Evolution of military tactical radios - · PDF fileInitial MS Page Sequence Stamp: Article Title: Evolution of military tactical radios Article ID: ... RF modulation was a mere scientiﬁc

30 March 2017 20:35 YB150721.tex McGraw Hill Encyclopedia of Science & TechnologyKeystroked: 24/02/2017Initial MS Page Sequence Stamp:Article Title: Evolution of military tactical radiosArticle ID: YB1507211st Classification Number: 6620002nd Classification Number: 700000Contributor: 18711PUB Year: 2017

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Evolution of military tactical radios 1

Evolution of military tactical radiosThe discovery of the technique of modulating aradio-frequency (RF) signal initiated the journeyof the ever-evolving military communications field.However, RF modulation was a mere scientific cu-riosity until hardware improvements and better un-derstanding of the nature of modulated signals trig-gered the development of practical and continuouslyimproving military radios. Examples of hardware im-provements in the early stages of military radiosinclude the use of the micrometer spark gap, mag-netic detectors, and electrolytic capacitors. The de-velopment of vacuum tubes and the three-electrodetube used for signal amplification made possiblea well-connected battlefield. See also AMPLITUDE-

MODULATION RADIO; CAPACITANCE; MAGNETOME-

TER; MODULATION; SPARK GAP; VACUUM TUBE.

Development from 1900 through World War II

During the first decade of the 1900s, military ra-dios were very bulky. The U.S. military used mulesand wagons to deploy a single radio to allow a fieldunit to communicate with their commanders. Dur-ing World War I (WWI), the U.S. military and majorelectrical firms leveraged vacuum tubes to achievemajor progress in radio engineering that was madepublic after the war. Post-WWI publications showedin-depth understanding of how to use vacuum tubesto build advanced circuits for modulation and de-modulation, filtering, base-band detection, and sig-nal amplification. See also AMPLIFIER; AMPLITUDE-

MODULATION DETECTOR; DEMODULATOR; ELECTRIC

FILTER.After WWI, the improvement of military radios

relied on advances in vacuum-tube technology thatmade them smaller in size, last longer, and use lesscurrent. The period between WWI and World WarII (WWII) saw leaps in new techniques of buildingradios, including those introduced by Harry Nyquistin a 1928 paper that used a raised cosine function tomodel the RF power spectrum; this work opened thedoor to developing modulation techniques that min-imized interference and could digitize the RF signal.The U.S. Army pioneered the adoption of frequencymodulation in place of amplitude modulation, radi-cally reducing noise interference. See also ELECTRI-

CAL INTERFERENCE; ELECTRICAL NOISE; FREQUENCY-

MODULATION RADIO; INFORMATION THEORY.Although the revolutionary understanding of

solid-state physics that made it possible to refineoscillating crystals into a “transfer resistor” or tran-sistor was developed after WWII, the United Statesentered WWII with highly developed radios thatwere vacuum-tube–based (Fig. 1). The U.S. ArmyAir Forces (the predecessor of the U.S. Air Force)had long-range, medium-range, and short-range ra-dios for air-to-ground and air-to-air communications.The U.S. Army fielded portable radios down to theplatoon-commander level; every tank had at leastone radio, and commanding tanks had up to three

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2 Evolution of military tactical radios

(b)(a)Fig. 1. A World War II hand-held, two-way, battery-powered radio (handie-talkie), the SCR 536 (BC-611), is viewed(a) obliquely from front (Credit: Dave Hollander N7RK), and (b) from side, where push-to-talk button is visible(Credit: National Electronics Museum).

radios to coordinate operations; tactical headquar-ters had telephone switchboards. The U.S. Navy hadship-to-shore links. WWII is also credited for thedevelopment of radio relays that used newfrequency-modulation approaches and techniquesfor time-division multiplexing (TDM) and time-division multiple access (TDMA) to carry multiplevoice channels on the same link. Relays were alsoused to communicate typed messages from the con-tinental United States to war theaters around theglobe. See also MULTIPLEXING AND MULTIPLE ACCESS;TRANSISTOR.

Development from the Vietnam War to the present

During the Vietnam War, the advance of radio tech-nology was fueled by the Cold War scientific com-petition that included communications electronics.That war started with the United States using ra-dios lighter than those of the World War II era,employing the high-frequency (HF) and ultrahigh-frequency (UHF) bands. The U.S. Army divided theUHF band among armor, infantry, and artillery com-munications. The middle infantry band overlappedthe armor and artillery bands to call in support. TheU.S. Air Force used the HF band for over-the-horizoncommunication with ground-to-air links. While theVietnam War was still ongoing, the U.S. militarystarted new groundbreaking programs in satellitecommunications and in antijamming military radios.Because these antijamming radios preexisted the In-ternet and the common use of the Internet Protocol(IP), they used proprietary protocols, and we nowrefer to them as legacy radios. At the turn of the mil-lennium, the U.S. military introduced another gener-


