Chapter 14 14308A
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14 EXTERNAL COMMUNICATIONS AND DATA LINKS
Learning Objectives After you finish this chapter, you should be able to do the following: 1. Indentify the basic principles of rf communications. 2. Recognize the basic equipment used for rf communications. 3. Determine frequency spectrums allocated to rf communications. 4. Describe and discuss various data links and their operations.
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14.0.0 INTRODUCTION Communications in general, and especially in system s, covers a broad spectrum, from a simple single channel voice circuit, to satellite communications.
14.1.0 RADIO COMMUNICATIONS Navy ships, planes, and shore bases operate as a team working together to accomplish a specific task. Radio equipment is used to coordinate the activities of the many fleet units by linking them with each other and with shore stations.
Radio can be defined as the transmission and reception of electronic impulses or signals through space by means of electromagnetic waves. Usually, the term is used in referring to the transmission of intelligence code and sound signals, although television and radar also depend on electromagnetic waves.
At one time, the term radio communications brought to mind telegraphy (CW), voice (AM), and possibly teletype communications. Today’s radio communications has become a highly sophisticated field of electronics.
The primary means of communicating between ships and between ships and stations is known as telecommunications. Telecommunications refers to communications over a distance and includes any transmission, emission, or reception of signals, writing, images, and sounds. Intelligence produced by visual or oral means or by wire, radio, or other electromagnetic systems is also included. Electrical, visual, and sound telecommunications are all used by the Navy.
14.2.0 COMMUNICATIONS SYSTEMS A communications system consists of two or more units, each having its own separate identity, arranged and interconnected to perform a circuit operation that cannot be performed by one of the individual units alone. Navy communications systems vary from simple to very complex, depending upon the circuit operations involved. Each system requires the integrated use of various types of equipment, so flexibility is of the utmost importance. This flexibility is provided through a complex arrangement of interconnections that allow the physically separated sets, groups, and units to be selectively switched (patched) into the different circuit configurations.
Most shipboard communication equipments do not operate independently. A particular piece of electronic gear may be designated “primary” and still be used in many different system operations. 14-2 UNCLASSIFIED
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14.3.0 BASI C SYSTEM REQUIREMENTS Radio equipment can be divided into three broad categories: transmitting equipment, receiving equipment, and terminal equipment. Transmitting equipment generates, amplifies, and modulates a transmitted signal. Receiving equipment receives a radio wave, then amplifies and demodulates it to extract the original intelligence. Terminal equipment is used primarily to convert the audio signals of encoded or data transmission into the original intelligence.
A basic radio communications system may consist of only a transmitter and a receiver, connected by the medium through which the electromagnetic waves travel (see figure 14- 1). The transmitting equipment creates a radio-frequency (rf) carrier and modulates it with audio intelligence to produce an rf signal. This rf signal is amplified and fed to the transmitting antenna, which converts it to electromagnetic energy for propagation.
Figure 14-1.—Basic radio communication system.
The receivin g antenna converts the portion of the electromagnetic wave it receives into a flow of alternating rf currents. The receiver then converts these currents into the intelligence that was contained in the transmission.
Terminal equipment is used primarily where coded transmissions are employed, to convert the modulated signal into the original intelligence. 14-3 UNCLASSIFIED
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14.4.0 THE FREQUENCY SPECTRUM Figure 14-2 shows the overall electrom agnetic frequency spectrum as defined by the International Telecommunications Union. Pay particular attention to the part used for communications. Rapid growth in the quantity and complexity of communications equipment and increased worldwide international requirements for radio frequencies have placed large demands upon the rf spectrum. These demands include military and civilian applications, such as communications, location and ranging, identification, standard time, industrial, medical, and other scientific uses.
Figure 14-2.—Frequency Spectrum.
The m ilitary has modified the frequency spectrum for its use as shown in table 14-1. A few general characteristics are described in the following paragraphs.
The extremely-low-frequency (elf), very-low frequency (vlf), and low-frequency (lf) bands require high power and long antennas for efficient transmission (antenna length varies inversely with the frequency). Transmission of these frequencies is normally limited to shore stations.
The commercial broadcast band extends from about 550 kHz to 1700 kHz. This limits naval use to the upper and lower ends of the medium frequency (mf) band.
Long-range shipboard communications were conducted exclusively in the high-frequency (hf) band, so a large percentage of shipboard transmitters and receivers are designed to operate in this band. On board your command, you may find satellite communications has pushed hf into aback-up role.
A significant portion of the very-high-frequency (vhf) band is assigned to the commercial television industry. Some naval uses of the vhf band are mobile communications, repeater operation, navigation, amphibious and special operations, short range line-of sight (LOS) communications, and satellite communications. 14-4 UNCLASSIFIED
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The ultra-high-frequency (uhf) band is used extensively by the Navy for LOS and satellite com munications. Mobile communications, radar (over 400 MHz), and special operations are some other uses.
The super-high-frequency (shf) band is the workhorse of microwave communications. LOS communications, terrestrial, and satellite relay links, radar, and special operations are some other uses.
The Fleet Satellite (FLTSAT) Ehf Package (FEP) is attached to two modified uhf FLTSATs. The FEP is currently providing ehf communications capability to Army, Navy, and Air Force ground, airborne, and oceangoing terminals.
FREQUENCY DESCRIPTION 30-300 GHz Extremely-high-frequency 3-30 GHz Super-high-frequency 300 MHz-3 GHz Ultra-high-frequency 30-300 MHz Very-high-frequency 3-30 MHz High-frequency 300 kHz-3 MHz Medium-frequency 30-300 kHz Low-frequency 3-30 kHz Very-low-frequency 300 Hz-3 kHz Voice frequency Up to 300 Hz Extremely-low-frequency
Table 14-1.—Frequency Bands.
14.5.0 TRANSMITTERS For rf communications to take place, a signal has to be generated. Generating the signal is the job of the transmitter. The following paragraphs will very briefly discuss basic transmitters and transmitter fundamentals.
14.5.1 Transmitter Fundamentals Equipment used for generating, amplifying, and transmitting an rf carrier is collectively called a radio transmitter. Transmitters may be simple, low-power units, for sending voice messages a short distance or highly sophisticated, using thousands of watts of power for sending many channels of data (voice, teletype, telemetry, t.v., etc.,) over long distances.
Basic transmitters are identified by their method of modulation: continuous wave (CW), amplitude modulation (AM), frequency modulation (FM), or single side band (ssb). We will first describe the types of modulation. We will then describe briefly the basic transmitters themselves. 14-5 UNCLASSIFIED
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14.5.1.1 Modulation Modulation is the process of varying som e characteristic of a periodic wave with an external signal. The voice frequencies (about 110-3,000 Hz) are contained in the audio frequency spectrum, 10-20,000 Hz. In naval communications the terms voice communications and audio communications are sometimes used interchangeably.
