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amps cellular

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AMPS, which stands for Advanced Mobile Phone System, was one of the first analog cellular systems widely deployed in North America. It was introduced in the early 1980s and played a significant role in the development of mobile telephony. Here's a technical overview of AMPS:

1. Multiple Access Scheme:

  • FDMA (Frequency Division Multiple Access):
    • AMPS uses FDMA to divide the frequency spectrum into individual channels. Each channel is allocated a 30 kHz bandwidth.

2. Frequency Bands:

  • 800 MHz Band:
    • AMPS operates in the 800 MHz frequency band, specifically in the range of 824 MHz to 849 MHz for the uplink (mobile-to-base) and 869 MHz to 894 MHz for the downlink (base-to-mobile).

3. Channel Structure:

  • Channel Types:
    • AMPS channels consist of two types: control channels and voice channels.
    • Control channels handle call setup, handovers, and other signaling functions.
    • Voice channels carry the actual voice conversations.

4. Modulation:

  • Analog Modulation:
    • AMPS uses analog modulation for voice transmission. The original modulation scheme was Frequency Modulation (FM).

5. Cellular Architecture:

  • Cell Structure:
    • Cellular networks using AMPS are divided into cells, each served by a base station (cell site).
    • The cell size is determined by factors like population density and terrain.

6. Handoff Mechanism:

  • Soft Handoff:
    • AMPS uses a soft handoff mechanism, allowing a mobile device to communicate with multiple base stations simultaneously during a handover.

7. Control Channels:

  • Forward Control Channel (FOCC) and Reverse Control Channel (RECC):
    • FOCC is used by the base station to communicate with mobile devices.
    • RECC is used by mobile devices to communicate with the base station.

8. Call Setup and Management:

  • Call Setup Procedure:
    • Call setup involves multiple steps, including registration, paging, access grant, and assignment of a voice channel.

9. Security:

  • Analog Encryption:
    • Basic analog encryption mechanisms were employed to enhance security.

10. Power Control:

  • Mobile Transmit Power Control:
    • Power control mechanisms help manage interference and conserve battery power in mobile devices.

11. Roaming:

  • Roaming Agreement:
    • Roaming agreements between different cellular operators allow subscribers to use their mobile devices in different regions.

12. Infrastructure Components:

  • Mobile Switching Center (MSC) and Cell Site:
    • MSC handles call switching and network management.
    • Cell sites consist of base station equipment serving specific geographic areas.

13. AMPS Evolution:

  • TDMA and CDMA Versions:
    • Later versions of AMPS incorporated TDMA (Time Division Multiple Access) and CDMA (Code Division Multiple Access) for improved capacity and efficiency.

14. Data Services:

  • Data Transmission:
    • While primarily designed for voice, AMPS was adapted for low-speed data transmission for services like text messaging.

15. Limitations:

  • Capacity and Interference:
    • AMPS had limited capacity due to the analog nature of the system and was susceptible to interference.

16. Sunset of AMPS:

  • Digital Migration:
    • AMPS was gradually replaced by digital cellular technologies, such as GSM, CDMA, and later, 3G and 4G LTE.

The deployment of AMPS marked a significant milestone in the history of mobile communication. However, as digital technologies offered enhanced capacity, security, and features, AMPS was gradually phased out, leading to the widespread adoption of more advanced cellular systems, including 3G, 4G, and now 5G.