Wireless Common Terms

Radio Frequency

Radio frequencies are high frequency alternating current (AC) signals that are
passed along a copper conductor and then radiated in to the air via an antenna. An
antenna converts/transforms a wired signal and vice versa. When the high frequency AC signal is radiated into the air, it forms radio waves. These Radio waves propagate away
from the source (the antenna) in a straight line in all directions at once.

Spread Spectrum

Spread Spectrum is a communication technique characterized by wide bandwidth and low peak power. Spread Spectrum communication uses various modulation techniques in wireless LANs and possesses many advantages over its precursor, narrow band communication. Spread Spectrum signals are noise-like, hard to detect, and even harder to intercept or demodulate without the proper equipment.

Narrow Band Transmission

A narrow band transmission is a technology that uses only enough of the frequency
spectrum to carry the data signal, and no more. It has always been the FCC's mission
to conserve frequency usage as much as possible, handling out only what is
absolutely necessary. Spread spectrum uses much wider frequency bands than is necessary to transmit the information. A signal is a spread spectrum signal when the bandwidth is much wider then what is required to send the information.
More power is required to send a transmission when using a smaller frequency range.
A compelling argument against narrowband transmission - other than the high peak power required to send it - is that narrow band signal can be jammed or experience
interference very easily. Jamming is the intentional over powering of a transmission
using unwanted signals transmitted on the same band.

Spread Spectrum Technology

Spread Spectrum technology allows us to take the same amount of information that we
previously would have sent using a narrow band carrier signal and spread it out over a
much larger frequency range. For example, we may use 1 MHz at 10 Watts with narrow band, but 20 MHz at 100mW with spread Spectrum. By using a wider frequency spectrum, we reduce the probability that the data will be corrupted or jammed.

SSID (Service Set Identifier)

The Service Set Identifier (SSID) is a unique, case sensitive, alphanumeric value from 2- 32 characters used by wireless LANs as a network name. This naming handle is used for
segmenting networks, as a rudimentary security measure, and in the process of joining
a network. A client station must be configured for the correct SSID in order to join a network.
HomeRF

HomeRF operates in the 2.4 GHz band and uses frequency-hopping technology.
The Home Radio Frequency Working Group developed a single specification (Shared
Wireless Access Protocol-SWAP) for a broad range of interoperable consumer devices. SWAP is an open industry specification that allows PCs, peripherals, cordless telephones and other consumer devices to share and communicate voice and data in and around the
home without the complication and expense of running new wires. The SWAP specification provides low cost voice and data communications in the 2.4GHz ISM band.

Bluetooth

Bluetooth is another frequency technology that operates in the 2.4 GHz ISM band. The
hope rate of Bluetooth devices is about 1600 hops per second, so it has considerably more overhead than 802.11- compliant frequency hopping systems. The high hop rate also gives the technology greater resistance to spurious narrow band noise. Bluetooth systems are not designed for high throughput, but rather for a simple use, low power, and short range. Bluetooth devices have a maximum range of 33 feet (10 meters).

IEEE 802.11

The 802.11 standard was the first standard describing the operation of wireless LANs.
This standard contained all of the available transmission technologies including Direct
Sequence Spread Spectrum (DSSS), Frequency Hopping Spread Spectrum (FHSS), and infrared. 802.11 compliant products operate strictly in the 2.4 GHz ISM band between 2.4000 and 2.4835 GHz.

IEEE 802.11a

The IEEE 802.11a standard describes wireless LAN device operation in the 5 GHz UNII bands. Operation in the UNII bands automatically makes 802.11a devices incompatible with all other devices complying with the other 802.11 series of standards. The reason for this incompatibility is simple: system using 5GHz frequencies will not communicate with systems using 2.4GHz frequencies.

IEEE 802.11a specifies data rates of only 6, 12 and 24 Mbps. A wireless LAN device must support at lease these data rates in the UNII bands in order to be 802.11a-compliant.

IEEE 802.11b

802.11b is a wireless Ethernet specification by IEEE.IEEE 802.11bis referred to as
"High-Rate" and Wi-Fi. 802.11b was originally designed to enable high performance radio to support roaming in large offices or business campus environments. 802.11b is quiet expensive compared to SWAP. It must be remembered that 802.11b supports voice over Internet protocol.

IEEE 802.11g

80211.g provides the maximum data transfer rate of 54Mbps and is backward compatible
with 802.11b devices. IEEE 802.11g specifies operation in the 2.4 GHz ISM band. IEEE 802.11g utilizes Orthogonal Frequency Division Multiplexing (OFDM) modulation technology. These devices can automatically switch to QPSK modulation to communicate with the slower 802.11b and 802.11- compatible devices.