77 replies to this topic

[ravnicar]

Ovo bi trebalo da bude dovoljno: http://www.albrecht-...ct_sheet_ef.pdf

 

SAJ-1030

INTELLIGENT GPS JAMMER

• Programmable GPS spoofing
• Operation modes: Deception/Confusion/Denial
• Difficult to localise
• Remotely-programmable position info offset
• Protects limited geographical areas
• Protects against GPS guided weapons and UAVs
• Adjustable high power output
• Remote control over air
• Simple operation
• High performance
• Compact size
• Rugged, watertight construction
• According to MIL-STD 810F

 

The SAJ-1030 is suitable for a range of applications. It has been specially developed to influence navigation information derived from GPS or GLONASS satellite networks, as well as from the upcoming GALILEO system. It is thus applicable for officials, official security organisations and the 

military and for defence against terrorist hazards.

Depending on the tactical situation, various operation modes can be set for deception or confusion.Owing to its innovative design, the SAJ-1030 is able to perform its missions either independently or as part of a superposed EW system. It exploits a sophisticated technique for jamming navigation satellite receivers.

Simple GPS jammers, on the other hand, generate easily recognisable signals, which are then neutralised by anti-jamming technology built into modern tactical GPS devices (guided missiles, etc). Worse, such simple GPS jammers can be easily sited and therefore become open to military targeting. In contrast, our highly sophisticated SAJ-1030 GPS jammer generates complex signals, which effectively cannot be evaluated as jamming signals. The ECCM measures built into e.g., guided missiles, UAVs etc., are therefore notactivated. Typical countermeasures such as beam-steering and beam-forming techniques thus become ineffective.

Due to the complexity of the jamming signal, localisation using currently known methods is essentially impossible. This makes our SAJ-1030 GPS Jammer eminently suitable for protection of sensitive areas such as air fields, command posts, etc. An option allows differentiation among GPS receivers to be jammed and friendly receivers.

 

...

 

Ovo je proizvod manje firme i ima ih vise koje proizvode slicne prenosne ometace i trguje se iskljucivo sa vladinim institucijama. Sta li tek ima Raytheon ili pomenuti Northrop Grumman i slicne firme u Aziji.

 

Edited by ravnicar, 08 August 2013 - 23:51.

[st.maurice]

 

Ovo bi trebalo da bude dovoljno: http://www.albrecht-...ct_sheet_ef.pdf

 

SAJ-1030

INTELLIGENT GPS JAMMER

• Protects against GPS guided weapons and UAVs

 

Jasno, ali nismo pricali o navigaciji i gps jammer-ima (koji kostaju i po 50 funti) vec o komunikaciji, Have Quick i vojnim satelitima koje koriste UAV operateri... tj. valjda smo pricali o tome, obzirom da smo obojica spomenuli da UAV bez problema koriste terten za navigaciju a ne gps jos od 90-tih.

 

Mislim da se samo oni relativno jeftini UAV oslanjaju samo na gps uredjaje, a onim mikrodronovima se na nivou voda upravlja i iz neposredne blizine.

Edited by st.maurice, 09 August 2013 - 00:04.

[ravnicar]

Jasno, ali nismo pricali o navigaciji i gps jammer-ima (koji kostaju i po 50 funti) vec o komunikaciji, Have Quick i vojnim satelitima koje koriste UAV operateri... tj. valjda smo pricali o tome, obzirom da smo obojica spomenuli da UAV bez problema koriste terten za navigaciju a ne gps jos od 90-tih.

 

A pitanje je?

[st.maurice]

A pitanje je?

 

Pitanje je isto koje ti postavio ranije Atreid, kako se moze omesti npr. HAVE QUICK komunikacija sa brzo-rotirajucom frekfencijom, koja je pri tome i sifrovana?

[ravnicar]

Pitanje je isto koje ti postavio ranije Atreid, kako se moze omesti npr. HAVE QUICK komunikacija sa brzo-rotirajucom frekfencijom, koja je pri tome i sifrovana?

