What Is 3G Mobile Communication?

3G mobile communication is the third generation of cellular network technology, defined by the International Telecommunication Union under the IMT-2000 framework, that introduced packet-based broadband data services to mobile devices alongside the voice telephony provided by earlier networks. Operating on licensed spectrum bands centered around 2100 MHz in most regions, 3G systems support peak downlink rates from 384 kbps in the original UMTS Release 99 specification to over 40 Mbps in later HSPA+ variants, enabling mobile internet browsing, video streaming, and real-time multimedia applications on handsets and mobile modems. Commercial service began in Japan in 2001 through NTT DoCoMo's FOMA network and expanded across Europe, North America, and Asia over the following several years.

3G draws from prior generations of cellular radio while introducing multiaccess schemes and packet-routing architectures absent in 2G. The two dominant global families, UMTS/WCDMA developed by 3GPP and CDMA2000 developed by 3GPP2, share the use of spread spectrum transmission but differ in their radio channel widths, synchronization approaches, and core network protocols. A third family, TD-SCDMA (Time Division Synchronous Code Division Multiple Access), was developed in China and deployed commercially there, using time-division duplexing in a 1.6 MHz channel.

Spread Spectrum and CDMA Multiaccess

The distinguishing characteristic of WCDMA and CDMA2000 is their use of direct-sequence spread spectrum, in which each user's signal is spread across a 5 MHz channel by multiplication with a unique pseudorandom spreading code. Multiple users transmit simultaneously in the same frequency band, and receivers separate their signals using the orthogonality of the codes. This contrasts with the time-division and frequency-division approaches of 2G GSM and TDMA systems. The power control mechanisms required to manage near-far interference in CDMA systems, with update rates of 1500 Hz per link in WCDMA, represent one of the most demanding real-time processing tasks in 3G radio hardware. IEEE Xplore coverage of third-generation cellular WCDMA and TD-CDMA provides a detailed technical treatment of the spread-spectrum design principles.

Radio Access Network Architecture

The UMTS radio access network (UTRAN) is organized around Node B base stations that handle the physical radio link and Radio Network Controllers (RNCs) that coordinate handover, radio resource management, and the interface to the core network. The core network's packet-switched domain routes IP traffic to the public internet while the circuit-switched domain handles voice calls through the traditional telephone network. High Speed Packet Access (HSPA), introduced in 3GPP Release 5 and Release 6, relocated scheduling from the RNC to the Node B, reducing round-trip latency and enabling the higher peak data rates that extended 3G competitiveness into the 4G era. ETSI's 3G technology resource page documents the standards layering from the original UMTS specifications through the HSPA family.

MIMO and Advanced Antenna Techniques

MIMO (Multiple Input Multiple Output) antenna techniques were incorporated into later 3G releases to increase spectral efficiency without additional spectrum allocation. HSPA+ Release 11 included dual-stream spatial multiplexing, allowing two independent data streams to be transmitted simultaneously between a base station and a receiver equipped with multiple antennas. While MIMO's full potential was realized in 4G LTE with its OFDM physical layer, the introduction of multi-antenna processing in 3G established the engineering foundations that the transition to LTE-Advanced would build upon. The ITU press release on the path from 3G to 4G IMT-Advanced traces how the IMT-2000 framework was extended to accommodate the more demanding requirements of IMT-Advanced.

Applications

3G mobile communication underpinned a wide range of services and laid infrastructure for subsequent generations, including:

• Mobile internet access for smartphones and laptop data cards
• Video telephony using H.324M on UMTS circuit-switched video channels
• Machine-to-machine communication for fleet management and telematics
• Mobile television delivery through dedicated broadcast overlays
• Ambient network connectivity for remote sensor and monitoring deployments