Cellular networks — UMTS system

After first-generation analog systems in the 1980s [E 7 361] and GSM in the 1990s [E 7 364], cellular radiocommunications in 2000 are on the threshold of third-generation systems. UMTS (Universal Mobile Telecommunication System) is the European version of IMT2000 (International Mobile Telecommunication), the global standard for these third-generation systems. The target market is no longer simply that of radiotelephony, but that of mobile multimedia, with high-speed Internet access on a handheld mobile terminal, or real-time transmission of high-resolution images and videos.

In Europe, the introduction of these new systems gives rise to a redistribution of licenses by the national regulatory authorities, in the form of either auctions or comparative selection. In some countries, the auction mechanism means that the cost of a license is much higher than that of a GSM license. In France, the comparative selection mechanism adopted by the ART (Autorité de Régulation des Télécommunications) was accompanied by economic conditions that were deemed too risky by some candidates. By mid-2001, only two licenses had been allocated, whereas four had been planned.

The air interface of the system chosen for UMTS uses a spread-spectrum technique known as CDMA (Code Division Multiple Access), which consists in transmitting the information emitted by each user at the same time, on the same carrier frequency, by multiplying them by pseudo-random sequences of orthogonal codes, at a higher rate than the information to be transmitted. It is the decorrelation between these code sequences that separates the signals of the different users on reception. This system, which is particularly sensitive to interference, requires a high-performance power control mechanism, but allows the same carrier frequencies to be used in neighboring cells, facilitating cell planning and inter-cell call transfers.

Finally, this system will be available in both Frequency Duplex Division (FDD) and Time Duplex Division (TDD) modes, the latter being less advanced and more suitable for microcellular networks.