Koliko sam upoznat, Data linkovi za UAV rade na prilicno visim frekvencijama, ne koriste Have Quick vec posebno dizajniran sistem koji se opciono enkriptuje, tezak za ometanje ali ipak moguce. Kako i zasto? Pretpostavljam zbog vrste, kolicine i brzine podataka koje treba preneti. Mislim da nisam daleko, za detaljniji odgovor to je pitanje za nekog drugog.

 

 

... tj. valjda smo pricali o tome, obzirom da smo obojica spomenuli da UAV bez problema koriste terten za navigaciju a ne gps jos od 90-tih.
Mislim da se samo oni relativno jeftini UAV oslanjaju samo na gps uredjaje, a onim mikrodronovima se na nivou voda upravlja i iz neposredne blizine.

Sto se tice pozicioniranja svi se oslanjaju na GPS a neki i na inercijalni sistem i TERCOM sistem za pracenje terena koji si pomenuo. TERCOM takodje ima svojih mana jer je osetljiv na sezonske promene, nepouzdan iznad tundre i tajge, sneznih predela i vode. Ometa se tako sto mu se ometa radarski visinomer. Zbog svih nedostataka, vrsi povremene provere preko GPS-a koji se opet najlakse ometa.

Koristi se jos od ranih sedamdesetih.

 

...

 

Pricali smo uopsteno o UAV iako je to prilicno siroka tema sto zbog razlicitih modela i namena, sto zbog razlicitih tehnologija i proizvodjaca kojih ima podosta. Mislim da sam odgovorio na veci deo pitanja.

 

Ne potcenjuj navigaciju, to je prva stvar koja se napada, ako letelica ne zna gde se nalazi od zadatka nema nista. U zavisnosti od modela, u slucaju otkaza ili ometanja neke mogu dobiti podatke o svojoj poziciji od druge letelice koja ima podatke sa radara  ili transpondera cime se donekle otkriva polozaj i povecava mogucnost pracenja.

Edited by ravnicar, 09 August 2013 - 01:01.

[st.maurice]

Koliko sam upoznat, Data linkovi za UAV rade na prilicno visim frekvencijama, ne koriste Have Quick vec posebno dizajniran sistem koji se opciono enkriptuje

 

Ne razumem zasto mislis da bi komunikacioni linkovi za recimo f-22 imali frequency hopping i enkripciju, ali ne i za x-47?

 

, tezak za ometanje ali ipak moguce. Kako i zasto? Pretpostavljam zbog vrste, kolicine i brzine podataka koje treba preneti. Mislim da nisam daleko, za detaljniji odgovor to je pitanje za nekog drugog.

 

Ali to je upravo ono sto me zanima!

 

Don't get me wrong, ne insistiram na pitanju da bih ubio raspravu vec da bih saznao nesto novo. Volim kada procitam nesto sto nisam ranije znao kao recimo to za Have Quick. Ovako nisam nista saznao, sem da mislis da moze.

 

Sad sto se tice x-47(c,b) on koristi kao datalink link 16*

 

"Link 16 is a TDMA-based secure, jam-resistant high-speed digital data link which operates in the radio frequency band 960–1,215 MHz, allocated in line with the ITU Radio Regulations to the aeronautical radionavigation service and to the radionavigation satellite service."

 

odnosno Tactical Targeting Network Technology** koji izgleda funkcionisu slicno Have Quick-u (na slici se i vide razlicite frekfencije u okviru svakog paketa):

 

 

* fas.org: uav roadmap 2005

** Navy Completes TTNT For X-47B Deck Handling Trials

 

Inace taj sistem ne koristi samo x-47 i druge UAV, vec cela vojska i prilicno je integrisan:

 

http://www.youtube.com/watch?v=QZRrNIdJSAU

 

prilicno impresivne karakteristike (ceo sistem je ustvari zanimljiviji od samog x-47 ili bilo kog borbenog sistema koji ga koristi)

• Doppler estimate supports TTNT data transfer closure rates at 4,800 knots – Mach 8 at sea level
• At the strongest signal level, test have shown data speeds of Mach 12 are achievable
• In an Airborne Tactical Edge scenario, TTNT’s optimum throughput is 10 Mbps of system traffic at a range of 300 nm, enough coverage for an area the size of the entire state of Iowa

rockwellcollins.com

 

edit: Yup, link 16 def. koristi f. hopping

 

