Tactical Data Link

Link 11 What does NCS stand for?

Net Control Station

Link 11 Describe the mode Radio Silence

No transmission; however, PU still receives tactical data from other units

L16 ____________________ ensures there is no interference with IFF

Notch Filter Assembly (NFA) ensures there is no interference with IFF

Link 11 How many tones are there?

16

L16 How many Ae does it have?

2 1x Receive Ae 1x Tx/Rx Ae

Link 11 How big are the words being transmitted? How many bits?

30

Link 11 How many preambles are there in transmission?

5

Link 16 How many frequencies available on L16?

51

Link 11 What tones are in a data frame?

605 Hz and 15 other tones

Link 11 What tones are in a preamble?

605 Hz and 2915 Hz

Link 11 What are the 2 special tones among the 16? What are they used for?

605 Hz: used for doppler shift calculation 2915 Hz: used for synchronization

L16 How long/big are L16 words?

70 bits

L22 How many bits comprise of a F series message?

72 bits

L16 What is NTR? What does it stand for?

8Network Time Reference (NTR)* Like Link 11, we need to know where to start! TDMA will require all users to be synchronised so their time-slots align.

Link 11 Name three reasons that makes NCT variable

•# of Pus •Amount of data transmitted •Fast or slow net timing rate

Link 11 Describe the mode Net Synchronization

-*Used to establish communications.* -It is a *continuous* series of *preambles* and is the first step in verifying RF connectivity between units. -NS is initiated manually by the operator and continues until manually stopped by the operator

What is the reference frame?

-1st frame after preambles is phase reference -Gives starting point to calculate phase shifts

Link 11 What is a crypto frame?

-1st frame generated by KG40 as it encrypts first frame of actual message data

L22 What are two techniques that allow L-22 achieve BLOS?

-By using HF sky-wave (ionosphere reflectivity of RF) -By using Relay technique

Link 11 What is the start code for?

-Immediately follows the phase reference frame. It specifies that a data report is about to begin. Recognizing the start code causes the DTS to issue a Prepare-to-Receive interrupt to the TDS computer. -Consists of 2 frames of 30 bit words -If a start code is not received at the NCS's DTS within 15 frames of call-up, NCS will poll the unit a second time. -Sent by the PU

L22 What does LLC stand for?

-Link Level COMSEC

L16 What are the two types of security/cryptovariables?

-Message Security (MSEC), KGV-8 encrypts the message data -Transmission Security (TSEC), controls the specifics of the JTIDS waveform -frequency hopping -Jitter - deviation from true periodicity, all time-varying signals -pseudorandom pattern of noise that is mixed with the signal prior to transmission.

L16 What is the N series message used for? Where is it converted to from what?

-N Series Messages: the interface between the TDS and the C2P is defined by N-series message formats -N and J series message conversion occurs in the C2P for both ways

Link 11 What is the purpose of preamble frames?

-Preamble frames ensure that subsequent data frames have a *reference phase*. -*synchronization*

Link 11 Describe the mode Roll Call

-Roll Call is the *normal operation mode* for the Link-11 net. -In roll call, one unit is designated as the *Net Control Station (NCS)*. The remaining units (PU's) serve as picket stations. The NCS's DTS *controls the sequence* in which the other PU's are polled. -Each *PU transmits its data when it is polled*. During the remainder of the time, a PU is receiving reports from other PU's. -If a PU does not answer its call, the NCS will automatically poll it a second time. If a PU still does not respond, the NCS polls the next PU in the sequence. -The assignment of the NCS only determines which unit's DTS will perform the NCS function and is in no way related to the command or authority to control the operation of the link or force units. -When each polling sequence, or *net cycle, is complete, the NCS reports its own information* and begins a new cycle. -The operation of the DTS, once initiated, is *automatic*.

Link 11 Describe the mode Broadcast

-Short Broadcast (SBC) is a single data transmission to all members of the net by a station that may be acting as a either a PU or the NCS. It is *manually initiated* by the operator at the DTS -Broadcast (BC) mode consists of a *continuous series of short broadcasts, separated by 2 frames of dead time*. It is manually initiated by the operator at a station acting as either picket or NCS. It continues until the operator manually stops it. This mode would be used in a tactical situation where other ships in the fleet are operating in EMCON reduced states

Link 11 What are all the control codes?

