Contents 1 Spread-spectrum 2 Military use 3 Civilian use 4 Technical considerations 5 Multiple inventors 6 Variations of FHSS 7 See also 8 Notes 9 References 10 External links

Spread-spectrum[edit] Main article: Spread-spectrum A spread-spectrum transmission offers three main advantages over a fixed-frequency transmission: Spread-spectrum signals are highly resistant to narrowband interference. The process of re-collecting a spread signal spreads out the interfering signal, causing it to recede into the background. Spread-spectrum signals are difficult to intercept. A spread-spectrum signal may simply appear as an increase in the background noise to a narrowband receiver. An eavesdropper may have difficulty intercepting a transmission in real time if the pseudorandom sequence is not known. Spread-spectrum transmissions can share a frequency band with many types of conventional transmissions with minimal interference. The spread-spectrum signals add minimal noise to the narrow-frequency communications, and vice versa. As a result, bandwidth can be used more efficiently.

Military use[edit] Spread-spectrum signals are highly resistant to deliberate jamming, unless the adversary has knowledge of the spreading characteristics. Military radios use cryptographic techniques to generate the channel sequence under the control of a secret Transmission Security Key (TRANSEC) that the sender and receiver share in advance. By itself, frequency hopping provides only limited protection against eavesdropping and jamming. Most modern military frequency hopping radios also employ separate encryption devices such as the KY-57 Speech Security Equipment. U.S. military radios that use frequency hopping include the JTIDS/MIDS family, the HAVE QUICK Aeronautical Mobile (OR) communications system, and the SINCGARS Combat Net Radio, Link-16.

Civilian use[edit] In the US, since the Federal Communications Commission (FCC) amended rules to allow frequency hopping spread spectrum systems in the unregulated 2.4 GHz band, many consumer devices in that band have employed various spread-spectrum modes. Some walkie-talkies that employ frequency-hopping spread spectrum technology have been developed for unlicensed use on the 900 MHz band. Several such radios were marketed under the name eXtreme Radio Service (eXRS). Despite the name's similarity to the FRS allocation, the system is a proprietary design, rather than an official FCC allocated service. Frequency-hopping spread spectrum technology is also used in many hobby RC (radio controlled) transmitters and receivers used for model cars, airplanes, and drones. A type of multiple access is achieved allowing hundreds of transmitter/receiver pairs to be operated simultaneously on the same band in contrast to previous FM or AM RC systems that had limited simultaneous channels.[1] Motorola has deployed a business-banded, license-free digital radio that uses FHSS technology: the DTR series, models 410, 550 and 650.

Technical considerations[edit] The overall bandwidth required for frequency hopping is much wider than that required to transmit the same information using only one carrier frequency. However, because transmission occurs only on a small portion of this bandwidth at any given time, the effective interference bandwidth is really the same. While providing no extra protection against wideband thermal noise, the frequency-hopping approach does reduce the degradation caused by narrowband interference sources. One of the challenges of frequency-hopping systems is to synchronize the transmitter and receiver. One approach is to have a guarantee that the transmitter will use all the channels in a fixed period of time. The receiver can then find the transmitter by picking a random channel and listening for valid data on that channel. The transmitter's data is identified by a special sequence of data that is unlikely to occur over the segment of data for this channel, and the segment can also have a checksum for integrity checking and further identification. The transmitter and receiver can use fixed tables of channel sequences, so that once synchronized they can maintain communication by following the table. On each channel segment, the transmitter can send its current location in the table. In the US, FCC part 15 on unlicensed spread spectrum systems in the 902–928 MHz and 2.4 GHz bands permits more power than is allowed for non-spread-spectrum systems. Both frequency hopping and direct sequence systems can transmit at 1 Watt, a thousand-fold increase from the 1 milliwatt limit on non-spread-spectrum systems. The Federal Communications Commission (FCC) also prescribes a minimum number of channels and a maximum dwell time for each channel. In a real multipoint spread spectrum radio system, space allows the possibility of multiple transmissions on the same frequency using multiple radios in a geographic area. This creates the possibility of system data rates that are higher than the Shannon limit for a single channel. Spread spectrum systems do not violate the Shannon limit. Spread spectrum systems rely on excess signal to noise ratios for sharing of spectrum. This property is also seen in MIMO and DSSS systems. Beam steering and directional antennas also facilitate increased system performance by providing isolation between remote radios.