Link-16 uses the Time-Division  Multiple  Access (TDMA)  principle  of  data  communications.  Using this  architecture  with  time  interlacing  provides  the system  with  multiple  and  apparently  simultaneous communications nets. Instead of assigning each unit a  PU  number,  Link-16  assigns  each  unit  a  JTIDS Unit number, or JU. The JU identifies the units and determines  a  preassigned  set  of  time  slots  that designate when the unit transmits and receives data. Each  time  slot  is  1/128  of  a  second,  or  7.8125 milliseconds, in duration. When a JU transmits data, the frequency that the data   is   transmitted   on   is   changed   every   13 microseconds  (µsec),  according  to  a  predetermined pseudo-random  pattern. Link-16  uses  51  different frequencies   for   data   exchange.   This   frequency hopping   adds  to  the  security  and  integrity  of  the system by making it nearly impossible to jam.

 

http://firecontrolma...ss/14103_77.htm

 

etc. etc.

Edited by st.maurice, 09 August 2013 - 05:03.

[Atreid]

Predstavnicima americkog kongresa je cak omoguceno da uzivo prate ometanje i potpuno preuzimanje manje bespilotne letelice. Posto su bili sumnjicavi po tom pitanju, otprilike tako kao ti, i nisu bas kapirali koliku i kakvu pretnju moze da predstavlja njihova imovina kada dospe gde ne treba, uprilicili su im hijacking.

 

Sam kazes "manje", znaci sa jeftinijim sistemom za komunikaciju, a moguce i starijim. Osim toga, cista predstava za politicare da bi izvukli pare za razvoj novih.

 

Imas ovako:

 

- Emitovanje u prosirenom spektru;

- Frekventno skakanje;

 

I ne mozes joj nista. Ne mozes:

 

- detektovati signal;

- ometati signal;

- upasti u komunikaciju;

- prisluskivati;

 

        edit: Ni ti ni Atreid ne citate sta sam pisao. Rekao sam da je moguce a vas dvojica od " nema tu sta da se ometa" do "ima al' je mnogo tesko".  Moguce je a da li je tesko - pa kako kome. 

 

Pogledaj samo gdje je Predatoru komunikacioni link:

 

 

Ova antena na sredini je za komunikaciju ka satelitu, i sad neka ti je na 10 000 metara visine, iznad tebe + ono sto sam nabrojao, pri tome su GHz veze strogo usmjerene, pa ne mozes ni fizicki da pridjes liniji komunikacije (morao bi biti iznad nje), kako mislis bilo sta da uradis?

Edited by Atreid, 09 August 2013 - 09:43.

[ravnicar]

Sam kazes "manje", znaci sa jeftinijim sistemom za komunikaciju, a moguce i starijim. Osim toga, cista predstava za politicare da bi izvukli pare za razvoj novih.

 

To me ne interesuje. Pricali smo uopsteno a UAV a ne o pojedinacnim slucajevima.

 

 

 

Imas ovako:

 

- Emitovanje u prosirenom spektru;

- Frekventno skakanje;

 

I ne mozes joj nista. Ne mozes:

 

- detektovati signal;

- ometati signal;

- upasti u komunikaciju;

- prisluskivati;

 

- namerno emitovanje nepravilnih signala s tim sto se moraju znati izvori koje prijemnik posmatra 

- ometanje šumom usmerenim na odredjenu frekvenciju a koji deluje na prosireni spektar 

- emitovanje snage da bise zahvatili potrebni opsezi.

 

Moguce/nemoguce? U odredjenom procentu je efikasno. Avioni koji se koriste za elektronsko ratovanje i ometanje se lako nadju na liniji vidljivosti izmedju prijemnika i satelita. 

 

 

Ova antena na sredini je za komunikaciju ka satelitu, i sad neka ti je na 10 000 metara visine, iznad tebe + ono sto sam nabrojao, pri tome su GHz veze strogo usmjerene, pa ne mozes ni fizicki da pridjes liniji komunikacije (morao bi biti iznad nje), kako mislis bilo sta da uradis?

