Wireless Facts

Wireless Facts

Four organizations influence the standards used for wireless communication:

Organization	Details
Federal Communication Commission (FCC)	The FCC is the regulating US government agency over communication frequencies, including the frequencies used by wireless networking devices.
International Telecommunication Union Radiocommunications Sector (ITU-R)	The ITU-R is the regulating international agency over communication frequencies.
Wi-Fi Alliance	The Wi-Fi Alliance is an industry consortium that encourages interoperability of products that implement wireless standards.
Institute of Electrical and Electronics Engineers (IEEE)	The IEEE is a technical professional group that, among other contributions, developed the 802.11 series that became the national and international standard.

Wireless networks use radio waves for data transmission instead of electrical signals on Ethernet cables. In order to use radio waves as the medium for transmission, specific characteristics of radio waves are defined:

Characteristic	Description
Frequency range or band	Many radio devices operate within a specified frequency range which limits the frequencies on which it is allowed to transmit. In the United States, radio frequency wireless LANs use one of two frequency ranges defined by the FCC: Industrial, Scientific, and Medical (ISM) operating between 2.4 - 2.4835 GHz. Unlicensed National Information Infrastructure (U-NII) operating between 5.75 - 5.85 GHz.
Channel	The frequency range is divided into equal segments called channels. Wireless networking channels are much like television channels, where each channel allows for separate data transmission. However, channels within the range overlap with adjacent channels. By using specific channels and not others, you can ensure that the channels do not overlap, eliminating interference caused by wireless devices operating on different channels. In the 5 GHz range, there are 23 total channels. 12 channels are non-overlapping channels. In the 2.4 GHz range, there are 11 total channels, with 3 non-overlapping channels.
Modulation technique	When a device sends data over a wireless network, it can change (or modulate) the radio signal's specifications. The three common modulation techniques used in wireless networking include: Frequency Hopping Spread Spectrum (FHSS) uses a narrow frequency band and 'hops' data signals in a predictable sequence from frequency to frequency over a wide band of frequencies. This type of modulation is no longer used with current wireless standards. Direct Sequence Spread Spectrum (DSSS) uses an 11-bit Barker sequence to break data into pieces and sends the pieces across multiple frequencies in a defined range. Orthogonal Frequency Division Multiplexing (OFDM) is not a spread spectrum frequency. It uses 48 discreet radio frequency channels that can carry data. Most newer devices use additional modulation techniques and enhancements including: Complementary Code Keying (CCK) Quadrature Phase-shift Keying/Differential Quadrature Phase-Shift Keying (QPSK/DQPSK) Binary Phase-Shift Keying/Differential Binary Phase-Shift Keying (BPSK/DBPSK)

 

 

Credit: Testout 640-802 CCNA Notes