Multiple inventors[edit] In 1899 Guglielmo Marconi experimented with frequency-selective reception in an attempt to minimise interference.[2] The earliest mentions of frequency hopping in the open literature are in US patent 725,605 awarded to Nikola Tesla in March 17, 1903 and in radio pioneer Jonathan Zenneck's book Wireless Telegraphy (German, 1908, English translation McGraw Hill, 1915), although Zenneck himself states that Telefunken had already tried it. Nikola Tesla doesn’t mention the phrase “frequency hopping” directly, but certainly alludes to it. Entitled Method of Signaling, the patent describes a system that would enable radio communication without any danger of the signals or messages begin disturbed, intercepted, interfered with in any way [3]. The German military made limited use of frequency hopping for communication between fixed command points in World War I to prevent eavesdropping by British forces, who did not have the technology to follow the sequence.[4] A Polish engineer and inventor, Leonard Danilewicz, came up with the idea in 1929.[5] Several other patents were taken out in the 1930s, including one by Willem Broertjes (U.S. Patent 1,869,659, issued Aug. 2, 1932). During World War II, the US Army Signal Corps was inventing a communication system called SIGSALY, which incorporated spread spectrum in a single frequency context. However, SIGSALY was a top-secret communications system, so its existence did not become known until the 1980s. The most celebrated use of frequency hopping was a patent awarded to actress Hedy Lamarr and composer George Antheil, who in 1942 received U.S. Patent 2,292,387 for their "Secret Communications System". This intended early version of frequency hopping was supposed to use a piano-roll to change among 88 frequencies, and was intended to make radio-guided torpedoes harder for enemies to detect or to jam, but there is no record of a working device ever being produced. The patent was rediscovered in the 1950s during patent searches when private companies independently developed Code Division Multiple Access, a non-frequency-hopping form of spread-spectrum, and has been cited numerous times since. A practical application of frequency hopping was developed by Ray Zinn, co-founder of Micrel Corporation. Zinn developed a method allowing radio devices to operate without the need to synchronize a receiver with a transmitter. Using frequency hopping and sweep modes, Zinn's method is primarily applied in low data rate wireless applications such as utility metering, machine and equipment monitoring and metering, and remote control. In 2006 Zinn received U.S. Patent 6,996,399 for his "Wireless device and method using frequency hopping and sweep modes."

Variations of FHSS[edit] Adaptive Frequency-hopping spread spectrum (AFH) (as used in Bluetooth) improves resistance to radio frequency interference by avoiding crowded frequencies in the hopping sequence. This sort of adaptive transmission is easier to implement with FHSS than with DSSS. The key idea behind AFH is to use only the “good” frequencies, by avoiding the "bad" frequency channels—perhaps those "bad" frequency channels are experiencing frequency selective fading, or perhaps some third party is trying to communicate on those bands, or perhaps those bands are being actively jammed. Therefore, AFH should be complemented by a mechanism for detecting good/bad channels. However, if the radio frequency interference is itself dynamic, then the strategy of “bad channel removal”, applied in AFH might not work well. For example, if there are several colocated frequency-hopping networks (as Bluetooth Piconet), then they are mutually interfering and the strategy of AFH fails to avoid this interference. The problem of dynamic interference, gradual reduction of available hopping channels and backward compatibility with legacy bluetooth devices was resolved in version 1.2 of the Bluetooth Standard (2003). Other Strategies for dynamic adaptation of the frequency hopping pattern have been reported in the literature.[6] Such a situation can often happen in the scenarios that use unlicensed spectrum. In addition, dynamic radio frequency interference is expected to occur in the scenarios related to cognitive radio, where the networks and the devices should exhibit frequency-agile operation. Chirp modulation can be seen as a form of frequency-hopping that simply scans through the available frequencies in consecutive order to communicate. The other concept also can use the combination of frequency hopping spread spectrum with OFDM or non-orthogonal frequency-division multiplexing (N-OFDM) of signals. It can increase data performance.[7]