The audio signal is impressed upon the rf carrier because it is impractical to transmit frequencies in the audio range due to their excessive wavelength.
Three characteristics of the carrier wave may be varied, or modulated, at an external signal rate: amplitude, frequency, and phase. The following paragraphs discuss each type of modulation.
Amplitude Modulation (AM) Amplitude modulations the process of combining audio frequency and radio frequency signals so that the amplitude of the radio frequency waves varies at an audio frequency rate.
Frequency Modulation (FM) Frequency modulation is a process in which the frequency of the carrier wave is made to vary. An FM signal should remain constant in amplitude and change only in frequency.
Frequency-Shift Keying (FSK) Frequency-shift keying is considered a form of FM. It is a digital mode of transmission commonly used in radioteletype applications. In FSK the carrier is present all the time. In a keyed condition, the carrier frequency changes by a predetermined amount called the mark frequency. The unkeyed state is called a space.
Phase-Shift Keying (PSK) Phase-shift keying is similar to FSK except that the phase, not the frequency, is shifted. The primary advantage of PSK is that it can be accomplished in an amplifier stage.
Pulse Modulation Pulse modulation is accomplished by varying the characteristics of a series of pulses. This can be done by varying the amplitude, duration, frequency, or position of the pulses. It can also be done through coding. Pulse modulation is especially suited for use with communications systems incorporating time-division mutiplexing. 14-6 UNCLASSIFIED
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14.6.0 RECEIVERS Earlier you were introdu ced to one link in a communications system, the transmitter. All that is needed to complete the system is a radio receiver. A receiver processes modulated signals and delivers, as an output, a reproduction of the original intelligence. The signal can then be applied to a reproducing device, such as a loudspeaker or a teletypewriter.
14.6.1 Receiver Functions To be useful, a receiver must perform certain basic functions. These functions are reception, selection, detection, and reproduction.
Reception occurs when a transmitted electromagnetic wave passes through the receiver antenna and induces a voltage in the antenna.
Selection is the ability to distinguish a particular station’s frequency from all other station frequencies appearing at the antenna.
Detection is the extraction of the modulation from an rf signal. Circuits that perform this function are called detectors. Different forms of modulation require different detector circuits.
Reproduction is the action of converting the electrical signals to sound waves that can be interpreted by the ear.
14.7.0 TRANSCEIVERS A transceiver is a unit, usually enclosed in a single case that combines a transmitter and receiver using a common frequency control. Transceivers are used extensively in two- way radio communications at all frequencies, and in all modes.
The primary advantage of using a transceiver rather than a separate transmitter and receiver is cost. In a transceiver, many of the components can be shared during both transmit and receive operations. Another advantage is that transceivers can be tuned more easily than separate units.
A disadvantage of using a transceiver is that while duplex operation is not possible with most transceivers, communication must sometimes be carried out on two different frequencies. Although this is a problem with most transceivers, some do have provisions for separate transmit and receive operations, allowing them to overcome the problem.
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14.8.0 RADIO SET CONTROL The radio s et control provides the capability to control certain transmitter functions and the receiver output from a remote location. Some control units contain circuits for turning the transmitter on and off, voice modulating the transmission, keying when using CW, controlling receiver output, and muting the receiver when transmitting.
Figure 14-3.—Radio set control.
14.9.0 TRANSMITTER TRANSFER SWITCHBOARD The transm itter transfer switchboard allows the remote control station functions and signals to be transferred selectively to the transmitters.
14.10.0 REVEIVER TRANSFER SWITCHBOARD The receiver switchboard allows the audio outputs from the receivers to be transferred to remote control station audio circuits.
14.11.0 ANTENNAS An antenna is a conductor or system of conductors that radiates or intercepts energy in the form of electromagnetic waves. An antenna can be simply apiece of wire; but in practice, other considerations make the design of an antenna system complex. The height above ground, conductivity of the earth, antenna shape and dimensions, nearby objects, and operating frequency are just a few of the factors affecting the radiation field pattern.
14.12.0 COMMUNICATIONS NETS Radio circuit between several stations (ships or aircraft) established on a radio frequency for a specific purpose. 14-8 UNCLASSIFIED
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Controlled Net • One station designated as Net Control Station (N ECOS) • NECOS • opens, closes and controls net • stations must request permission from NECOS to transmit
Uncontrolled Net No Net Control Station
Unsecure Net • No protection • Everyone in the world can hear and understand you • “Red light” on handset • Use call signs • Sensitive information must be encoded manually
Secure Net • Protected by cipher • Everyone in the world hears static • “Green light” on handset • Tone burst when you key handset • Voices sound “artificial” • Call signs not used
14.12.1 Call Signs Every station on a comm net has a call sign.
• Plain Language (USS) Vincennes • Daily Changing R6D • JANAP Trinity Sword
14.12.2 Collective Call Sign Call sign to refer to all stations.
CARGRU THREE G4J Carl Vinson M9X Antietam A4V Stetham L6R
Collective Call Sign = G4J Spoken as: ALL UNITS IN G4J Answered back as: Unit’s individual Call Sign. 14-9 UNCLASSIFIED
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14.12.3 Monitoring Comm Nets There are four ways to monitor a co mmunications net, each is briefly described below:
Guard • listen, ready to transmit • keep log on all transmissions
Cover • listen, may not be ready to transmit • keep log on all transmissions
Copy • listen • keep log on all transmissions
Listen • listen • log required on transmissions to or from your station
14.12.4 General RT Procedures Before going over the radio: • Know what you are going to say. • Write message down if you must. • Keep messages brief and concise. • Use standard military phraseology and brevity codes.
On the air: • Speak clearly, slowly and naturally. • Keep your pitch level. • Don’t yell or shout. • Use standard pronunciation, use phonetic alphabet and numbers as necessary. • Keep transmissions short, pause in the middle of long messages. • Avoid double call-ups. 14-10 UNCLASSIFIED
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14.13.0 TACTICAL DIGITAL INFORMATI ON LINKS (TADIL) Tactical Data Links or “Data Link” involve transmissions of bit-oriented digital information which are exchanged via data links known as Tactical Digital Information Links (TADILs). The TADILs program applies to all “bit” oriented message formats used in support of joint and combined operations. A TADIL is joint, readable, digital information. The United States Navy uses the NATO designation such as Link-11 or Link-16, when referring to Tactical Data Information Link.
Link-11 is synonymous with TADIL A/B and Link-16 is synonymous with TADIL J.
