WCDMA

WCDMA is a step further in the CDMA technology. It uses a 5 MHz wide radio
signal and a chip rate of 3.84 Mcps, which is about three times higher than
the chip rate of CDMA2000 (1.22 Mcps). The main benefits of a wideband
carrier with a higher chiprate are:

  1. Support for higher bit rates
  2. Higher spectrum efficiency thanks to improved trunking efficiency
  (i.e. a better statistical averaging)
  3. Higher QoS



 Further, experience from second-generation systems like GSM and cdmaOne has
enabled improvements to be incorporated in WCDMA. Focus has also been put on
ensuring that as much as possible of WCDMA operators' investments in GSM
equipment can be reused. Examples are the re-use and evolution of the core
network, the focus on co-sitting and the support of GSM handover. In order
to use GSM handover the subscribers need dual mode handsets.
In order to keep the received power at a suitable level, WCDMA has a fast
power control that updates power levels 1500 times every second. By doing
that the rapid change in the radio channel is handled. To ensure good
performance, power control is implemented in both the up-link and the
down-link, which means that both the output powers of the handset and the
base station are frequently updated.

A drawback with soft handover is that it requires additional hardware
resources on the network side, as the handset has multiple connections. In a
well-designed radio network, 30–40 % of the users will be in soft or softer
handover.

-Inter-frequency handover (intra-system handover)
-Channel type switching
-Admission control
-Congestion control
-Synchronization