Wireless Terminology

Here’s a brief glossary of wireless networking and security terms and definitions, written and edited by Tom Sharples and other team members. This is a work in process, and soon, we’ll be following up with a guide for the beginning WiFi wireless installer.

Glossary of Wireless Terminology:

802.11B IEEE Standard for Wireless Communications
802.11b (also referred to as 802.11 High Rate or Wi-Fi) — an extension to 802.11 that applies to wireless LANS and provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1 Mbps) in the 2.4 GHz band. 802.11b uses only DSSS (Direct Sequence Spread Spectrum). 802.11b was a 1999 ratification to the original 802.11 standard, allowing wireless functionality comparable to Ethernet.

Access Point (AP)
A device, typically equipped with an antenna, a wireless modem and an ethernet port, that transports data between a wireless network and a wired ethernet network.

The wired or wireless connection between an access point and the wide-area network e.g. the Internet.

Cable Loss
The RF signal loss that occurs in lengths of cable. This varies from one type of coaxial cable to another and becomes significant at frequencies above around 500 Mhz. It is usually expressed in db of loss per 100 feet, at a given frequency. The cable loss in a typical installation using ordinarily-available cable, makes it difficult to remote-mount a 2.4 gigahertz WiFi antenna further than around 10 feet away from the host computer or Access Point.

CDPD Cellular Digital Packet Data
CDPD, or Cellular Digital Packet Data, is an obsolete method to get wide-area wireless Internet connectivity into a laptop or PDA. The service was discontinued in 2005. It used an extension of TCP/IP and is therefore directly compatible with standard IP addressing schemes. Suppliers included AT&T and Verizon.

CDMA2000 / 3G
(code division multiple access 1xRTT data) one of several competing 3G wireless data services that piggyback on digital voice networks. Currently the best solution (IMO) for stand-alone wireless data connectivity especially in rural areas. Offered by Sprint and verizon in 100% of their network.

Denial of Service(DOS)attack:
A common method of disrupting legitimate communications between client and server, is to generate a condition under which either one is unable to respond to requests from the other. This can be done simply for the sake of malicious mischief, or for the purpose of "spoofing" or substituting a non-legitimate device at one end or the other, and then using that device to steal confidential information from the other end.  The basic idea is to overwhelm either the client or server with spurious IP traffic, to the point where valid traffic can no longer get through. This is sometimes accomplished by hijacking unwitting internet-connected systems and installing a "worm" in those systems, that assists in attacking the target.

Workstations, servers, and other devices that are potential victims for denial of service attacks, are easily discovered using one of several techniques.  For example, it is commonly known that AT&T owns the unique IP addresses located between and, and ?rents? these addresses to its clients, who range from simple cable-modem users, to Fortune 500 corporations. A hacker using readily?available tools can scan the IP space ranging from to 12.x.x.x, looking for devices that will respond to industry-standard SNMP (Simple Network Management Protocol) and DNS (Domain Name Service) probes. Such devices, which are very widespread, include routers, most web servers, print servers, and so forth. Knowing the identity and IP address of each device, it is then a relatively easy step to exploit particular (and often well-known) security holes in the device. In the process, it would be possible to add malicious code capable of, e.g. echoing print files containing private information to an outside device under the hacker’s control.If a hacker has a narrower target than the AT&T network, knowing what IP range  to scan (since scanning a range like AT&T can take days), is usually easy to determine. Quite often, the IP addresses of a company’s public web site, are numerically close to those reserved for various private uses such as engineering development, finance and payroll, internal HR servers, etc. Once the public Webster’s IP address is determined (trivial using any free DNS lookup services) the hacker scans the IP range within, say 256 addresses an either side of that assigned to the web server. Surprisingly often, the target company’s servers, workstations (often with the names of individual employees) and other confidential information is displayed in broad daylight.

DHCP (Dynamic Host Configuration Protocol)
Issues IP addresses (and sometimes other information such as DNS addresses) automatically within a specified range to client devices when they are first powered on. The device retains the use of the IP address for a specific license period that the system administrator can define. This allows a device to enter and leave a wireless area without manually assigning a specific static IP address to each device.

Direct Sequence Spread Spectrum (DSSS)
Technique to reduce and avoid interference by taking advantage of statistical means to send a signal between two points. A variety of spread-spectrum radio transmission methods that continuously change frequencies or signal patterns. ALT Definition: Direct sequence spread spectrum (DSSS), multiplies the data bits by a very fast pseudo-random bit pattern (PN sequence) that "spreads" the data into a large coded stream that takes the full bandwidth of the channel, but reduces the RF energy in any one frequency within the channel. This reduces the likelihood of interference from other RF devices like microwave ovens, etc.

