AMPS

First-generation mobile networks are analog systems. Some of the more widely deployed first-generation networks include AMPS and NMT. In this section we focus the discussion on AMPS.The Advanced Mobile Phone Service (AMPS) is in wide use even today, almost 25 years after it was introduced. AMPS was conceived by Bell Labs in the 1970s, and improvements in the form of digital AMPS (D-AMPS) were made in the late 1980s. The AMPS air interface is specified in EIA/TIA-553. AMPS is based on FDMA.

The FCC allocated a total of 50 MHz (25 MHz on the A side and B side) in the 800-MHz spectrum for AMPS. Each voice channel is allocated a 30-KHz portion of the bandwidth within the AMPS frequency allocations. Because each carrier has 25 MHz of spectrum, this provides a total of 832 (25 MHz/30 KHz) cellular channels (forward and reverse). However, since the same frequency cannot be used in adjacent cells, the 416 duplex channels are a theoretical maximum (actual number of valid voice channels equals 312). AMPS uses the seven-cell frequency reuse method. Control channels are used to set up and clear calls as well as other control messages. Each band (25 MHz) contains 21 control channels.

When a mobile station is not in session, it must monitor designated control channels. It tunes and locks into the strongest channel to receive system information. The forward control channel (FOCC) is a data stream from the base station to the mobile, and the reverse control channel (RECC) is from the mobile to the base station. Voice conversation is carried over the forward voice channel (FVC) and the reverse voice channel (RVC).The ESN for a mobile is a 32-bit number that uniquely identifies a mobile and is set up by the mobile manufacturer. System IDs (SIDs) are 15-bit binary numbers that are assigned to cellular systems. One of the uses of the SID is to determine a home network from a roaming network.

The MIN is a 34-bit number that is derived from the mobile terminal's 10-digit telephone number.The network utilizes the IS-41 protocol for mobility and authentication procedures. The MSC provides the capability for call processing, and the HLR and VLRs keep track of the mobile as it moves. The mobile terminal is responsible for updating its location as it moves in the cellular network. Data services in AMPS are straightforward and analogous to dial-up networking. Because AMPS is an analog technology, it is possible to make use of standard modems directly with AMPS. Data rates are at a maximum of 14.4 Kbps irrespective of the modem protocol (v.90 or others).