UMTS uses CDMA (Code Division Multiple Access) as its multiple access technique. CDMA is a spread spectrum technology that allows multiple users to share a common frequency band by using unique codes to distinguish between users. This is in contrast to FDMA (Frequency Division Multiple Access), which divides the available frequency band into separate channels for each user, and TDMA (Time Division Multiple Access), which divides the available time into separate slots for each user.
CDMA has several advantages over FDMA and TDMA, including:
- Increased capacity: CDMA can support more users than FDMA or TDMA in the same frequency band.
- Improved performance in noisy environments: CDMA is less susceptible to interference than FDMA or TDMA.
- Reduced power requirements: CDMA can operate at lower power levels than FDMA or TDMA, which can extend battery life.
However, CDMA also has some disadvantages, including:
- Increased complexity: CDMA is more complex to implement than FDMA or TDMA.
- Reduced security: CDMA signals are more difficult to encrypt than FDMA or TDMA signals.
- Increased cost: CDMA systems are typically more expensive than FDMA or TDMA systems.
Overall, CDMA is a powerful multiple access technique that offers several advantages over FDMA and TDMA. However, it is also more complex and expensive to implement.