A glossary of terms related to wireless network technologies
10BaseT: An IEEE standard (802.3) for operating 10 Mbps Ethernet networks (LANs) with twisted pair cabling and a wiring hub.
Ad-Hoc Mode: A client setting that provides independent peer-to-peer connectivity in a wireless LAN. An alternative set-up is where PCs communicate with each other through an AP. See AP and Infrastructure Mode.
AP (Access Point): A hardware device, or software used in conjunction with a computer, that serves as a communications "hub" for wireless clients and provides a connection to a wired LAN. An AP can double the range of wireless clients and provide enhanced security.
Application software: A software program running on top of the operating system (Windows, UNIX, Mac) that has been created to perform a specific task for a user. Examples include word processing software like Word/Word Perfect, spreadsheets like Excel or Lotus 123, home finance packages like Quicken, etc.
Client: Any computer connected to a network that requests services (files, print capability) from another member of the network.
CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance): CSMA/CA is the principle medium access method employed by IEEE 802.11 WLANs. It is a "listen before talk": method of minimizing (but not eliminating) collisions caused by simultaneous transmission by multiple radios. IEEE 802.11 states collision avoidance method rather than collision detection must be used, because the standard employs half duplex radios—radios capable of transmission or reception—but not both simultaneously. Unlike conventional wired Ethernet nodes, a WLAN station cannot detect a collision while transmitting. If a collision occurs, the transmitting station will not receive an ACKnowledge packet from the intended receive station. For this reason, ACK packets have a higher priority than all other network traffic. After completion of a data transmission, the receive station will begin transmission of the ACK packet before any other node can begin transmitting a new data packet. All other stations must wait a longer pseudo randomized period of time before transmitting. If an ACK packet is not received, the transmitting station will wait for a subsequent opportunity to retry transmission.
CSMA/CD (Carrier Sense Multiple Access/Collision Detection): The LAN access method used in Ethernet. When a device wants to gain access to the network, it checks to see if the network is free. If it is not, it waits a random amount of time before retrying. If the network is free and two devices access the line at exactly the same time, their signals collide. When the collision is detected, they both back off and each wait a random amount of time before retrying.
DSSS and FHSS: Wireless LAN products are available in three different technologies -- direct-sequencing spread-spectrum (DSSS), frequency-hopping spread-spectrum (FHSS) and infrared. DSSS and FHSS are spread-spectrum techniques that operate over the radio airwaves in the unlicensed ISM band (industrial, scientific, and medical). DSSS uses a radio transmitter to spread data packets over a fixed range of the frequency band. FHSS uses a technique by which the signal transmitted hops among several frequencies at a specific rate and sequence as a way of avoiding interference. WECA’s focus is on the use of DSSS for 11 Mbps high rate wireless LAN communications.
Ethernet: The most widely used LAN access method, which is defined by the IEEE 802.3 standard. Ethernet is normally a shared media LAN meaning all devices on the network segment share total bandwidth. Ethernet networks operate at 10Mbps using CSMA/CD to run over 10BaseT cables.
Gateway: A network point that acts as an entrance to another network.
Hz (Frequency) (Hertz): The international unit for measuring frequency, equivalent to the older unit of cycles per second. One megahertz (MHz) is one million hertz. One gigahertz (GHz) is one billion hertz. The standard US electrical power frequency is 60 Hz, the AM broadcast radio frequency band is 535 - 1605 kHz, the FM broadcast radio frequency band is 88 -108 MHz, and wireless 802.11b LANs operate at 2.4 GHz.
IEEE: Institute of Electrical and Electronics Engineers, New York, www.ieee.org. A membership organization that includes engineers, scientists, and students in electronics and allied fields. It has more than 300,000 members and is involved with setting standards for computers and communications.
IEEE 802.11: IEEE 802.xx is a set of specifications for LANs from The Institute of Electrical and Electronic Engineers (IEEE). Most wired networks conform to 802.3, the specification for CSMA/CD based Ethernet networks or 802.5, the specification for token ring networks. 802.11 define the standard for wireless LANs encompassing three incompatible (non-interoperable) technologies: Frequency Hopping Spread Spectrum (FHSS), Direct Sequence Spread Spectrum (DSSS), and Infrared. WECA’s focus is on 802.11b, an 11 Mbps high rate DSSS standard for wireless networks.
Infrastructure Mode: A client setting providing connectivity to an AP. As compared to Ad-Hoc Mode where PCs communicate directly with each other, clients set in Infrastructure Mode all passes data through a central AP. The AP not only mediates wireless network traffic in the immediate neighborhood, but also provides communication with the wired network. See AD-Hoc and AP.
IP: The Internet Protocol (IP) is a method or protocol by which data is sent from one computer to another on a network, i.e. the Internet. Each computer on the Internet has at least one address that uniquely identifies it from all other computers on the Internet. When you send or receive data (for example, an e-mail note or a Web page), the message gets divided into little chunks called packets. Each of these packets contains both the sender's Internet address and the receiver's address. Any packet is sent first to a gateway computer that understands a small part of the Internet. The gateway computer reads the destination address and forwards the packet to an adjacent gateway that in turn reads the destination address and so forth across the Internet until one gateway recognizes the packet as belonging to a computer within its immediate neighborhood or domain. That gateway then forwards the packet directly to the computer whose address is specified. Because the data is divided into a number of packets, each packet can, if necessary, be sent by a different route across the Internet. A packet is treated as an independent unit of data so packets can arrive at their destination in a different order than they were sent in. Another protocol, the Transmission Control Protocol, (TCP) then reassembles the packets in the right order.
