Day 2: Sat Networks Flashcards
System of communication satellites in space to facilitate various forms of communication (voice, data, video)
Satellite Networks
What are the four applications of satellite networks?
- Telecommunications
- Broadcasting
- Internet
- GPS
Relies on stationary ground equipment at predetermined locations; point-to-point and point-to-multipoint comms (ex=VSATS)
Fixed Satellite Service (FSS)
Distribution of TV, radio, etc via satellite to a wide audience (fan-out); stands out for high transmission power
Broadcasting Satellite Service/Direct Broadcast Service (BSS/DBS)
Employs transportable receiver and transmitter equipment; provides voice, data, and messaging services to land, maritime, remote environments
Mobile Satellite Services (MSS)
Fixed Satellite Service (FSS) Common Bands
C, Ku, Ka
Broadcasting Satellite Service/Direct Broadcast Service (BSS/DBS) Common Bands
C, Ku, Ka
Mobile Satellite Services (MSS) Common Bands
L, S, C
VSAT stands for?
Very Small Aperture Terminal
VSATs utilize ______ dish antennas to transmit and receive data via satellite
Small
Enables _______ comms between ______ _________ and a _______ ___, typically located at a network operations center or data center
two-way
remote locations
central hub
What kind of solution is for connecting remote locations to broader comm infrastructure?
Versatile and reliable
What are VSAT applications?
- Internet
- Telecomms
- Broadcasting
- Military
Biggest advantages of VSAT
Easy to install and inexpensive to operate
VSAT Common Bands
C, Ku, Ka
Wider coverage (suitable for global comms); less signal degradation due to rain/atmosphere
C-Band Advantage
Limited BW availability compared to higher frequency bands, lower data transmission rates
C-Band Disadvantage
Higher data transmission rates compared to C, so suitable for higher BW applications
Ku-Band Advantage
More susceptible to rain attenuation, smaller coverage area because more susceptible to atm absorption
Ku-Band Disadvantage
Higher bandwidth, enabling very high data transmission rates; allows for the use of smaller antennas, making it more suitable for mobile and broadband applications
Ka-Band Advantage
Highly susceptible to rain attenuation, and easily absorbed by atmospheric gases, limiting their effective range and coverage area
Ka-Band Disadvantage
What are the 4 segments of VSAT network?
- Ground Station
- RF Links
- Satellite
- Users
Requires constant communication with VSAT ground station to pass data between nodes and cannot communicate directly with other nodes
Star
Nodes can communicate directly with other nodes within the VSAT network but still require a master control station to ensure timing and access to the network is maintained
Mesh
Mix of star and mesh that allows the hub to send information to the remote components
Hybrid
What is AUPC?
Automatic Uplink Power Control
What is the first step of Automatic Uplink Power Control (AUPC)?
Remote station receives signal and demodulates
What is the second and third step of Automatic Uplink Power Control (AUPC)?
Remote station demodulator identifies Eb/No beyond lower threshold, and
Requests an increase in power using reserved bytes in overhead structure
What is the fourth step of Automatic Uplink Power Control (AUPC)?
Local MODEM adjusts output power level to attempt to maintain the Eb/No at the remote MODEM
What is the ALC?
Automatic Leveling Control
What does the Automatic Leveling Control (ALC) do?
Automatically changes the power in the individual channels on the transponder in the channelizer to overcome interference
When the receive signal level drops below a certain SNR, the individual downlink or uplink subchannel will boost power
Automatic Leveling Control (ALC)
If the power is too high, what will lower the power to meet the average SNR threshold?
Automatic Leveling Control (ALC)
What is the ACM?
Adaptive Code Modulation
When the signal reaches the receiving modem and drops below a certain threshold, the receiving modem will send a burst to the transmitting modem to change to a more robust MODCOD to mitigate interference
Adaptive Code Modulation (ACM)
What is MODCOD?
- Mod - Modulation Scheme
- COD - FEC