Directional Antenna
An antenna that exhibits more signal gain in one direction than in the others. The directional pattern can be quite varied, however, it is easiest to think of it as being in the shape of an egg lying on its side, with the antenna at one end pointed at the center of the egg. As the directional gain of the antenna goes up, the egg gets narrower, and longer. Almost as important as the gain in the direction of interest, is the rejection of signals from the back (front-to-back ratio) and the sides (side lobes). All directional antennas are compromises with respect to one or more of these parameters.

Diversity Antenna
Dual antenna arrangement that allow the RF device to receive the the stronger of multipath signals.

(1) Short for Domain Name System (or Service), an Internet service that translates domain names (URL’s) into IP addresses. Because domain names are alphabetic, they’re easier to remember. The Internet however, is really based on IP addresses . Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address. For example, the domain name www.example.com might translate to The DNS system is, in fact, its own network. If one DNS server doesn’t know how to translate a particular domain name, it asks another one, and so on, until the correct IP address is returned.

Refers collectively to all types of digital subscriber over POTS telephone lines, the two body categories being ADSL and SDSL. Two other types of xDSL technologies are High-data-rate DSL (HDSL) and Symmetric DSL (SDSL). DSL technologies use sophisticated channel-coding modulation schemes to pack large amounts of data onto low-grade copper phone wires. They are sometimes referred to as last-mile technologies because they are used only for connections from a telephone switching station to a home or office, not between switching stations. xDSL is similar to ISDN inasmuch as both operate over existing copper telephone lines (POTS) and both require the short runs to a central telephone office (usually less than 20,000 feet). However, xDSL offers much higher speeds – up to 32 Mbps for downstream traffic, and from 32 Kbps to over 1 Mbps for upstream traffic.

Dynamic IP
An IP address that is automatically assigned to a client station in a TCP/IP network, typically by a DHCP server. Network devices that serve multiple users, such as servers and printers, are usually assigned static IP addresses. See static IP
address, IP address and DHCP.

A 10, 100, or 1000 Mbps LAN medium-access method that uses CSMA (collision sensing multiple access)to allow the sharing of a bus-type Network.

Ethernet Switch
More intelligent than a hub, having the capability to route signals from the sending station directly to the receiving station by decoding part of the IP data packet on the fly.

FID Frame Identifier
A 4-digit hexadecimal number used to identify a specific data element in the packet.

Gain (antenna gain)
The extent to which a transmitted or received RF signal is greater than that which would be received or transmitted by a reference stub antenna (e.g. a short piece of wire).

The computer or device onto which the first hop needs to go to get out of your local network. A TCP/IP route uses several hops to get from here to there. Typically the gateway is embedded within the wireless access point / router and is assigned the same IP address.

(general packet radio service) Part of the family of newer (than CDPD) wide-area wireless data technologies currently being rolled out by several major carriers like AT&T EDGE. Runs at 1.9 gigahertz. Supported by USB cards made by Novatel, Sierra Wireless, and Yiso for mini PC (compact flash form factor for use in PDAs).

Short for HyperText Transfer Protocol, the underlying protocol used by the World Wide Web. HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. For example, when you enter a URL in your browser, this actually sends an HTTP command to the Web server directing it to fetch and transmit the requested Web page. The other body standard that controls how the World Wide Web works is HTML, which covers how Web pages are formatted and displayed. HTTP is called a stateless protocol because each command is executed independently, without any knowledge of the commands that came before it. This is the body reason that it can be difficult to implement Web sites that react intelligently to sequential user input. This shortcoming of HTTP is addressed in a number of newer technologies, including ActiveX, Java, JavaScript, XHTML, and cookies. Currently, most Web browsers and servers support HTTP 1.1. One of the body features of HTTP 1.1 is that it supports extensions.

IP cameras are CCTV cameras that use the TCP/IP protocol over wired or wireless ethernet to transmit digitized video images to the end-user’s computer or smartphone, rather than using baseband NTSC video transmission through coaxial cable, as was the previous standard. This results in more consistent video quality (and potentially much higher quality e.g. megapixel) due to the use of standard IT methodologies and equipment for handling, directing, and storing video data. Major suppliers of  these cameras include Mobotix, Axis, Arecont, Acti, as well as a number of the previously-dominant players in analog CCTV such as Pelco, American Dynamics, and Bosch.

Input/Output e.g. serial ports, USB, or discrete single-purpose connections (sensors, lights, etc)

Acronym for Japan Electronic Industry Development Association.

Local Area Network

MAC Address (BSSID)
Media Access Control Address (MAC Address) – This is a unique 128-bit address of a network card or device. The first part of the address is unique to the company that produced the device, and beyond that, it is a sequence of digits unique to a single hardware network interface card or device manufactured by a company.