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Fig. 2. Korean War military radio, model 71 B, used by vehicles and signal officers.(Credit: Diego Granados, www.diegogranados.com)

ation of mobile ad-hoc networking (MANET) radiosbased on the IP, which are now referred to as IPradios. Today’s forward-looking research programsfocus on developing cognitive radio (CR) and cogni-tive networking capabilities. The increase in capabil-ity was accompanied by a significant size reductionof military radios, from those of WWII (Fig. 1) andthe Korean War (Fig. 2) to current models (Fig. 3).The most significant technological breakthroughs oflegacy radios, IP radios, and CR will be discussed. Seealso COMMUNICATIONS SATELLITE; INTERNET; RADIO

SPECTRUM ALLOCATION.Legacy radios and antijamming. While WWII com-

munications relied on message encryption and in-terception of the enemy’s signals to break its en-cryption code, the Vietnam War introduced the useof jammers to disable enemy communications. Theuse of jammers raised the need for antijamming (AJ)radios. AJ radios divide time into epochs. Each epochis divided into time slots (TDMA). The radio is de-signed, as well, for a wide frequency range, and thisfrequency range is divided (frequency-division multi-


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Fig. 3. Prototype Rockwell Collins airborne radio. (Credit: Rockwell Collins)

freq

uenc

y

time

123

netnumber

timeslice

timeslot

epoch

Fig. 4. AJ radios’ use of TDMA and FDMA with spreadspectrum and frequency hopping.

ple access; FDMA) into bands (nets), creating a gridof time slots and frequency bands (Fig. 4). Hard-ware was developed to frequency hop. Hoppingwas very fast (of the order of microseconds), andthe hopping pattern followed an encryption code(seemingly random) that was hard to break. Overthe frequency band selected for transmission, spreadspectrum was also used to further diminish the ef-fect of jammers. (Spread spectrum was first usedby military radios for antijamming, but the commer-cial industry adapted it for cellular technology fordifferent reasons, including its increased over-the-air capacity and better penetration through build-ings.) In addition, the understanding of error-controlcoding that was achieved in the 1950s and 1960swas leveraged in building these radios, further in-creasing jamming resistance. New antenna technolo-gies allowed operation at lower signal-to-noise ratios(SNRs), further increasing jamming resistance. TheseAJ radios also used message security in addition tothis transmission-layer security. See also CRYPTOG-

RAPHY; ELECTRONIC WARFARE; JAMMING; SIGNAL-TO-

NOISE RATIO; SPREAD SPECTRUM COMMUNICATION.The U.S. military radios from this era included the

EPLARS, SINCGARS, and Link-16. EPLARS and SINC-GARS were widely used by the Army, and Link-16by Air Force and Navy planes. Ship-to-shore com-munications moved to secure satellite links. Link-16was the first program out of the space program to


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use concatenated codes (two layers of error-controlcoding). It was the most complex military radio pro-gram in that era, and allowed fighter jets traveling atMach 3 speed and at distances up to 500 km (300 mi)to communicate (voice and data) in the presence ofjamming. Link-16 connected fighter jets together andto ground command and control (C2).

IP MANET radios and rich apps. The U.S. militarysucceeded in developing IP-based core networks,and used gateways to create seamless communi-cations between core IP networks and legacy ra-dios, connecting the entire battlefield seamlessly.The First Gulf War (1990–1991) demonstrated a fullyconnected battlefield to the individual soldier, withapplications such as red force–blue force tracking(where a solider could see on a screen the location ofenemy and friendly nodes), close air support and tar-geting, and full cooperation between U.S. and alliedforces in joint missions. However, the advantages ofusing IP all across the battlefield and the develop-ment of new concepts to meet the ever-increasingneed for more bandwidth strongly favored the de-velopment of the IP MANET generation of radios.Consequently, today’s warfighters, who are used tosmartphones and tablets, can tether a smart deviceto an IP port in their radios and use a myriad of richapps for situational awareness, fire support, chat,and many other applications, with capabilities thatmatch the needs of the warfighter and the mission.See also MOBILE COMMUNICATIONS.

In addition to using the IP as the network layer,IP MANET radios have made many technologicalleaps, including the use of cross-layer signaling, anddynamic resource allocation (including frequencyreuse) to increase bandwidth and radio throughput.IP radios are also software-defined radios (SDRs),which means that different waveforms (software)can be downloaded on the same hardware. A newwaveform with new capabilities can be developed(all in software) and downloaded into existing hard-ware. With SDR, the term radio can mean the hard-ware (commonly referred to as the form factor) andthe term waveform can mean the software. Conse-quently, SDR means the ability to develop separateadd-on modules at the different protocol stack layersto enhance the radio performance. See also APPLICA-

TION OF SOFTWARE-DEFINED RADIO; DATA COMMUNI-

CATIONS; SOFTWARE-DEFINED RADIO.One of the most funded IP waveforms is the Wide-

band Networking Waveform (WNW), which has dif-ferent modes of operation that allow it to be used ondifferent platforms including ship-to-ship communi-cations, tanks and light vehicles, and airborne nodes,and can be downloaded to a form factor for an in-dividual dismounted soldier.The WNW made use ofthe SDR concepts to create a highly capable MANETradio. In addition to the AJ capabilities, the WNW hasan IP encryption layer known as the high-assuranceInternet protocol encryption (HAIPE), making it themost secure IP waveform to enter service. HAIPEcreates a cipher-text layer fully separated from theplain-text layer where applications run. Below the