-Start Code -Picket Stop Code -Control Stop Code -PU Address Code

Link 11 What is an integration interval?

-The integration interval is the interval of time within the center of a frame during which the data is stable -This is the period of time from which data is taken for processing

Link 11 What is the PU Address Code used for?

-Used by the NCS to specify which PU is to transmit next. -As soon as a picket station receives its address code, the picket station switches from receive to transmit and sends its message data.

Link 11 Describe the mode Net Test

-Used for *connectivity checks* --> ensure everyone has connectivity -Consists of normal 5 preambles, the phase reference and then instead of regular data frames, there are repeating Net Test word sequence

Link 11 What is the picket stop code for?

-Used only by PU's to indicate the end of its message data. When other PU's receive this stop code, they prepare to receive another transmission. -Whenever NCS receives this code, it initiates an interrogation message or an interrogation-with-a-message transmission -

L22 What are DLP servers?

DLP functions: •Track management •Correlation •Data filtering •Data forwarding

Link 11 What modulation scheme is used to encode data?

DQPSK

Link 11 How many bits compose of the tactical data? How many bits are added on to this? For what reason?

DTS requests and accepts tactical data in the form of a 24-bit data word from the NTDS computer. To these *24 bits*, it adds a *6-bit* *Error Detection and Correction (EDAC) code*. The DTS then converts this encrypted data from digital format to an analog audio signal which is then directed to the Link 11 transmitter.

Link 16 How does frequency hopping work on L16?

Every 13 microseconds, switches frequency in the same transmission allotted slot

Link 11 What are the two transmission data rates? What are their integration intervals?

Fast, 9.09 Slow, 0.09, 18.18

Link 11 uses what kind of frequencies?

HF and UHF

Describe Link 11 data link as 3 main ideas

Half-duplex, netted, secure data link

L16 What are three types of messages used in L-16?

J-series M-series (backwards compatibility) N-series

Link 16 vs Link 11 *Message Capacity* J Series message can carry ___ times the amount of data than Link 11 M series message

J-series message can carry *two to three times* the amount of data found in a L11 M-series message.

What does JREAP stand for?

Joint Range Extension Applications Protocol ("JREAP")

Link 11 crypto unit is called

KG-40A

L16 What crypto unit does L16 use in MSEC?

KGV-8

Link 16 vs Link 11 *Track quality*. How do they differ? What's the accuracy provided by highest TQ for Link 16?

L16: 1-15 L11: 1-7 •The highest L16 TQ provides better than 50 feet accuracy

L22 uses less bandwidth by only passing information that is ....

L22 use less bandwidth by only passing information that is *BLOS*.

L22 What type of architecture is it?

L22 uses a layered communications stack approach to produce an *Open System Architecture* with well defined interfaces between the subcomponents •This approach maximizes extensions •Enables contributions from multiple providers Or maybe it's talking about *TDMA* and *Dynamic TDMA*

What are the STANAGS for Link 11, Link16, and translation between the two?

Link 11: STANAG 5511 Link 16: STANAG 5516 Translation between the two: 5616

Link-22 is NATO secure radio system that provides ...

Link-22 is NATO secure radio system that provides BLOS communications

L22 What is in a FJ series message?

Link-22 message can contain a *complete* Link-16 message or can *contain parts of Link-16 messages*

Link 11 What are the components that make up a Link 11 transmission?

Preamble, phase reference, control codes, crypto frame, and message data

Link 11 What is gridlock?

Procedure for *eliminating induced track position errors* caused by navigational errors, radar alignment errors and data transformation errors between 2 TDS units

What protocol does Link 11 use?

Roll call protocol

L22 What is the STANAG for L22?

STANAG 5522

L22 What is SNC? What does it stand for?

System Network Controller (SNC), a piece of software used by all L-22 participants

L16 What kind of channel access does L16 use?

TDMA (Time-division multiple access)

L16 What does the data path diagram look like for transmission?

TDS --> C2P --> JTIDS Terminal --> Ae

Link 11 What is NCT (Net Cycle Time)?

The *time it takes for all the units to transmit their information* is called the Net Cycle Time (NCT). The NCT is variable and depends on the number of units in the net, the amount of data each transmits, and the net timing rate specified (fast or slow).

L22 What are the two types of F series messages?

