Mobile radio systems around the world

AMPS Radio System

1. To extend the capacity in large AMPS markets, Motorola developed an AMPS- like system called N- AMPS (narrowband AMPS) in 1991.
2. N-AMPS were a useful transition technology before 2 G equipment became available.
3. N-AMPS provided three users during a 30 kHz AMPS channel by using FDMA and 10 kHz channels, and provided 3 times the capacity of AMPS.
4. By replacing AMPS channels with three N- AMPS channels at just one occasion , service providers were able to provide more trunked radio channels (and thus a way better grade of service) at base stations in heavily populated areas.
5. N- AMPS used the SAT and ST signalling and blank and burst functions in just an equivalent
6. manner as AMPS, except the signalling was done by using sub-audible data streams.
7. Since 10 kHz channels are used, the FM deviation is decreased in N-AMPS.
8. This I turn reduces the S/ (N+1) which degrade the audio quality with reference to AMPS. To counteract this, N-AMPS uses voice companding to supply an artificial voice channel quieting.
9. Ti counteracts this, N-AMPS, except the signalling was done by using sub-audible data streams.
10. N-AMPS specify a 300Hz high pass audio filter for every voice channel in order that supervisory and signalling data could also be sent without blanking the voice.
11. The SAT and ST signalling is shipped employing a continuous 200 bps NRZ data stream that's FSK modulated.
12. SAT and ST are called as DSAT and DST in N- AMPS because they're sent
13. digitally and repetitiously in small, predefined code blocks.

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