Wireless CH3

American National Standards Institute (ANSI)

A clearinghouse for standards development in the United States.

mixer

A component that combines two inputs to create a single output.

amplifier

A component that increases a signal's intensity.

filter

A component that is used to either accept or block a radio frequency signal.

high-pass filter

A filter that passes all signals that are above a maximum threshold.

low-pass filter

A filter that passes all signals that are below a maximum threshold.

bandpass filter

A filter that passes all signals that are between the maximum and minimum threshold.

Telecommunications Industries Association (TIA)

A group of more than 600 companies that manufacture or supply the products and services used in global communications.

attenuation

A loss of signal strength.

passband

A minimum and maximum threshold that spells out which range of frequencies will pass through a filter.

Internet Society (ISOC)

A professional-membership organization of Internet experts that comments on policies and practices and oversees a number of other boards and task forces dealing with network policy issues.

Frequency Division Multiple Access (FDMA)

A radio transmission technique that divides the bandwidth of the frequency into several smaller frequency bands.

adaptive array processing

A radio transmission technique that replaces a traditional antenna with an array of antenna elements.

packet

A smaller segment of the transmitted signal.

European Telecommunications Standards Institute (ETSI)

A standards body that develops telecommunications standards for use throughout Europe.

Institute of Electrical and Electronics Engineers (IEEE)

A standards body that establishes standards for telecommunications.

Internet Engineering Task Force (IETF)

A standards body that focuses on the lower levels of telecommunications technologies.

circuit switching

A switching technique in which a dedicated and direct physical connection is made between two transmitting devices—for example, between two telephones during a call.

Code Division Multiple Access (CDMA)

A technique that uses spread spectrum technology and unique digital codes to send and receive radio transmissions.

Time Division Multiple Access (TDMA)

A transmission technique that divides the bandwidth into several time slots.

radio frequency (RF) communications

All types of radio communications that use radio frequency waves.

International Telecommunication Union (ITU)

An agency of the United Nations that sets international telecommunications standards and coordinates global telecommunications networks and services.

directional antenna

An antenna that radiates the electromagnetic waves in one direction only. As a result, it can help reduce or eliminate the effect of multipath distortion if there is a clear line of sight between the two antennas.

International Organization for Standardization (ISO)

An organization to promote international cooperation and standards in the areas of science, technology, and economics.

Unlicensed National Information Infrastructure (U-NII)

An unregulated band approved by the FCC in 1996 to provide for short-range, high-speed wireless digital communications.

Industrial, Scientific and Medical (ISM) band

An unregulated radio frequency band approved by the FCC in 1985.

de facto standards

Common practices that the industry follows for various reasons.

packet switching

Data transmission that is broken into smaller units.

consortia

Industry-sponsored organizations that have the goal of promoting a specific technology.

electromagnetic interference (EMI)

Interference with a radio signal; also called noise.

noise

Interference with a signal.

ultra-wideband transmission (UWB)

Low-power, precisely timed pulses of energy that operate in the same frequency spectrum as low-end noise, such as that emitted by computer chips and TV monitors.

switching

Moving a signal from one wire or frequency to another.

PN code

Pseudo random code; a code that appears to be a random sequence of 1s and 0s but actually repeats itself. Used in CDMA cellular telephone technology.

official standards

See de jure standards.

unregulated bands

See license exempt spectrum.

crosstalk

Signals from close frequencies that may interfere with other signals.

de jure standards

Standards that are controlled by an organization or body.

harmonics

Stray oscillations that result from the process of modulating a wave and that fall outside the range of frequencies used for transmission. Harmonics also occur when a signal goes through a mixer and must be filtered out at several points before the signal is finally fed to the antenna for transmission.

radio frequency spectrum

The entire range of all radio frequencies that exist.

signal-to-noise ratio (SNR)

The measure of signal strength relative to the background noise.

Internet Architecture Board (IAB)

The organization responsible for defining the overall architecture of the Internet, providing guidance and broad direction to the IETF. The IAB also serves as the technology advisory group to the Internet Society and oversees a number of critical activities in support of the Internet.

intermediate frequency (IF)

The output signal that results from the modulation process.

Federal Communications Commission (FCC)

The primary U.S. regulatory agency for telecommunications.

sidebands

The sum and the differences of the frequency carrier that serve as buffer space around the frequency of the transmitted signal.

half-duplex transmission

Transmission that occurs in both directions but only one way at a time.

simplex transmission

Transmission that occurs in only one direction.

full-duplex transmission

Transmissions in which data flows in either direction simultaneously.

license exempt spectrum

Unregulated radio frequency bands that are available in the United States to any users without a license.

multipath distortion

What occurs when the same signal reflects and arrives at the receiver's antenna from several different directions and at different times.