CDPD (cellular digital packet data) Telecommunications companies can use CDPD to transfer data on unused cellular networks to users. If one section, or "cell," of the network is overtaxed, CDPD automatically allows for the reallocation of resources.

Cellular Technology that sends analog or digital transmissions from transmitters that have areas of coverage called cells. As a user of a cellular phone moves between transmitters from one cell to another, the user’s call travels from transmitter to transmitter uninterrupted.

Circuit switched Used by wireless carriers, this method lets a user connect to a network or the Internet by dialing in, such as with a traditional phone line. It’s a dial-in Internet service provider for wireless device users. Circuit-switched connections can be slow and unreliable compared with packet-switched networks, but for now circuit-switched networks are the primary method of Internet and network access for wireless users in the United States (see Packet-switched network).

Dual-band mobile phone Phones that support both analog and digital technologies by picking up analog signals when digital signals fade. Most mobile phones are not dual-band.

EDGE (enhanced data GSM environment) A faster version of the GSM standard. It is faster than GSM because it can carry messages using broadband networks that employ more bandwidth than standard GSM networks (see GSM).

FDMA (frequency division multiple access) An analog standard that lets multiple users access a group of radio frequency bands and eliminates interference of message traffic.

Frequency hopping spread spectrum A method by which a carrier spreads out packets of information (voice or data) over different frequencies. For example, a phone call is carried on several different frequencies so that when one frequency is lost another picks up the call without breaking the connection.

GPRS (general packet radio service) A technology that sends packets of data across a wireless network at speeds of up to 114Kbps. It is a step up from the circuit-switched method; wireless users do not have to dial in to networks to download information. With GPRS, wireless devices are always on--they can receive and send information without dial-ins. GPRS is designed to work with GSM.

GSM (global system for mobile communications) A standard for how data is coded and transferred through the wireless spectrum. The European wireless standard also used in Asia, GSM is an alternative to CDMA. GSM digitizes and compresses data and sends it down a channel with two other streams of user data. The standard is based on time division multiple access (see TDMA).