See also[edit] Dynamic frequency hopping List of multiple discoveries Maximum length sequence Orthogonal frequency-division multiplexing Radio frequency sweep

Notes[edit] ^ "Most RC model aircraft airborne simultaneously". Guinness World Records. Retrieved 2018-02-16.  ^"Frequency-Selective"&source=bl&ots=OS5QiNlwU2&sig=y30NftAXUC3E1_J8nCFKjAjB4oo&hl=en&sa=X&ved=0ahUKEwi7jIPJwLTXAhVQ4KQKHTvaBTwQ6AEIKDAA#v=onepage&q=Marconi%201899%20%22Frequency-Selective%22&f=false ^ A short history of spread spectrum ^ Denis Winter, Haig's Command - A Reassessment ^ Danilewicz later recalled: "In 1929 we proposed to the General Staff a device of my design for secret radio telegraphy which fortunately did not win acceptance, as it was a truly barbaric idea consisting in constant changes of transmitter frequency. The commission did, however, see fit to grant me 5,000 złotych for executing a model and as encouragement to further work." Cited in Władysław Kozaczuk, Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the Allies in World War II, 1984, p. 27. ^ Petar Popovski; Hiroyuki Yomo; Ramjee Prasad (December 2006). "Strategies For Adaptive Frequency Hopping In The Unlicensed Bands" (PDF). IEEE Wireless Communications. Archived from the original (PDF) on 2009-02-27. Retrieved 2008-03-02.  ^ Патент Украины на полезную модель № 122771. МПК H04B 3/60 (2006.01), H04B 1/58 (2006.01), H04B 1/56 (2006.01). Способ повышения скорости передачи данных сигналами с псевдослучайной перестройкой частоты./ Слюсар В.И.- Заявка на выдачу патента Украины на полезную модель № u201707800 от 25.07.2017.- Патент опубл. 25.01.2018, бюл. № 2. [1]

References[edit] Władysław Kozaczuk, Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the Allies in World War Two, edited and translated by Christopher Kasparek, Frederick, MD, University Publications of America, 1984, ISBN 0-89093-547-5.

External links[edit] FCC Part 15 Rules that cover frequency hopping Frequency hopping in unlicensed spectrum describes strategies for adaptive hopping in crowded spectrum, while considering the issues of radio etiquette and compliance with FCC Part 15 Rules v t e Spread spectrum in digital communications Main articles Spread spectrum Code-division multiple access (CDMA) History Hedy Lamarr Commercial use More... Spread spectrum methods Direct-sequence spread spectrum (DSSS) Frequency-hopping spread spectrum (FHSS) Chirp spread spectrum (CSS) Time-hopping spread spectrum (THSS) CDMA schemes W-CDMA TD-CDMA TD-SCDMA DS-CDMA FH-CDMA MC-CDMA Major implementations Space Network (NASA) GPS Galileo GLONASS Bluetooth Cordless phones: DECT Cellular EV-DO Mobile IS-95 (aka cdmaOne) CDMA2000 (aka IS-2000) Also Qualcomm Verizon Major concepts PN (pseudorandom noise) code Chip Near–far problem Power spectral density (PSD) Process gain Rake receiver Low probability of intercept See also Digital communication Modulation Statistical multiplexing Waveform Retrieved from "" Categories: Channel access methodsApplications of cryptographyMultiplexingQuantized radio modulation modesRadio frequency propagationRadio resource managementMilitary radio systemsHidden categories: Wikipedia articles needing context from January 2013All Wikipedia articles needing contextWikipedia introduction cleanup from January 2013All pages needing cleanupWikipedia articles that are too technical from January 2013All articles that are too technicalArticles needing expert attention from January 2013All articles needing expert attentionArticles with multiple maintenance issues