14.13.1 Link-11 (TADIL A/B) Link-11, or Tactical Digital Information Link (TADIL) A, employs netted communication techniques and a standard message format — the M-series messages — for exchanging digital information among airborne, land-based, and shipboard tactical data systems.
Link-11 data communications must be capable of operation in either the high-frequency (HF) or ultrahigh-frequency (UHF) bands. When operating in the HF band, Link-11 provides gapless omnidirectional coverage of up to 300 nautical miles (nm) from the transmitting site. When operating in the UHF band, the link provides omnidirectional gapless coverage to approximately 25 nm ship-to-ship, or 150 nm ship-to-air.
There are many different Link-11 configurations. A representative Link-11 system configuration consists of a computer system, an encryption device, a data terminal set (DTS), an HF or UHF radio, a coupler, and an antenna. An external frequency standard is often a part of the system.
The computer system is called a Tactical Data System, or TDS.
Figure 14-4.—Link-11 equipment.
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14.13.1.1 Data Flow on Transmission Data flow on transmission is depicted in Figure 14-5. The TDS receives data from sensors, such as radar, navigation systems, and operators. It collects this information into a data base. In order to share this data base with other TDS computers, the information must be formatted into messages which have a specific, well-defined structure. Commands and other administrative information are also formatted into messages for distribution to other units.
Figure 14-5.—Sensor Data and other input formatted into messages.
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14.13.1.2 Data Flow on Reception When a transmitted signal is received, the audio portion is demodulated from the RF signal by the receiver. The resultant audio signal is sent to the DTS, where it is converted back into digital data. The digital data is then passed to the KG-40A one frame at a time, where its information is decrypted. Finally, this decrypted data, once again in the format of the message originating at the transmitting unit, is sent on to the TDS computer, where it is collected in an input buffer for processing.
Figure 14-7.—KG-40A Encryption device.
Figure 14-6.—Received signal demodulated to obtain audio signal.
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14.13.2 Tactical Data System Tactical Data System (TDS) computers in use in the U.S. Navy include the AN/UYK-7 and the AN/UYK-43. Physically, these TDS computers may appear quite different, but their Link-11 functions remain identical:
Supplying tactical digital information to net participants Retrieving and processing incoming tactical digital information received from net participants.
Figure 14-8.—TDS Computer processes sensor data.
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The software executing in the TDS com puter performs many other functions in addition to maintaining the tactical data base. It manages the displays, performs interim updates of track locations, responds to operator entries and inquiries, and controls all peripheral input and output (I/O). All TDS software is required to pass rigorous testing to be certified. This certification testing is performed by the Navy Center for Tactical Systems Interoperability (NCTSI).
14.13.3 Operator Entries The TDS accepts operator entries, such as the Data Link Reference Point (DLRP), participating unit (PU) identification, track block data, and various filter select modes. It is very important that these selections be entered correctly. Improperly entering any one of these values will cause the link either to degrade or to break down completely.
For example, a PU is transmitting good data with a strong signal. All of that data is input to the TDS computer system for processing. The TDS operator has failed, however, to enter the number of that unit correctly into the TDS system. So, as a result, none of the tracks originating from that PU will show on the TDS display.
After information is received, it must be correlated, or matched, with information already existing in the data base. Of particular importance is matching the positions of objects. An incorrect operator entry could prevent proper correlation and may confuse the tactical picture with numerous uncorrelated tracks.
Correctly matching the positions held by your own ship with those of other units is known as gridlock. Failure to maintain gridlock may be the result of inaccurate positioning data from a ship’s sensor or from the Ship’s Inertial Navigation System (SINS) or gyro data. It may also be the result of an inaccurate operator entry. Fortunately, external audio or visual alarms will usually alert the operator when navigation input failures occur. There are no such alerts, however, for inaccurate operator entries.
14.13.4 DTS-to-TDS Interface The interface between the TDS computer and the Data Terminal Set, called the TDS interface, is controlled by the DTS. The KG-40A encryption device operates between the TDS computer and the DTS. Although it encrypts the data, it does not otherwise affect this interface.
The DTS is designed as a Modulator / Demodulator (MODEM). Normally, it operates in Half Duplex mode, during which it can either send or receive data, but cannot do both simultaneously. The single exception is during system test, when it operates in Full Duplex mode and can send and receive data at the same time. 14-15 UNCLASSIFIED
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14.13.5 Modes of DTS Operation There are six m odes of DTS operation:
Net Synchronization Net Test Roll Call Short Broadcast Broadcast Radio Silence
Net Synchronization (NS), also called “Net Sync”, is used to establish communications initially. Net Test (NT) is used for connectivity checks and for checking or setting line levels. Roll Call (RC) is the normal mode of operating the Link-11 net. Short Broadcast (SBC) and Broadcast (BC) may be required for certain tactical situations. Not all Data Terminal Sets support the Broadcast and Short Broadcast modes. Radio Silence disables all DTS output transmissions while continuing to allow for data reception.
Many parameters affecting the operation of the DTS are under the operator’s control. You must select the net mode of operation, whether your ship is picket (PKT) or net control station (NCS), which sideband is to be processed, what type of timing is to be used, whether errors are to be labeled or corrected, whether or not frequency correction is enabled, which data rate to use, and so on. You must always enter your own PU number. As the NCS, you must also enter the numbers of PUs to poll.
Unfortunately, not all DTSs have default settings for these entries and selections. On DTSs without default settings, the operator must explicitly check all settings on every occasion. The usual mode of operation is fast data rate, automatic sideband selection, roll call net mode, fast and continuous synchronization.
The Net Sync transmission is a continuous series of preambles. Net Sync is initiated manually by the operator and continues until manually stopped by the operator. Operationally, it is often used as a first step in verifying RF connectivity between units.
Net Test mode is a test of connectivity between units. It is also a useful signal for setting the DTS audio input and output levels. The Net Test signal should be input to the DTS at 0 dBm. Net Test also checks the DTS’s control code recognition circuits.
Roll Call is the normal mode of operation for Link-11. In roll call, one unit is designated as the Net Control Station (NCS). The remaining units serve as picket stations, or participating units (PUs). The NCS’s DTS controls the sequence in which the other PUs are polled. Each PU transmits its data when it is called. During the remainder of the time, a PU is receiving reports from the other members of the net. 14-16 UNCLASSIFIED
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Figure 14-9.—Example of Roll Call.
If a PU does not answer its call, the NCS will autom atically poll him a second time. If he still does not respond, the NCS polls the next unit in the sequence. When each polling sequence, or net cycle, is complete, the NCS reports its own information. In this way, tactical data is exchanged among the net members. The operation of the DTS, once initiated, is automatic.
The types of transmissions that occur during roll call are: the NCS callup (interrogation), the picket reply, and the NCS report (interrogation with message).
