Evolved HSPA (HSPA+) in LTE
A parallel 3GPP R8 project to LTE and SAE is the Evolved High Speed Packet Access, eHSPA, project (also referred to as HSPA+). The proposed eHSPA features represent a logical evolution from today’s HSDPA and HSUPA systems.
Roughly speaking, the eHSPA project focuses on three areas:
• Optimising HSPA for real-time packet data services, like VoIP. A large part of achieving this goal relates to a more efficient use of the HSPA control channels.
• Increasing the system and user throughput. This is achieved by the introduction of higher order modulation (64QAM) and MIMO for HSPA. The theoretical maximum bit rate is around 40Mb/s for the DL and around 20Mb/s for the UL.
• Simplifying the network architecture. The eHSPA NodeB will take on parts of, or all of, the functionality of the RNC. In addition, the SGSN will be removed from the User Plane path (the so-called ‘one-tunnel solution’) allowing IP packets to be routed directly between eHSPA NodeB and GGSN. This can be seen in figure above, where ‘cSGSN’ is the SGSN Controller, and ‘xGGSN’ is the enhanced GGSN.