Direct-sequence spread spectrum

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Topic: Direct-sequence spread spectrum

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	Transceiver employing direct sequence spread spectrum techniques - Patent 4979183
		Since a direct sequence spread spectrum receiver does not readily distinguish between signal and noise, and, in particular, since the incoming signal is a data modulated carrier that is spread by a pseudonoise sequence, synchronization between the transmitter and receiver is often troublesome.
		The transceiver employs direct sequence spread spectrum communications techniques for reducing interference among multiple users in a communications network environment.
		Spread spectrum provide a means for communicating by purposely spreading the spectrum of the communications signal well beyond the bandwidth of the unspread signal.
	www.freepatentsonline.com /4979183.html (9149 words)

	Spread spectrum - Wikipedia, the free encyclopedia
		Spread-spectrum telecommunications is a signal structuring technique that employs direct sequence, frequency hopping or a hybrid of these, which can be used for multiple access and/or multiple functions.
		Frequency hopping (FHSS), direct sequence (DSSS), PN spreading(using PN_Sequences), time scrambling, chirp, and combinations of these techniques are forms of spread spectrum.
		Spread spectrum generally makes use of a sequential noise-like signal structure to spread the normally narrowband information signal over a relatively wide band of frequencies.
	en.wikipedia.org /wiki/Spread_spectrum (934 words)

	Spread Spectrum Tools & Resources - Direct Sequence Spread Spectrum (DSSS) Generators
		In a direct-sequence spread spectrum transmitter, the digital data stream to be transmitted is multiplied by a PN sequence running at a much higher clock rate, or chip rate, than the baud rate of the data.
		So, in direct sequence applications, the data stream to be transmitted is input to the generator, and the output of the generator drives a double-balance mixer to upconvert the spread signal to some specified RF frequency.
		One useful feature found in many spread spectrum generators is the ability to momentarily turn off either the PN sequence, the data stream, or both with a quick press of a button.
	www.newwaveinstruments.com /products/direct_sequence_spread_spectrum_dsss.htm (1827 words)

	Direct-sequence spread spectrum - Wikipedia, the free encyclopedia
		In contrast, frequency-hopping spread spectrum pseudo-randomly retunes the carrier, instead of adding pseudo-random noise to the data, which results in a uniform frequency distribution whose width is determined by the output range of the pseudo-random number generator.
		A system (a) for generating spread-spectrum transmissions by phase-modulating a sine wave pseudorandomly with a continuous string of pseudonoise code symbols, each of duration much smaller than a bit and (b) that may be time-gated, where the transmitter is keyed periodically or randomly within a specified time interval.
		This noise signal is a pseudorandom sequence of
	en.wikipedia.org /wiki/Direct_sequence_spread_spectrum (394 words)

	DSSS - Direct Sequence Spread Spectrum
		Direct Sequence Spread Spectrum - a transmission technology in which a data signal at the sending station is combined with a higher data rate bit sequence, or chipping code, that divides the user data according to a spreading ratio.
		Acronym for Direct-Sequence Spread Spectrum DSSS is a transmission technology used in WLAN (wireless LAN) transmissions where a data signal at the sending station is combined with a higher data rate bit sequence, or chipping code, that divides the user data according to a spreading ratio.
		Direct Sequence Spread Spectrum One of the two major classes of RF modulation used in spread spectrum communications.
	www.auditmypc.com /acronym/DSSS.asp (405 words)

	direct sequence spread spectrum - a Whatis.com definition
		Direct sequence contrasts with the other spread spectrum process, known as frequency hopping spread spectrum, or frequency hopping code division multiple access (FH-CDMA), in which a broad slice of the bandwidth spectrum is divided into many possible broadcast frequencies.
		Direct sequence spread spectrum, also known as direct sequence code division multiple access (DS-CDMA), is one of two approaches to spread spectrum modulation for digital signal transmission over the airwaves.
		Find white papers, products and vendors related to direct sequence spread spectrum.
	whatis.techtarget.com /gDefinition/0,294236,sid7_gci525721,00.html (303 words)

