Tagged: amps

Wireless communication : AMPS technology

Advance Mobile Phone System (AMPS) is the analog mobile system standard which is introduce in Amarica during 1980s.Now,these days analog system is no longer advance,almost whole world become degital system.

Technology :

It was a first-genaration technology,using FDMA(Frequency division multiple access) technology.It means that each cell site would transmit on different frequencies, allowing many cell sites to be build near each other.But it had disadvantage that each site did not have much capacity for carrying calls.It has also poor security,but latter it was improved by introducing newer digital TDMA(Time division multiple access).

AMPS Channels :

The frequencies allocated to AMPS by the FCC range between 824 to 849 MHz in reverse channels (mobile to base) and 869 to 894 MHz in forward channels (base to mobile). They are not contiguous blocks because the initial 40 MHz allocation by the FCC was later extended by 10 MHz when the service’s popularity became evident. There are now a total of 416 channels available in each direction, numbered from 1 to 1024 with gaps in the numbering.

Frequency bands :

In that time, there were to be two licensee (networks). Each network is authorized to use 416 channels in the 800 MHz band. Each channel is consists of 2 frequencies. 416 of these are in the 824~849 MHz range for transmissions from mobile stations to the base stations and paired with 416 frequencies in the 869~894 MHz range for transmissions from base stations to the mobile stations. Each cell site will use a subset of these channels, and must use a unique set to avoid interference. This significantly reduces the number of channels available at each site in real-world systems. Each AMPS frequency is 30kHz wide.

The AMPS band was taken from the same 806~890 MHz frequency band which was originally UHF TV channels 70~83. This meant that these UHF channels could not be used for UHF TV transmission as these frequencies were to be used for AMPS transmission.