Communication Subsystem
Introduction
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Hardware
Protocol Description
Interface
Examples
Test
Link Budget
Conclusion
Table of Contents
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Hardware
Protocol Description
Interface
Examples
Test
Link Budget
Conclusion
Hardware
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OSSS
Vital Part
Testing
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MIL-STD-1540
Power Interface?
Specifications
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Frequency: 430-450 MHz
Bitrate: 9600 baud
Voltage: 3.3-5 V and 7.5-12 V
Power output: 2W@9.6V
Current Drain:
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Transmitting: 940mA@2W
Receiving: 60mA
Mass: 100 g
Interface
D0:7
D0:7
Data Bus
A0:1
A0:1
Address Bus
A2:7
C
Address Decode
Circuit
A2:7
MODEM
IRQ
IRQ
WR
WR
RD
RD
Ground Station
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Modem from OSSS
No Final Solution
Yagi Antenna  16 dB gain
NOVA Rotor Control
Price  10.000 - 20.000 Kr.
Brian Lodahl from KOM
Table of Contents
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Hardware
Protocol Description
Interface
Examples
Test
Link Budget
Conclusion
Requirements
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Flawless Link
Support Call-names
Pause / Resume
Prioritizing
Channels
Half Duplex
Layer Structure
OSI Layers
Ground Station
Satellite
Application
A1..An
A1..An
T55X
T55X
Data Link
AX.25
AX.25
Physical
Radio
Radio
Presentation
Session
Transport
Network
AX.25
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Error Detection
Supports Call-names
Supports Half Duplex
Connections
Widely Used
Well Documented
T55X Structure
Channels
T55X
Transport
Controller
De-Multiplexer
T55X Transport Layer
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Channels
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Priorities
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16 Channels
Fixed Priorities
Pause / Resume
Example
Application
Data-A
Channel 2
Channel 1
Scheduler
De-Mul
Channel 1
Channel 2
Packet-A1
Packet-A1
Packet-A1
Data-B
Packet-A2
Packet-B1
Packet-B1
Packet-B1
Data-B
Packet-A2
Packet-A2
Data-A
Application
Table of Contents
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Hardware
Protocol Description
Interface
Examples
Test
Link Budget
Conclusion
Interface
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Callback Functions
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Receive Data
Receive Events / Beacon
Send Connection Less Data
Send Data
Connect / Disconnect
Complete API on WWW
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www.control.auc.dk/~01gr555/api/
Table of Contents
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Hardware
Protocol Description
Interface
Examples
Test
Link Budget
Conclusion
Start Communication
Satellite:
while(true) do
sendConLess(housekeeping)
sleep(rtt+ct)
if status=CONNECTED then break
sleep(30 s)
Ground Station:
SetupCall-back(handleEvent(type, data))
handleEvent(type,data) {
If type=DATA_RECEIVED then
store(data)
connect
}
Sequence Chart
Ground
protocol
Ground
applications
Satellite
protocol
Satellite
applications
sendConLess
Lost in space
getStatus
30 sec
sendConLess
handleEvent
connect
getStatus
Send/Receive
Ground Station:
Start:
createChannel(8,receiveImage)
createChannel(2,commandChannel)
Main:
.......
sendData(2,Take Picture)
........
Callback:
receiveImage(data){
Save(data)
sendEventToAdmin(Received Image)
}
Send/Receive
Satellite:
Start:
createChannel(8,imageChannel)
createChannel(2,receiveCommand)
Callback:
receiveCommand(data){
if data=’take image’ then
takeImage
sendData(8,image)
}
Time Synchronization
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Several Solutions
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Connection Less
Channel With Estimation
No Requirements Yet
Table of Contents
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Hardware
Protocol Description
Interface
Examples
Test
Link Budget
Conclusion
Modelling and Verification
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Why?
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What:
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Short Implementation Test Time
New Protocol
Satellite
SDL Modelling
Exhaustive Testing
Code Generation
Tools:
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ObjectGeode
Table of Contents
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Hardware
Protocol Description
Interface
Examples
Test
Link Budget
Conclusion
Link Budget
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Link Budget equation or Ebno
Eb
G
d
f
b
 EIRP  196,15  20 log(
)  20 log(
)  10 log(
)[dB]
No
T
1Km
1MHz
1Hz
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EIRP:
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(Equivalent Isotropically Radiated Power)
G/T:
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EIRP  Pt  Gt
G
251K
 16 dB  10  log(
) dB  8dB
T
1K
Quality factor of receiver
Link Budget
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Max distance to satellite
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Using Pythagoras:
d
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(Re h) 2  Re 2
6002  2  600 6378  2830
Inserting into the equation
Eb
 0dB  8dB  196.15dB  69.0dB  52.7dB  39.8dB  26.7dB
No
Effective Throughput
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I frame size: 24 - 276 bytes
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23 bytes overhead
S frame size: 19 bytes
Effective Throughput
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Data:
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Beacon:
(I frame  S frame - Data) 276  19  253
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 16,6%
Data
253
(UI frame - Data) 275  253
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 8,7%
Data
253
Table of Contents
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Hardware
Protocol Description
Interface
Examples
Test
Link Budget
Conclusion
Conclusion
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Work So Far:
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Analysis / Design / Modelling / API
Hardware
To Do:
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Implementation
Verification / Test
Purchase from OSSS
Ground Station