 

Znas li ti kakve su mogucnosti letecih platformi za elektronsko ratovanje i ometanje? Upravo sluze tome da se nadju na linijama komunikacije kad treba.

 

 

Ne razumem zasto mislis da bi komunikacioni linkovi za recimo f-22 imali frequency hopping i enkripciju, ali ne i za x-47?

 

 

Ja to nisam rekao. Rako sam da se na nekim UAV enkripcija na Data linku koristi opciono.

 

 

Ali to je upravo ono sto me zanima!

 

Don't get me wrong, ne insistiram na pitanju da bih ubio raspravu vec da bih saznao nesto novo. Volim kada procitam nesto sto nisam ranije znao kao recimo to za Have Quick. Ovako nisam nista saznao, sem da mislis da moze.

 

 

Moraces da nadjes nekog strucnjaka da ti objasni. Bojim se da je to malo komplikovanija tema.

Edited by ravnicar, 09 August 2013 - 12:15.

[ravnicar]

Izgleda da vas dvojica ne kapirate sustinu elektronskog ometanja i posmatrate suvise usko. To nije stoprocentno efikasna tehnika iz dobro poznatih razloga i tu je da pomogne a ne da u potpunosti resi problem. Sto je oprema slozenija, to ju je moguce napadati iz vise pravaca.

 

Na samom pocetku sam rekao da je ometanje moguce i da oprema postoji ili se razvija. Nije stvar mog misljenja vec cinjenica. Ako proizvodjac kaze da je moguce da mu se oprema u odredjenoj meri ometa i time joj narusi funkcionisanje, ne vidim problem da isto  prihvatite.

 

Ne postoji vojna tehnologija bez mane kojoj se nije moguce suprotstaviti. Da li za to treba manje ili vise novca i znanja druga je stvar kao i koliko ce kontramere biti uspesne.

[Atreid]

To me ne interesuje. Pricali smo uopsteno a UAV a ne o pojedinacnim slucajevima.

Pa ne, logicno je da "manje" imaju prostiji sistem, samim tim su i ranjivije, a sa druge strane ni ne nose neku previse bitnu opremu (za spijuniranje, npr.) pa i ako tako neka padne i nije neki uspijeh.

 

- namerno emitovanje nepravilnih signala s tim sto se moraju znati izvori koje prijemnik posmatra
- ometanje šumom usmerenim na odredjenu frekvenciju a koji deluje na prosireni spektar
- emitovanje snage da bise zahvatili potrebni opsezi.

Moguce/nemoguce? U odredjenom procentu je efikasno. Avioni koji se koriste za elektronsko ratovanje i ometanje se lako nadju na liniji vidljivosti izmedju prijemnika i satelita.

Drugim rijecima u sva ta tvoja tri slucaja moras znati u kom opsegu ti radi link, a ja u onom mom primjeru rekoh da cu 1/4 signala da stavim po sred tvog vojnog komunikacionog kanala, i sta onda, ometat ces samog sebe, pri tome kako ces uopste znati da ti je tu 1/4 mog signala?

 

 

Znas li ti kakve su mogucnosti letecih platformi za elektronsko ratovanje i ometanje? Upravo sluze tome da se nadju na linijama komunikacije kad treba.

Te letece platforme nemaju drzave srednje razvijenosti u koje spada i Srbija, npr. A, jos manje ih imaju neke teroristicke organizacije. Takve platforme imaju sile tipa Kine, Amerike, Rusije,... a one, sto vec neko napisa, mogu fino da direktno rijese stvar sa komandnim mjestom ili da obore satelit.

Edited by Atreid, 09 August 2013 - 14:04.

[ravnicar]

Pa ne, logicno je da "manje" imaju prostiji sistem, samim tim su i ranjivije, a sa druge strane ni ne nose neku previse bitnu opremu (za spijuniranje, npr.) 

