What is WCDMA?
WCDMA (Wideband CDMA) is the 3G radio access technology standardised by 3GPP as the air interface for UMTS (Universal Mobile Telecommunications System). It uses direct-sequence spread spectrum with a 5 MHz carrier bandwidth — significantly wider than the 200 kHz channels of GSM — to provide mobile broadband data rates up to 2 Mbps initially, extended to 42 Mbps with HSPA+ evolution. WCDMA was the dominant 3G technology worldwide and remains operational in many networks alongside 4G and 5G.
How Does WCDMA Work?
WCDMA spreads each user’s signal across the full 5 MHz bandwidth using unique orthogonal spreading codes (Walsh-Hadamard codes for downlink, Gold codes for uplink). Multiple users share the same frequency simultaneously — they are separated by their unique codes (CDMA principle). The base station (NodeB) assigns different spreading factors to users, trading off between data rate and processing gain. Higher spreading factors provide more robust transmission at lower data rates. WCDMA uses power control (1,500 updates per second) to manage near-far interference. The HSPA evolution added shared channels (HS-DSCH, E-DCH), HARQ, adaptive modulation (16-QAM, 64-QAM), and 2×2 MIMO to achieve speeds up to 42 Mbps.
Use Cases
3G mobile broadband services, voice services (circuit-switched and AMR codec), 3G video calling, IoT/M2M connectivity on 3G networks, and legacy coverage in areas without LTE/5G deployment.
3GPP / Standards Reference
3GPP TS 25.211-215 (UTRAN physical channels), 3GPP TS 25.308 (HSPA), 3GPP TS 25.300 (UTRAN overall description)
Related Terms
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This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