A wireless networking and autorouting system that allows client data to hop from one (wireless) node to the next and on to its final destination (usually a gateway to the Internet) without backhaul connections except at the gateway.

MIB (Management Information Base)
A collection of managed objects residing in a virtual information store. Used to remotely manage devices like AP’s from a central location via SNMP.

Multipath Effect
Multipath is the radio wave propagation phenomenon that results in a signal reaching the receiver by two or more paths. In a typical wireless LAN environment this is due primarily to reflections from nearby objects, such as walls, furniture, etc. Multipath effects the signal through constructive and destructive interference and phase shifting. These effects in turn influence WLAN signal integrity and coverage range.

Network Driver Interface Specification

Network Interface Card

Non-Routable IP

These are IP addresses have specifically been set aside to use when it isn’t necessary (or desirable) for anyone on the Internet to be able to instantly navigate to your computer. It is especially useful to the DSL user who has multiple computers connected to a single proxy server, firewall or router. Reserved IP’s for private networks are –, –, – These IP addresses are invisible to anyone on the other side of your router or firewall.

Omnidirectional Antenna
An antenna that exhibits equal gain in all compass directions. It is useful to think of this antenna’s pattern as a donut lying on its side, with the antenna located in the center of the donut. As the gain of this antenna is increased, the pattern starts to look less like a donut, and more like a plate.

Patch Antenna
A directional antenna that has been manufactured using micro-strip techniques on a planar surface, usually in the shape of a small square or rectangle. These antennas typically feature small size and low profile, but also suffer from relatively narrow bandwidth and low efficiency and gain. They make a good choice for use with a host computer when an unobtrusive directional antenna with some gain is needed, and when a flat mounting surface, that allows the antenna to be correctly oriented toward the Access Point, is available nearby.

PC Card
A memory or I/O card compatible with the PC Card (PCMCIA) Standard. When the term PC Card is used, what is being addressed is those characteristics that are common to both 16-bit Cards and CardBus PC Cards. 16-bit PC Cards use the PC Card Standard interface originally defined in the PCMCIA1.0/JEIDA 4.0 and PCMCIA 2.0/JEIDA 4.1 publications.

The orientation of radio signals from and to an antenna. A vertical antenna mounted normally, radiates vertically-polarized signals. A horizontal antenna (e.g. a Yagi with its tines horizontally oriented) radiates horizontally-polarized signals. If a horizontally-polarized antenna attempts communications with a vertically-polarized one, a signal-path loss of around 20db will occur. Polarization can sometimes be an effective method of combating interference. If vertically-polarized interference is present (most RF interference in the 2.4 gigahertz region is vertically oriented), try orienting the antennas horizontally.

Short for Point-to-Point Protocol, a method of connecting a single computer temporarily to the Internet. PPP is more stable than the older SLIP protocol and provides error checking features

Acronym for Point-to-Point Protocol over Ethernet. PPPoE relies on two widely accepted standards: PPP and Ethernet. PPPoE is a specification for connecting the users on an Ethernet to the Internet through a common broadband medium, such as a single DSL line, wireless device or cable modem. All the users over the Ethernet share a common connection, so the Ethernet principles supporting multiple users in a LAN combine with the principles of PPP, which apply to individual serial connections

A usually opaque plastic cover, that protects antenna elements against damage from weather or contact. Most patch antennas, and many vertical antennas as well as some Yagi’s, come with, or can be ordered with radomes.

A device that connects any number of LANs. Routers use headers and a forwarding table to determine where packets go, and they use ICMP to communicate with each other and configure the best route between any two hosts. Traditionally very little filtering of data is done through routers. Routers do not care about the type of data they handle. However, new-generation SOHO routers (like SMC or Netgear combo wireless AP / broadband routers) often include user-specifiable port or protocol filtering.

(Simple Network Management Protocol) A standard and extensible method for remote management of network devices such as routers, switches, etc. In the last few years also being used for other embedded devices connected to an iI network. Other remote management tools in widespread use include telnet, RMON and embedded HTTP servlets.

or Wired Equivalent Privacy is an obsolescent security standard for 802.11 wireless networks promulgated by the IEEE. It provides two levels of encryption, 40 and 128 bit, and uses a standard method of mixing data with a secret encryption key that is supposed to be known by only the client and the host. While this standard is generally secure enough to discourage a casual snooper (who will probably just move on to easier targets) it is rather vulnerable to attack from a serious hacker. The easiest attack is based on sending a known text message to an unsuspecting email client and waiting for him to read the message using a WEP enabled laptop. For more info read the excellent article here