WCDMA ( Wideband Code Division Multiple
Access) is a wideband spread-spectrum 3G mobile telecommunication system to
support wideband services like high-speed Internet access, video and high
quality image transmission with the same quality as the fixed networks. In WCDMA systems the CDMA (Code Division Multiple Access) air interface is combined with GSM based networks. The WCDMA standard was evolved through the Third Generation Partnership Project (3GPP) Formulated by the European standardization organization, aims to support by different equipment manufacturers, component suppliers and operators. It will become one of the mainstream future 3G systems.
The core network evolves on the basis
that can be compatible with the existing GSM/GPRS networks. It can be based on
the TDM, ATM and IP technologies to evolve towards the all-IP network
architecture. Logically, the core network comprises two parts
- The
circuit domain to complete the circuit-switched services
- The packet domain to complete the packet-switched services.
MAP and GPRS tunneling technologies are the core of
the mobility management mechanism in the WCDMA system. The air interface adopts
the WCDMA technologies with the signal bandwidth of 5 MHz and the chip rate of
3.84 Mcps. It uses the AMR voice encoding scheme and supports the
synchronous/asynchronous Node B operation mode.
Besides, the following modes are applied in the
WCDMA system
- Uplink/downlink closed loop power control plus
outer loop power control
- Open loop (STTD & TSTD) and closed loop
(FBTD) transmit diversity
- Pilot-assisted coherent demodulation
- Convolutional coding and Turbo coding
- QPSK modulation in both the uplink and the downlink.
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