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LTE for UMTS: Evolution to LTE-Advanced, 2nd Edition by Antti Toskala, Harri Holma

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Chapter 3

System Architecture Based on 3GPP SAE

Atte Länsisalmi and Antti Toskala

3.1 System Architecture Evolution in 3GPP

When the evolution of the radio interface started, it soon became clear that the system architecture would also need to be evolved. The general drive towards optimizing the system only for packet switched services is one reason that alone would have set the need for evolution, but some of the radio interface design goals—such as removal of soft handover—opened up new opportunities in the architecture design. Also, since it had been shown by High Speed Packet Access (HSPA) that all radio functionality can be efficiently co-located in the NodeB, the door was left open for discussions of flatter overall architecture.

Discussions for System Architecture Evolution (SAE) then soon followed the radio interface development, and it was agreed to schedule the completion of the work in Release 8. There had been several reasons for starting this work, and there were also many targets. The following lists some of the targets that possibly shaped the outcome the most:

  • optimization for packet switched services in general, when there is no longer a need to support the circuit switched mode of operation;
  • optimized support for higher throughput required for higher end user bit rates;
  • improvement in the response times for activation and bearer set-up;
  • improvement in the packet delivery delays;
  • overall simplification of the system compared to the existing 3GPP and other cellular ...

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