Short Broadcast is a single data transmission to all members of the net by a station that may be acting as either picket or NCS. It is manually initiated by the operator at the DTS.
The Broadcast, or Long Broadcast, net mode consists of a continuous series of short broadcasts, separated by two 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.
Radio Silence is the absence of any transmission. A PU in radio silence will receive data from other members of the net, but will not respond if it is polled. 14-17 UNCLASSIFIED
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14.13.6 Radios for Lin k-11 Communications The Link-11 transmitters and receivers provide point-to point connectivity between widely separated units in the net. The radios can be transmitter/receiver combinations in which the transmitter and receiver have independent functions. Or, the radios can have interdependent functions. Radios having interdependent functions are called transceivers.
Two types of radio are used in Link-11. One type provides spectrum coverage from 2 - 30 megahertz in the HF band. The other provides coverage from 225 - 400 megahertz in the UHF band. HF is used to establish a net when the range between units in the net is from 25 to 300 nm. UHF is used when the range between units is less than 25 nm.
Link-11 radios must meet requirements that are different from radios designed for voice- only operation. The primary differences include the transmit-to-receive switching time, the keyline interface, the audio band-pass characteristics, the automatic gain control, the attack and release timing, and the audio input and output level conditioning. Because of the speed at which the link operates, all link communication equipment must be able to keep up with the repetitive cycles of transmission and reception.
14.13.7 Net Management A successful team, whether in sports or in a tactical data network, is the product of a good management policy as implemented by a good manager. In sports, that manager is the coach. In Link-11, according to the Link-11 SOP, he is called the Net Coordinator. In areas of Link-11 net management, he is responsible to the Force Track Coordinator.
A manager must know both his assets and his liabilities, limiting to the highest possible degree the liabilities while encouraging the full employment of assets. In the Link-11 network, he must work on improvements to obtain the realistic goals of minimum net cycle time and maximum data throughput — that is, net efficiency.
In this section we discuss ways to maximize net efficiency. In discussing net management topics such as selecting NCS, selecting frequency, minimizing net cycle time, and maximizing data throughput, you will also learn how these are related to the overall efficiency of the net.
The NCS is the central controller for the Link-11 net. No rank or authority is associated with this function. Communication with NCS is of primary importance. If a unit fails to recognize its own address, it will never transmit. If the NCS fails to recognize the unit’s start code, it will jam the unit’s response with a second callup.
The degree of communication among units is called connectivity. Perfect connectivity is when all units are exchanging tactical data accurately and completely. Connectivity can degrade as a result of equipment performance, RF propagation characteristics, and range. Selecting the unit to act as NCS is one of the most important decisions to be made in managing the net. 14-18 UNCLASSIFIED
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Figure 14-10.—Link management issues.
Two principal features should determ ine the assignment of the NCS: equipment and location. The NCS should have the best operating Link-11 system, and the NCS also should be in the optimum location to remain in communication with all other units.
The NCS should be located in a position that allows it to receive each unit in the net by direct RF communication. The HF surface and air ranges are about 300 miles. A surface range for UHF is about 25 miles. For surface-to-air, the UHF range can be extended to 150 miles. The use of an AEW platform with a UHF relay capability (Auto Cat) can be used to extend the UHF surface range. 14-19 UNCLASSIFIED
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14.13.8 Net Cycle Time One m easure of Net Cycle Time (NCT) is the time required for NCS to complete a polling sequence of all PUs. This is the NCT of the net. Another measure of NCT is the average time between PU reporting opportunities. This is the PU NCT. It is calculated and reported by each PU in the net. The value measured by one PU may be different from that measured by other PUs, however, as well as being different from the NCT of the entire net.
Factors affecting NCT include: The number of PUs polled The number of PUs that reply to the initial call The number of PUs that reply to the second call The number of PUs that do not reply to either call The amount of data that each PU is transmitting
In order to allow timely responses to orders and keep display information accurate, each PU must transmit as often as possible. The frequency of a PU’s transmission is determined by the NCT. Reducing the NCT allows more frequent transmission opportunities for each PU in the net. To reduce the NCT, only net variables are under the control of the operator or net manager. These net variables are:
Number of PU addresses polled, and The amount of data reported by each unit.
The remainder of the NCT is consumed in overhead, such as preambles, phase reference frames, and control codes. Because they administer net functions, these cannot be altered. NCT can be minimized by ensuring that all PUs respond to their first callup. Any PUs not responding to their first call can, if necessary, be removed from polling. Thereafter, you can reduce NCT only by reducing the number of PUs called by NCS, and/or by limiting the quantity of data exchanged. Remember that a PU need not be called to receive net data.
Also bear in mind that every dummy PU will add 0.6 seconds to the link’s NCT. If a PU has dropped out of the net to repair or reconfigure equipment, remove his number from the polling sequence until he is ready to rejoin the net. In the case of an aircraft scheduled to participate in a link, wait until the aircraft has been launched or is known to be within the OpArea before activating his PU number.
One way to reduce the quantity of transmitted data is by having PUs activate specific track filters in the NTDS. Another way to reduce the quantity of transmitted data is to ensure that all dual track designations have been resolved. 14-20 UNCLASSIFIED
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14.13.9 Operating w ith the Strike Group Over the past several years, several techniques and capabilities have been developed to improve connectivity in the Link-11 Strike Group. In addition to the development of the single-tone waveform, there are now wireline and satellite Link-11, Multifrequency Link- 11, Dual Net Link-11, and other capabilities and techniques to improve data link connectivity.
Wireline converts encrypted TDS data, Hamming codes, and control codes to a digital format for transmission through a modem, satellite, or other communication device with a synchronous digital interface.
Figure 14-11.—Wireline over pho ne line via RS232C interface.
Satellite Link-11 Satellite co mmunications (SATCOM) systems include the Defense Satellite Communications System (DSCS), the Military Satellite Communications (MILSATCOM) System, the Fleet Satellite Communications System (FLTSATCOM), and the Maritime Satellite (MARISAT) Communications System, as well as leased satellites (LEASAT). During the previous decade, the UHF portion of the MARISAT satellites was leased by the U.S. Navy and given the name “Gapfiller.”
An early example of satellite Link-11 occurred in 1984, when the Saratoga transmitted Link-11 audio over a 25-kHz Gapfiller SATCOM channel in a one-way link to provide the Western Mediterranean track picture to East Med units in the Lebanon Op Area. Since that time, the use of satellites in long-range communications has expanded rapidly.
