Overview About RF 3G

Overview about fundamentals of 3G

Evolution to UMTS

UMTS Network UMTS can be considered as an evolution of GSM. While UMTS has its own radio access network Known as UTRAN (UMTS Terrestrial Radio Access Network), usually UMTS and GSM/EDGE Have a shared Core Network. Generally UMTS networks are built up on existing GSM networks and both networks co-exist. UMTS networks in general have lesser coverage due to the fact that most of them operate at higher frequency bands. This is not a big issue as UMTS-GSM handover is possible.

UMTS–Universal Mobile Telecommunications System Provides mainly Speech, Video, R99 data and HS services

Please note that the network below has a common core network for both 3G and 2G.

Fig1: UMTS/GSM Network

Why do we need 3G? Is 2G not enough? 3G gives much higher data rates compared to2G.2G was mainly designed keeping in Mind the requirements for Speech traffic.3G has been developed mainly to cater to data services, in addition to Speech traffic. Multiplexing of services with different QOS requirements on a single connection is possiblewith3G.

Why does 3G have less coverage compared to GSM900?

GSM900 works at a lower frequency band than 3G, which usually works at the2GHz band. Lower frequency signals are attenuated less, which gives them greater propagation capability.

Why WCDMA is called Wideband CDMA? WCDMA has a higher bandwidth of 5 MHz compared to IS-95 (cdma One), which has Only 1.25MHz.

What are the frequency bands used in 3G? FDD-Frequency Division Duplexing is mainly used for UMTS. Hence, for uplink and downlink, we have different frequency bands. UL–Uplink (mobile to base station) 1920-1980MHz DL-Downlink (base station to mobile) 2110-2170MHz

QOS Classes in 3G CSIB–Conversational, Streaming, Interactive, Background