Mod 8 Flashcards
Advantages of Rubidium over Cesium
Lower cost, more compact, and more power efficient
Least accurate oscillator
Quartz
4 types of synchronization
Plesiochronous, mutual, master clock. master slave
Does not require synchronization, highly stable clock at each station
Plesiochronous
Requires all nodes to have their own clocks, but not as precise
Mutual
Average clock data is collected so all stations can operate off the same frequency
Mutual
Requires one node to be the master station
Master Clock
A small network can benefit from this sync method, does not scale well
Master Clock
This sync method has a single point of failure
Master Clock
Most reliable and robust synchronization, domino effect
Master-Slave
One node is the master station
Master Clock
Master Slave
Stable timing and synchronization are necessary for successful..
Multiplexing
The key to multiplexing is
Having more transmitting bandwidth than the total amount needed
2 types of multiplexing
Frequency Division Multiplexing
Time Division Multiplexing
Multiplexing technique uses modulation to create analog signals for each user
Frequency Division Multiplexing
In FDM, each distant end receiver has what kind of filter
Band Pass
Type of multiplexing used in telephone systems, LOS, and troposcatter
Frequency Division Multiplexing
Multiplexing method considered the round robin use of a frequency
Time Division Multiplexing
Subdivides the intelligence across a bandwidth, interleaves the smaller portion together when all transmitted
Time Division Multiplexing
In TDM, each bit of sampled intelligence is separated by..
Short period of time
In TDM, how can the original signal from the transmitter be received and understood
Multiplexer and de-multiplexer are synchronized, and individual samples are recombined quickly enough
Demultiplexing
The distant end multiplexer receives an aggregate signal and de-multiplexes all individual signals
Must be managed properly to prevent a delay or loss of data
Bandwidth
4 types of bandwidth allocations
Conventional
Demand assigned
Dynamic
Time of day restriction
Conventional
Fixed amount of bandwidth
Most predictable, least efficient
Inactive channels = wasted bandwidth
Demand Assigned
Individual bandwidth needs of the user, as needed basis
inactive channels = bandwidth for next user ( may not be enough, slow)
Example: Internet
Dynamic
Combined data rates exceeds total bandwidth
Only a problem if all users go online at the same time
Example: circuit breaker
What affects overall bandwidth
Protocols, transmission media, cables and connectors
EIA
Electronics Industries Association
Determine how computers communicate with each other
If the data travels beyond the minimum distance set by EIA, they will require a _________
Modem
Maintain integrity of the transmitted data by converting it to analog before transmission to prevent signal deterioration
Modem
Oldest EIA standard for serial com
EIA-232C
The military equivalent of EIA-232C
Military Standard 188C
Was created along side the EIA-232 standard, computer or user nodes on both sides of network
DTE
Created alongside the EIA-232, the modem on both sides of the network
DCE
DCE
Connects two DTE devices together using serial cables
Examples: CSU, DSU
EIA-530
Developed in response to the disadvantages of the EIA-449
25 pin D-type connector
eliminates slower data rates, shorter distances of EIA-232
Twisted pair
Balanced transmission
categorized by amount of data they transmit, categories ranges from
1-8
Coaxial Cable
Unbalanced Transmission
supports baseband or broadband
Baseband
Transmits one signal at a time
Broadband
Modulates different frequencies to transmit multiple signals simultaneously
Balanced Transmission
Carry two identical input signals 180 out of phase
Unbalanced transmissions
Carry signals on just one input/output while the second wire is grounded
Maximum distance of Fiber
2000 meters
Wireless
Major disadvantage is time delay
can be directional or omnidirectional
Satellite and troposcatter
Directional wireless
Line of sight
Directional or omnidirectional
DSU
Operates alongside a CSU or in the same device with the CSU
Manages interface with the DTE
Digital equivalent to an analog modem
CSU
Responsible for the connection to the telecommunications network
operates alongside the DSU
Digital equivalent to an analog modem
Digital Network Hierarchy
Logical sequence in building transmission rates in a network from one user into a TDM multiplexer up to multiple TDM multiplexers
Number of users on DS0
1
Number of users DS1
24
Number of users DS2
96
Number of users DS3
672
Number of users DS4
4032
TDM Hierarchy
How communications systems get larger and larger as the demand grows for more access
Multiple access
a satellites ability to multiplex signals from numerous terminals in a variety of ways
Which multiple access method has guard bands
FDMA
Spectrally inefficient for the satellites total capacity
FDMA
Advantageous to support connection oriented applications
FDMA
Spread spectrum technique that uses pseudorandom noise codes
CDMA
All terminals transmit at the same time, over the same frequency, however receiving looks for a specific coded waveform
CDMA
A 5ghz carrier is used