The availability of satellite communications depends on positioning. A communications satellite is said to be in geosynchronous orbit when it travels from west to east at a constant altitude at the same speed as the rotation of the earth, so that its position appears to be stationary with respect to the earth’s surface. Satellites in geosynchronous orbit maintain their positions approximately 23,000 miles above the equator. 14-21 UNCLASSIFIED
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For a one-w ay SATCOM link, all data received on the audio network is simply retransmitted to the satellite. Normally this is accomplished by patching the digital interface of the DTS to a satellite-capable WSC-3. The DTS is operated in mixed mode, both audio and digital. All data received over the audio interface is retransmitted digitally over the serial interface. The serial data must be delayed to allow the radio to power up and synchronize with the satellite, but these delays associated with the serial interface do not affect the exchange of data on the audio portion of the Link-11 network. A one-way satellite link may be established over either a dedicated 25-kHz channel or over a 2.4- kbps DAMA channel assignment.
A two-way satellite link may be desirable when HF or UHF connectivity is unreliable or participants are out of range. Again, the DTS is operated in mixed mode. Data from the audio interface is forwarded to the digital interface, and data from the digital interface is forwarded to the audio interface. A unit operating in this mixed-mode configuration is sometimes referred to as the gateway unit.
Figure 14-12.—Satellite Link.
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Multifrequ ency Link-11 (MFL), a technique whereby a single Link-11 network operates on multiple frequencies simultaneously. MFL was designed to improve Link-11 connectivity while ensuring backward compatibility with existing Link-11 equipment. The PUs in an MFL network are connected on multiple frequencies. Aboard a participating platform, an MFL DTS consists of four single-board DTSs in one chassis. The four DTS boards are controlled by a single controller. All incoming data is passed to the DTS controller, which chooses the best (error-free) data for transferring to the TDS.
Figure 14-13.—Mul tifrequency Link.
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Dual Net Link-11 (DN L) is one of the capabilities specified for the DTS. It requires that the DTS operate simultaneously on two independent Link-11 networks, called Link-11 Network A (Primary) and Link-11 Network B (Secondary).
The requirement for operating on two independent links simultaneously and independently grew out of the lessons learned from Operation Desert Storm. The primary network normally belongs to the Strike Group, while the secondary network belongs to the Joint Forces. All DNL-capable units in the Strike Group can receive on both networks. However, only one PU is designated to transmit on the Joint network and this unit forwards selected data from the Strike Group network to the Joint network. One of the benefits of this arrangement is to maintain a low NCT for the Strike Group network.
Figure 14-14.—Dual Net Link.
Simulcas t is the simultaneous broadcast of one signal on two or more frequencies. AEGIS ships with the Black SAS can, for example, simulcast Link-11 by patching the USB signal to a UHF radio and the LSB signal to an HF radio. Because the USB and LSB signals are generated by a single DTS acting as NCS, PUs are interrogated on both frequencies simultaneously. 14-24 UNCLASSIFIED
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The inten tion behind simulcast is to extend the range of connectivity. With the signal being transmitted on both HF and UHF simultaneously, a PU can receive and respond on whichever frequency is most advantageous.
Figure 14-15.—Simulcast Link.
Multi-TADIL networks can be created that interface participating units ov er Link-11, Link-11B, and Link-16. To participate in a Link-16 network, units must be equipped with the Joint Tactical Information Distribution System (JTIDS). Units so equipped are called JTIDS Units, or JUs. One of the functions, or roles, that a JU can perform is that of forwarding data to and from Link-11. A JU designated to perform this forwarding function is called a Forwarding JU, or FJU. The only Navy Link-16 systems that can act as FJUs for Link-11 are those which include the Command and Control Processor (C2P). This forwarding capability can be employed to establish connectivity between multiple, separate, simultaneous Link-11 nets. Data from one Link-11 net can be routed to another Link-11 net via FJUs on the JTIDS network. 14-25 UNCLASSIFIED
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By piggybacking on the JTIDS network, it is pos sible to operate multiple Link-11 nets simultaneously. In such a multi-TADIL network, one PU in each Link-11 net is also a JU in the Link-16 network. This unit is designated as an FJU for that Link-11 net. Data is forwarded by each FJU in both directions between the Link-16 net and the particular Link-11 net on which it is participating, allowing all nets to share a common tactical picture.
There is no limit to the number of Link-11 nets that can be set up in this way, and they can operate with either waveform — conventi onal or single-tone. For example, while one FJU is forwarding data in both directions between the Link-16 network and one Link-11 net operating on a certain frequency, another FJU is forwarding data in both directions between the Link-16 net and a second Link-11 net operating in Single-Tone Link-11 Waveform (SLEW) on another frequency, while yet another FJU forwards data in both directions between the Link-16 net and a third Link-11 net operating in Conventional Link-11 Waveform (CLEW) on yet another frequency! In this case, the Link-16 net is interoperating with three simultaneous Link-11 nets, and all four networks benefit in sharing the same tactical information.
Figure 14-16—Multi-TADIL Link.
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14.13.10 Operating w ith Land-Based Facilities Link-11’s usage is not limited to the exchange of tactical data solely among naval vessels within a Battle Group. Land-based control centers also employ Link-11 to augment and extend the radar coverage of their surveillance areas. Common military specifications and standards ensure interoperability for all Link-11 users. However, differences in operational procedures and equipment at land-based facilities may affect the tactical data exchange capabilities among the military services.
Ground-based radars are limited to a 40-mile surface range by the horizon. Additionally, uneven terrain and ground clutter can cause gaps in coverage. Land-based centers can extend their radar horizon, however, and fill in these gaps by utilizing airborne assets. The radar picture provided by these airborne assets is communicated to the land-based centers over Link-11. Land-based facilities include:
The Navy’s Fleet Area Control and Surveillance Facility (FACSFAC) and the Tactical Surveillance Centers (TSCs), formerly known as the Anti Submarine Warfare Operations Centers (ASWOCs)
o Fleet Area Control and Surveillance Facility (FACSFAC) coordinates and schedules all fleet operating, target, test, and special use areas within its jurisdiction. FACSFAC publishes a consolidated schedule of events. In addition, FACSFAC acts as the air traffic controller for its OpArea, interacting with the Federal Aviation Administration (FAA) as necessary.
o The TSCs support squadrons of the Maritime Patrol Aircraft (MPA), which consist of P-3 aircraft. Before, during, and after a flight, TSCs provide these squadrons with near-real-time operational control, mission planning, coordination, and evaluation support. Digital information is conveyed between the MPA and the TSC over Link-11. The TSCs also are able to exchange information with each other.
