Post on 04-Jan-2016
transcript
ALeRT Project
Georgia Tech and UMass AmherstDARPA DTN Meeting
2 August 2005Washington, DC
DARPA DTN August Meeting
Overview: DTN Design
1. Reliable delivery – enhancement of basic routing for increased reliability
2. Network design – design and evaluation of novel devices (ferries and throwboxes) to enhance DTN performance
DARPA DTN August Meeting
Project Goal: Reliability
• Design and evaluate intelligent bundle discard policies
• Design an efficient drive-by transfer (DBT) protocol and efficient link layer system design
• Demonstrate high performance drive-by transfer
DARPA DTN August Meeting
Bundle Discard Policies
Testbed30 bus vehicular DTN network
Each bus: Linux “brick” computer; USB 802.11b adapter; 802.11b AP; GPS receiver, 40GB hard drive
Buses route messages as they pass by each other and via available hot spots
Traces collected everyday
Bundle Discard Sort packets for transmission opportunities
based on likelihood of eventual delivery; delete in reverse order
Network-wide ACKs clear buffers
Priority given to new packets over old
Evaluations based on traces of real bus movement, 802.11/TCP transfers
Performs better than a Dijkstra-based protocol with a meeting oracle
DARPA DTN August Meeting
Link Layer System Design
SolutionTwo Bluetooth radios on one
device provides a duplex channel.
SR = single radio; DR = dual radio
ProblemDTN nodes must find each other,
connect, and send data.
Most widely-deployed wireless technology – Bluetooth - thwarts neighbor discovery, since radios cannot be found while searching for others.
EvaluationSR = single radio; DR = dual radioCurrently evaluating performance
of 802.15.4 and 802.11
Comparing energy efficiency and achievable transfer rates of both.
DR allows much faster node speeds higher achievable rates
DARPA DTN August Meeting
Project Goal: Network Design
• Design and evaluate message ferries in a DTN environment to improve performance metrics
• Design and evaluate schemes for improving the reliability of DTNs that use message ferrying capability
• Investigate the potential for power savings through the use of message ferries in DTNs
• Develop strategies for deploying throw-boxes to enhance DTN performance
DARPA DTN August Meeting
Network Design: Message Ferries
ObjectiveImprove DTN performance by intelligent network design. Develop new components --- ferries and throw-boxes. Design the network via control over initial component placement, component mobility, and power consumption.
ImpactOrder of magnitude improvement using MF forwarding (MFv) versus epidemic routing (ER), when movement is area-based. MURA = ferries with multiple routes; more ferries directly increases capacity and decreases delay
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MURA, m=2MURA, m=4MURA, m=8
MURA, m=16
DARPA DTN August Meeting
Component Design: Throwboxes
SolutionHeterogenous embedded systems:
Stargate: 300-1000mW, TelosB: 10s of mW
Combined in a single DTN throwboxShare battery power and solar chargingIntelligently switch between modules/radios
for bundle transfers and exchange of routing data
PrototypeStargate Xscale processor plus low-power
Atmel processorWiFi (802.11) and Zigbee(802.15)Cheap (<$1k), built with COTS, can be
made rugged for battlefieldImproves lifetime/availability by more than
order of magnitude over Stargate
Solar Cells
Stargate w/Wifi
TelosB w/802.15.4
Batteries
Durable Case
Problem
DTN nodes need “throw and forget” capability
inexpensive, long-lived
DARPA DTN August Meeting
Programmatics: Spending
• 37% expended at end of July 2005• 5 months into 14 month contract
• Spending is on track
DARPA DTN August Meeting
Programmatics: Schedule
Activity Months 1-6 Months 7-12
Months 13-14
Reliable delivery
• discard policies
• drive-by transfer
• demonstration
Network design
• message ferries
• MF reliability
• MF power control
• throw-boxes
DARPA DTN August Meeting
Go/No-Go Metrics
• DTN Testbed– Integrated bundle discard, message ferry
routing, Throwboxes
• Throwbox Platform– Completion of first prototype – Order of magnitude increase in lifetime over
Stargate alone
• Network Design– Order of magnitude increase in performance
over unplanned and uncontrolled networks
DARPA DTN August Meeting
Questions?