Enabling Broadband Data Access for the Digital Watershed with Heterogeneous Wireless Networks

Gayatri Venkatesh, Graduate Student, Electrical and Computer Engineering, Clemson UniversityK.-C. Wang, Assistant Professor, Electrical and Computer Engineering , Clemson University

Christopher Post, Assistant Professor, Forestry and Natural Resources , Clemson University

A Broadband Network Connecting the Digital WatershedsChallenges Reside at the Edge – The Wireless Networks

In the Woods

AT&T Data

Coverage

Along the River

Over Woods & Hills

To

campus

In Woods & Ditches

To

campus

The Intelligent RiverTM

Cyberinfrastructure

Challenges and Objectives

• Wireless networking challenges

• Foliage: Deep woods impede wireless communication range

• Remote: Lack of cellular coverage

• Terrains: Hills create absolute blockage for long distance links

• Costs: Cellular/satellite links incur recurring cost for limited bandwidth

• Our research objectives

• To develop a methodology for building wireless network infrastructure for current and future Intelligent RiverTM sites

• The solution will

• provide adequate and reliable bandwidth to all sensors

• economically scale to a large area

Wireless around the Woods: State of the Art

• Great Duck Islands – UC Berkeley• Monitors bird nest microclimate• Wireless sensor “patches” + base station + satellite

• Redwood Macroscope – UC Berkeley• Monitors microclimate at different heights• Wireless sensor “chain” + base station (line of sight)

• Costa Rica Rainforest Station – UCLA• Monitors above-ground below-canopy climate• Wireless sensors + slide links between high towers

• Quail Ridge Reserve – UC Davis• Long range Wi-Fi + high towers with solar power

• HPWREN Res. and Edu. Network – UCSD• Very broadband wireless links over desert terrains

covering large parts of southern California

Our Unique Challenges and Strategies• Diverse sensing site characteristics

• Challenge• Site characteristics change from river source to estuary

• Optimal solution cannot be one-size-fit-all

• Strategy• Study multiple technologies performance-cost tradeoff

• Pushing sensors “deeper” into the woods• Challenge

• Taming the forest rather than avoiding it

• Strategy• Quantify forest impact on wireless networks

• Exploring network reliability and controllability• Challenge

• Forest network condition changes over time

• Strategy• Identify control knobs for tuning forest wireless networks

Background: Wireless Mesh Networks

• Wireless mesh networks are widely deployed today• Metropolitan mesh networks: Firetide, Motorola, Cisco, etc.

• Open/research mesh networks: MIT Roofnet, Houston TFA, Seattle wireless, etc.

• A wireless mesh network is composed of• Distributed base stations forming wireless network mesh covering a large area

• Distributed portable/mobile terminals connecting to a nearest base station

• Wireless mesh networks are known to• (+) Be a fast and economical solution for wide area coverage

