Third generation (3G) mobile radio standards are the result of a massive worldwide effort involving many companies since the mid-1990s. These systems will support a wide range of services, with voice and low rate data to high data rate services up to 144 Kbps in vehicular outdoor environments, 384 Kbps in pedestrian outdoor environments, and 2 Mbps in indoor environments. Both circuit and packet switched services with variable quality of service requirements will be supported.
The key challenges in designing 3G modems arise from the signal processing dictated by the underlying CDMA-based air interface with a chip rate of 3.84 Mcps (for the FDD DS mode explained later), the high data rate requirements, and the multiple and variable rate services that need to be supported simultaneously. Due to the various service scenarios – low-end voice to high-end high data rate – flexibility of the design is imperative.
In telecommunications, a “multi-mode” mobile is one that can support many different telecommunication standards with different radio access technologies. For example, the dual-band mobiles GSM + DCS are not considered as multi-mode mobiles because it uses the same radio access technology and the difference is only on the frequencies. By looking at the origin of the dual-mode system, we find two main drivers.