 

Nije logicno. Pitanje je sta ti smatras pod manjom UAV a iznenadio bi se koliko umeju da budu skupe i kakvu takticki veoma vaznu opremu nose. Uredjaji nisu vise glomazni i zauzimalu relativno malo prostora. Kakvi ce sistemi biti ugradjeni najvise zavisi od namene a male dimenzije su ponekad prilcna prednost. Velike dimenzije UAV su vezane za dolet autonomiju leta i naoruzanje a takvih za sada ima malo.

 

Da oprema nije bitna ne bi je ni bilo, niti bi se bacale pare na nebitne stvari.

 

 

Pa ne, logicno je da "manje" imaju prostiji sistem, samim tim su i ranjivije, a sa druge strane ni ne nose neku previse bitnu opremu (za spijuniranje, npr.) 

 

Pa i takve se koriste, zar ne! Da li je uspeh, zavisi od toga sta bi se dobilo njihovim onemogucavanjem i kakva bi steta bila sprecena ukoliko bi ometanje uspelo.

 

 

Drugim rijecima u sva ta tvoja tri slucaja moras znati u kom opsegu ti radi link, a ja u onom mom primjeru rekoh da cu 1/4 signala da stavim po sred tvog vojnog komunikacionog kanala, i sta onda, ometat ces samog sebe, pri tome kako ces uopste znati da ti je tu 1/4 mog signala?

 

Posmatraj siru sliku. Opsezi su u odredjenom procentu poznati, ima ko treba da se tim bavi i prikupi informacije. Dovoljno je onemoguciti neku od funkcija na letelici a to je na prvom mestu navigacija. 

 

Zasto si se vezao za taj 1/4 signal? Mozda i ne moram da znam za postojanje tvog signala, posmatra se kompletan link i ako dodje do 30% pada kvaliteta, informacije postaju nerazumljive. Pitanje i kakve uredjaje bi koristio, nekad se cilja na sam uredjaj bez obzira na signale koje treba da primi.

 

Da li bi ta tvoja dvominutna konstrukcija icemu sluzila, za sta bi uopste bila korisna? Daj neku namenu. 

 

 

Te letece platforme nemaju drzave srednje razvijenosti u koje spada i Srbija, npr. A, jos manje ih imaju neke teroristicke organizacije. Takve platforme imaju sile tipa Kine, Amerike, Rusije,... a one, sto vec neko napisa, mogu fino da direktno rijese stvar sa komandnim mjestom ili da obore satelit.

 

Pa sta ce im kad vec mogu da obore satelite? Ti mislis da se UAV razvijaju samo za zaprasivanje talibana koji se kriju po kolibama i barakama? Nisam se fokusirao ni na koga posebno.

Edited by ravnicar, 09 August 2013 - 15:11.

[st.maurice]

Na samom pocetku sam rekao da je ometanje moguce i da oprema postoji ili se razvija. Nije stvar mog misljenja vec cinjenica. Ako proizvodjac kaze da je moguce da mu se oprema u odredjenoj meri ometa i time joj narusi funkcionisanje, ne vidim problem da isto prihvatite.

Poceli smo od toga da je moguce ometati linkove "uz pomoc relativno jeftine opreme" do toga da ih je "nearly impossible to jam". Slozices se da postoji razlika izmedju ta dva koncepta.

Ok bar smo saznali kako funkcionisu ti linkovi (ne samo za UAV).

Ono sto zahteva jos kopanja je kako bi ometanje takvih linkova bilo moguce bar u teoriji, posto ocigledno ne postoji sistem za koji se navodi da je to u stanju da uradi.

edit: mislim da sam iskopao nesto relevantno.

Ometanje je izgleda mnogo veci problem za GPS signal jer je on znatno manje snage od signala za linkove (dizajniran je da bude ispod nivoa suma zbog sakrivanje signala i konzervacija baterija):

 

"Ironically, these are a direct result of the system’s original aim of making the GPS satellites’ signals extraordinarily difficult to detect and use, through a combination of very low transmitted signal power and signal concealment techniques, and this remains true today. Low power was desirable in any event to assure long battery, hence long orbital life, but dropping it to -160dBm, a level well below the ambient radio “noise,” called for unique technology to detect and recover its full characteristics, while still preventing its use by adversaries.