• (+) Be a robust fault-tolerant solution for changing environments

• (!!) Have variable link rate at different location and time

• (!!) Need bandwidth provisioning to assure sufficient capacity

A Forest Mesh Network Architecture

Long range transit link

In-forest mesh link

Sensor mesh linkInternet

Cyberinfrastructure

Fiber optic

network

Wireless sensor

Mesh router

Transit gateway

Clemson Forest and Hunnicut Creek

• Two network testbeds for demonstration and characterization

1. Clemson Forest/Lake Issaqueena Reservoir

• 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

2. 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

325 m

240 m

160 m

325 m

240 m

160 m

4 miles

1 mile

4 miles

1 mile

Clemson Forest

Network

Hunnicut Creek

Network

sensor

cluster

transit

gateway

Internet

gateway

Long range Wi-Fi

over forest hill

• Cisco 1310

• IEEE 802.11b/g

• 2.4GHz band

• 21 dBi dish antenna

• Data rate: TBD

Long range Wi-Fi

over downtown

• Cisco 1410

• IEEE 802.11a

• 5GHz band

• 21 dBi dish antenna

• Data rate: 16 Mbps

Long range Wi-Fi

Steerable

• Fidelity Phocus

• IEEE 802.11b/g

• 2.4 GHz band

• steerable 22.5

• Data rate: 12 Mbps

Wi-Fi across woods

• Linksys WRT54G

• IEEE 802.11b/g

• 2.4 GHz band• Data rate: 2 Mbps

Wi-Fi into ditch

• Linksys WRT54G

• IEEE 802.11b/g

• 2.4 GHz band• Data rate: 5 Mbps

Long Distance Transit Links

• Links must overcome distance, foliage, and hills

• Radio placement on high structure to get line-of-sight

• Directional antenna and power amplifiers

• Available control parameters

• Radio transmission power

• Antenna type (gain) and direction

• Layer 2 and 3 protocol parameters

Server side gatewayRelay gatewaysSensor side gateway

Forest

Mesh

NetworkIEEE

802.11b/g

IEEE

802.11a

Ethernet

Clemson Forest Sensor Network• The Spring 2008 ECE 453

senior capstone project

• Undergraduate seniors

• inflow, outflow, temperature sensors

• Wireles sensors, relays, cellular modems

Zigbee

ZigbeeZigbee

Zigbee

Zigbee

Zigbee

ZigbeeZigbee

AT&T

cellular

Sensor

Cluster

Data

Outflow

pressure sensor

Inflow

aquarod

Temperature

sensor

Broadband Forest Mesh Network

In Summer 2008• Evolved the senior project network to larger scope and bandwidth with

distributed sensor clusters and broadband mesh backbone• Evaluated control parameters: radio power, direction, foliage blockage

Sensor

Cluster

Sensor

Cluster

Sensor

Cluster

Sensor

Cluster

Sensor

Cluster

Lake

Issaqueena

Sensor

Cluster

Sensor

Cluster

Wi-Fi mesh

routers in forest

Wi-Fi linkZigbee link

* If router has steerable

directional antenna

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

• Current price is high as technology just released from military; expected future price reduction as it gain popularity

Sensor

Cluster

Sensor

Cluster

Sensor

Cluster

Sensor

Cluster

Sensor

Cluster1

2

3

4

5

Measurement Studies of the Links

• Long range links: throughput v.s. direction and power

• Forest mesh links: throughput v.s. tree obstruction distance and power

• Steerable antenna links: throughput v.s. antenna alignment and power

• Study leveraged help from SC Governor School summer interns

• Study results published at ACM Wintech 2008 poster session

-90

-85

-80

-75

-70

-65

-60

-55

-50

-45

-40

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

Sig

na

l S

tren

gth

(d

Bm

)

0

4

8

12

16

20

Th

rou

gh

pu

t (M

bp

s)

Signal Strength Throughput

-80

-75

-70

-65

-60

-55

-50

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

Receiv

ed

Sig

nal

Str

en

th (

dB

m)

0 45 90 135 1800

10

20

Th

ro

ug

hp

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

20 40 60 80 100 120 140 160 180 2000

5

10

15

Th

rou

gh

pu

t (M

bp

s)

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

-80

-60

-40

Router Distance (ft.)S

ign

al

Str

en

gth

(d

Bm

)

26mW 50mW 70mW

Long range link:

Throughput v.s.

signal strength v.s.

antenna direction

Long range link:

Signal strength v.s.

transmit power

Forest mesh link:

Throughput v.s.

signal strength v.s.

distance in forest

Steerable link:

Throughput v.s.

signal strength v.s.

antenna direction

Summary

• Completed building Clemson Forest and Hunnicut networks

• Support sensor data reporting and video camera streaming

• 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 wireless model for studying wireless network performance and design

• Further studies on assessment and control techniques for wireless network performance and reliability

• Further studies on large scale wireless network managementtechniques and software

Can’t Do All This Without Them

Dan Schmiedt

CCIT Chief Network Engineer

Gayatri Venkatesh

ECE Grad StudentKnight Cox

Clemson Forest Manager

Sam, Forestry Grad Student

Larry, CCIT

Mike ECE Grad Student