o The TSC’s Mobile-miniature Operations Control Center (MOCC) is a rapidly deployable command and control support system that is capable of operations from advanced bases. Its modular design provides the flexibility to meet a variety of specific mission requirements. A MOCC, which is fully self-contained for power, communications, analysis, and computer resources, can be transported by two P-3 aircraft. 14-27 UNCLASSIFIED
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The Air Force’s Region and Sector Operations Control Centers (ROCCs and SOCCs) and Theater Air Control Sys tem (TACS)
o ROCCs and SOCCs support the North American Aerospace Defense (NORAD) Command’s strategic air defense mission. Specific missions among ROCCs and SOCCs may differ, but in general they have responsibility for the peacetime air sovereignty of the United States. These centers operate the Joint Surveillance System (JSS), maintaining a real- time air picture of the entire U.S. airspace. Input to this system is received from radar, the FAA, and other sources. This air picture can also be augmented with radar track data supplied by the AWACS over Link-11.
o The U.S. Air Force’s Theater Air Control System (TACS) consists of units having a Link-11 capability. The ground TACS units having a Link-11 capability are Air Operations Centers (AOCs) and the Modular Control System (MCS).
o The TACS provides the Air Force Component Commander with the means to plan, direct, and control air operations and to coordinate Joint operations with component forces of other military services. It is composed of operational elements which are mobile and flexible, permitting the type and number of elements deployed to be tailored to large- or small-scale operations.
The Marine Corps’ Marine Air Command and Control System (MACCS).
o The Marine Air Command and Control System (MACCS) consists of certain units having a Link-11 capability. Those MACCS units having a Link-11 capability are the Tactical Air Operations Center (TAOC) and the Tactical Air Command Center (TACC). The TAOC is a section of the Marine Air Control Squadron. In addition to Link-11, these units also support data link communications over TADIL-B (Link-11B), NATO Link-1, TADIL-C (Link-4A), and ATDL-1 (Army Tactical Data Link-1).
o The MACCS performs the functions of air defense, air control, and air support for the Marine Aircraft Wing. Once the system has been initialized, the hardware and associated software automatically receives, translates, reformats, and outputs messages from one data link to another, without operator intervention.
Additional land-based facilities employ Link-11 for testing and training or to support drug interdiction missions. These facilities typically have site-specific, unique equipment configurations. 14-28 UNCLASSIFIED
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14.13.11 Operating w ith Link-11 Aircraft The airborne Link-11 platforms described in this topic are the Navy’s E-2C, P-3C, and the Air Force’s E-3. The E-2C is a carrier-based Airborne Early Warning (AEW) system. The E-3 is an Airborne Warning and Control System (AWACS). The P-3C is an antisubmarine warfare (ASW) patrol and attack plane. The E-2C aircraft are based on carriers and form the AEW arm of a U.S. Navy Strike Group.
The Navy P-3C is shore-based and typically works with the Tactical Surveillance Centers (TSCs). Although the Air Force E-3 AWACS primarily supports the ROCCs and SOCCs, the AWACS often participates in Navy Strike Group operations as well.
All these airborne platforms are used to extend and augment the tactical information available to ships and to land-based facilities. The P-3C provides information on subsurface contacts. The E-2C and AWACS greatly expand the radar picture available to surface units. The radar horizon at the earth’s surface is only about 40 miles. The radar range of an AWACS or E-2C at altitude, on the other hand, is greater than 200 miles.
Naval airborne tactical computers, or Airborne Tactical Data Systems (ATDSs), are configured with Data Terminal Sets and radios to exchange information over Link-11. Airborne Link-11 equipment differs from shipboard equipment. Airborne equipment must be compact and lightweight and must meet more stringent environmental specifications.
The functions performed by airborne Link-11 system components are essentially identical to those performed by their shipboard counterparts. There are differences, however, in the way they work.
14.14.0 Link-16 (TADIL J) Link-16 is the designation of a tactical data link which has been introduced into operations of the United States Navy, the Joint Services, and forces of the North Atlantic Treaty Organization (NATO). It became operational in U.S. Navy ships and aircraft during 1994. Link-16 does not significantly change the basic concepts of tactical data link information exchange supported for many years by Link-11. Rather, Link-16 provides certain technical and operational improvements to existing tactical data link capabilities.
The general purpose of Link-16 is the same as that of Link-11: the exchange of real-time tactical data among units of the force. While Link-16 is identical in purpose to these links, it also provides some data exchange elements which they lack, and it provides significant improvements as well, such as nodelessness, jam resistance, flexibility of communication operations, separate transmission and data security, increased numbers of participants, increased data capacity, network navigation features, and secure voice. 14-29 UNCLASSIFIED
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The U.S Na vy uses the NATO designation Link-16 when referring to Tactical Digital Information Link (TADIL) J. “Link-16” is thus synonymous with TADIL J.
14.14.1 Joint Tactical Information Distribution System (JTIDS) Link-16 uses the Joint Tactical Information Distribution System (JTIDS). The acronym JTIDS refers to the communications component of Link-16. It encompasses the Class 2 terminal software, hardware, RF equipments, and the high-capacity, secure, antijam waveform that they generate. Among NATO subscribers, the equivalent term for JTIDS is the Multifunctional Information Distribution System (MIDS).
Figure 14-17—Shared Tactical Data via JTIDS.
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Link-16, using the JTID S data terminal, represents major improvements in data link communications over the current Link-11. Link-16 will not replace these links entirely, but it will become the preferable alternative when feasible. Because JTIDS uses only the UHF spectrum, Link-16 communications are limited to line of sight unless suitable relay platforms are available. Furthermore, many current Link-11 platforms will not be equipped with JTIDS. It is therefore anticipated that Strike Group operations will employ both Link-11 and Link-16.
14.14.2 Features of Link-16 Link-16 includes many features which improve on Link-11. These include:
Jam resistance Improved security Increased data rate (throughput) Increased amounts/granularity of information exchange Reduced data terminal size, allowing installation in fighter and attack aircraft Digitized, jam-resistant, secure voice capability Relative navigation Precise participant location and identification.
14.14.3 Link-16 and Link-11 Comparison Because Link-16 is functionally equivalent to an improved Link-11 with voice, comparing the architecture, capacity, and data rates of these three links is worthwhile.
Link-11 uses a polling protocol and a netted architecture. A net is an ordered conference whose participants have common information needs or similar functions to perform. A net operates under the supervision of a controller, who permits access and maintains circuit discipline.
Figure 14-18—Link-11 Nettted Architecture. 14-31 UNCLASSIFIED
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The Link -11 net is normally operated according to a protocol called Roll Call. Participating Units (PUs) transmit all data eligible for reporting when they are polled by the Net Control Station (NCS). After transmission, they revert to the receive mode while, one by one, the other PUs transmit their data. This cycle continues until all PUs have transmitted at least once, and then it is repeated. The time required to poll all PUs and to transmit all their eligible data at least once is known as net cycle time. At any given time, a PU is either transmitting or receiving data on a single Link-11 net.