WCDMA
WCDMA uses wider frequency bands so it can…
Achieve higher throughput data transmission
200khz wide carrier for…
CDMA
Which multiple access method is synchronous
CDMA
Which multiple access method is asynchronous
WCDMA
Operates on a first come first serve, as needed
DAMA
The frequency is returned to a pool to be used by the next user
DAMA
4Ghz-8Ghz
C band
8ghz - 12ghz
X band
12-18ghz
Ku band
18ghz- 27ghz
K band
27ghz-40ghz
Ka band
Longer wavelength and often larger parabolic dishes
C band
Highly resistant to rain fade
C band
Examples of C band uses
Weather radars, Wifi 802.11a, TV networks, some radio networks in the 5ghz range
Primarily used in military applications
X band
Example uses of X band
civil, military, and government weather radars, air traffic control, vehicle speed detection
Can be affected by rain fade, requires more precise pointing
Ku band
Examples of Ku band uses
Digital TV, radio astronomy, radio navigation, and commercial aircraft
Not useful for long distance, high atmospheric attenuation
K band
very short wavelength, inclement weather causes significant reliability issues
Ka band
the 3 segments of satellite comms
Space
Command and control
Terminal
5 subsystems of satellites
Power
propulsion
tt and C
Beacon
Communications
3 controls of satellites
Spacecraft
Payload
Network
Space Segment
Comprised of the space vehicles that carry satellite communication payloads
Satellites
Diverse and complex pieces of equipment, performs a specific function for a specific length of time
Propulsion
perform periodic position changes, aid in stabilizing a satellite against atmospheric drag
TT & C subsystem
Enables controllers on the ground to monitor the spacecraft and its subsystems
Can execute commands sent from the control segment
TT & C
Beacon Subsystem
Enables the control segment to determine a spacecrafts position in space
Allows the satellite to send radio signals between terminals or between other satellites
Communications Subsystem
Transponder
Equipped on satellites
receives a signal and retransmits it, changes the frequency the send back
The signals sent by the transponder are known as
Downlink and uplink frequencies
Command and control Segment
Systems on the ground that send commands to and from the satellite
responsible for overall system operation of spacecraft, payload, and communications network control
Command and control Segment
Facilitates the sending and receiving of commands and data from ground stations
TT&C
Spacecraft control
The stabilization, maneuvering, repositioning and proper functioning of systems onboard spacecraft
Payload Control
Operation and control of the payload on spacecraft
The primary reason a spacecraft is in orbit
Payload
Refers to the inter workings of the spacecraft
Payload control
Network Control
Encompasses satellite control and monitoring stations
Terminal Segment
The personnel, equipment, and facilities that use the capabilities provided by the satellite
Defense satellite Communications System
(DSCS)
provides a reliable, high capacity, quality comm in support of peacetime, contingency, and wartime operations . Specifically high availability
DoD manages satellites from directions of..
DISA
How many channels does DSCS have?
6
DSCS channels 1-5 have what translation frequency?
725MHz
DSCS channel 6 has what translation frequency
200MHz
Guard bands
Prevent interference, spaced 25MHz apart
DSCS operate at which band?
X band
What is the beacon frequency of DSCS
7600 MHz
Wideband Global Satellite (WGS)
Fall under DSCS, slowly replacing DSCS
No fixed translation frequencies
Cross band frequencies
What bands does WGS operate in?
X band and KA band
Military Strategic and tactical relay (MILSTAR)
Operated by US Air Force
Secure and Jam resistant
10 year design life
Crosslinks between MILSTARs
allow worldwide comm without the use of multihop ground stations, providing increased anti jam capability
MILSTAR provides anti scintillation, which is
protection from EMP effects of a nucelar explosion
enables SATCOM systems to overcome jamming attacks, combination of TRANSEC, modulation and interleaving techniques that hop, permute and spread comms over usable bandwidth
Advanced Extremely High Frequency (AEHF)
JOINT SERVICE
Provides surviable, global, secure, protected, and jam resistant comms
Follow on system to the MILSTAR
AEHF
Throughput is 10 times higher than MILSTAR
How many satellites is AEHF
6
provides 24 hour coverage between 65 degrees south and 65 degrees north Latitude
AEHF
Mobile User Objective System (MUOS)
Developed for the Navy
UHF
IP based
will provide 16 times the capacity of legacy
Each MUOS satellite has how many payloads
2
Supports both WCDMA and legacy UHF
MUOS
Soon to be operational
MUOS
How many satellites are configured for MUOS
4 orbiting and 4 relay ground stations
Commercial operates in which bands
C band and Ku Band
GPS is owned by _______ and operated by _____________
United states government, Airforce
Air Force Satellite Control Network (AFSCN)
Provides support for the operation, control, and maintenance of a variety of US DoD and some non DoD satellites
Maintains the catalog of space objects and distributes various data, almanacs
AFSCN