Navigation menu Personal tools Not logged inTalkContributionsCreate accountLog in Namespaces ArticleTalk Variants Views ReadEditView history More Search Navigation Main pageContentsFeatured contentCurrent eventsRandom articleDonate to WikipediaWikipedia store Interaction HelpAbout WikipediaCommunity portalRecent changesContact page Tools What links hereRelated changesUpload fileSpecial pagesPermanent linkPage informationWikidata itemCite this page Print/export Create a bookDownload as PDFPrintable version Languages العربيةCatalàČeštinaDanskDeutschEestiEspañolفارسیFrançaisItalianoעבריתNederlands日本語PolskiPortuguêsРусскийSimple EnglishSuomiУкраїнська中文 Edit links This page was last edited on 19 February 2018, at 07:42. Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. Privacy policy About Wikipedia Disclaimers Contact Wikipedia Developers Cookie statement Mobile view (window.RLQ=window.RLQ||[]).push(function(){mw.config.set({"wgPageParseReport":{"limitreport":{"cputime":"0.188","walltime":"0.295","ppvisitednodes":{"value":1039,"limit":1000000},"ppgeneratednodes":{"value":0,"limit":1500000},"postexpandincludesize":{"value":54730,"limit":2097152},"templateargumentsize":{"value":6919,"limit":2097152},"expansiondepth":{"value":15,"limit":40},"expensivefunctioncount":{"value":5,"limit":500},"entityaccesscount":{"value":0,"limit":400},"timingprofile":["100.00% 226.994 1 -total"," 31.29% 71.036 3 Template:Ambox"," 29.32% 66.550 1 Template:Reflist"," 25.45% 57.774 1 Template:Multiple_issues"," 15.99% 36.306 1 Template:Cite_news"," 13.64% 30.971 1 Template:ISBN"," 10.64% 24.156 1 Template:Redirect"," 9.12% 20.708 1 Template:Context"," 7.11% 16.140 1 Template:Catalog_lookup_link"," 6.90% 15.664 1 Template:Multiplex_techniques"]},"scribunto":{"limitreport-timeusage":{"value":"0.066","limit":"10.000"},"limitreport-memusage":{"value":2606363,"limit":52428800}},"cachereport":{"origin":"mw1234","timestamp":"20180219074256","ttl":1900800,"transientcontent":false}}});});(window.RLQ=window.RLQ||[]).push(function(){mw.config.set({"wgBackendResponseTime":80,"wgHostname":"mw1323"});});

