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Golden Gate Club Connectivity

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Studies of Wireless Networks with Realistic Physical Layer Emulation:

The ORBIT Test-Bed Facility

Funded by NSF NRT project #ANI-0335244 and DARPA IPTO

Rutgers, The State University of New Jersey

www.winlab.rutgers.eduContact: Prof. D. Raychaudhuri

ray@winlab.rutgers.edu

PnP Networkswww.pnphome.com

Contact: Richard E. Howardreh@pnphome.com

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Modeling Wireless Networks:The Radio Problem Ethernet Modeling:

All nodes in a subnet receive all packets Low error rate Emphasis on collision, routing, congestion, ...

Wireless Network Modeling Packet reception depends on complex, changing RF conditions

Hidden nodes and range of link qualities Hard to model—non-local, sensitive dependence on environment

Computationally intractable—”Hall of Mirrors” Extra control “knobs”—transmit power, channel, packet length, ... High error rates under the best conditions

Conventional network modeling must be done after getting RF right.

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Blocked Mission Traffic--Weighted Fraction (BloMiT-WeFra)

100%

10%

1%

0. 1%

Mission Time (mtime)

Blo

MiT

-WeFr

a

H-H

our

100

MPU

add

ed in

Sec

tor

C —

loca

l ove

rloa

d

Reconfigure network, power/rate management, delay low priority data.

200

MPU

leav

e Se

ctor

M

—lo

cal c

apac

ity

exce

ss

Reconfigure network, power/rate management, send buffered data.

Loca

lized

bur

sty

radi

o

inte

rfer

ence Adjust fragmentation

threshold, manage power/data rate.

Waterloo

MidwayA1 B

A2

C2

C

B

A

100

MPU

add

ed in

Sec

tor

C —

loca

l ove

rloa

dLo

caliz

ed b

urst

y ra

dio

inte

rfer

ence

C1

Legend

Cognitive control (CogCon)Static configuration (SOA)

Perfect control

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ORBIT: Testbed Overview ORBIT consists of radio grid emulator + field trial network Emulator used for detailed protocol evaluations in reproducible complex radio

environments Field trial network for further real-world evaluation & application trials

Mobile node(robotic control)

Static radio node

Radio link emulation

1. Radio Grid for Lab Emulation

Dual-mode Radio device

2. Field Trial Network

“Open” APIAccess Point(802.11b)

End-user devices

Ad-hoclink

3Gaccess

link

HighSpeed

Net

Firewall

MobilityServer

Wiredrouters

EmulatorMapping

“Open” API

3G BTS

Global Internet Global Internet

ns-2+ scripts &

code downloads

ResearchUser of Testbed

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ORBIT: Testbed Facilities Simulation (Cluster)

Compute facility to run simulations (NS) Create extensions to ns-2 PHY modules for improved realism and cross-layer

Emulation Grid 802.11a radio nodes (~20x20 @ 1m spacing) Mapping of various “typical” wireless net scenarios Open API for complete flexibility of OS/protocol software; Linux libraries

Field Trial System Outdoor system for greater realism in protocol testing & for application

development, live demos, etc. 3G base station router with IP interface ~50 open API 802.11a AP’s covering RU NB campus, some downtown

areas… Mobile AP’s on buses, etc.

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ORBIT: Physical Facilities

•~12,000 sq ft (Grid + Lab. space + Offices)

•Rt 1 South @ Technology Center of NJ

•“Move in” late 2004

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ORBIT: Radio Grid Scenarios

Use programmable, controlled interference in a physically small environment. An n x m array of identical radios on grid. A secondary array of programmable interferers

Mapping algorithm which matches “real-world” SNR vectors to selected nodes on grid, using some nodes as interferers

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ORBIT: Field Trial System

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Interference Measurements Using ORBIT Testbed

1,4 1,3 1,2 1,1

2,4 2,3 2,2 2,1

~3m~4m

~5m

~1m ~1.5m

Link Nodes

Interfering Nodes

Walls

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0 1 2 3 4 5

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1 256 B; 1.0 Mb/sec 512 B; 1.9 Mb/sec 768 B; 2.9 Mb/sec1024 B; 3.9 Mb/sec1280 B; 4.8 Mb/sec