 

Signal concealment relied on the then top secret “frequency hopping” concept, now known as today’s unclassified and widely used spread spectrum technology. But the combination of very low power and spread spectrum continues in use with America’s GPS and compatible foreign systems."

Zato je moguce ometati ga civilnim jammerima u neposrednoj blizini. Oni vojni GPS jammeri imaju veci domet:

 

"And while this statement only concerned unmanned systems, adversary jamming at long ranges and high altitudes is an equal DoD concern across its air, land and sea forces, demonstrated by its twice yearly NOTAM’d exercises on the east and west coasts, where very powerful jammers, emulating U.S. and foreign jamming technologies, radiate interference signals out to beyond 350 miles, from ground level to above 40,000 feet."

I DoD resenja za ometanje GPS-a:

Enhanced GPS receiver jamming protection: Some corporate aircraft are reported to have installed military controlled reception pattern antennas (CRPA) that evaluate all incoming signals throughout 360 degrees and block reception of segments that appear to include jamming.

Increased satellite transmitter power: the next generation GPS III constellation, with its first launch in 2015, will be able to direct higher power “spot beams” against areas of the earth’s surface where jammers have been detected.

Anti-spoofing technology: Reportedly, the military GPS M-Code is virtually immune to spoofing due to its strong encryption and therefore all M Code-equipped aircraft are protected. However, it is understood that most non-front line military aircraft use the unencrypted GPS Standard Positioning Service (SPS), as do virtually all civil aircraft

Inertial reference systems (IRS): IRS does not rely on incoming signals and, in newer airline aircraft, IRS outputs are generally integrated with GPS via the flight management system computer. In a jamming situation causing the loss of GPS, the flight management system would automatically switch to sole IRS guidance

Scanning DME plus VOR: This year, FAA proposed this combination as its solution to GPS jamming. Its appeal lies in the fact that CONUS airspace has a well established DME and VOR network

eLoran: eLoran is a modernized derivative of the earlier Loran-C system, and still employs high-powered, long range, unjammable low frequency signals extending from the surface to above jet altitudes, transmitted from widely separated ground stations.

Current military alternatives: Through the years, DoD has investigated a number of positioning systems that could support military GPS-denied situations For example, much work has gone into development of miniaturized IRS units for UAVs and small aircraft

Area positioning systems used by the surveying industry have particularly been evaluated, due to their high accuracy, GPS jamming and spoofing immunity, rapid set up and breakdown procedures and ease of portability to new areas of concern.

First, an alternative means to continue operations, even when less efficient, is essential to safe navigation. But second, and perhaps less appreciated, is that the knowledge that an alternative system, having different failure paths, will activate should the primary navaid be disabled, would be a significant deterrent to an attacker from the start. A backup to GPS would therefore not only enhance safety, but would also enhance GPS longevity.

The Future

In June, however, the Defense Advanced Research Programs Agency (DARPA) solicited industry bids for the development and tests of systems proposed for its conceptual All Source Positioning and Navigation (ASPN) program.

http://www.aviationt...-GPS_77077.html

Edited by st.maurice, 10 August 2013 - 15:43.

[ravnicar]

Poceli smo od toga da je moguce ometati linkove "uz pomoc relativno jeftine opreme" do toga da ih je "nearly impossible to jam". Slozices se da postoji razlika izmedju ta dva koncepta.

Poceo sam od toga da je moguce ometati UAV uz pomoc relativno jeftine opreme. Relativno ne znaci 50-100 usd, mozes shvatiti kao nesto sto mozes dobiti po prihvatljivoj ceni razvoja i proizvodnje.

Danas je u vojnoj upotrebi blizu 100 razlicitih modela i sistema proizvedenih u 20 drzava ne ulazeci u namenu i dimenzije. Da li ti ovo objasnjava razliku koju pominjes? 

Cini mi se da ti ciljas na nesto sasvim drugo.

Edited by ravnicar, 10 August 2013 - 18:20.

