rate, long-range radios
Chain-Relay Model
(Henkel D., Brown T., On Controlled Node Mobility in Delay Tolerant Networks of Unmanned Aerial Vehicles, ISART ‘06)
- Graphical representation

20. Conclusion We have built a reliable DTN for sensor data collection.
We have theoretical results on ferry scheduling.
Integration of both looks promising.

21. Extensions / Outlook Real DTN: persistent storage in db
Plane trajectory design depending on observed traffic
Integration of sensor traffic notification and plane mobility control in network protocols
Scalability: what happens if traffic increases?
Real-time monitoring and alerts when packets about to be dropped

22. Questions.
Daniel Henkel - augnet.colorado.edu recuv.colorado.edu

23. Hiker Rescue System CenWits:
Loosely-Coupled Sensor-Based Search and Rescue System using Witnesses