RD Glossary
- data rate
- The number of bits per second (bps) that data is sent. For example, 802.11b wireless LANs operate at up to 11Mbps.
- DCF (distributed coordination function)
- A part of the 802.11 standard that defines how stations will contend for access to the air medium. DCF makes use of CSMA to regulate traffic on the network.
- DHCP (Dynamic Host Configuration Protocol)
- A protocol that automatically assigns unique IP addresses within an assigned range to network devices. Most home and public wireless LANs implement DHCP, making it very easy for users to gain access to the network. DHCP automatically assigns a valid IP address to these users.
- digital certificate
- An electronic message that contains the credentials of a particular user. Digital certificates are used as a means for authenticating users or their computer devices.
- digital signal
- A signal that varies in amplitude steps as time advances. Digital signal represent data within a computer device. The digital signal must be converted to an analog form (know as modulation) before the data can be sent through the air medium.
- direct sequence spread spectrum
- A type of spread spectrum where a spreading code increases the signal rate of the data stream in order to spread the signal over a wider portion of the frequency band. 802.11b wireless LANs make use of direct sequence.
- directional antenna
- A type of antenna that focuses radio waves and range more in one direction than others. Directional antennas are commonly found in wireless MANs and wireless WAN systems. The directivity of the antenna increases range in one direction and decreases range in other directions.
- distribution system
- A wired system that physically interconnects access points in a wireless LAN. A common distribution system for wireless LANs, for example, is Ethernet.
- encryption
- The scrambling of data bits according to a key prior to sending the data over a network. WEP and WPA are examples of encryption that wireless LAN utilize.
- Ethernet
- A name that depicts 802.3 wired local area networks. Ethernet is a common type of network that companies use to interconnect PCs and servers. Ethernet provides the distribution system of most wireless LANs.
- FDMA (frequency division multiple access)
- A process that divides a relatively wide frequency band into smaller sub-bands, where each user transmits voice and data over their assigned sub-band.
- FHSS
- See frequency hopping spread spectrum
- firewall
- A device that keeps users connecting to a specific part of the network from accessing important resources. Because of their vulnerability, access points of wireless LANs are often placed outside the firewall.
- frequency
- The number of times per second that a signal repeats itself. Often measured in Hertz (Hz), which is the number of cycles occurring each second. Frequencies of wireless LANs, for example, are within the 2.4GHz and 5GHz bands.
- frequency hopping spread spectrum
- A type of spread spectrum where the transceiver hops from one frequency to another according to a known hopping pattern in order to spread the signal over a wider portion of the frequency band. Older 802.11 wireless LANs utilize frequency hopping.
- FSK (frequency shift-keying)
- A modulation process that makes slight changes to the frequency of the carrier signal in order to represent information in a way that’s suitable for propagation through the air.
- GPS (global positioning system)
- A system that enables people having a GPS client device to easily determine their geographical position. GPS offers the basis of an excellent navigation system, as well as location-based services over wireless networks.
- Hacker
- A person who has the desire and ability to steal information that resides on a network. Hackers often try breaking into corporate systems for fun and exploit the vulnerabilities of wireless networks.
- hotspot
- The location of a public wireless LAN. Hotspots are found within areas where people congregate with computer devices, such as at airports, hotels, convention centers, and coffee shops.
- interference
- Unwanted signals that disrupt the operation of a wireless network. The presence of interference decreases the performance of a wireless network.
- interoperability
- A condition whereby computer devices are able to successfully interface with a wireless network.
- IP (Internet Protocol)
- A protocol that routes packets between computer devices attached to a network. The IP protocol places a header field in front of each packet that contains the source and destination IP address of the packet.
- IP address
- A number that represents the address corresponding to a connection of a network device to the network. For example, every wireless network NIC will have an IP address. Each NIC must have an IP address associated with it if the user will be making use of TCP/IP applications, such as sending and receiving email, browsing the web, or interfacing with a corporate application server.
- IPSec (IP Security)
- A protocol that supports secure exchange of packets at the Network Layer of a network. IPSec is commonly implemented in VPNs and encrypts data packets across the entire network (often referred to as end-to-end encryption).
- IrDA (Infrared Data Association)
- A standard specifying an interoperable, low-cost, low-power, serial data communications standard for short-range applications. IrDA is found in many laptops and PDAs.
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RD Glossary by Run Digital
