HSPA+ Advanced

With rising mobile data traffic, efficient network resource utilization techniques are becoming increasingly important. Circuit-switched enhancements as part of WCDMA+ reduce the amount of radio resources (e.g., Tx power & transmission time) needed for voice calls. This frees up significant spare capacity that can then be utilized for HSDPA data.

A comparison of the benefits is shown below.

Some of the WCDMA+ Downlink techniques that help accomplish these improvements are described below, similar techniques are being proposed for Uplink improvements as well.

• Downlink Overhead Optimization: A substantial portion of the power allocation for CS voice transmission is attributed to overheads. Optimizations such as the following allow for improved efficiencies for CS voice calls:
  • Removing the dedicated pilot
  • Re-use DL TPC bits for SINR estimation
• Downlink Frame Early Termination (FET): A large portion of the CS voice frames can be successfully decoded much earlier than the end of the 20ms frame duration. The technique of providing feedback to the transmitter of successful early frame decoding allows both, the transmitter and the receiver to shut down for the remainder of the frame. This allows for reduced interference in the system leading to increased system capacity, improved UE talk time and battery savings.

Simulation results below illustrate early decode success rates , highlighting the fact that as early as 12ms ( a full 8ms early) there is more than a 70% chance that the 20ms voice frame has been successfully decoded.

The Enhanced Voice Services (EVS ) family of voice codecs is currently under standardization in 3GPP R12. The Source-Controlled Variable Bit Rate (SC-VBR) 5.9k variant of this family approaches voice quality equivalent to that of AMR-WB 12.65k. It has superior voice quality to AMR 12.2k but at only half the average bit rate.