Packet Loss as a Function of Channel SpacingFor Different Packet Payload Sizes

Channel Spacing from Interferer

Fra

ctio

n o

f D

rop

ped

Pac

kets

PnP-20040524 One sender, 1 receiver, 3 interferers1 microsecond packet spacing set

Packet Payload; Offered Load

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0 1 2 3 4 5

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Packet Loss as a Function of Channel SpacingFor Different Packet Sizes at 1/3 Lower Rate

Fra

ctio

n o

f D

rop

ped

Pac

kets

Channel Spacing from Interferer

PnP-20040526 One sender, 1 receiver, 3 interferers100 microsecond packet spacing set, 1 mW

256 B; 0.67 Mb/sec 512 B; 1.35 Mb/sec 768 B; 2.0 Mb/sec1024 B; 2.7 Mb/sec1280 B; 3.4 Mb/sec

Packet Payload; Offered Load

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0 0.5 1 1.5 2 2.5 3 3.50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

PnP-20040526 One sender, 1 receiver, 3 interferers

Packet Loss as a Function of ThroughputFor Different Channel Spacings

Net Throughput (Mb/sec)

Fra

ctio

n o

f D

rop

ped

Pac

kets Same

12345

Channel Spacing

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High Power Increases Channel Overlap

0 1 2 3 4 5 6 7 8 9 1mW

10mW

50 mW0.001

0.01

0.1

1

10

100

Packet Loss %

Channel Separation

Packet Loss % at 4 MbpsFar

FN

FN

Sending Nodes

Receiving Nodes

Near

Far

0 1 2 3 4 5 6 7 8 9 1mW

10mW

50 mW0.001

0.01

0.1

1

10

100

Packet Loss %

Channel Separation

Packet Loss % at 4 MbpsNear

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Optimizing Wireless Networks

Ch 1

Ch 2

Ch 10

Ch 5

Video

Data

Net A

Net B

Adjacent Channel Interference Both networks have reduced capacity

Partition Network Based on Application Requirements

Requires Knowledge of Application Behavior

Greatest Improvement

Video subnet optimized for QOS

FN

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Network States (Measured)

StateBloMIt-WeFr

RateTraffic Rate

(kb/sec)

1 One pair of nodes communicating 0.00 1,350

2 Add 3 pairs of nodes with similar traffic on nearby channel 0.40 3,240

3 Change new nodes to same channel as original 0.08 4,960

4 Three nodes leave and traffic rate increased for single link 0.00 2,700

5Add 3 pairs of nodes with similar traffic on adjacent channel, higher

data rate and longer packets than state (2) 0.89 1,224

6 Change new nodes to same channel as original 0.40 6,480

7Change new nodes to channel 6 as it becomes available (other

nodes leave). 0.22 8,380

8 Same as state (7) with command traffic switched to channel 1 link 0.07 8,380

9Three nodes leave and traffic rate increased again for single link by

shortening time between packets. 0.00 3,830

10 Add 3 pairs of nodes with similar traffic on adjacent channel 0.98 260

11Change new nodes to channel 6 as it becomes available (other

nodes leave). 0.38 9,400

12 Same as state (11) with command traffic moved to channel 1 link 0.14 9,400

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Integrated Mission IT Metrics--Static Path Through Mission

Integrated BloMIt-WeFr Static Network

0

500

1000

1500

2000

0 1000 2000 3000

Mission Time (sec)

Integrated Mission Traffic (GB) Static Network

0

24

6

8

1012

14

16

0 500 1000 1500 2000 2500

Mission Time (sec)

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Integrated Mission IT Metrics--Optimized Path Through Mission

Integrated BloMIt-WeFr Optimized

0

20

40

60

80

100

120

140

160

180

200

0 500 1000 1500 2000 2500

Mission Time (sec)

Integrated Mission Traffic (GB) Optimized

0

10

20

30

40

50

60

70

0 500 1000 1500 2000 2500

Mission Time (sec)

Improvement potential for this mission profile

BloMiT-WeFr: 1,578 => 182

Mission Traffic: 14 GB => 62 GB

Note: This is wireless link-layer characterization only. Guaranteed delivery protocol (e.g. TCP) would add “thrashing” and increase the difference.