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MI layer

MDL layer

SiS layer

segmentationand assembly

resourcemanagement

neighbormonitoring

queuing

linkadaptation ODMA

channel access

transmitstatus

queuestatus

closed-loopmetrics

1

1 received cells for reassembly2 queued cells3 pulled cells for transmission4 adjusted TDMA schedule5 filtered metrics6 closed-loop metrics7 transmit parameters8 list of neighbors9 control packets

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tran

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rece

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Key:

Fig. 5. Cross-layer signaling with the WNW. ODMA = dynamic resource allocation.

cipher-text IP layer, the WNW has a mobile Internet(MI) layer, followed by a highly capable mobile datalink (MDL) layer, with a myriad of software modules.The lower layer, referred to as the signal-in-space(SiS) layer, has the ability to switch between differ-ent modulation modes to adapt to the needs of thewar theater. Figure 5 shows some of the cross-layersignaling across the protocol stack layers, as well assignaling between the different MDL modules thatcreate the dynamic adaptation of the WNW.

Cognitive radios and cognitive networking. CRs arebuilt on SDR concepts, and they leverage hardwareadvances such as more computational power at smallsize, advances in sensors that make it possible toequip a radio with sensors that are very light-weightand very capable, and advances in fast-steering di-rectional antennas to create radios that morph inresponse to battlefield needs. CRs have the ability tocreate new waveforms on their own (more than justchanging modulation modes, as the WNW does), inwhich a variety of modulation modes is available atwide ranges of frequency bands; antenna patterns,packetization, routing and dissemination of multi-cast and broadcast packets, and application behav-ior can all change; and error-control coding capa-bilities can increase or decrease. CRs can negotiatenew interfaces with the hardware and adjust quality-of-service parameters, based on not only missionneeds, but also sensed environments and applica-tion demand. These waveforms can make collabo-rative decisions internal to a node and between thedifferent nodes, using advanced game-theory con-cepts. Testing is ongoing for radios that can sensejammers and eavesdropping enemy nodes, and route


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9

omnidirectionalantenna pattern

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directional antenna pattern

Fig. 6. Cognitive radio sensing of a compromised area (the yellow disk), and routing around it (red arrows) using directionalbeams.

around them while minimizing spectrum footprints.Figure 6 shows routing between nodes 2 and 8through an omnidirectional antenna pattern that awaveform such as the WNW could have selectedas well as directional antenna patterns that routearound compromised areas (yellow color), wherejammers or eavesdropping nodes are sensed. CRtechniques are also developed to increase radio re-silience when routing through compromised areasis needed. The radios can move to a different fre-quency band (outside of a jammer band) or increaseerror-control coding and signal power to communi-cate over jammers.

Although there is ongoing research in both com-mercial and military applications of CR and cognitivenetworking, military research emphasizes the role ofpolicies governing radio propagation to the CRs andensuring that these radios morph within the mission-defined boundaries.Military research also empha-sizes security architectures in which the presence ofseparated plain-text and cipher-text IP layers is pre-served. Military research on CRs also explores theuse of game-theory–based techniques to discover anattacking node and to isolate it through distributedcollaborative decisions. See also GAME THEORY.

The use of CRs by the defense industry is tiedto cognitive networking principles that are of spe-cial interest to military missions in which different


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types of radios and networks are used. Making theseheterogeneous networks work together seamlesslyrequires use of cognitive techniques in the up-per protocol stack layers. Researchers are explor-ing the use of an adaptation layer with distributedcognitive techniques between the IP layer and theradio, as well as adding new modules to the IPlayer for intelligent networking functions that re-act to sensed environments. Routing, multicast dis-semination, and throughput efficiency of heteroge-neous, highly dynamic networks are among the areasexplored in current research. See also COGNITIVE

RADIO. George F. ElmasryKeywords: military radios; antijamming; MANET;

cognitive radios; cognitive networksLinks to Primary LiteratureBibliography. C. D. Young and A. D. Amis, UCDS:

Unifying connected dominating set with low mes-sage complexity, fault tolerance, and flexible domi-nating factor, in IEEE Communications Society andArmed Forces Communication and Electronics Asso-ciation, Proceedings of MILCOM 2011: 2011 IEEEMilitary Communications Conference, Baltimore,MD, November 7–10, 2011, pp. 1357–1362, IEEE,2011, DOI: 10.1109/MILCOM.2011.6127493.Additional Readings. H. Arslan (ed.), Cognitive Ra-dio, Software Defined Radio, and Adaptive Wire-less Systems, Springer, 2007; G. F. Elmasry, TacticalWireless Communications and Networks: DesignConcepts and Challenges, Wiley, 2012; NorthropGrumman Corporation, Understanding Link-16:A Guidebook for New Users, 2001.

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Evolution of military tactical radios - · PDF fileInitial MS Page Sequence Stamp: Article Title: Evolution of military tactical radios Article ID: ... RF modulation was a mere scientiﬁc