Wideband Code Division Multiple Access (WCDMA) is a radio access system used for 3G cellular networks popular over many parts of the globe. The third generation systems sustain wideband services like video, fast Internet access, and premium image transmission.
In this system, the air interface of CMDA is integrated with GSM based networks. The standard for this system was developed by way of the Third Generation Partnership Project (3GPP), which aims to facilitate interoperability among the 3G networks. The standard that has developed by way of this collaboration venture is based on the Terrestrial Radio Access of the Universal Mobile Telecommunication System (UMTS).
The information is transmitted over a band of approximately 5MHz. The wide bandwidth spread by this system paved way for its name, Wideband CDMA.
Modes of Operation
There are two different methods of operation in WCDMA:
- Frequency Division Duplex (FDD) employs two separate frequency bands for the uplink and downlink transmissions of this duplex method. Paired frequency bands with assigned separation are given for a connection;
- Time Division Duplex (TDD) transmits the uplink and downlink transmissions over similar frequency band through coordinated time intervals. Hence, a physical channel’s time slots are separated into reception and transmission parts.
Since different areas have varying frequency allocation schemes, the system’s ability to work in either mode enables effective use of the available spectrum.
Key Features of WCDMA
The key features for this system are:
- 5MHz wide radio channels;
- Support of high data transmission rate: 2 Mbps for local coverage and 384 Kbps for wide area coverage;
- Chip rate of 3.84 Mbps;
- Ability to support two modes of operation: time division duplex and frequency division duplex. Frequency division is used with one frequency for downlink and another for uplink. For time division, 16 slots per radio frame are used by FOMA, 15 by UMTS.M;
- High service flexibility or the ability to sustain numerous parallel changeable rate services on each connection;
- Consistent detection on both uplink and downlink transmissions depending on the channels and pilot symbols;
- Efficient packet access;
- Built-in transmitter diversity, advanced receiver structures, and adaptive antennas for future capacity; and
- Multi-code transmission.