Link-16 uses the principle of Time Division Multiple Access (TDMA), an automatic function of the JTIDS terminal. The TDMA architecture uses time interlacing to provide multiple and apparently simultaneous communications nets. All JTIDS Units, or JUs, are preassigned sets of time slots in which to transmit their data and in which to receive data from other units.
Multiple nets can be “stacked” by allowing time slots to be used redundantly, with the data transmitted in each net on different frequencies. There are 51 frequencies available for JTIDS transmissions. The frequency is not held constant during the time slot but is changed rapidly (every 13 microseconds) according to a predetermined pseudo-random pattern. This technique is called frequency hopping. Each net is assigned a number which designates a particular hopping pattern. There are 128 possible numbers, with the number 127 reserved to indicate a stacked net configuration. During any given time slot, a unit is either transmitting or receiving on one of a possible 127 nets.
Figure 14-19—JTIDS Stacked Net. 14-32 UNCLASSIFIED
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14.14.4 Data Exchange The Link-11 data is divided into 24-bit frames, with two f rames constituting a Link-11 message. The messages used to exchange information over Link-11 are known as the M- series messages.
In Link-16, three types of messages are possible: fixed format, free text, and variable format. The fixed-format messages exchanged over Link-16 are known as the J-series messages.
Because of the increased data rate of JTIDS, far more data can be transmitted on Link-16 than on Link-11 during the same period of time. Recognizing this, the developers of the Link-16 J-series message standard have added J-series data elements that cannot currently be exchanged over Link-11. The Link-16 J-series messages allow the reporting of two to three times as much tactical information as Link-11.
The capacity of the JTIDS network can be increased further by using multinetting techniques. Statistical analysis has shown that approximately 20 different nets can be collocated without mutual interference.
14.14.5 Shipboard Link-16 Equipment To understand the operation of the shipboard Link-16 system, it is important to be able to identify the hardware components which comprise it and the functions they perform.
You will learn about the components of the U.S. Navy’s shipboard Link-16 system, including the Tactical Data System (TDS), the Command and Control Processor (C2P), the Joint Tactical Information Distribution System (JTIDS) Terminal, the JTIDS Antennas, and the interfaces between them.
Link-16 improves on existing tactical data link communications in two ways—through more complete and more accurate tactical information and through superior communications technology. The major components of the Navy shipboard Link-16 system include:
Tactical Data System (TDS) Command and Control Processor (C2P) JTIDS Terminal JTIDS Antennas
The TDS and C2P provide the tactical data to be exchanged. The JTIDS terminal and antennas provide the secure, antijam, increased-capacity waveform. There are two configurations of Link-16, known as Model 4 and Model 5. 14-33 UNCLASSIFIED
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Figure 14-20—Shipboard Link-16 equipment.
14.14.6 Model-4 Link-16 The Model-4 im plementation of Link-16, also referred to as Block 0 on ACDS platforms, was designed as a “transparent” equipment upgrade to existing ships’ tactical systems.
For both AEGIS and ACDS platforms, the Model-4 Link-16 upgrade consists of the addition of new hardware: the Command and Control Processor, and the JTIDS terminal and antennas. The tactical systems, including the Combat Direction Systems (CDS), Shipboard Gridlock System (SGS), Command and Decision (C&D), and Weapons Control Systems (WCS), are virtually unchanged.
For the transmit function, the Model-4 C2P receives the M-series messages normally output for Link-11 from the CDS.
It reformats the data contained in these messages in accordance with Link-16’s J-series message standard and passes them to the JTIDS terminal for transmission over the link.
For the receive function, the Model-4 C2P receives the J-series messages from the Link- 16 network via the JTIDS terminal. These are reformatted as M-series messages and passed to the CDS.
Because Model-4 C2P directly translates the existing Link-11 messages, Model-4 Link- 16 does not implement any of the expanded data-exchange capabilities provided by the J- series messages. Instead, it supports the existing capabilities with its jam-resistant, increased-capacity JTIDS waveform. Note that the C2P can be placed in bypass mode to run Link-11 directly. 14-34 UNCLASSIFIED
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14.14.7 Model-5 Link-16 The Model 5 im plementation of Link-16, also referred to as Block 1 on ACDS platforms, is the full and complete implementation of Link-16.
Its implementation requires major modifications to the TDS computer program and data base. The displays and the operator interface to support the new Link-16 capabilities are implemented in a new console.
The installation of the Model-5 system is both an equipment upgrade and a computer program upgrade.
The C2P for Model 5, also referred to as Version 1, receives data from the updated tactical system. This data has been normalized to be independent of any particular link. The messages exchanged between the TDS and the C2P, which contain this normalized data, are referred to as the N-series messages. The C2P reformats this normalized data as J-series messages for transmission over Link-16, and/or as M-series messages for transmission over Link-11.
14.14.8 The Tactical Data System The shipboard Link-16 TDS consists of one or more AN/UYK-43 computers. The Model-5 operator interface is implemented on the UYQ-70 console, which supports color graphics and overlaid windows-based displays.
The major functions of the TDS are:
Providing tactical digital information to data link participants Receiving and processing incoming tactical digital information from data link participants Maintaining the tactical data base.
The program residing in the TDS computer performs many other functions in addition to these. It supports system management, Link-11 and Link-16 management, identification, and weapons selection. It permits operators to perform control and integration functions for the combat system, and it also manages the data displays.
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Figure 14-21—TDS Data Exchange.
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14.14.9 The Command and Control Processor The Comm and and Control Processor subsystem, or C2P, is a message distribution system that provides the interfaces between the TDS computer and the JTIDS terminal.
It consists of a computer, which runs the C2P computer program, controlled by a data terminal set (DTS). The DTS serves as the Man-Machine Interface (MMI), also known as the Human-Computer Interface (HCI), to the C2P hardware and software.
The C2P is at the heart of the Link-16 system and performs a multitude of critical functions. It receives outgoing information from the TDS computer, translates it, and formats it for subsequent transmission on Link-16 or Link-11. Conversely, the C2P receives incoming information from these tactical data links, translates it, and provides it to the TDS computer. The C2P also automates many link-protocol, message formatting, and message-receipt/compliance functions. Finally, it performs data forwarding whereby information received on one data link is translated and retransmitted on another data link.
Figure 14-22—C2P Translation and Distribution System. 14-37 UNCLASSIFIED
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To control the data links, the operator m ay select any of over 30 displays from the HCI’s “Table of Contents” screen. Operator entries, such as Participating Unit or JTIDS Unit (PU/JU), Data Link Reference Point (DLRP), track block assignments for both Link-16 and Link-11, and operational mode, must be entered at the HCI before a link can be initiated. Improperly entering any of these values may cause the link to degrade or to break down completely.
