Wireless Technology Terminology

     The following is a simple guide to some terms commonly used in the wireless industry. It is not our intention to make it comprehensive, but it may be handy as a reference tool.

AMPS - The Mobile Phone System (AMPS) is the analog system used in the United States for cellular telephones. It uses Frequency Modulation (FM).  AMPS use the FDMA air interface.  The channels are 30 KHz wide. The frequency band for AMPS is 824 MHz to 849 MHz and 869 MHz to 894 MHz.

NAMPS - Narrow-band Advanced Mobile Phone Service (NAMPS).  The 30 kHz channels used in AMPS were divided into three 10 KHz channels to add more capacity to the cellular system.

GSM - was established in 1982 as a European standard for digital wireless communications. The first system was on line in 1991.  GSM is now used in many countries around the world. The most accepted name is Global System for Mobile Communications.  GSM uses a combination of Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA). FDMA: The 25 MHz band is divided into 125 frequencies of 200 kHz each. One or more of those frequencies are assigned to each base station.  TDMA: Each of those frequencies uses 8 time slots.

TDMA - Time Division Multiple Access is an air interface that allows mobile stations to use the same frequency, but are separated by time slots. TDMA uses its spectrum by assigning each user on a channel a different "slot" in time.  IS-136 and iDen have 3 slots per channel, while GSM has 8 slots per channel. A GSM channel is much wider than an IS-136 or iDen channel.  Each user "takes turns" transmitting and receiving in their designated time slot.

CDMA - Code Division Multiple Access is an air interface that allows mobile stations to use the same frequency, but are separated by unique digital codes. CDMA uses spread spectrum techniques.  CDMA has everyone on the channel transmitting and receiving at the same time. It works because of a modulation technique known as Spread Spectrum.  A CDMA channel is very wide (1.25 MHz).  Each user is only transmitting a small amount of data, which would normally fit well into a much smaller channel. What the transmitter does is to take this small number of bits and spread it out over the entire 1.25 MHz channel.  It does so using an encoding technique.  The receiver's job is to "unspread" the bits and extract only the data from each desired user.

Spread Spectrum - A communications technology where a signal is transmitted over a broad range of frequencies and then reassembled when received.

PCS - The Federal Communications Commission (FCC) opened a new frequency band for digital phones and named the new service Personal Communication Services (PCS).  The band is generally referred to as the 1900 MHz ((1.9 GHz) band.  The band is from 1850 MHz to 1990 MHz.

GSM 1900 - GSM system used in the United States on the PCS band.

SMS - (Short Messaging System) A feature of PCS phones (primarily GSM) that allows users to receive and sometimes transmit short text messages using their wireless phone; very popular in Europe and Asia.

Bandwidth - Describes a communications medium in terms of a range of frequencies.  A greater bandwidth indicates the ability to transmit a greater amount of data over a given period of time.

BTA - (Basic Trading Area A geographic region defined by a group of counties that surround a city, which is the area's basic trading center. The boundaries of each BTA were formulated by Rand McNally & Co. and are used by the FCC determine service areas for PCS wireless licenses.  The entire US and some of its territories are divided into 493 non-overlapping BTAs.

MTA - (Major Trading Area) An area consisting of tow or more Basic Trading Areas as defined by Rand McNally & Co. These large areas are used by the FCC determine service areas for some PCS wireless licenses.  The US is divided into 51 MTAs.

RSA - (Rural Service Area) Areas not included in MSAs are divided into RSAs.  Generally these are the rural areas of the US.  The FCC used RSAs to license cellular carriers in areas not included in MSAs. There are 428 RSAs in the US.

MTSO - (Mobile Telephone Switching Office) An office housing switches and computers to which all cell sites in an area are connected for the purpose of eventual connection to the PSTN.  The MTSO handles the connection, tracking, status, and billing off all wireless call activity in an assigned area.

ESN - The Electrical Serial Number (ESN) is a 332-bit number that is stored in the phone. It is used to identify your phone. In addition, there are lock and identity codes used in each handset to reduce fraud, and identity-stolen units.

Authentication & Encoding Systems - A featured used to reduce fraud by confirming the identity of a phone to the wireless network.

Radio-Frequency Fingerprinting - An electronic process that identifies each individual wireless handset by examining its unique radio transmission characteristics.  Fingerprinting is used to reduce fraud since the illegal phone cannot duplicate the legal phone's radio-frequency fingerprint.

SIM Card - The Subscriber Identity Module (SIM) card is a "smart card" used by a subscriber to GSM. The card contains information about the user and can be plugged into another GSM phone.  This allows the user to use another GSM phone as if it was on his/her own phone.

Vocoder Rate - The voice coder rate is the manner of digitizing a voice signal in a wireless transmission. The common standards are 8 kilobits per second and 13 kilobits per second.

EVRC - The Enhanced Variable Rate Coder (EVRC) is an 8 kbps vocoder that is designed to sound as good as the current 13 kbps vocoder. Thus, you can have the same voice quality while improving the capacity of the system, (which can handle more 8 kbps calls than 13 kbps calls.

RFI - (Radio Frequency Interference) An undesired radio signal that interferes with a radio communications signal causing extraneous noise and/or signal dropouts.