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  • Print publication year: 2010
  • Online publication date: June 2012

2 - An overview of wireless communications

Summary

Roadmap of cellular communications

First-generation systems

The 1G mobile cellular systems were analog speech communication systems. They were mainly deployed before 1990. They are featured by FDMA (frequency division multiple access) coupled with FDD (frequency division duplexing), analog FM (frequency modulation) for speech modulation, and FSK (frequency shift keying) for control signaling, and provide analog voice services. The 1G systems were mainly deployed at the frequency bands from 450 MHz to 1 GHz. The cell radius is between 2 km and 40 km.

The AMPS (Advanced Mobile Phone Services) technique was developed by Bell Labs in the 1970s and was first deployed in late 1983. Each channel occupies 30 kHz. The speech modulation is FM with a frequency deviation of ±12 kHz, and the control signal is modulated by FSK with a frequency deviation of ±8 kHz. The control channel transmits the data streams at 10 kbits/s. AMPS was deployed in the USA, South America, Australia, and China. In 1991, Motorola introduced the N-AMPS to support three users in a 30 kHz AMPS channel, each with a 10 kHz channel, thus increasing the capacity threefold.

The European TACS (Total Access Communication System) was first deployed in 1985. TACS is identical to AMPS, except for the channel bandwidth of 25 kHz. Speech is modulated by FM with a frequency deviation of ±12 kHz, and the control signal is modulated by FSK with a frequency deviation of ±6.4 kHz, achieving a data rate of 8 kbits/s.