	CDMA & Spread Spectrum Technology - Tools & Resources
		New Wave Instruments maintains a comprehensive directory of exceptional spread spectrum, CDMA, and WCDMA resources, ranging from tutorials, theory, and circuit diagrams, to development tools, OEM products, and spread spectrum consultants.
		Spread spectrum generators are used in both the development and testing of spread spectrum systems, such as
		The early sequence is always 1/2 chip early relative to the punctual sequence, and the late sequence is 1/2 chip late.
	www.newwaveinstruments.com /resources/glossary.htm (3483 words)

	CommsDesign - Tutorial on Spread Spectrum Technology
		Direct sequence and frequency hopping are the most commonly used methods for the spread spectrum technology.
		Figure 3: Diagram illustrating the despreading process in a direct-sequence system.
		In addition, with the proper designing of pseudo-random sequences, multiple spread spectrum systems can co-exist without creating severe interference to other systems.
	www.commsdesign.com /design_corner/OEG20030506S0029 (5622 words)

	Center for Wireless Telecommunications
		This is probably the most widely recognized form of spread spectrum.
		Therefore, the bandwidth of a DSSS system is a direct function of the chip rate; specifically 2Rc/RINFO.
		Note that this is just the spectrum of a BPSK signal with a (sin x / x)2 form.
	www.cwt.vt.edu /faq/dsss.htm (404 words)

	DSSS - Direct Sequence Spread Spectrum
		Direct Sequence Spread Spectrum is based on the multiplying of the baseband signal data with a broadband spreading code.
		The characteristics of the broadband spreading code are that of pseudorandom noise.
		All other receivers will see the spread signal as white or coloured noise.
	www.mpirical.com /companion/Multi_Tech/DSSSSpectrum.htm (56 words)

	Frequency Hopping vs. Direct Sequence Spread Spectrum Techniques
		The spreading architecture used in the direct sequence physical layer is not to be confused with CDMA.
		Spread spectrum transmitters send their signals out over a multiple range of frequencies at very low power, in contrast to narrow band radios that concentrate all of their power into a single frequency.
		Spread spectrum technology was first introduced about 50 years ago by the military as a way of sending secure communications.
	www.bazar-e.net /raylink/docs/doc_frecuencehoping.htm (1152 words)

	Encyclopedia.it: Direct Marketing
		DSSS La DSSS, acronimo di Direct Sequence Spread Spectrum, altrimenti nota...
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		Direct connect file-sharing application: Tutte le informazioni su Direct connect file-sharing application su Encyclopedia.it
	www.encyclopedia.it /web_marketing/direct_marketing (484 words)

	Direct Sequence Spread Spectrum (DSSS)
		Chipping spreads modulated data across the spectrum in a fashion that makes it possible to tolerate some signal loss.
		A DSSS radio chipping with the 1997 standard Barker Code modulates data using binary or quadrature phase shift keying, operating at 1 or 2 Mbps, respectively.
		DSSS divides the same 2.4 GHz band into overlapping channels that are each 22 MHz wide.
	expertanswercenter.techtarget.com /eac/knowledgebaseAnswer/0,295199,sid63_gci976087,00.html (326 words)

	PANSAT - Spread Spectrum Overview
		With Direct Sequence Spread Spectrum (DSSS), the modulated carrier is expanded to the extent that it occupies a bandwidth that is much greater than the information bandwidth of the signal.
		Spread spectrum modulation provides the advantages of low probability-of-intercept (LPI), low probability-of-detection (LPD), resistance to jamming and low probability-of-interference (to and from other users in the band) [Ref. 1].
		This is accomplished by multiplying the information signal by a pseudo-noise (PN) spreading sequence which has a bit rate that is significantly greater than the information data rate.
	www.sp.nps.navy.mil /pansat/ssovrvw.html (692 words)

	A Comparison of Slow-Frequency-Hop and Direct-Sequence Spread-Spectrum Communications Over Frequency-Selective Fading Channels
		S. Ghassemzadeh, D. Schilling, Z. Haddad, and K. Parsa, "Multipath fading statistics of a direct sequence CDMA signal at 2 GHz, in microcellular and indoor environment," in 1994 IEEE Military Communications Conf.
		The results illustrate the tradeoffs in performance between SFH and DS spread-spectrum systems as a function of the parameters of the signals and the channel model.
		The performance of the SFH system is shown to be less sensitive to the exact characterization of the channel delay spectrum than the DS system.
	www.comsoc.org /comm/private/1999/may/732_47comm05-gass.html (664 words)

