Wireless Computing

Introduction to Wireless

Wireless Technologies


Network Security



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Access point (AP) - An IEEE 802.11 station that provides distribution services to other stations.

Acknowledgement (ACK) - An acknowledgement that data has been received successfully. An ACK message is used as part of the MAC distributed coordination function.

Ad hoc network - A self-contained group of stations communicating directly with each other in a peer-to-peer network. Generally formed spontaneously and existing for a limited time, an ad hoc network does not include an access point or distribution system.

Authentication service - The station service that enables a station to establish an identity recognized by other stations. Authentication services are provided by each station. Open system authentication enables any station to become authenticated. Shard key authentication uses a shared secret key. In IEEE 802.11, this key is implemented through the use of WEP encryption.

Bandwidth - A range of continuous frequencies.

Bits per second (bps) - A measurement of how quickly data is being transmitted.

Bluetooth - Bluetooth is a wireless personal area network (PAN) technology developed by Ericsson in 1994. It is maintained by an industry group called the Bluetooth Special Interest Group. Bluetooth is a 2.4 GHz technology optimized for a large number of devices communicating in a peer-to-peer relationship.

Broadcast message - A message addressed to all stations.

Carrier sense multiple access with collision avoidance (CSMA/CA) - CSMA/CA is a basic medium access protocol in which network nodes listen for traffic before accessing the medium. This mechanism, used by IEEE 802.11, minimizes the amount of data collisions that occur when the medium may be accessed by two nodes simultaneously.

Clear to Send (CTS) - A message that indicates the intent to send data.

Direct sequence spread spectrum (DSSS) - DSSS is a spectrum management technique that spreads the signal over a larger frequency band by converting each individual bit into a larger pattern of bits, lowering power used at a particular frequency and allowing for error checking.

Forward Error Correction (FEC) - The automatic correction of faulty bits in a transmission by the receiving unit, made possible by certain types of data encoding.

Frequency - The number of periodic oscillations or waves that occur per a particular unit of time. Frequency is almost always measured in hertz (Hz), the number of cyles per second.

Frequency-hopping spread spectrum (FHSS) - FHSS is a spectrum management technique that spreads the signal over a larger frequency band by allocating channels across the available frequencies and transmitting on different channels in a specific pattern.

Gigahertz - One billion cycles per second.

Hidden node - In a wireless LAN environment, a station that cannot detect the transmission of another station and thus fails to recognize that the medium is busy.

Hold mode - A Bluetooth low-power operating mode under which a device's cloth continues to operate and remain in synchronization with the master but does not participate in the network.

IEEE 802.11 - The standard that governs the operation of wireless LANs.

IEEE 802.11b - A revised wireless LAN standard that uses Direct Sequence Spread Spectrum (DSSS) to support a data rate up to 11 Mbps.

Impulse noise - Noise caused by periodic disturbances, ranging from lightning and the operation of machinery to solar flares.

Local area network (LAN) - A network connecting multiple electronic devices to each other and potentially to other networks. LANs are typically found in offices, schools, and or other area with multiple computers.

Mbps - Abbreviation for megabits (1 million bits) per second.

Medium Access Control (MAC) - The MAC layer is the lower sublayer that IEEE 802.11 specifications provide for managing access to the physical layer (PHY).

Personal area network (PAN) - A smaller network generally covering an area less than 10 meters. Commonly used for communication between multiple personal electronic devices such as cell phones, PDAs, and laptops.

Physical (PHY) layer - The lowest layer in the IEEE 802.11 protocol model. The PHY layer in IEEE 802.11 provides the interface to the physical transmission media (radio, infrared, etc) for the MAC layer.

Piconet - Under Bluetooth, any network with one master and one or more slaves that can support up to seven active slaves and 256 parked slaves.

Scatternet - Under Bluetooth, a scatternet represents the overlapping of wireless coverage from two piconets.

Signal-to-noise (S/N) ratio - The ratio of the signal power divided by the noise power on a transmission medium.

Thermal noise - Noise caused by the movement of electrons or radiation from the sun.

Wired Equivalent Protocol (WEP) - The optional cryptographic algorithm used to provide privacy in wireless data transmissions. The WEP, based on a 40-bit shared key, provides a minimum amount of privacy but is vulnerable to attack.

Wireless Application Protocol (WAP) - A mobile device protocol that provides Internet access for a variety of Internet-based applications.

Some definitions care of Gil Held's 'Data Over Wireless Networks' and the LaRocca's '802.11 Demystified'.

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