System 3 DATA LINK Flashcards
How many epochs are in day?
112.5 epochs
How long is an epoch?
12.8 minutes
How many frames in an epoch?
64 frames in an epoch
How long is a frame?
12 sec or 1536 time slots
How many time slots are there per second?
128 time slots
How long is a time slot (msec)?
7.8125 msec
How many simultaneous nets can link 16 support
127 simultaneous nets
What frequency range does link 16 operate in
960 MHz to 1215 MHz
List 3 items for Link 16 frequency agility (frequency hopping)
- Hops between 51 freqs spaced 3 MHz apart
- Hop rate in excess of 70,000 hops per sec
- Hop pattern based on net number
- Avoids IFF freqs 1030 & 1090 MHz
What Security and Interference Protection Features does link 16 have?
Security:
- Error Detection And Correction (EDAC): Helps protect info from being corrupted by jamming or interference
- Pseudorandom Noise: The transmission signal is masked with noise within the Link 16 signal; transmitted data appears as incoherent noise
Interference Protection:
Link 16 terminals monitor their own transmissions in several areas, and if authorized levels are exceeded the Interference Protection Feature (IPF) automatically disables transmission
What are the 4 types of link 16 messages?
Fixed format: J-series msgs.
Variable message format (VMF): user-defined msgs.
Round-trip timing (RTT): Used for net sync.
Free text: digital voice or video
How many possible fixed-format J-series messages are there? What are the 2 general types of J-series messages?
256 possible fixed-format messages: 32 categories (e.g. J12), 8 subcategories (e.g. J12.6)
2 General Types:
1. Addressed messages: sent to specific JU.
2 .Broadcast messages: sent to everyone.
What is the J-Series message structure?
Jitter Sync Time refinement Header Data Propagation
What are stacked nets in link 16?
Separate units performing the same function within one NPG. Same time slot, NPG, and function; Different hopping patterns.
What are multinetting in link 16?
Allows different NPGs to utilize a single time slot for different functions. Different crypto variables or net numbers, hopping patterns, NPG, and functions
What is dedicated access mode in link 16?
Each JU is positively assigned a unique allocation of time slots. The normal mode for most NPGs. No transmission conflicts for optimum data fidelity.
What is contention access mode in link 16?
Groups of JU’s share a pool of time slots.
Explain time quality in link 16
The highest time quality is 15 and reserved for the NTR;
Units joining must be within 6 sec of NTR and once sync’d with NTR they remain sync’d
What is the Standard Double Pulse (STD-DP) data packing
3 words x 2 transmission of 258 Pulses
On the EPLRS radio what are the 4 lights
ALM = on when there is no crypto
OUT OF NET= pulse every 4 sec in a net; pulse every 2 sec searching for a net
PWR = power
KAB = on when 9V battery is low or failed
What are the four power levels of the EPLRS radio, and what in the normal level
- low (.4 W), med low (3 W), med high (20 W), and high (100 W).
- Med high (20 watts) is normal operating power
What is dedicated access in SADL
exclusive transmit slot assignment to each terminal.
What is contention access in SADL
All members of a group are assigned a common pool of time slots
What are the Host Interfaces in SADL
SCU
Generic
Gateway
Define Guard Channel in SADL
The physical RF Channel required to enter the network
Define Secondary Channel in SADL
Defines the allowable frequency set the radio will use for hopping
Define Net Shape (4:4) for SADL
Digit 1 is number of flights in the Air key (1 - 4)
Digit 2 is number of aircraft per flight (1 - 4)
Define Net Position (4:4) for SADL
Digit 1 is flight # that ownship is in (1 - 4)
Digit 2 is ownship’s position in the flight (1 - 4)
How is an extended Data Net created and how many aircraft can it support
Possible by using Air key number 90 - 94, and can support up to 80 aircraft.
Explain Link 16 TDMA timing
24 hour day divided into 112.5 epochs Epoch = 12.8 minutes = 64 frames Frame = 12 seconds 128 time slots per second 1536 time slots per frame
How many J series message possibilities are there?
256 possible fixed=format J-series messages
Explain Pack 4 Single Pulse data packing
12 words x 1 transmission, 444 pulses. No jitter scheduled in time slot