	USS Clueless - Direct sequence spread spectrum
		But the ultimate spreading pattern for each sector for the paging channel is different because the short code phase assigned to that sector is different.
		The signal in DSS is scrambled using what's known as "pseudo-noise", or PN, which is a carefully crafted sequence of bits known to both transmitter and receiver, and because of how the receiver works, it will very strongly reject anything which is not encoded with exactly the right PN sequence.
		This is important for CDMA because each phone operating on a given frequency looks like a jammer to all the others, but each phone uses a different PN sequence, so the ability to ignore any PN sequence except the one intended for you makes it so that your call will still get through to you.
	www.denbeste.nu /cd_log_entries/2002/09/Directsequencespreadspect.shtml (1813 words)

	Frequency Hopping verus Direct Sequence Spread Spectrum
		Direct sequence systems, for instance, require about a second to achieve synchronization.
		Near-far performance describes the behavior of the spread spectrum system with other users both near and far away from the intended users.
		DSSS use their bandwidth more efficiently can result in a much higher data throughput than FHSS systems.
	www.qsl.net /n9zia/wireless/fhss_vs_dsss.html (1461 words)

	direct sequence spread spectrum (DSSS) - NI Developer Zone - National Instruments
		-long pseudorandom spreading code (also known as the chip sequence)
		The spreading code appears random to all receivers except the intended one, which uses the knowledge of the spreading code to demodulate and recover the transmitted information.
		DSSS is accomplished by spreading each bit of signal data is spread at the transmitter into
	zone.ni.com /devzone/nidzgloss.nsf/webmain/E8CFF5C073ADFC2586256F8D006B0310 (185 words)

	Spread Spectrum
		The terms direct sequence and pseudo-noise are used interchangeably throughout the literature and both of them pertain to the same spread spectrum techniques.
		This information signal is multiplied by PN sequence with narrow pulses of time duration Tc and zero crossings at 1/Tc thus forming a spread spectrum signal.
		Bandwidth expansion in spread spectrum systems is achieved by using a function that is independent of the message, thus it is more susceptible to white noise as opposed to other communication techniques, such as FM and PCM.
	webpages.charter.net /witek/ss/ss.html (6573 words)

	What is FHSS? - A Word Definition From the Webopedia Computer Dictionary
		FHSS is one of two types of spread spectrum radio, the other being direct-sequence spread spectrum.
		This technique reduces interference because a signal from a narrowband system will only affect the spread spectrum signal if both are transmitting at the same frequency at the same time.
		FHSS is a transmission technology used in LAWN transmissions where the data signal is modulated with a narrowband carrier signal that "hops" in a random but predictable sequence from frequency to frequency as a function of time over a wide band of frequencies.
	www.webopedia.com /TERM/F/FHSS.html (296 words)

	Frequency Hopping vs Direct Sequence
		In DSSS systems, the spreading code is a sequence of bits (known as chips), and the first modulation step is a XOR operation executed between the message and the spreading code (process known as "chipping").
		The effect of redundancy is that Spread Spectrum systems present a high resistance to noises and interference, being able to recover their messages even if noises are present on the medium.
		On condition that the sequences used are highly distinguishable one from the other one (property known as orthogonality) each receiver will be able to "read" only the information dedicated to it (receiver and transmitter use same spreading code).
	www.cs.technion.ac.il /Labs/Lccn/projects/spring99/wireless/frequenc.htm (2882 words)

	cm2prs03.doc
		Direct Sequence Spread Spectrum (VisSim Simulation) The number of students per team is between three and four.
		NAME ________________________________________________________ # ___________ NAME _________________________________________________________ # ___________ NAME _________________________________________________________# ____________ NAME _________________________________________________________#____________ Part I) Design a VisSim simulation that illustrates the concepts of spectral spreading and despreading in Direct Sequence Spread Spectrum.
		(You may use the VisSim PN sequence generator block, the 1 Hz square pulse block, the correlator block, and the sample and hold block among others, you may also try different configurations).
	www.pupr.edu /mteixeir/cm2prs03.doc (444 words)

