Use of a Software Simulator forModeling the ACTS Link

Roy Laurens

Parag Manihar

Ioannis Pavlidis

Satish Shetty Information Networking Institute

Carnegie Mellon University

ACTS Propagation Workshop

Oklahoma City, OK

October 22-23, 1998

Agenda

¥ CMU/NASA ACTS Experiment

¥ Network Simulator (ns)

¥ Error Modeling for the ACTS Link

¥ Data collection and analysis

¥ Conclusions and Future Research

Goals

¥ ACTS Error Modeling module for NS

¥ Performance analysis and Improvementof TCP behavior over ACTS

¥ Mobile IP performance over ACTS

CMU/NASA ACTS Experiment

LET

ACTS

EFData SDM9000 Comstream CM701

USAT

Comstream CM701 EFData SDM9000

Cisco 3640 Router Cisco 3640 Router

Cisco 1548Dual Speed Hub

NASA RouterCorrespondent

Node

100Mbps

RS449HSSI RS449 HSSI

Internet

NASA CMU45Mbps

6 Mbps

6 Mbps

45Mbps

Network BCMU ChaosNet

Network ANASA

FreeBSD Router

FreeBSD Router

Wean Hall

Hammershlag Hall

"Mobile Node"

Hub

Correspondent

Ethernet"Mobile Node" Ethernet

Network Simulator (ns)¥ Collaborative effort: USC/ISI, PARC,

LBNL & UCB

¥ Event based queue modeling

¥ Easily extendable modular framework

¥ Protocol definition and simulationconfiguration using scripting language

¥ Graphical tools for animation andconfiguration

ns Architecture

Traffic

Routing

Queues

Error Model

Application

Transport

Network

Link

Demux

Agent

Error modeling in ns

¥ Bit Error Rate

¥ Error inter-arrival time

0

2

4

6

8

10

12

14

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60

Time (sec.)

Fre

qu

ency

First Second Third Model

Experiment Data

¥ Eb/No, BER, Beacon Fade and TCP data

¥ Signal Degradation on a Rainy day

¥ Effect on the TCP tests performed

Fade data on Rainy Day from Beacon Signals at 20Ghz and 30Ghz

-35

-30

-25

-20

-15

-10

-5

0

10.00 10.50 11.00 11.50 12.00 12.50 13.00 13.50 14.00

Time (Hour of Day)

Fad

e L

evels

Co

mp

are

d t

o C

lear

Sky (

dB

)

TCP Test Near Fade Event

0.0E+00

1.0E+06

2.0E+06

3.0E+06

4.0E+06

5.0E+06

6.0E+06

7.0E+06

8.0E+06

9.0E+06

0 20 40 60 80 100 120 140

Time (seconds)

Receiv

er A

CK

Seq

Nu

ms

Simulation verification

¥ Modeling the Observed Link Conditions

¥ Model vs Observed Link Behavior

¥ Multiple Simulation Run Results

Multiple Simulation Run Results

0

2

4

6

8

10

12

14

16

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60

Time (sec.)

Fre

qu

en

cy

Conclusions

¥ BER and error inter-arrival time usedfor modeling

¥ NS : modular extendable tool formodeling propagation

¥ ACTS ns model can be used for researchof current and future protocols oversimilar links

Future Research

¥ ns in emulation mode

¥ Mapping of fade data and atmosphericconditions to predict expected Bit ErrorRate

Special Thanks

¥ Kul Bhasin

¥ Bob Bauer

¥ Mike Zernic

¥ Rich Reinhart

¥ Adesh Singhal

¥ ACTS Control Room Team at NASALewis