AMPS Basic concepts

  • AMPS - Advanced Mobil Phone Service: it was developed by AT&T in 1980, (1st generation).

  • North America: two 25 MHz allocated to AMPS base station to transceiver (869-894 MHz) and mobile to base station (824-849 MHz). An operator uses 12.5 MHz in each direction.

  • The channels are spaced 30kHz apart, which allows 416 channels per operator: 21 channels for control and 395 to carry calls. (Note: 25000/30/2 = 416).

  • Analog using frequency modulation (FM). Reuse frequency is used, but needs to be spaced to avoid interference AMPS N= 395, and n=7 = 57 frequencies per cell, cell sizes can be reduced to the minimum practical size 1.5km.

  • AMPS mobile: electronic serial number (32-bit hardwired), system identification number (15-bit system operator code, allows identify roamer in other operator network), mobile identification number (34-bit representing the 10 digit phone number).

  • Base Transceiver: full-duplex with mobile, connected to a MSC by microwave or wire.

  • MSC: switch in the network (handoffs from cell to cell), backup data for billing, monitor the system, connects to public switched network.