	CHAPTER 2 – DIRECT SEQUENCE SPREAD SPECTRUM
		ASICs are not reconfigurable thus they are mainly used for the implementation of static functions, such as spectrum spreading in CDMA based software radios.
		Direct conversion or zero-IF architectures eliminate all but one of the down-conversion stages of the super-heterodyne.
		A compromise between super-heterodyne and direct conversion architectures is the low-IF design shown in Figure 3.
	www.eng.auburn.edu /users/akhifra/chapter2.htm (3798 words)

	(WO 02/060081) A BASEBAND DIRECT SEQUENCE SPREAD SPECTRUM TRANSCEIVER [Repub: 14.08.2003]
		(WO 02/060081) A BASEBAND DIRECT SEQUENCE SPREAD SPECTRUM TRANSCEIVER [Repub: 14.08.2003]
		This datasignal is then broadcast baseband, absent a carrier, by a relatively short, mismatched antenna.The baseband signal is spread out across the DC to 30 MHz spectrum.
		Consequently, the sameantenna can be used to receive incoming baseband RF signals as well as transmit baseband RF signals, thereby providing full duplex operation.
	www.wipo.int /ipdl/IPDL-CIMAGES/view/pct/getbykey5?KEY=02/60081.030814 (173 words)

	Direct Sequence Spread Spectrum
		Data is multiplied with a higher rate digital sequence (spreading code).
		Multiple system can co-exist in the same band if they use different (orthogonal) spreading sequence;
		The sequence has many “chips” for every data bit;
	www.ictp.trieste.it /~radionet/1997_workshop/wireless/notes/tsld014.htm (102 words)

	A Transceiver Chipset for 2.4 GHz Direct Sequence Spread Spectrum Applications
		A Transceiver Chipset for 2.4 GHz Direct Sequence Spread Spectrum Applications
		A 6 dBm power amplifier (PA) driver is integrated that can drive an antenna directly or drive various highly efficient GaAs heterojunction bipolar transistor (HBT) PAs, which can deliver 1 W of power.
		The chipset was designed specifically for an IEEE802.11-compliant DSSS system using biphase-shift keying (BPSK), quadrature phase-shift keying (QPSK) or the complementary code keying (CCK) modulation scheme proposed for the 11 Mbps standard but, with built-in flexibility, it can be used for many other applications and is not confined to the 2.4 GHz band.
	stewks.ece.stevens-tech.edu /EE683/TechArticles/mwjournal/article22/Transc.html (2883 words)

	Complex Processing In Quaternary Direct-Sequence Spread-Spectrum Receivers (ResearchIndex)
		Abstract: The processing that is often employed in receivers for quaternary direct-sequence spread-spectrum communications operates separately on the inphase and quadrature components of the spread-spectrum signal.
		Recent results on quaternary complex sequences, which are also referred to as four-phase sequences, provide a strong motivation to employ processing methods that permit the receiver to benefit from the correlation properties of the complex sequences.
		1 Aperiodic correlation properties of quaternary sequences wit..
	citeseer.ist.psu.edu /144020.html (270 words)

	Blind Estimation Of The Pseudo-Random Sequence Of A Direct Sequence Spread Spectrum Signal - Burel, Bouder (ResearchIndex)
		Blind Estimation Of The Pseudo-Random Sequence Of A Direct Sequence Spread Spectrum Signal (2000)
		Burel, C. Bouder, Blind estimation of the pseudo-random sequence of a directsequence spread spectrum signal, IEEE 21st Century Military Communications Conference (MILCOM'2000.
		Abstract: Direct sequence spread spectrum transmissions SSS) are now widely used for secure communications, as well as for multiple access.
	citeseer.ist.psu.edu /burel00blind.html (309 words)

	DSSS (direct sequence spread spectrum)
		The choice is direct sequence spread spectrum (used by 802.11b systems) or frequency hopping spread spectrum (used by HomeRF and Bluetooth).
		Spread spectrum in general was originally used by the military.
		From Comparing spread spectrum technologies, Network World Wireless Newsletter, 06/25/01.
	www.networkworld.com /details/600.html?def (888 words)

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