N-GEN Communications Web-based Seminars ©NGCS

Seminar - An Overview of Communications Technologies

Module 9 - Wireless Systems and Technologies                                                                                 Slide 21 of 80                                                                                                    ________________

First -Generation (1G) System Technologies

                                    Analogue Cellular 

                                    Spectrum

                                    Frequency Division Multiplexing Access (FDMA)

                                    Carrier Channels

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AMPS was first deployed in Chicago in 1976. It used 3 K Hz voice channels modulated onto 30 K Hz FM carrier frequency pairs, one frequency for transmitting and another frequency for receiving. FDMA is used to access the network.

AMPS - Spectrum:     824 M Hz - 849 M Hz (Reverse direction)
                              869 M Hz - 894 M Hz ( Forward direction)
Narrow-band AMPS uses 10 K Hz carrier frequency

AMPS-1 used 4 hexagonal shape cells to cover a metropolitan area. Adjacent cells never use the same frequency. Each cell can use 1/4 of the available frequency channel pairs. A base station in a cell uses one frequency to communicate reliably with any mobile within its coverage area. The radius of the cell is typically 0.5 Km for urban areas to 20 Km for rural areas.

AMPS-2 used 7 hexagonal shaped cells to cover a metropolitan area.

E-TACS - Operates at 900 M Hz. It uses 25 K Hz carrier frequency and supports analogue voice and data / Fax up to 14.4 K bps.

NMT-900 - Operates at 900 M Hz and uses 12.5 K Hz carrier frequency