Delay-Tolerant Communication using Aerial

Mobile Robotic Helper Nodes

Daniel HenkelApril 4, 2008

recuv.colorado.edu

Overview

• DTN Test Bed• Direct, Relay, Ferry Models• Relay Optimization• Choosing Optimal Mode• Sensor Data Collection

University of ColoradoLocation

Unmanned Aerial Vehicles (UAVs)

• Small (10kg) Low-Cost (<$10k) UAVs• 60-100km/h, 1hr endurance• 5HP gas engine• Built in-house

Ad hoc UAV-Ground Networks

NOC

Scenario 1: increase ground node connectivity.

Scenario 2: increase UAV mission range.

Applications

Military Intelligence, Surveillance, Reconnaissance (ISR) Border Patrol

Scientific Atmospheric Research (NIST, NCAR) Tornado/Hurricane & Arctic Research

Civil / Commercial Disaster Communication & Intelligence (Fire) Sensor Data Collection

AUGNet

241cm

Ad Hoc UAV Ground Network

Group 1

Group 2

16cm

recuv.colorado.edu

AUGNET as Delay Tolerant / Challenged Network

• Plane bankingSimultaneous end-to-end paths might not exist

• Antenna configurationLinks might be very lossy

• Unmanned planesNodes might move at high speeds

• Links might have extremely long delays• Links might be intermittently up or

down

Research Goal

GS1

UAV1UAV3

UAV2

GS2

Using node mobility control to enhance

network performance

DirectRelayFerrying

Assumptions

• Controllable helper nodes

• Known communication demands

• Single link perspective

• Theoretical rather than implementation

x

yz

S R

λ

Direct Communication

)1(log2 SINRWR

d

KdS )(

KWTkB /0

)1

1(log2 dWRD

Shannon capacity law

Signal strength

Thermal noise (normalized)

Data rate

Relay Network

S R

d

dk

End-to-end data rate: RR

Packet delay: τ = L/RR

Direct transmission(zero relays)

Relay transmission

“Single Tx” Relay Modela.k.a., the noise-limited case

11

1

k

dR

kR DRS

1

)1(

kd

R

Lk

D

RS

S Rdk

t=0

“Parallel Tx” Relay Modela.k.a., the interference limited case > Optimal distance between transmissions?

),,(

,1min

1max

kdR

kR IRP

)1(log2NI

SI PP

PWR

iI iid

kP

)1(

1

)1(

1)

1(

S Rρ

t=0 t=0 t=0

A BF

Conveyor Belt Ferrying Model

1

1

)2/()1(

11

1

2)(

ddRbv

d

bvdR

D

F

Optimizing “Single Tx”• Where is the trade-off?

dk vs. # of transmissions

• Optimal number of relays:

),( KCdkopt

1

K

dckopt

c

cc

1

)1ln(with

Optimizing “Parallel Tx”

• Where is the trade-off?– interference vs. # parallel transports

• Use Matlab!

k

ρ

R

link reuse factor

“Triple Play”

2km 4km 8km 16km

eps=5 PN=10-15 W

Distance—Rate Phase Plot

Delay—Rate Phase Plot

Delay—Rate Animation

Sensor Data Collection

Sparsely distributed sensors Limited radio range, power

Sensor-1

Sensor-2

Sensor-3

SMS-1

External Network

SMS-2

Gateway-1

SMS-3

Gateway-2CDMA

Multiple monitoring stations

Challenges:• No end-to-end connection• Intermittent connectivity • Sensors and SMS unknown

RTT 40ms, 15hrs sustained operation

Soekris SBC, embedded Gentoo Linux Atheros miniPCI, Madwifi-ng driver

Hardware Implementation

FS1

FS2

82

81

8584

83 on & off

Functional Evaluation

Functional Evaluation II

Next Steps

• Ferry route planning with Reinforcement Learning

• Multi UAV operations/hybrid with MAVs

• UAV Swarming• Phased array antenna• WiMAX trial

Research and Engineering Center forUnmanned Vehicles (RECUV)Daniel Henkel, henk@gmx.com

recuv.colorado.edu