Frequency-hopping_spread_spectrum - Photos and All Basic Informations

Frequency-hopping_spread_spectrum More Links

FHSS (disambiguation)Talk:Frequency-hopping Spread SpectrumHelp:Maintenance Template RemovalWikipedia:Writing Better ArticlesHelp:Maintenance Template RemovalWikipedia:Make Technical Articles UnderstandableHelp:Maintenance Template RemovalHelp:Maintenance Template RemovalModulationModulationAmplitude ModulationFrequency ModulationPhase ModulationQuadrature Amplitude ModulationSpace ModulationSingle-sideband ModulationDigital ModulationAmplitude-shift KeyingAmplitude And Phase-shift KeyingContinuous Phase ModulationFrequency-shift KeyingMultiple Frequency-shift KeyingMinimum-shift KeyingOn-off KeyingPulse-position ModulationPhase-shift KeyingQuadrature Amplitude ModulationSingle-carrier FDMATrellis ModulationWavelet ModulationHierarchical ModulationQuadrature Amplitude ModulationWavelet ModulationSpread SpectrumChirp Spread SpectrumDirect-sequence Spread SpectrumTime-hoppingCategory:Capacity-approaching CodesDemodulationLine CodeModemAngle ModulationPolar ModulationPulse-amplitude ModulationPulse-code ModulationPulse-width ModulationDelta-sigma ModulationOrthogonal Frequency-division MultiplexingFrequency-division MultiplexingMultiplexingTemplate:Modulation TechniquesTemplate Talk:Modulation TechniquesMultiplexingModulationAmplitude ModulationFrequency ModulationPhase ModulationQuadrature Amplitude ModulationSpace ModulationSingle-sideband ModulationCircuit SwitchingTime-division MultiplexingFrequency-division MultiplexingWavelength-division MultiplexingSpace-division Multiple AccessPolarization-division MultiplexingSpatial MultiplexingOrbital Angular Momentum MultiplexingStatistical MultiplexingPacket SwitchingTime-division Multiple AccessDirect-sequence Spread SpectrumOFDMASingle-carrier Frequency-division-multiplexMulti-carrier Spread SpectrumChannel Access MethodMedia Access ControlTemplate:Multiplex TechniquesTemplate Talk:Multiplex TechniquesCarrier SignalChannel (communications)PseudorandomTransmitterReceiver (radio)Multiple Access MethodCode Division Multiple AccessDirect-sequence Spread SpectrumBluetoothSpread-spectrumNarrowbandInterference (communication)Radio JammingMilitaryCryptographyTRANSECKY-57United StatesHAVE QUICKSINCGARSLink-16Federal Communications CommissionSpread SpectrumWalkie-talkiesEXtreme Radio ServiceFamily Radio ServiceInformationCarrier FrequencyThermal NoiseChecksumTitle 47 CFR Part 15Federal Communications CommissionShannon–Hartley TheoremMIMODSSSBeam SteeringGuglielmo MarconiNikola TeslaJonathan ZenneckTelefunkenWorld War IPolesLeonard DanilewiczWorld War IIUS Army Signal CorpsSIGSALYHedy LamarrGeorge AntheilPiano RollTorpedoCode Division Multiple AccessRay ZinnBluetoothCo-channel InterferenceDSSSFrequency Selective FadingPiconetUnlicensed SpectrumCognitive RadioFrequency-agileChirpOrthogonal Frequency-division MultiplexingDynamic Frequency HoppingList Of Multiple DiscoveriesMaximum Length SequenceOrthogonal Frequency-division MultiplexingRadio Frequency SweepPolish General StaffZłotyWładysław KozaczukWładysław KozaczukChristopher KasparekInternational Standard Book NumberSpecial:BookSources/0-89093-547-5Template:CdmaTemplate Talk:CdmaSpread SpectrumSpread SpectrumCode-division Multiple AccessHedy LamarrSpread SpectrumSpread SpectrumDirect-sequence Spread SpectrumChirp Spread SpectrumTime-hoppingW-CDMATD-CDMATD-SCDMADirect-sequence CDMAMulti-carrier Code-division Multiple AccessSpace NetworkGlobal Positioning SystemGalileo (satellite Navigation)GLONASSBluetoothCordless TelephoneDigital Enhanced Cordless TelecommunicationsMobile PhoneEvolution-Data OptimizedIS-95CDMA2000QualcommVerizon WirelessPseudorandom NoiseChip (CDMA)Near–far ProblemSpectral DensityProcess GainRake ReceiverLow Probability Of InterceptData TransmissionModulationStatistical Time-division MultiplexingWaveformHelp:CategoryCategory:Channel Access MethodsCategory:Applications Of CryptographyCategory:MultiplexingCategory:Quantized Radio Modulation ModesCategory:Radio Frequency PropagationCategory:Radio Resource ManagementCategory:Military Radio SystemsCategory:Wikipedia Articles Needing Context From January 2013Category:All Wikipedia Articles Needing ContextCategory:Wikipedia Introduction Cleanup From January 2013Category:All Pages Needing CleanupCategory:Wikipedia Articles That Are Too Technical From January 2013Category:All Articles That Are Too TechnicalCategory:Articles Needing Expert Attention From January 2013Category:All Articles Needing Expert AttentionCategory:Articles With Multiple Maintenance IssuesDiscussion About Edits From This IP Address [n]A List Of Edits Made From This IP Address [y]View The Content Page [c]Discussion About The Content Page [t]Edit This Page [e]Visit The Main Page [z]Guides To Browsing WikipediaFeatured Content – The Best Of WikipediaFind Background Information On Current EventsLoad A Random Article [x]Guidance On How To Use And Edit WikipediaFind Out About WikipediaAbout The Project, What You Can Do, Where To Find ThingsA List Of Recent Changes In The Wiki [r]List Of All English Wikipedia Pages Containing Links To This Page [j]Recent Changes In Pages Linked From This Page [k]Upload Files [u]A List Of All Special Pages [q]Wikipedia:AboutWikipedia:General Disclaimer

view link view link view link view link view link