[ravnicar]

 Prelistaj ovo mozda dobjes jasniju sliku. http://www.fas.org/i...ct/uas-vuln.pdf

 

THE VULNERABILITIES OF UNMANNED AIRCRAFT SYSTEM COMMON DATA LINKS TO ELECTRONIC ATTACK

A thesis presented to the Faculty of the U.S. Army Command and General Staff College in partial fulfillment of the requirements for the

degree

MASTER OF MILITARY ART AND SCIENCE

General Studies

 

2010-01

 

 

 

 

Kako se ometaju data linkovi:

 

Sustina:

 

Their dependence on a constant control signal has contributed to a UAS accident rate 100 times greater than manned aircraft A threat could exploit this need for an uninterrupted data feed by using Electronic Warfare to disrupt this signal, potentially crippling unmanned systems.

 

 

Cilj:

 

The goal of noise jamming is to send a threat signal sufficient strength to “out shout” the transmitter sending the attacked frequency (Schlesinger 1961, 13). Noisejamming disrupts the communication waveform by inserting noise onto the receiver. The bandwidth of the signal may be as wide as the entire spectrum used by the communications system or it may occupy only a single channel

 

 

Tehnike:

 

Broadband jamming is also known as full band or barrage jamming. This type of jamming can be effective against all forms of anti-jamming (AJ) communication systems (Poisel 2003, 216). This type of jamming raises the background noise level at the receiver, creating a higher noise environment for an AJ system. If the noise is increased, it makes it difficult for a communications system to operate. Effective noise jamming may reduce the range of the communications or if the noise is sufficient, the jammer may deny communication (Poisel 2003, 216). An effective noise jamming attack can disrupt UAS CDL communications and cause the UAS to execute its lost link programming.

The greatest advantage of broadband noise jamming is the simplicity of the system. A jammer operator selects a frequency band and creates as much noise as possible to degrade an entire frequency spectrum. It does not require a smart means to acquire the specific transmitting frequency or the need to chase a frequency hopping system. The greatest disadvantage of broadband noise jamming is the strength of the jamming signal. The larger the spectrum being jammed, the less power is available to create noise.

 

Sweep jamming, or swept jamming, occurs when narrowband noise is swept across afrequency band of interest (Poisel 2003, 235). The jammer focuses on a specific frequency and a small portion of the band around the single frequency. This sweep can jam a selected band in rapid succession and have effects similar to a barrage jammer. However, a swept jammer concentrates its full power against specific frequencies on theband of interest and this allows swept jammers to have greater range than broadband jammers.

The greatest advantage of swept jamming is the ability to jam a broadband while maintaining adequate power to project its signal (Vakin, Shustov, and Dunwell 2001). Timing is the key to effective sweep jamming and if timing is correct, the jammer can hop around a spectrum with sufficient power to degrade communications. Timing is also the greatest disadvantage to swept jamming. If the jammer hops the spectrum too quickly, it may not loiter on a selected frequency long enough to achieve the degradation desired (Poisel 2003, 235).  

 

Spot jamming, or single tone jamming, occurs when a jammer concentrates all of its power on a single frequency (Poisel 2003, 229). These jammers are effective against communications systems that do not hop and are in use by the opposition. Spot jamming does not move along the frequency spectrum and this limits the utility of such jammers against modern military equipment.

The greatest advantage of spot jamming is the power available to project on its disrupting power at a target. These jammers may have greater range than systems that attack a broad frequency spectrum (Vakin, Shustov, and Dunwell 2001). The greatest disadvantage of spot jamming is its inability to target modern frequency hopping communications and the intelligence requirement of identifying the specific target frequency (Poisel 2003, 230). 

 

...

 

Man-Portable UAS are the systems most likely to experience an EA against their CDLs. These systems operate at low altitudes and in close proximity to threat forces. Their flight profile allows enemy forces to visually or acoustically acquire and track thesystem throughout their mission. Man-Portable UAS CDLs communicate on an L-band UHF frequency that is easy to jam (Poisel 2003, 213). The CDL does not use any electronic protection (EP) such as a frequency hopping radio or a coded receiver. Lastly, the UAS uses an omnidirectional that can receive commands from any direction throughout its flight profile. The C-IED devices in Iraq and Afghanistan use this type of jammer and their tendency to jam UAS CDLs is a testament to the vulnerabilities of these systems (Gaub 2010).

