g.,VoIP over WLAN). Bottlenecks that arise due to these options should
be optimized for latency and power.
As shown above we have identified three areas of concern. First is maintaining the quality of service
for the data pipes delivered from the CP to the AP. The second is the interface between the two
processors which becomes more problematic as the data rates increase (which is especially true when
MIMO technology is used to bring tens of Mbps to the terminal). The last area of concern is within
the AP, dealing with other radio access technologies and high quality graphic, 3D gaming, etc.
9.4 HIGH-SPEED PACKET ACCESS EVOLUTION
In this section, we will discuss evolutionary paths to enhance the capabilities of HSPA systems [17,
36]. The optimal path is one that would provide a smoother transition toward supporting Long Term
Evolution (LTE). Some general requirements of the evolution are higher data rates, increased system
capacity, reduced latency, increased system coverage, reduced system operating costs, just to name a
few. These requirements not only assume backward compatibility to legacy systems, but also apply to
packet-based networks. In fact, IP multimedia subsystem (IMS) is a key component in the driving force
to upgrade networks from circuit-switched services (CS) to packet-switched services (PS) domains.
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