Universal Mobile Telecommunications System (UMTS) networks have been deployed world-wide as 3rd generation (3G) mobile communications systems. Developed by the 3GPP (3rd Generation Partnership Project), UMTS employs Wideband Code Division Multiple Access (WCDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators. UMTS specifies a complete network sys- tem. Unlike EDGE, UMTS requires new base stations and new frequency allocations.
The maximum UMTS data rate is 384 kbps at the moment, but in the future it will be possible to combine several code channels to a multi-code link, allowing data rates up to 2 Mbps. UMTS provides a clear evolutionary path to High-Speed Packet Access (HSPA). HSPA refers to the combination of High-Speed Downlink Packet Access (HSDPA) and High-Speed Uplink Packet Access (HSUPA). HSDPA allows data rates up to 14.4 Mbps in the downlink. HSUPA makes uplink data rates of 5.76 Mbps possible.
UMTS supports maximum theoretical data transfer rates of 84 Mbps when HSPA+ is implemented in the network. HSPA+ as specified in 3GPP Release 7 includes downlink MIMO (Multiple-Input Multiple-Output) operation, higher-order modulation and protocol improvements that specifically allow a high number of “always on” users to be supported in the network.
The specific frequency bands originally defined by the UMTS standard are 1885–2025 MHz for the Mobile-to-Base (Uplink) and 2110–2200 MHz for the Base-to-Mobile (Downlink). UMTS phones usually support several different frequencies in addition to their GSM fallback. Different countries support different UMTS frequency bands. Europe initially used 2100 MHz while the most carriers in the USA use 850 MHz and 1900 MHz.
W-CDMA uses the DS-CDMA channel access method and Quadrature Phase Shift Keying (QPSK) modulation with a pair of 5 MHz wide channels. UMTS uses different power classes with a maximum output power in power class 1 of 33 dBm, class 2 it is 27 dBm, in class 3 it is 24 dBm and in class 4 it is 21 dBm.