University of Kansas Multi-Link Iridium Satellite Data Communication System Overview, Performance and Reliability from Summer 2004 SUMMIT, Greenland Field Experiments July 14-July 25, 2004 Abdul Jabbar Mohammad, Said Zaghloul, Graduate Research Assistants Dr.Victor Frost, Dan F. Servey Distinguished Professor (August 22, 2003)
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Multi-Link Iridium Satellite Data Communication System
Multi-Link Iridium Satellite Data Communication System. Overview, Performance and Reliability from Summer 2004 SUMMIT , Greenland Field Experiments July 14-July 25, 2004 Abdul Jabbar Mohammad, Said Zaghloul, Graduate Research Assistants Dr.Victor Frost, Dan F. Servey Distinguished Professor - PowerPoint PPT Presentation
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University of Kansas
Multi-Link Iridium Satellite Data Communication System
Overview, Performance and Reliability from Summer 2004 SUMMIT, Greenland Field Experiments
July 14-July 25, 2004
Abdul Jabbar Mohammad, Said Zaghloul, Graduate Research Assistants
Dr.Victor Frost, Dan F. Servey Distinguished Professor
(August 22, 2003)
University of Kansas2
Presentation Outline
Previous Work 4-Channel System
Conclusions from 2003 Field Experiments
8-Channel Iridium System Design
Integrated Unit
GUI Software
Analysis
Network Architecture
2004 Field Experiments Field Implementation
Results
Conclusions and Future Work
University of Kansas3
4-Channel Iridium System (Tested in Summer
2003)
Iridium Gateway
PSTN
US
B-
SE
RIA
L I. Modem 3
I. Modem 4
I. Modem 2
I. Modem 1 An
ten
na
G
ridM
ulti-
po
rt PC
I ca
rd
Remote System
PPP client
Local System
PPP Server
Modem Pool
Remote Subsystem
Local Subsystem
4 Iridium – 4 PSTN data configuration
Discrete components
Patch antennas
Control software on a rugged Laptop
University of Kansas4
Conclusions from 2003 field experiments
Developed a reliable multi-channel data communication system based on Iridium satellites
that provide round the clock, pole-to-pole coverage.
Developed console based link management software that ensures fully autonomous and
reliable operation
An end-to-end network architecture providing Internet access to science expeditions in
Polar Regions was demonstrated.
The system efficiency was observed to be >90%. With 4-modems the average end-to-end
throughput was found to be 9.26 Kbps
The round trip time of the system in Iridium-PSTN configuration was significant ~1.8 sec
The average up-time of the overall connection was approx 90%. The average time interval
between primary call drops was 100 minutes
Mobile tests showed performance very similar to that of stationary system up to speeds of
20mph
4-Iridium to 4-PSTN configuration was found to be stable of autonomous operation
University of Kansas5
The USB-to-serial converter used for multiple serial ports was not stable
resulting in system failures.
Interaction of PPP level compression with control software results in corrupted
modem termination, resulting in significant packet loss
Identified areas for additional research
Evaluate the new data-after-voice (DAV) service from Iridium
Improve the user friendliness of the system
Research into the spacing and sharing of antennas to reduce the antenna footprint
Increase the the system capacity by scaling the system from 4 to 8 channels
Develop a fully integrated plug and play system that can be deployed easily in the field
Conclusions from 2003 field experiments
University of Kansas6
8-channel Iridium System – Design Elements
Integrated 8 Iridium modems and all the components in an 19” rack mount unit.
On-board computer to run the control software
Single board EBX format system ( P-III, 1 GHz, 512 MB RAM)
Extended temperature operation (-300 C to + 800 C )
PC104 type multi-port serial card with 8 DB9 ports (extended temp
operation)
Integrated 5”x4” LCD screen, front panel flips down to hold the keyboard/mouse
Single linear power supply for the 8 modems and on-board computer
Developed a new GUI based management/control software, that configures the
unit in all the data modes: a) Iridium-Iridium DAV mode, b) Iridium-Iridium data
mode, c) Iridium-PSTN mode
Replaced the patch antennas with inverted cone antennas that can be easily
mounted on field and do not need a external ground plane.
University of Kansas7
8-channel Iridium System – Integrated Unit
9”
19”
24”
Bottom View Top View
Front View
Dimension : 9x19x24 inch
Weight : 50 lbs
Operating temp : -30 to 60
c
Power input : 120 V
AC
Replication Costs :
~$18,000
University of Kansas8
8-channel Iridium System – Client Software
Client Software consists of three modules:
Graphical User Interface
Easy Configuration and Operation
Does not require experienced users
Control Software
It is the core of the software
Automatic Modem Control
XML Database
Registers all call drops and retrials
Makes it possible for future analysis of
network performance data
University of Kansas9
8-channel Iridium System – Client GUI
University of Kansas10
8-channel Iridium System – Client GUI
University of Kansas11
8-channel Iridium System – Analysis
App
Agent
8 Modem Links
MLPPP MLPPP
Iridium Network
System Model
Application: FTP, HTTP
Agent: TCP, UDP
MLPPP
8 Modem Links
Modems Model
Each link has a dropping probability
Each link has a probability of error
App
Agent
Machine A Machine B
HTTP
FTP
TCP
UDP
University of Kansas12
8-channel Iridium System –Network Architecture
SUMMIT Camp, Greenland
ITTC Network, University of Kansas
World Wide Web
User 2
User 3
User 1
ppp0 eth0
PPP Server
ppp0 eth0
PPP Client
P-T-P Satellite link
ITTC Default Router
(Default gateway)(Default gateway) user 4
user 3
user 2user 1
Camp WI-FI
100 Mbps Ethernet
100 Mbps Ethernet
University of Kansas13
Field Experiments – System Implementation
8-Channel system in a weather-port at
SUMMIT camp in Greenland, July 2004
University of Kansas14
Field Experiments – Antenna Setup
4 ft
10 ft
8 Antenna setup at SUMMIT camp in Greenland, July 2004
University of Kansas15
Results – Throughput
Variation of throughput with number of modems
2.49
4.97
6.93
8.98
12.08
13.90
16.43
18.60
02468
101214161820
1 2 3 4 5 6 7 8Number of modems
Thr
ough
put (
Kbp
s)
Average throughput efficiency was observed to be 95%
The above results are from the test cases where no call drops were experienced
In event of call drops the effective throughput of the system will be less than the above values
University of Kansas16
Results – Throughput
Size of file in MB Approx. Upload Time Effective Throughput in Kbps
1.38 0:11:24 16.53
3.77 0:35:42 14.42
5.62 0:46:12 16.61
15.52 2:30:00 14.12
20.6 3:00:00 15.62
35.7 5:15:00 15.47
55.23 9:00:00 13.96
FTP throughput observed during data transfer between the field camp and KU
Average throughput during the FTP upload of large files was observed to be 15.38 Kbps
Due to call drops, the efficiency was reduced to ~80%
Detailed TCP analysis based on IPERF and FTP data is in progress