BUILDING CYBERINFRASTRUCTURE IN DEEP WOODS AND REMOTE

WATERSHEDS

Gayatri Venkatesh, Kuang-Ching Wang

Department of Electrical and Computer Engineering

The Intelligent RiverTM Pilot Sites

Over Woods & Hills

To campus

In Woods & Ditches

To campus

In the Woods

AT&T Data Coverage

Along the River

Challenges and Objectives

• Wireless networking challenges– Deep woods – impedes wireless communication range– Lack of cellular coverage– Hilly terrains – absolute blockage, often over long

distances– Recurring cost and limited bandwidth of cellular/satellite

service

• Wireless networking objectives– A methodology for building wireless network

infrastructure for current and future Intelligent RiverTM sites that

• provides adequate and reliable bandwidth• scales to a large area physically and economically

Clemson Forest and Hunnicut Creek

• Explore higher bandwidth, lower cost technologies– Clemson Forest

• Long range Wi-Fi (fixed direction): IEEE 802.11a & b/g

• Wi-Fi mesh network: IEEE 802.11b/g

• Zigbee sensor network: IEEE 802.15.4

– Hunnicut Creek

• Long range Wi-Fi (steerable direction): IEEE 802.11b/g

• Wi-Fi mesh network: IEEE 802.11b/g

• Zigbee sensor network: IEEE 802.15.4

Forest and Hunnicut Network Overview

Long Distance Transit Links

• To overcome long distance, forests, hills– Radio placement on high structure on both ends– High gain directional antenna and power

amplifiers– Potential control parameters

• Radio transmit power• Antenna direction• Antenna gain• Radio layer 2 and 3 protocol parameters

Clemson Forest Sensor Network

• Zigbee

• Zigbee• Zigbee• Zigbee• Zigbee

• Zigbee• Zigbee• Zigbee

• Long range Transit Link

• SensorCluster

• Data

Short range Wireless Communication: ISM 2.4 GHz

operating frequency .

1 mW (+0 dBm) power output.

Up to 120m range.

Supports up to 16 simultaneous channels.

Steerable Directional Antenna Radio

• Potentially higher bandwidth at substantially longer distance

• Software controls radio to focus one direction at a time– Fidelity Comtech Phocus System (tested 15 miles line-of-sight

range)– Potential use as 1) forest mesh routers and 2) long range

gateways

Measurement Studies of the Links

Long Range LinksIPERF – Bandwidth measurement tool used for the performance studies

Laptop connected to the a radio on the fire tower ran as Iperf server and the laptop connected to radio on clemson campus ran as Iperf Client.Observation: The long range line-of-sight link stayed connected for about 30° with a throughput insensitive to transmit power changes.

Iperf server

Iperf client

-90-85-80-75-70-65-60-55-50-45-40

-20 -10 0 10 20 30Horizontal Antenna Angle (Degrees)

Sign

al S

tren

gth

(dBm

)

0

4

8

12

16

20

Thro

ughp

ut (M

bps)

Signal Strength Throughput

-80

-75

-70

-65

-60

-55

-50

12 14 16 18 20 22 24Transmit Power (dBm)

Recei

ved S

ignal

Stren

th (dB

m)

Long range link:Throughput v.s. signal strength v.s.antenna direction

Long range link:Signal strength v.s.transmit power

Measurement setup

Measurement Studies of the Links

Forest Mesh LinksTwo Linksys routers with manufacturer default omni-directional antennas were placed in a wooded area with roughly uniformly grown trees.

It was found that the received signal strength decreased consistently with distance.Throughput remained steady for over 120 ft and had an unexpected rise afterwards before losing connectivity.Increasing transmit power did not increase the received signal strength and throughput in this environment.

20 40 60 80 100 120 140 160 180 2000

5

10

15

Thro

ughp

ut (M

bps)

20 40 60 80 100 120 140 160 180 200-100

-80

-60

-40

Router Distance (ft.)

Sign

al S

tren

gth

(dBm

)

26mW 50mW 70mW

Forest mesh link:Throughput v.s. signal strength v.s.distance in forest

Measurement Studies of the Links

Steerable Antenna LinksTwo Fidelity routers with phased array directional antennas

were placed 525 ft a part on an empty parking lot. The antenna beam width was configured to be 35 vertical and 43

horizontal. Starting from line of sight (0), one antenna rotated away in 22.5

steps until reaching 180 (facing away from the other antenna).

0 45 90 135 1800

10

20

Th

rou

ghp

ut

(Mb

ps)

0 45 90 135 1800

20

40

60

Antenna Orientation (Degrees from Line-of-Sight)

SN

R (

dB

)

10 dBm 4 dBm 2 dBm 1 dBm

Throughput v.s. signal strength v.s. antenna direction

The short range directional antenna link’s angular range of connection depended sensitively on transmit power.

Throughput was stable when connected but dropped steeply at the edge

Future Work

• Clemson Forest and Hunnicut networks ready for integration– Sensor packets pushed to server successfully (server

integration TBD)– Video camera to be installed in Clemson forest– Mesh routers ready for larger scale deployment

• Reliability and controllability are key concerns for a large scale sensing system– Further measurement studies to develop forest model for

studying wireless network performance and design– Further studies on assessment and control techniques for

wireless network performance and reliability– Further studies on developing large scale wireless network

management techniques and software

Acknowledgements

• Dan Schmiedt , CCIT Chief Network Engineer• Knight Cox, Clemson Forest Manager• CCIT Intelligent River Project Team• Clemson Public Services Activities Team• Cisco Systems Inc.