In earlier chapters we have provided the current WCDMA network architecture and we would like
to present a possible evolutionary path. The simplified architecture is provided in Fig. 9.21.
3G AND BEYOND DISCUSSION 499
E-CN
Rel. 8
RNC
SRNC
CRNC
Rel. 7
NodeB
Rel. 8
NodeB
CN
~Iu-PS
E-HSPA
NodeB
IuB IuB
Iur
Iu-PS Iu-CS
Gn
FIGURE 9.21 Possible evolutionary path for HSPA.
The basic premise behind the enhanced HSPA NodeB is that the less entities that actually ???touch???
the data and control before being sent through the CN the better off the system is in terms of reducing
overall system latency. This statement has profound effect in that changes in signaling, functionality,
and protocol stacks need to be seriously addressed. In Fig. 9.21 the functionality of the RNC
and NodeB come closer together to reduce the overall system latency.
In an effort to address some of the other evolutionary requirements, such as increased data rates,
additional signal processing functions are required. For example, HSDPA Release 6 and below
assume use of QPSK and 16-QAM modulation schemes. Higher Order Modulation (HOM) scheme
such as 64-QAM is used in the Release 7 version. Due to the increased number of modulation
states, the most notable usage scenario would be in a large geometry setting with large NodeB
power allocation in a slow moving, pedestrian-like environment.
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