Radio Access Network (RAN) Standards for 3G UMTS and CDMA2000 Networks

A radio access network (RAN) refers to the network that sits between the mobile phones, and the core network (CN). Both UMTS and CDMA2000 networks have their own radio access network air interface definitions. RAN provides radio bearers between the core network and the mobile station for the transport of user data and non-access stream signaling, thus enabling mobile stations to access the service offered by the PSTN and Internet. The main RAN function includes establishment, maintenance, and termination of radio channels; radio resource management; and mobility management. The RAN consists of the base station (BS) and packet control function (PCF). The base station is further decomposed in one control and one or multiple radio-terminating equipment portions named base station controller (BSC) and base transceiver station (BTS), respectively.

W-CDMA (Wideband Code Division Multiple Access) is the first 3G air interface for the UMTS technologies, a third generation follow-on to the 2G GSM networks deployed worldwide. W-CDMA can be implemented by migrating via GPRS and EDGE on the 2G network infrastructure of the GSM standard that is used in Europe and worldwide. W-CDMA allows transmission of signals for various services with variable data rates on 5 MHz bandwidths. Key features of WCDMA are cited below:

• Radio channels are 5MHz wide.
• Chip rate of 3.84 Mcps
• Supports two basic modes of duplex, frequency division and time division. Current systems use frequency division, one frequency for uplink and one for downlink. For time division, FOMA uses sixteen slots per radio frame, where as UMTS uses 15 slots per radio frame.
• Employs coherent detection on uplink and downlink based on the use of pilot symbols.
• Supports inter-cell asynchronous operation.
• Variable mission on a 10 ms frame basis.
• Multicode transmission.
• Adaptive power control based on SIR (Signal-to-Interference Ratio).
• Multiuser detection and smart antennas can be used to increase capacity and coverage.
• Multiple types of handoff between different cells including soft handoff, softer handoff and hard handoff.

New air interface technologies such as HSPA and HSPA+ are defined for the UMTS systems with better performance and functionalities.

On the other hand, CDMA2000 covers a family of mobile communication technologies that further develop the 2G mode CDMAOne, whose use is restricted to the USA, South America, Korea and Japan. CDMA2000 3G network, uses its own radio access network technologies. The CDMA2000 standards CDMA2000 1xRTT, CDMA2000 EV-DO, and CDMA2000 EV-DV are approved radio interfaces for the ITU's IMT-2000 standard and a direct successor to 2G CDMA, IS-95 (cdmaOne). CDMA2000 is standardized by 3GPP2. CDMA2000 is designed to use transmission bandwidth of 1.25 MHz.