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Backbone

A central cabling or wireless system that attaches servers and routers on a network and handles all network traffic. Because of its configuration, the network backbone often decreases the time needed for transmission of packets and the amount of traffic on a network. At the local level, a backbone is a cable, set of cables, set of wireless connections, or a combination of wireless and cables that local area networks connect to for a wide area network connection or within a local area network to span distances efficiently.

Band

Electromagnetic waves can be classified by their wavelengths. Those wavelengths are classified into sections called bands. The electromagnetic spectrum is the collection of these bands.

Bandwidth

Technically, the difference, in Hertz (Hz), between the highest and lowest frequencies of a transmission channel is called bandwidth. But in a general sense, the term describes a medium's information-carrying capacity. It can apply to radio frequency signals, as well as networks, system buses, and monitors. However, as typically used, the term refers to the amount of data that can be sent through a given communications circuit. Although bandwidth is most accurately measured in cycles per second, or Hertz (Hz), it's also common to use bits or bytes per second to measure bandwidth.

Barcode

A sequence of rectangular bars and intervening spaces used to encode a string of data. A barcode symbol typically consists of five parts: a leading quiet zone, a start character, data character(s) including an optional check character, a stop character, and a trailing quiet zone; together these five parts form a complete, scannable entity to identify a carton or individual item.

Barcode Scanner

These electronic devices read barcodes and convert them into electrical signals understandable by a computer device.

Barker Code

Originally developed for radar, Barker codes, also known as "spreading codes" or "chipping codes," are short (13 bits or less) sequences that are normally used in one-shot schemes, as compared to most other spreading codes, which run continually. For example, one code might be used as a preamble to a long Pseudonoise (PN) sequence for the sole purpose of simplifying synchronization. The most notable property of Barker codes is that the minor peaks of their autocorrelation functions always consist of -1,0, and +1. Barker sequences are not the natural product of linear feedback shift registers, but rather they are hard-coded. The complete list of Barker codes are as follows: R2: 10 (or 11), R3: 110, R4: 1011 or (1001), R5: 11101, R7: 1110010, R11: 11100010010, R13: 1111100110101.

Base Station

In an 802.11 network, the term refers to the access point. In cellular networks, base station refers to a networking installation which houses the equipment needed to set up and complete calls on cellular phones—transmitter and receiver equipment, antennas, and computers. The base station works along with the subscriber's handset and the Mobile Switching Center (MSC) to complete call and/or data transmission. In a personal communications system network, the base station is comprised of a base station controller (BSC) and a base transceiver station (BTS). A base station is also sometimes referred to as a "cell site."

Base Station Controller (BSC)

This is a networking component of a cellular network's base station system. A BSC supervises the functionality and control of multiple Base Transceiver Stations and acts as a small switch by managing handoffs.

Base Transceiver Station (BTS)

This networking component of a cellular network's base station system consists of all radio transmission and reception equipment. A BTS provides coverage to a geographic area, and is controlled by a Base Station Controller.

Basic Service Set (BSS)

A term that refers to a set of 802.11-compliant stations that operate as a fully connected wireless network. Each set of wireless devices communicating directly with each other is called a basic service set (BSS). BSS is that includes at least one access point sometimes referred to as "Infrastructure Basic Service Set" or "Infrastructure Basic Service Set Mode." Compare with Ad Hoc Network and Extended Basic Service Set.

BER

See Bit Error Rate (BER).

Binary Phase Shift Keying (BPSK)

A technique employed to shift the phase of the carrier signal by 0 or by 180 degrees, depending upon the bits to be transferred. While BPSK is simple to implement and is robust, it's inefficient in terms of using the available bandwidth.

Bit

This term is actually an abbreviation for "Binary Digit." A bit is the smallest unit of computerized data. It is also the basic unit in data communications and all computer communication is in bits. A bit is either a 1 or 0, reflecting the use of a binary numbering system (only two digits) and bits are used because the computer recognizes either of two states: ON or OFF. If you go to the lowest level, a bit is the presence or absence of an electrical (signal) charge. To understand how bits work, think of a bit as a switch. If the switch is in the "on" position, it is a 1, and if the switch is "off," it is a 0. The speed at which bits are transmitted or bit rate is usually expressed as bits per second or bps; for instance, bandwidth is usually measured in bits-per-second. Eight bits make up one byte.

Bit Error Rate (BER)

The percentage of bits that have errors relative to the total number of bits received in a transmission, usually expressed as ten to a negative power. For example, a transmission might have a BER of 10 to the minus 6 (10e-6), which means that out of 1,000,000 bits transmitted, one bit was in error. The BER provides an indication of how often a packet or other data unit must be retransmitted because of an error. A high BER may indicate that a slower data rate would actually improve overall transmission time for a given amount of transmitted data. By reducing the data rate, you reduce the BER, which in turn means that the number of packets needing to be resent is reduced, thus the overall transmission rate is increased.

Bluetooth

A short range wireless protocol that operates at 2.4 GHz. Bluetooth allows mobile devices to share information and applications over a short distance (less than 30 feet or 9.14 meters) without the worry of cables or interface incompatibilities. Bluetooth is named for a Danish Viking King Harald Blåtand (Bluetooth in English) who united the countries, much as the wireless counterpart is designed to unite individual system.

bps (bits per second)

When the "b" is lower case (bps) it means bits per second. When the "B" is upper case (Bps) it means bytes per second. Be careful, many people get these two terms and their corresponding acronyms confused. One "bit" of advice to keep you on track—in the telecommunications industry, LANs, WANs, USB, local loops, etc., the term should always refer to "bits per second" regardless of whether an upper case "B" or a lower case "b" is used.

BPSK

See Binary Phase Shift Keying (BPSK).

Bridge

This data communications device connects two or more network segments and forwards data packets between them.

Broadband

This term refers to a type of data transmission in which a single medium (wire or radio frequency) can carry several channels at once. While initially the term "broadband" referred to data transmission over 1 Mbps, the FCC and others have lowered the criteria. In many instances, the definition of broadband is any system capable of transmitting data in excess of 200 Kbps upstream and downstream. All communications systems that operate at a slower speed than broadband are called "narrowband."

Broadband Connection

This term refers to the ability to carry multiple signals by dividing the total capacity of the medium into multiple, independent bandwidth channels, where each channel operates only on a specific range of frequencies.

BSC

See Base Station Controller (BSC).

BSS

See Basic Service Set (BSS).

BTS

See Base Transceiver Station (BTS).

Byte

A set of bits of a specific length that represent a value in a computer coding scheme. A byte is comprised of eight bits. A byte is to a bit what a word is to a character.



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Going Wi-Fi. A Practical Guide to Planning and Building an 802.11 Network
Going Wi-Fi: A Practical Guide to Planning and Building an 802.11 Network
ISBN: 1578203015
EAN: 2147483647
Year: 2003
Pages: 273

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