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UCLA ENGINEERING
Computer Science
A SDN-Controlled Underwater
MAC and Routing Testbed
Ruolin Fan∗, Li Wei†
Pengyuan Du*, Ciarán Mc Goldrick♠
and Mario Gerla∗
* University of California Los Angeles, Los Angeles, CA, USA
† Michigan Technological University, Houghton, MI, USA
♠ Trinity College Dublin, Dublin, Ireland
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Outline
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Introduction
Background
Design
Testbed Implementation
Testbed Usage
Conclusion
Computer Science
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Introduction
• Scientific and military operations
• Ocean floor mapping
• Ancient shipwrecks exploration
Computer Science
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Introduction
• Search and rescue missions (downed
airplanes)
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Supervised Search
• Man guides search from
vessel in real time
• Tether support fiber optic
communications
• Supplies power to USV
(Underwater Support
Vehicle) and in turns UUVs
• Covert operations
possible by using optics
only for the swarm search
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Autonomous search
• Non real time search
• No man in the loop
• Wave actioned generator
• Guarantees resupply
• Unlimited searches
• Several km fronts can be
explored with multiple
USVs
• Video inputs processed
on USVs
• Results reported to base
via satellite
Computer Science
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Outline
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Introduction
Background
Design
Testbed Implementation
Testbed Usage
Conclusion
Computer Science
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Computer Science
Choices for PHY Under Water
• Conventional radio waves are absorbed too quickly:
not feasible
• Acoustic PHY
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Long propagation distances (kilometers)
Very high latency (speed of sound)
Small transmission rates (kbps)
Complexity: high latency require different packet collision
models
• Optic PHY
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Short propagation distances (tens of meters)
Lower latency (speed of light in water)
Fast transmission rates (mbps)
Complexity: requires line of sight for transmission
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Acoustic vs. Optical
Telemetry
Method
Range
Data Rate
Efficiency
Propagation
Speed
Acoustic
Several km
1 kbps
100 bit/Joule
1500 m/s
Optical
100 meter
1 Mbps
30,000
bit/Joule
2.55 * 108 m/s
* Farr, N.; Bowen, A.; Ware, J.; Pontbriand, C.; Tivey, M.; , "An integrated, underwater
optical /acoustic communications system," OCEANS 2010 IEEE - Sydney , vol., no., pp.1-6,
24-27 May 2010
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Optical or acoustic?
• It depends on many things:
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Water quality
Turbulence
Covertness
Mobility
• Optical needs alignment
• Energy availability
• May need to support multiple modes on the
same UUV, switching from one mode to the
next dynamically
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Proposal: Underwater SDN
• Software defined networking (SDN):
separation of control plane with data plane
• Allows for flexibility and simplicity
• Centralized network controller defines network
behavior of other nodes
• Control plane: acoustics
• Data plane: (mostly) optics, acoustics optional
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Outline
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Introduction
Design
Testbed Implementation
Testbed Usage
Conclusion
Computer Science
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General SDN Framework
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Architecture and Components
• SDN components for Software-Defined Mobile
Network
• SDN controller: The central intelligence of an SDNbased Mobile Cloud
• Communicates with UUVs using long-range acoustics
• Directs UUV movements in addition to networking
• SDN wireless node: The UUVs that explore the
ocean
• Sends data to the controller mainly using optics
• Networks as directed by the controller
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The Underwater SDN Architecture
Active UUV
Recharging UUV
Centralized Network
Controller
Docking Station
Sleeping UUVs
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Architecture (cont)
• SDN wireless node internals
Acoustic
Local Agent contains
recovery mechanisms so
that system can still
function when
communications with SDN
controller are lost or
disrupted
Optic
Acoustic
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The U/W SDN Control Channel
Requirements:
• Both positioning and commands
• Covert, encrypted, secure..
• One to many – efficient broadcast
• Virtual Nets ( different missions)
• Network function virtualization
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Control Channel Standard - JANUS
• The primary advantages:
• Simplicity of design
• Among the least complicated forms of acoustic
communications yet devised.
• Robust to noise
• This signal should be detected when the signal to noise
ratio (SNR) in a given band is at better than -2 dB.
• Robust without tracking for “reasonable” amounts
of relative speed (range rate).
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Control Channel Standard - JANUS
• Optimal approach for asynchronous, multi-access
(multi-user) applications
• Optimal for robustness in the presence of all
types of interference, including intentional
jamming.
• Potentially difficult for third parties
• Undetectable by energy detectors
• A “constant envelope” waveform
• Transmitters not concerned with amplitude crest
factors
• Allows for maximum power allocation to the
transmission.
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Outline
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Introduction
Design
Testbed Implementation
Testbed Usage
Conclusion
Computer Science
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Testbed Implementation
• Parts of the acoustic version of the system
implemented in our WaterCom testbed
• Small water tank
• Lined with foam to attenuate acoustic waves
• Compartmentalized with foam to limit
connectivity
• 6 OFDM acoustic modems
• 3 large models with long-range signals
• 3 educational models with short-range signals
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Testbed Implementation
• All modems connected to the WaterCom
server
• Doubles as the SDN controller
• Accessible remotely via <apus.cs.ucla.edu>
• Uses the underwater protocol stack SeaLinx
• Allows for flexible loading of protocols at different
layers
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WaterCom Implementation
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Testbed Network Topology
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Outline
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Introduction
Design
Testbed Implementation
Testbed Usage
Conclusion
Computer Science
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Comparing UW MAC Protocols
• Using our testbed, we compared 2 existing
UW MAC Protocols
• Slotted FAMA (S-FAMA)
• UW-Aloha
• Under-water multi-hop scenario using
acoustic radios
• 5-minute test cases
• Varying packet size
• Varying packet sending rates
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Experiment Network Topology
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Results: Throughput
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Results: Packet Delivery Ratio
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Outline
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Introduction
Design
Testbed Implementation
Testbed Usage
Conclusion
Computer Science
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Computer Science
Conclusion
• Design of an under-water SDN architecture
• Acoustic control plane
• (Mostly) optical data plane
• Implementation in the WaterCom testbed
• Comparison of S-FAMA and UW Aloha
• UW Aloha has higher throughput and packet
delivery ratio