It is far from the era of the analog mobile phone. Remember … “Radiowoman 2000, do not quit!” The laptops became digital with the GSM (global system for mobile communications), standard developed in 1982 which used the frequencies of the band of 900, then of 1 800MHz. But it was not until 1987 that the technological choices were finalized.
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In the early days of the digital mobile
The cells then formed circles of 50 km radius and implied for the device powers of 8 W. With the standards adopted in 1991; the mobiles have a more limited power: 2 W for the GSM 900 MHz, 1 W for the GSM 1800 MHz (or DCS 1 800).
In France, the networks were first exploited in 900 MHz by operators Itineracy (now Orange) and SFR. The third comer, Bouygues Telecom, inherited the band of 1,800 MHz with the development of the number of subscribers, the first two decided to launch dual-band devices, 900 and 1800 MHz.
The GSM 900 uses the 890-915 MHz band for sending digital data, and the 935-960 MHz band for receiving digital information. GSM 1800 uses the band 1 710-1 785 MHz for sending, and the band 1 805-1 880 MHz for receiving. The digitization of voice data is done on the mobile, just like the analog conversion for listening.
From the age of the Texto
The first devices only worked for voice communications, with a transmission rate of 9.60 kbit / s. Then came the SMS (short message service, Texto for SFR). By the mid-1990s, communications throughput, limited to 14.40 kbps, had to be increased to make the networks more compatible with non-voice data transmission at the origin.
GPRS (general packet radio service), which allows a bit rate of 115 kbit / s, was invented by pooling several channels (multiplexing). Using the same networks, it became possible to access the Internet via the WAP or to send e-mails.
In the era of video telephony
To be able to transmit video, download TV channels and movies, allow video telephony, send multimedia messaging service (MMS) with photos, it was necessary to pass to the third generation, 3G, that is to say, the UMTS (universal mobile telecommunications system). It is a global standard, on which Europe and Asia are ahead (the Apple iPhone is not 3G, despite its exorbitant price).
Only two networks have acquired the license: Orange and SFR. The transmission rate is, at a minimum, 384 kbps, but can go up to 2 Mbps, or even 3.60 Mbps (3G +). To do this, it was essential to redesign the networks and use different radio frequencies: 1,920-1,980 MHz for the uplink, 2 110-2 170 MHz for the downlink at first.
As these infrastructure modifications are very expensive, the operators use, according to the zones and the devices, the EDGE system (iMode broadband for Bouygues Telecom), which allows the downloads and the sending of MMS, but not the reception of chains TV nor videotelephony.
This gives them time to build their new networks. In any case, the phones remain GSM-GPRS compatible. This gives them time to build their new networks. In any case, the phones remain GSM-GPRS compatible. This gives them time to build their new networks. In any case, the phones remain GSM-GPRS compatible.