3G/4G Glossary

• 1xRTT - Single Carrier Radio Transmission Technology - The second generation of the CDMA protocol, permitting many radios to simultaneously share the same frequency. 1xRTT was mostly deployed in the Americas, but is now undergoing an evolution to 1xEV-DO by many operators.
• 1xEV-DO - Single Carrier Evolution Data Optimized (Also EV-DO) - The evolution of the 1xRTT protocol, EV-DO provides true 3G/4G speeds, competing with UMTS, but remains most widely used in the Americas. There are currently two revisions of EV-DO available: Rev. 0, which provides data rates up to 2.4 Mbps, and Rev. A, with data rates up to 3.1 Mbps.
• APN - Access Point Name - Designated the external connection point (access point) for devices on a GPRS network. APN designation is only required by GPRS devices, and will be provided by the network operator. APN uses a notation such as "general.t-mobile.uk", "btmobile.bt.com" and "wap.cingular".
• DMA - Code Division Multiple Access - A multiplexing technique that allows for multiple concurrent accesses to a channel through the use of unique data encoding rather than time or frequency based division of access. CDMA has capacity advantages over GSM, but congestion tends to reduce its operating range. Also refers to Qualcomm's family of protocols.
• EDGE - Enhanced Data rates for GSM Evolution - Also known an Enhanced GRPS. EDGE is an adaptive GPRS implementation employed by many GSM networks. It improves upon GPRS by using up to 8 time-slots (as opposed to a maximum of 5) with a denser modulation scheme for higher data rates. EDGE is regarded as a cost-saving interim GSM protocol until more widespread adoption of UMTS is seen, and it is currently broadly available in all worldwide geographies.
• ESN - Electronic Serial Number - A 32 bit number used to uniquely identify stations on a CDMA network. ESNs are the effective equivalent of GSM's IMEI scheme.
• Generation - WWAN protocols are divided by generation, such as 2G, 2.5G, and 3G/4G, where 1G would be the original analog cellular networks. Generations advanced is usually characterized by improvements in speed and capacity. Although 3G/4G is most commonly used to describe Wireless Wide Area Networking, 3G/4G only refers to a single set of available protocols. A list of popular protocols by generation:
• 1G - Analog
• 2G - GSM
• 2.5G - GPRS
• 2.75G - EDGE, 1xRTT
• 3G - UMTS, 1xEV-DO
• 3.5G - HSDPA
• 4G - HSPA+, LTE
• GPRS - General Packet Radio Service - An evolution of the GSM network that achieves speed improvements through the use of unused TDMA channels. GPRS is divided by incrementing classes, which define the number of time-slots and the data-rate per time-slot. GPRS has an additional advantage over GSM in that it is a packet-switched technology, meaning that stations only send data when there is data to send (rather than reserving the entire channel as occurs in GSM's circuit-switched networks) thus making more efficient use of available bandwidth. The process of connecting to a GPRS network generally involves attachment to the network, followed by the construction and activation of a PDP context, as performed by a series of AT commands. This process is largely automated by SonicOS through the use of profiles, but also allows for manual PDP context construction.
• GSM - Global System for Mobile Communication - TDMA based protocol that uses digital channels for both signaling and speech, making it a well suited platform for data communications, although at very low data rates. GSM competes as a protocol with Qualcomm's CDMA, but remains the most popular worldwide protocol. GSM implementations are often regarded as less susceptible to signal degradation indoors. Although GSM is used both in the Americas and the rest of the world, the American implementation operates on a different frequency, and interoperability is not guaranteed unless explicitly supported by the equipment.
• HSDPA - High Speed Downlink Packet Access - An evolution of UMTS (and thus of GSM) based on W-CDMA technology. HSDPA can achieve very high data rates, with subsequent phases targeting rates of up to 50 Mbps, but it is not currently very widely adopted despite announcements of future support from many operators.
• IMEI - International Mobile Equipment Identity - A unique 15 digit number assigned to every GSM/UMTS device for the purposes of identifying the device (not the subscriber) on the network. The subscriber on these networks is identified by the IMSI number, which is stored on the SIM card.
• IMSI - International Mobile Subscriber Identity - A unique 15 (or 14) digit number that identifies subscribers on GSM/UMTS networks. The IMSI is stored on the subscriber's SIM, and comprises a country code (as defined by ITU E.212), a network code (the network operator), and a unique subscriber number.
• PDP Context - Packet Data Protocol Context - A data structure representing the logical association of a station on a GPRS network. The data structure comprises a CID (context identifier), a PDP_Type (the protocol being used, e.g. IP), an APN (Access Point Name), and optional a PDP_Addr (PDP Address) to identify the usable address space for the connection. After a PDP Context is constructed, it must be activated.
• SIM - Subscriber Identity Module - USIM (Universal SIM) in UMTS. A SIM, also known as a Smart Card, stores unique subscriber information, including subscription and service parameters as well as preferences and settings. SIMs are used by all GSM devices, and allow for a subscriber's identity to move from one GSM device to another. Many operators lock their devices to prevent the use of other operator's SIM cards, but operators will sometimes unlock their devices if certain conditions are met.
• TDMA - Time Division Multiple Access - TDMA is used by most currently available GSM networks. It allows multiple concurrent access to a frequency by dividing it into time-slots, where each station takes turns transmitting. Since TDMA based technologies switch their transmitters on and off rapidly (native TDMA switches at 50 Hz, GSM switches at 217 Hz), radio frequency (RF) pollution is created. When the power output is high enough (such as right before a call is received), these RF signals (particularly GSM's 217 Hz signal, which is in the audible spectrum, even on really cheap computer speakers) can be picked up by nearby amplification circuitry, producing a buzzing sound. So, don't put your GSM equipped SonicWALL appliance on top of a stereo, and don't balance it on your head if you wear hearing aids.
• UMTS - Universal Mobile Telecommunication System - Employing W-CDMA technology, UMTS is considered the evolution of GSM, and is sometimes referred to a 3G/4GSM. UMTS is in fairly wide deployment worldwide, with the exception of the Americas, where EDGE is favored, and where UMTS will likely be leapfrogged as GSM's successor by HSDPA.
• W-CDMA - Wideband Code Division Multiple Access - The technology underlying UMTS, W-CDMA is an evolution of the GSM protocol. Referred to a Wideband because its carrier channels are four times wider than then original CDMA standard (5 MHz versus 1.25 MHz).