HSPA Evolution

HSPA Evolution (HSPA+) is the latest enhancement of the existing WCDMA/HSPA technologies as defined by 3GPP standards Releases 7&8. HSPA+ is aimed at improving the performance of current 3G networks while making another step closer to LTE/EPS implementations. It is an easy and cost effective solution as it can be realised by simply upgrading the software of RAN equipment.

In summary the main drivers of HSPA+ are:

• Higher data rates (up to 42Mbps DL and 11Mbps UL) and lower latencies for the support of new data services (e.g. VoIP, PTT, interactive gaming)
  
• Better spectrum utilisation will provide higher throughput and also lower cost for the operators
  
• Allow a packet-only operation for both voice and data (better support for VoIP)
  
• Strengthen the role of mobile technologies to the competition with fixed broadband networks and keep up with WiMAX technologies
  
• Exploit the full CDMA capabilities and provide a smooth migration towards LTE/EPS

The major technical characteristics introduced by HSPA+ are:

Higher Order Modulation Schemes
=> higher data rates

• 64QAM is the highest allowed modulation scheme for HSPDA (from 16QAM in Release 6)
  
• 16QAM is the highest allowed modulation scheme for HSUPA (from QPSK in Release 6)
  

MIMO for DL
=> higher data rates

• 2 Tx antennas at NodeB transmitting different streams with up to 64QAM modulation scheme and at least 2 Rx antennas at UE

L2 enhancements in both UL and DL
=> higher data rates, higher throughput

• Larger RLC PDU sizes can be used to support the higher rates achieved
  
• Flexible RLC size selection
  
• RLC PDU segmentation
  
• RLC PDU's of different RAB's can be multiplexed in one MAC PDU to reduce overheads
  

Continuous connectivity of data users (CPC)
=> lower latencies, improved battery life, lower interference, increased capacity

• Remain in the CELL_DCH even when inactive to reduce latencies
  
• UE DTX/DRX of the Dedicated Physical Control CHannel (DPCCH) when there is no data to send and receive
  
• No transmission of the High Speed - Shared Control CHannel (HS-SCCH) to reduce signaling and improve capacity; the decoding of the HS-DSCH is achieved blindly
  

Enhanced CELL_FACH
=> higher data rates, lower latencies

• HSDPA traffic can be carried on FACH
  
• HSUPA traffic can be carried on FACH

Improved Receivers
=> higher data rates, better efficiency

• Interference cancellation of ‘other cell’ power for HSDPA terminals
• Better equalisers
  

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