IP Address: An IP address is a 32-bit number that identifies each sender or receiver of information that is sent across the Internet. An IP address has two parts: the identifier of a particular network on the Internet and an identifier of the particular device (which can be a server or a workstation) within that network.
ISA (or PCI): A local bus standard for connecting peripherals to a personal computer. Within a computer, the bus is the transmission path on which signals and data transfers occur between the CPU, system memory, and attached devices such as a network card, sound card, or CD-ROM drive.
ISO Network Model: The International Standards Organization (ISO) has developed a network model that consists of seven different levels, or layers. By standardizing these layers, and the interfaces in between, different portions of a given protocol can be modified or changed as technologies advance, or systems requirements are altered. The seven layers are:
The IEEE 802.11 Standard encompasses the physical layer (PHY) and the lower portion of the data link layer. The lower portion of the data link layer is often referred to as the Medium Access Controller (MAC) sublayer.
ISP (Internet Service Provider): An organization that provides access to the Internet. Small ISPs provide service via modem and ISDN while the larger ones also offer private line hookups (T1, fractional T1, etc.). The major online services such as America Online provide Internet access but are still known as "online services", not ISPs. They offer the members only content, forums and services in addition to Internet access.
LAN (Local Area Network): A communications network that serves users within a defined geographical area. The benefits include the sharing of Internet access, files and equipment like printers and storage devices. Special network cabling (10BaseT) is often used to connect the PCs together. Wireless LANs use wireless communications, in a home or office, to network all PCs together so there is no need to run an extra set of cables.
MAC (Medium Access Control): In a WLAN network card, the MAC is radio controller protocol. It corresponds to the ISO Network Model's level 2 Data Link layer. The IEEE 802.11 standard specifies the MAC protocol for medium sharing, packets formats and addressing, and error detection.
NAT (Network Address Translation): The translation of an Internet Protocol address (IP address) used within one network to a different IP address known within another network. One network is designated the internal network and the other is the external. The internal network then appears as one entity to the outside world. In the case of wireless LANs with an outside Internet connection, the NAT capability of Internet sharing software allows the sharing of one Internet connection among all the wireless PCs connected.
PCI (or ISA): A local bus standard for connecting peripherals to a personal computer. Within a computer, the bus is the transmission path on which signals and data transfers occur between the CPU, system memory, and attached devices such as a network card, sound card, or CD-ROM drive.
PHY (Physical Layer): The PHY is the lowest layer within the OSI Network Model. It deals primarily with transmission of the raw bit stream over the PHYsical transport medium. In the case of wireless LANs, the transport medium is free space. The PHY defines parameters such as data rates, modulation method, signaling parameters, transmitter/receiver synchronization, etc. Within an actual radio implementation, the PHY corresponds to the radio front end and baseband signal processing sections.
Roaming: Moving seamlessly from one AP coverage area to another with no loss in connectivity.
TCP (Transmission Control Protocol): protocol A used along with the Internet Protocol (IP) to send data in the form of individual units (called packets) between computers over the Internet. While IP takes care of handling the actual delivery of the data, TCP takes care of keeping track of the packets that a message is divided into for efficient routing through the Internet. For example, when a web page is downloaded from a web server, the TCP program layer in that server divides the file into packets, numbers the packets, and then forwards them individually to the IP program layer. Although each packet has the same destination IP address, it may get routed differently through the network. At the other end, TCP reassembles the individual packets and waits until they have all arrived to forward them as a single file.
WAN (Wide Area Network): A wide area network connects local area networks together. Typical WAN interfaces include plain old telephone (POT) lines, digital subscriber lines (DSL), cable, T1/T3 and ISDN, T1/T3.
WECA: Short for Wireless Ethernet Compatibility Alliance, The Wi-Fi Alliance is a nonprofit international association formed in 1999 to certify interoperability of wireless Local Area Network products based on IEEE 802.11 specification. Currently the Wi-Fi Alliance has 202 member companies from around the world, and 580 products have received Wi-Fi certification since certification began in March of 2000. The goal of the Wi-Fi Alliance's members is to enhance the user experience through product interoperability.
WEP (Wired Equivalent Privacy): WEP data encryption is defined by the 802.11 standard to prevent (i) access to the network by "intruders" using similar wireless LAN equipment and (ii) capture of wireless LAN traffic through eavesdropping. WEP allows the administrator to define a set of respective "Keys" for each wireless network user based on a "Key String" passed through the WEP encryption algorithm. Access is denied by anyone who does not have an assigned key.
Wi-Fi: It's powerful. Wi-Fi networks use radio technologies called IEEE 802.11b or 802.11a to provide secure, reliable, fast wireless connectivity. A Wi-Fi network can be used to connect computers to each other, to the Internet, and to wired networks (which use IEEE 802.3 or Ethernet). Wi-Fi networks operate in the unlicensed 2.4 and 5 GHz radio bands, with an 11 Mbps (802.11b) or 54 Mbps (802.11a) data rate or with products that contain both bands (dual band), so they can provide real-world performance similar to the basic 10BaseT wired Ethernet networks used in many offices.
Wi-Fi Alliance: An organization made up of leading wireless equipment and software providers with the missions of certifying all 802.11-based products for interoperability and promoting the term Wi-Fi as the global brand name across all markets for any 802.11-based wireless LAN products.