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HSPA+ Advanced

CPC & Enhanced FACH: Smartphone Enhancements

The increasing popularity of mobile broadband, smartphone apps, and connected devices and services has created the following challenges in the mobile eco-system:

  • Network congestion resulting in user experience impact
  • Increasing network signaling due to short data sessions from chatty smartphone apps
  • Diminished smartphone battery life

The following HSPA+ features help mitigate these issues.

Continuous Packet Connectivity (CPC)

CPC was standardized in 3GPP Release 7 and has been commercially available in Qualcomm chipsets since 2011. It improves network capacity and battery life by applying the following techniques to data intensive applications that keep the cellular modem in a connected state (DCH).

  • Discontinuous Transmission (DTX): Allows the mobile terminal to turn off the modem transit chain between data bursts. This reduces uplink interference leading to lower noise rise.
  • Discontinuous Reception (DRX): Allows the modem receiver to sleep between downlink data bursts resulting in an improved battery life.

The figure above shows CPC gains from operator field trials conducted in 2013, using handsets using Qualcomm’s commercial chipsets. CPC is deployed in numerous networks worldwide.

Enhanced FACH

Chatty smartphone applications exchange small amounts of data with the network infrequently, taking the modem from idle to a connected state (DCH) repeatedly. While these exchanges involve only a few bytes to 100s of bytes of data, they impose a significant signaling load on the network. This results in wasted air-link capacity that could be used to carry revenue generating user traffic. Furthermore, it diminishes battery life by keeping the modems in mobile terminals awake longer than necessary.

Enhanced FACH allows mobile terminals to access the more efficient, high-speed shared data channel while in the Cell FACH state. It significantly reduces network signaling load, and enables a fast transition from inactive to active state to provide an “always on” user experience.

Enhanced FACH includes the eDRX feature which allows inactive mobile terminals to turn off their modem receive-chains to reduce battery consumption. The mobile terminals wake up intermittently to exchange short data bursts, and will return to PCH state after experiencing a long period of inactivity time out.

The above figure illustrates the reduction in signaling and NodeB resource occupancy achieved by Enhanced FACH during operator field trials using Qualcomm’s modem chipsets. Multiple trials have been completed with major infrastructure vendors. This solution is expected to be commercially deployed in 2014.