Spread-spectrum telecommunications is a technique in which a signal is transmitted in a bandwidth considerably greater than the frequency content of the original information. Telecommunication is the extension of communication over a distance. ... Signaling, or a signal, may mean: Scientific concepts In information theory, a signal is a flow of information that can be represented as a mathematical function. ... // Analog For analog signals, bandwidth is the width, usually measured in hertz, of a frequency band f2 − f1. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... Information is a term with many meanings depending on context, but is as a rule closely related to such concepts as meaning, knowledge, instruction, communication, representation, and mental stimulus. ...

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. This technique decreases the potential interference to other receivers while achieving privacy and increasing the immunity of spread spectrum receivers to noise and interference. 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. The receiver correlates the signals to retrieve the original information signal. In biology, hybrid has three meanings. ... In telecommunication, the term multiple access has the following meanings: 1. ... Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). ... Privacy is the ability of an individual or group to stop information about themselves from becoming known to people other than those they choose to give the information to. ... In general usage, noise can be considered data without meaning; that is, data that is not being used to transmit a signal, but is simply produced as an unwanted by-product of other activities. ... A band is a small section of the spectrum of radio communication frequencies, in which channels are usually used or set aside for the same purpose. ... Information is a term with many meanings depending on context, but is as a rule closely related to such concepts as meaning, knowledge, instruction, communication, representation, and mental stimulus. ... Signaling, or a signal, may mean: Scientific concepts In information theory, a signal is a flow of information that can be represented as a mathematical function. ...

Types of spread-spectrum transmission

Frequency hopping, direct sequence, PN spreading, time scrambling, chirp, and combinations of these techniques are forms of spread spectrum. Ultra Wideband (UWB) is another modulation technique that accomplishes much the same purpose, based on transmitting short duration pulses. Frequency-hopping spread spectrum (FHSS) is a spread-spectrum method of transmitting signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. ... In telecommunication, the term direct-sequence spread spectrum has the following meanings: 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... A pseudo-random number is a number belonging to a sequence which appears to be random, but can in fact be generated by a finite computation. ... 8:17 am, August 6, 1945, Japanese time. ... For the characteristic sounds of birds, see bird song. ... Ultra-wideband (also UWB, and ultra-wide-band, ultra-wide band, etc. ... Ultra-wideband (also UWB, and ultra-wide-band, ultra-wide band, etc. ...

Direct Sequence Spread Spectrum (DSSS)

This is the current wireless networking method. It includes the 802.11 wireless standards, collectively known as 802.11x. 802.11b (Wi-Fi) networks communicate as fast as 11 Mbps at 2.4 GHz, and 802.11b NICs have been available in stores for years.

802.11a DSSS networks can operate at 54 Mbps at 5.4 GHz. 802.11g NICs and networks are becoming increasingly common, and can operate at rates between 20 and 54 Mbps at 2.4 GHz. 802.11g wireless networks are backward-compatible with 802.11b networks. DSSS is considered a wideband networking method. Wideband is a relative term used to describe a wide range of frequencies in a spectrum. ...

Frequency-hopping spread-spectrum (FHSS)

This is a narrowband network that was originally meant to reach speeds of 2 Mbps, but can reach speeds of up to 3 Mbps. Narrowband (narrow bandwidth) refers to a signal which occupies only a small amount of space on the radio spectrum -- the opposite of broadband or wideband. ...

FHSS is ideal for networks in which interference is a problem. However, it is slower than DSSS.

Frequency-hopped spread spectrum was invented by actress Hedy Lamarr and musician George Antheil. U.S patent 2,292,387 was awarded in 1942. They proposed using punched paper rolls (like those in player pianos familiar to George Antheil) to coordinate the frequency shifts of sender and receiver [1]. Hedy Lamarr Hedy Lamarr (November 9, 1913–January 19, 2000) was an actress and communications innovator. ... George Antheil (June 8, 1900 – February 12, 1959) was an American composer and pianist of Polish descent. ... This article is about the year. ... The player piano is a type of piano that plays music without the need for a human pianist to depress the normal keys or pedals. ...

