Introduction to Mobile Telephone System

Wideband Digital Cellular Systems (3rd Generation)

The 3rd generation wireless requirements are defined in the International Mobile Telecommunications “IMT-2000” project developed by the International Telecommunication Union (ITU). The IMT-2000 project that defined requirements for high-speed data transmission, Internet Protocol (IP)-based services, global roaming, and multimedia communications. After many communication proposals were reviewed, two global systems are emerging; wideband code division multiple access (WCDMA) and CDMA2000.

Wideband Code Division Multiple Access (WCDMA)
WCDMA is a 3rd generation digital cellular system that uses radio channels that have a wider bandwidth than 2nd generation digital cellular systems such as GSM or IS-95 CDMA. WCDMA is normally deployed in a 5 MHz channel plan. The Third Generation Partnership Project (3GPP) oversees the creation of industry standards for the 3rd generation of mobile wireless communication systems (WCDMA). The key members of the 3GPP include standards agencies from Japan, Europe, Korea, China and the United States. The 3GPP technology, also known as the Universal Mobile Telecommunications System (UMTS), is based on an evolved GSM core network that contains 2.5G elements, namely GPRS switching nodes. This concept allows a GSM network operator to migrate to WCDMA by adding the necessary 3G radio elements to their existing network, thus creating ‘islands’ of 3G coverage when the networks first launch. A large number of GSM operators have secured spectrum for WCDMA and many network launches are imminent, with live networks presently in Japan, the United Kingdom and Italy.

Code Division Multiple Access 2000 (CDMA2000)
CDMA2000 is a family of standards that represent an evolution from the IS- 95 code division multiple access (CDMA) system that offer enhanced packet transmission protocols to provide for advanced high-speed data services. The CDMA2000 technologies operate in the same 1.25 MHz radio channels as used by IS-95 and offer backward compatibility with IS-95. The CDMA2000 system is overseen by the Third Generation Partnership Project 2 (3GPP2). The 3GPP2 is a standards setting project that is focused on developing global specifications for 3rd generation systems that use ANSI/TIA/EIA-41 Cellular Radio Intersystem Signaling.

Time Division Synchronous CDMA (TD-SCDMA)
On a global basis it likely that WCDMA and CDMA2000TM will dominate the 3G market, however in China there is growing support for a homegrown standard known as Time Division Synchronous CDMA (TD-SCDMA). TDSCDMA offers voice services and data services, both circuit-switched and packet-switched, at rates up to 2 Mbps. It uses a Time Division Duplex (TDD) technique in which transmit and receive signals are sent on the same frequency but at different times. The timeslots on the radio carrier can either be allocated symmetrically for services such as speech or asymmetrically for data services where the bit rates in the two directions of transmission may differ significantly.