Effective October 1, 2012, QUALCOMM Incorporated completed a corporate reorganization in which the assets of certain of its businesses and groups, as well as the stock of certain of its direct and indirect subsidiaries, were contributed to Qualcomm Technologies, Inc. (QTI), a wholly-owned subsidiary of QUALCOMM Incorporated. Learn more about these changes

You are here

HSPA+ Advanced

WCDMA+ Voice & Data Capacity Enhancements

With rising mobile data traffic, efficient use of network resources is becoming more important. WCDMA+ is a set of innovative features designed to improve UMTS circuit-switched voice efficiency and frees up radio resources, e.g. transmit power and duration, for improving HSPA data capacity. In addition, WCDMA+ supports wideband audio codecs that provides superior high-definition voice quality.

As shown below, an R99 circuit-switch system with 48 voice calls leaves little free resources for HSPA data traffic. However, using WCDMA+, the same 48 voice calls can be supported while leaving close to 40% of resources free for data. Yet even more impressive, using a high-definition EVS voice codec, WCDMA+ can now accommodate the same 48 voice calls while leaving 66% of resources free for data.

The following describes a number of WCDMA+ Downlink techniques that help to accomplish these improvements. Similar techniques provide corresponding gains on the uplink.

WCDMA+ Physical Layer Enhancements

  • Downlink Overhead Optimization: A substantial portion of the power allocation for CS voice transmission is attributed to overheads. Techniques such as the following allow for improved efficiencies for CS voice calls.
    • Removal of the dedicated pilot: The dedicated pilot was originally intended for transmit diversity which was never deployed and hence is a waste of radio resources.
    • Re-use downlink power control bits for SINR estimation: dedicated pilot’s other use was for SINR estimation which can now be performed reliably using the DL power control bits. This would eliminate the need for the dedicated pilot on the downlink.
  • Downlink Frame Early Termination (FET): Voice frames can often be successfully decoded long before the entire 20ms frame is transmitted. In WCDMA+, the receiver attempts early frame decoding and notifies the transmitter once it is successful. This allows both the transmitter and the receiver to shut down and save power for the remainder of the frame.

    The proposed techniques reduce interference in the system leading to increased system capacity, improved UE talk time and battery life.

    To further improve talk time, WCDMA+ also introduces a new frame structure that time-multiplexes two UEs by splitting the typical 20ms downlink frame into two 10ms units.

    Simulation results below illustrate early decode success rates, compared to the current 20ms voice frame format. As early as 6ms into the 20ms TTI (a full 14ms early) , we observe nearly 95% chance that the voice frame successfully decode early.

WCDMA+ Voice Codec Enhancements

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 or better than that of AMR-WB 12.65k. It provides superior voice quality to AMR 12.2k but at only half the average bit rate.

Codecs Bandwidth Quality
AMR 12.2k Narrowband (0-4 KHz) Today’s user experience
AMR-WB 12.65k Wideband (0-8 KHz) Better than AMR at 12.2k
EVS SC-VBR 5.9k Wideband (0-8 KHz) Target: equivalent to AMR-WB 12.65k and much better than AMR 12.2k