Spread-spectrum clock generation

Spread-spectrum clock generation (SSCG) is used in the design of synchronous digital systems, especially those containing microprocessors, to reduce the spectral density of the electromagnetic interference (EMI) that these systems generate. A synchronous digital system is one that is driven by a clock signal that, because of its periodic nature, has an unavoidably narrow frequency spectrum. In fact, a perfect clock signal would have all its energy concentrated at a single frequency and its harmonics, and would therefore radiate energy with an infinite spectral density. Practical synchronous digital systems radiate electromagnetic energy in a number of narrow bands at the clock frequency and its harmonics, resulting in a frequency spectrum that, at certain frequencies, can exceed the regulatory limits for electromagnetic interference (e.g. those of the FCC in the United States, JEITA in Japan and the IEC in Europe). Microprocessors, including an Intel 80486DX2 and an Intel 80386 A microprocessor (abbreviated as µP or uP) is an electronic computer central processing unit (CPU) made from miniaturized transistors and other circuit elements on a single semiconductor integrated circuit (IC) (aka microchip or just chip). ... Radio Frequency Interference (RFI) is electromagnetic radiation which is emitted by electrical circuits carrying rapidly changing signals, as a by-product of their normal operation, and which causes unwanted signals (interference or noise) to be induced in other circuits. ... sdf f sdf sd ... The Federal Communications Commission (FCC) is an independent United States government agency, created, directed, and empowered by Congressional statute. ... The Japan Electronics and Information Technology Industries Association (JEITA) is an electronics and IT industry trade organization. ... The initials IEC can stand for: Independent Electoral Commission Industrial Emergency Council Institut des Experts-comptables et des Conseils fiscaux Institut dEstudis Catalans, Catalan Studies Institute Interactive Evolutionary Computation International Education Centre International Electrical Congress International Electrotechnical Commission See also IEC connector for IEC cord International Engineering Consortium International...

To avoid this problem, which is of great commercial importance to manufacturers, spread-spectrum clocking is used. This consists of modulating the frequency of the clock signal by either a regular function such as a triangular wave, or by a pseudo-random function. This method distributes the energy of the clock signal over a wider frequency range, and so reduces its peak spectral density. The technique therefore reshapes the system's electromagnetic emissions to make them comply with the electromagnetic compatibility (EMC) regulations. It is a popular technique because it can be used to gain regulatory approval with only a simple modification to the equipment. Modulation is the process of varying a carrier signal, typically a sinusoidal signal, in order to use that signal to convey information. ... In telecommunication, the term electromagnetic compatibility (EMC) has the following meanings: Electromagnetic compatibility is the condition which prevails when telecommunications equipment is performing its individually designed function in a common electromagnetic environment without causing or suffering unacceptable degradation due to unintentional electromagnetic interference to or from other equipment in the...

Many personal computers have a BIOS setting to turn turn spread-spectrum clocking on or off [2] [3] [4]. BIOS,in computing, stands for basic input/output system. ...

It is important to note that this method does not reduce the peak electrical or magnetic field strength emitted by the system, nor the total energy, and therefore does not make the system any less likely to interfere with sensitive equipment such as TV and radio receivers. It works because the EMI receivers used by EMC testing laboratories divide the electromagnetic spectrum into frequency bands approximately 120 kHz wide. If the system under test were to radiate all of its energy at one frequency, then this energy would fall into a single frequency band of the receiver, which would register a large peak at that frequency. Spread-spectrum clocking distributes the energy so that it falls into a large number of the receiver's frequency bands, without putting enough energy into any one band to exceed the statutory limits. Television is a telecommunication system for broadcasting and receiving moving pictures and sound over a distance. ...

Notes

Source: some of this article is based on Federal Standard 1037C, the NTIA Manual of Regulations and Procedures for Federal Radio Frequency Management, MIL-STD-188 and the National Information Systems Security Glossary. Federal Standard 1037C entitled Telecommunications: Glossary of Telecommunication Terms is a U.S. Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. ... Also known as the Red Book, this publication of the Office of Office of Spectrum Management of the National Telecommunications and Information Administration or NTIA, is the official source for all technical regulations relating to the use of the electromagnetic frequency spectrum. ... MIL-STD-188 is a series of U.S. military standards relating to telecommunications. ... The National Information Systems Security Glossary, published by the National Security Telecommunications and Information Systems Security Committee of the United States federal government, is an unclassified glossary of Information Systems Security (INFOSEC) terms intended to provide a common vocabulary for discussing INFOSEC. External links Online copy in Adobe Acrobat format...

See also: open spectrum, electromagnetic compatibility (EMC), electromagnetic interference (EMI), frequency allocation. Open spectrum (also known as free spectrum) is a movement to get the government to provide more unlicensed spectrum, radio frequency spectrum that is available for use by all. ... In telecommunication, the term electromagnetic compatibility (EMC) has the following meanings: Electromagnetic compatibility is the condition which prevails when telecommunications equipment is performing its individually designed function in a common electromagnetic environment without causing or suffering unacceptable degradation due to unintentional electromagnetic interference to or from other equipment in the... Radio Frequency Interference (RFI) is electromagnetic radiation which is emitted by electrical circuits carrying rapidly changing signals, as a by-product of their normal operation, and which causes unwanted signals (interference or noise) to be induced in other circuits. ... Since the electromagnetic spectrum is a limited resource, the use of its radio frequency bands is regulated by governments in most countries, in a process known as frequency allocation or spectrum allocation. ...