Tactical UAS are less likely to experience an EA against their CDLs but it is still at greater risk than Theater UAS. These systems operational altitudes are higher than Man-Portable UAS but are often within audio or visual range of threat forces (Hill 2010). Directing a jamming signal able to disrupt Tactical UAS CDLs would likely require an advanced directional antenna in order to project and focus its signal (Wilson 2010). Tactical UAS Man-Portable UAS CDLs operates using S-band UHF/SHF frequency and although more jam resistant than the L-band, it is still vulnerable to jamming (Poisel 2003, 214). Lastly, the UA uses an omnidirectional that can receive commands from any direction throughout its flight profile but the GCS transmits its signal using a directional antenna (Hill 2010)

If a CDL experiences frequency interference, the system executes a self-recovery program known as a “lost link procedure” and attempts to reacquire the CDL from the GCS. If a Man-Portable UAS fails to reacquire its CDL, it continues its self-recovery program and attempts to return to a preprogrammed recovery point. If a Tactical UAS fails to reacquire its CDL, the operators may identify the UA as rogue and deploy the systems recovery parachute to avoid endangering manned aircraft.

Edited by ravnicar, 10 August 2013 - 20:28.

[st.maurice]

Poceo sam od toga da je moguce ometati UAV uz pomoc relativno jeftine opreme. Relativno ne znaci 50-100 usd, mozes shvatiti kao nesto sto mozes dobiti po prihvatljivoj ceni razvoja i proizvodnje.

Danas je u vojnoj upotrebi blizu 100 razlicitih modela i sistema proizvedenih u 20 drzava ne ulazeci u namenu i dimenzije. Da li ti ovo objasnjava razliku koju pominjes? 

Cini mi se da ti ciljas na nesto sasvim drugo.

 

Krenuli smo od x-47 i vrste linka koji on koristi, ove druge nas ne zanimaju.

 

Da ne pricamo u prazno, evo jednog rada koji se bavi upravo simulacijom otpornosti linka 16 na ometanje. Sustina je da se signal ometanjem (cak i opsega frekfencija) moze samo degradirati ne u potpuno prekinuti, kako i koliko zavisi od kola za sinhronizaciju i eventualno detekcije frekfencija koje se ometaju pri cemu je efekat ometanja prakticno zanemariv.

 

Cognitive Anti-Jamming

 

When the jamming signal is detected, the cognitive TDL terminal opportunistically avoids those jamming frequency channels. In the proposed simulator, for the practical considerations, we assume imperfect detection for the jammer signal. Assume ρ = 40%, miss-detection probability Pmd = 0.1 (which means that 10% of number of jamming channels are undetected (vulnerable to jamming attack)), and Eb/N0 = 20dB. Figure 8 shows the proposed TDL system (‘PROV’) performance gain of approximately 3dB at the 10-3 BER compared to existing TDL system (‘CONV’). The gain is approximately 0 dB when Eb/Nj > 18dB (it means that for that Eb/Nj range, the jamming effect is almost negligible) but the gain increases and approaches to 3 to 4dB as Eb/Nj decreases (smaller than 18dB). It shows that cognitive anti-jamming is so effective to partialband (or tone) jamming.

 

V. CONCLUSIONS

 

We designed a TDL simulator using Matlab/Simulink for the Link-16 performance analysis over jamming environments. In that simulator, we included a Doppler-faded Rician channel module and various jamming modules. We also added a timing synchronization circuit to that simulator to test the antijamming capability of Link-16 with/without synchronization. Simulation results verified that partial-band noise jamming is so severe to existing TDL system, compared to tone or pulse jamming. TDL system over partial-band or tone (even single tone) jamming is very much dependent on the performance of synchronization; it indicates that a robust synchronization circuit for secure tactical communications is mandatory. We proposed a modified TDL system with cognitive anti-jamming capability and verified its performance superiority to existing TDL system, especially over partial-band (or tone) jamming.

 

(Simulator for Tactical Data Link System with Anti-Jamming Capability; Bareum Lee, Eunkyeong Jeong, and Sangho Choe)