WCDMA

Wideband Code Division Multiple Access (W-CDMA) is a third generation (3G) mobile telecommunications standard developed by the 3GPP as part of the Universal Mobile Telecommunications System (UMTS). It uses a wideband spread-spectrum radio interface based on Code Division Multiple Access to support multiple users within the same 5 MHz channel through unique scrambling and channelization codes. W-CDMA can operate in paired frequency bands using frequency-division duplex (FDD) and, in some deployments, other duplex configurations; it is designed to provide higher data rates and greater capacity than second-generation systems while maintaining global roaming.

In the radio access network, W-CDMA defines the Uu interface between user equipment and the base station (Node B). The network architecture includes the radio network controller (RNC) and a core network that connects to packet-switched and circuit-switched domains. A notable feature is soft handover, enabled by CDMA, which allows a mobile to be simultaneously connected to multiple cells during transitions, improving reliability at the cost of increased signaling.

Performance-wise, baseline W-CDMA provides peak data rates in the hundreds of kilobits per second per user. The technology evolved with High-Speed Packet Access (HSPA), including HSDPA for downlink and HSUPA for uplink, to achieve peak downlink rates up to about 14 Mbps and uplink up to about 5 Mbps on a 5 MHz channel. W-CDMA remains in use in many networks and formed the foundation for subsequent generations, with LTE and 5G NR replacing it in new deployments, while some networks maintain backward compatibility.