14.14.10 Design Goals Link-16 was designed, and has been implemented in the U. S. Navy, to satisfy particular goals. These include:
Autonomous operation Maximum automation Standardization Backward implementation
14.14.10.1 Autonomous Link-16 Operation The Link-16 message standard is designed to support the full range of tactical information exchange requirements necessary in the great majority of operational scenarios. Ideally, a force should be able to operate quite sufficiently using Link-16 as the sole means of external real-time tactical communications, without reliance on voice or other forms of external communications. This is the reason for the greatly expanded volume of information that can be exchanged over Link-16, as compared with the volume that can be exchanged over Link-11.
14.14.10.2 Maximum Automation The Link-16 message standard, particularly the protocols for data exchange, are designed to support maximum automation of tactical functions, such as engagement tactics and combat decisions. This concept enables a system to be designed such that operator burden can actually be reduced over that required for operating on current Link-11. The digital hand-over process is a good example of the concept of maximum automation.
14.14.10.3 Standardization A general policy of maximum standardization is reflected in the Link-16 message standard in two important ways. First, data element definition and employment is standardized to the maximum feasible extent across the various warfare areas (AAW, ASW, etc.). Second, Naval implementation of all data items is standardized to the maximum appropriate extent among all platforms. Such standardized implementation is intended to: 14-38 UNCLASSIFIED
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Prom ote interoperability between platforms and services Improve operator (including staff) cross-training among participating ship types and classes Greatly reduce the need for operators to learn and accommodate differences between ships operating together Promote efficiency in the overall Naval system design process — to facilitate, for example, the introduction of the C2P.
14.14.10.4 Backward Implementation Systems which implement a Link-16 capability that is equivalent to a Link-11 capability not currently implemented will implement the Link-11 and Link-16 capabilities simultaneously. Furthermore, some of the Link-16 capabilities that were not previously available in the Link-11 message standard are now, where feasible, being added to Link- 11. This concept clearly promotes multilink interoperability, as well as cost-efficient system design.
Figure 14-23—Link-16 Concepts.
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14.14.11 Surveillance Surveillanc e consists of searching for, detecting, identifying, and tracking objects which have tactical significance to the Strike Group. These objects, which are assigned a unique track number, include land points, bearings, and fixes, as well as air, surface, and subsurface contacts acquired from radar, IFF, sonar, and other sensors. Automatic procedures exist to limit the reporting of a contact to a single unit. This unit is said to have reporting responsibility (R2) for the track. This minimizes the volume of tracks reported, while allowing each unit to track all contacts.
14.14.12 Track Reporting The concept of track reporting on Link-16 is identical to that of Link-11, with the new addition of land tracks. JUs originate tracks and assume reporting responsibility (R2) for Air, Surface, Subsurface, and Land Tracks using exactly the same rules as current Link- 11. Furthermore, in a multilink force with both JUs and PUs, which communicate with each other through a Forwarding JTIDS Unit (FJU), track reporting is homogeneous within the entire force. Only one Interface Unit (IU), either a PU or a JU, will have R2 for a track at any given time.
14.14.13 Electronic Warfare Link-16 is designed to support the concepts of cooperative electronic warfare (EW) and data fusion. EW data is of two types: parametric and product. Parametric data is the raw, unevaluated EW intercepts and parameters received from systems such as the SLQ- 32 or LAMPS. These include data on fixes, areas of probability (AOPs), and lines of bearing (LOBs). Product data is evaluated data and normally means that an EW coordinator or other qualified operator has evaluated the intercepts from one or more participants and has developed a product which is deemed to be of general tactical significance. Two different Network Participation Groups (NPGs) support the exchange of EW data: the EW NPG and the Surveillance NPG.
Figure 14-24—NPG Support. 14-40 UNCLASSIFIED
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14.14.14 Force Trainin g Link-16 fully supports the concept of “train the way you fight.” Unlike Link-11, it has been specifically designed to facilitate data link training and the use of data links in exercises. Associated with all Link-16 track and EW product messages are two special indicators: the Exercise Indicator and the Simulation Indicator.
14.14.14.1 Exercise Tracks The Exercise indicator signifies that a track is actually a Friend acting as the link-reported Identity for the purpose of the exercise. Friendly aircraft, ships, submarines, or emitters providing opposition in exercises can be identified thereby as Exercise Hostile (Faker), Exercise Suspect (Joker), Exercise Assumed Friend, Exercise Unknown, or Exercise Neutral. All other data normally reported for tracks, such as Platform, Activity, and Specific Type, can also be reported artificially for exercise tracks. Thus, an actually friendly track can be fully identified, just as though it were a genuine enemy track.
14.14.14.2 Simulated Tracks Both Link-16 and Link-11 enable full training scenarios to be conducted. Simulated tracks, based on simulated video, are initiated with or without the presence of actual live tracks. Both links allow the simulated video to be distributed to all ships in a Strike Group. The Simulation Indicator specifically identifies link tracks as simulated, not live.
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Review Questions
1. Link 11 data communications must be capable in what bands?
2. What is DLRP and what is it used for?
3. How many modes of operation does Link 11 have and what are they?
4. What is Net Cycle Time and the factors that affect it?
5. What is the difference between Link 11 and Link 16?
6. What are the features of Link 16?
7. Explain what frequency hopping is?
8. What are the major components of the Navy shipboard Link 16 system?
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14-43 UNCLASSIFIED ANSWERS TO CHAPTER QUESTIONS
1. High-frequency (HF) and ultrahigh-frequency (UHF)
2. Data Link Reference Point, to correlate multiple information coming from different sources (if improperly entered there will be a breakdown in the system).
3. 6, Net Synchronization, Net Test, Roll Call, Short Broadcast and Radio Silence.
4. a. Net Cycle Time (NCT) is the time required for Net Control Station (NCS) to complete a polling sequence of al PUs. b. Factors that affect it are: The number of PUs polled, number of PUs that reply to the initial call, number of PUs that reply to the second call, number of PUs that do not reply to either call and amount of data that each PU is transmitting.
5. Nodelessness, jam resistance, flexibility of communication operations, separate transmission and data security, increased numbers of participants, increased data capacity, network navigation features, and secure voice.
6. Jam resistance, improved security, increased data rate (throughput), increased amounts/granularity of information exchange, reduced data terminal size, allowing installation in fighter and attack aircraft, digitized jam-resistant secure voice capability, relative navigation and precise participant location and identification.
7. The frequency is not held constant during the time slot but is changed rapidly (every 13 microseconds) according to a pre determined pseudo-random pattern.
8. Tactical Data System (TDS), Command and Control Processor (C2P), JTIDS Terminal and JTIDS Antennas.