On-Line Encyclopedia - A

The Maui Communications Networks
On-Line Encyclopedia

Alphabetical List Of Definitions For Technical Terms

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Adaptive Antenna Array
A group of antennas that are placed in specific relative positions near to each other to allow transmitted (and received) signals to be focused in a particular direction. Individual antenna elements are activated either individually or in groups to achieve a directional antenna pattern from the array. Because an adaptive array has a directional antenna pattern it has both increased gain in the direction of transmission (or reception) as well as improved noise rejection from all "other" directions.Ruckus Wireless implements an adaptive antenna array in their ZoneFlex access points using the trade name "BeamFlex" to refer to the technology.

Access Point
An access point is a piece of equipment that serves as a point of logical connection for Wi-Fi devices like notebook computers, PDAs, and VoIP phones. In the common use of the term, an access point can confirm that a particular wireless user is authorized to connect to the network, manage the encryption and decryption of data packets, and convert packets from their wired Ethernet frame format into the 802.11 Wi-Fi frame format. Every access point is configured with a network name, called the Service Set Identifier (SSID). Wireless clients can then connect to a chosen network by selecting the SSID from a list, or by configuring it into their wireless device. Technically speaking, the "SSID" is more correctly called the Extended Service Set Identifier (ESSID) since every access point has its own unique identifier, called the Basic Service Set Identifier (BSSID). The BSSID is the hardware (MAC) address of the access point itself. When multiple access points act together to present an ESSID they are said to be part of a distribution system. A wired distribution system, consisting of access points connected together through Ethernet cables, can make a single SSID (i.e.: ESSID) available throughout a building, campus, or outdoor location. This is a greatly simplified explanation of the functions of an access point, but it does present a general idea of what an access point does. As seen on the left, access points may take on the classic "2-antenna" form, or may be enclosed in aesthetically pleasing designs.

ASCII (American Standard Code for Information Interchange)
A standard for representing letter, number, and special character ("!@#$%^&*()_+=[]{}\|/?.,><~`) strings. If a list of ASCII-encoded strings is sorted, strings beginning with numbers will sort ahead of strings beginning with letters. This is the opposite of the way IBM's EBCDIC (Extended Binary Coded Decimal Interchange Code) works. The following table shows ASCII character encoding values. The top row is the first hex character and the left-hand column is the second hex character. For example, a capital letter "A" is 0x41 (hex).
Antenna Pattern Graph
A polar-coordinate graph depicting the loss (in dB) relative to an antenna. Antenna Pattern Graphs are used for product comparison and for engineering design. Refer to the in-depth discussion of 802.11 Antenna Operation and antenna pattern graph interpretation here.

Azimuth
The term 'azimuth', as applied to Antenna Pattern Graphs, refers to the horizontal, top-down depiction of antenna coverage (also called the "H-Plane"). Refer to the in-depth discussion of 802.11 Antenna Operation and antenna pattern graph interpretation here.
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