Unique F series FJ series messages

Link 11 What is the control stop code used for?

Used only by the NCS to mark the end of the NCS's own report. Followed immediately by the address code of the next unit to transmit

Link 11 In demodulation, what happens in the DTS after 24 bits of the data frame has been extracted?

correct and flag bits are added (2 bits)

L16 Up to how many words in a message?

up to 40 words in the message

L22 After the Super Network has been started, units that arrive late can join the tactical data link by initiating the protocol called _________

•After the Super Network has been started, units that arrive late can join the tactical data link by initiating the protocol called *Late Network Entry (LNE)*

L16 What is the Command and Control Processor (C2P)? What are its functions?

•C2P is the *message distribution system* •It provides the *interface between TDS and the JTIDS terminal* •It consists of an AN/UYK-43 computer •It is *controlled by* an AN/USQ-69 Data Terminal Set (*DTS*) •C2P *automates message formatting* •Performs *data forwarding between L11 and L16* by down grading the level of detail in the tactical info and sending it out as an M-series message for L11

Link 16 vs Link 11 The Link16 messages allow more detailed reporting of Friendly Status which include:

•Equipment status •Ordnance inventory •Radar channels •Missile channels •Fuel available for transfer •Gun capability Inventory of specific surface missiles such as SM

Link 11 What is Data Link Reference Point (DLRP)?

•Fixed geographic reference point •All tracks reported in relation to the DLRP, not the reporting unit

L22 What does the COMSEC do?

•It is known as Link Level COMSEC (LLC) •LLC provides detection of the attempts to interrupt the network •Uses frequency hopping radios in both HF and UHF bands •Offers transmission in sealed envelopes

L16 What is JTIDS?

•JTIDS is an advanced radio system •It provides the rapid exchange of tactical information •Digital and voice communications •Operates in the 960 MHz to 1215 MHz •Employs TDMA architecture •Automatically determines distance between Jus •Supports two simultaneous voice channels, J1 and J2 •Employs a radio relay technique to achieve BLOS

Link 16 vs Link 11 *Track numbers*. How do they differ

•L16 up to 524,284 L11 up to 4,092

Link-22 Super Network •Max ____ Participating Units with ____ NILE Networks •PU within Link-22 network can be a member of up to ____ NILE Networks

•Max 125 Participating Units with 8 NILE Networks •PU within Link-22 network can be a member of up to 4 NILE Networks

Link 16 vs Link 11 *Number of participants*. How do they differ

•Maximum 127 JUs •JU addresses - 000 to 999 •PU addresses - 00 to 99

Link 11 What are the modes of operation?

•Net Synchronization •Net Test •Roll Call •Long Broadcast /Short Broadcast (EMCON reduced states) •Radio Silence

L16 L16 is described to be _____-less

•Node-less, no central controller (i.e No NCS) No NCS means no single point of failure, if a JU drops off, the network is still intact.

L16 What frequencies does JTIDS operate at?

•Operates in the 960 MHz to 1215 MHz

Link 16 vs Link 11 Tracks are reported on Link-16 with a detailed ID that includes things such as:

•Platform •Activity Nationality

Link 16 improvements over Link 11 are:

•Positioning quality - air track speeds, altitudes, LOB •Relative navigation - TDMA --> transmission times can be used to determine ranges between JU‟s --> exact pos. of JUs •Coordinate system - Geodetic (altitude, long., lat.) •Lines and areas - all sizes and shapes

L16 What is the Tactical Data System?

•Rx and processes tactical data from link participants •Provides tactical data to link participants •Maintains the tactical data base •L-16 is fitted with AN/UYK-43 computer that runs the C2P program

L22 What are three techniques of Congestion Management in Link 22?

•The routing of messages takes congestion into account and will *route messages using alternative paths* to reduce congestions. •Link 22 has a *Dynamic TDMA* protocol which, when enabled on a NILE network, allow congested units to automatically request and receive additional capacity on a permanent or temporary basis •The unit managing a NILE network can *change the configuration* of the network to *redistribute the available capacity*

Link 16 What does JTIDS stand for? What is it?

•Uses Joint Tactical Information Distribution System (JTIDS) - a communication component of L16

L22 Can go BLOS by the use of multiple ships. What is this called and how is it done?

•automatic relay function extends coverage without operator intervention •SNC calculates whether the relay is necessary