ST-Ericsson: Battery issues not a problem for newer VoLTE devices

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Chipmaker ST-Ericsson is battling the contention that phones offering voice over LTE have battery life issues, saying such issues are restricted to first-generation LTE chipsets and devices running simultaneous voice and LTE (SVLTE) service during VoLTE calls.

The company issued a white paper, which it says is aimed at addressing "the confusion and uncertainty around the topic" and demonstrating "the true potential of VoLTE." ST-Ericsson also said its white paper, written by Bjorn Ekelund, vice president, ecosystem, research and innovation, specifically targets "a measurement report by Metrico made in MetroPCS' (NYSE:PCS) CDMA+LTE network in late November."

However, the report from Metrico, which is now part of Spirent, actually did not identify MetroPCS as the network operator studied. At the time FierceBroadbandWireless wrote about the Metrico/Spirent study, MetroPCS declined our request for an interview regarding its customers' experiences with VoLTE and handset battery life.

Among other things, the Metrico/Spirent report revealed that a smartphone's estimated battery life was reduced by 50 percent when voice calls were placed over the targeted LTE network vs. voice calls placed over the CDMA network. The company said tests of multi-service simultaneous voice and data calls using just the LTE network, meaning only the LTE radio was in use, revealed 11 percent less current drain than multi-service sessions using CDMA for voice and LTE for data.

ST-Ericsson's Ekelund said the power-consumption problems uncovered by Metrico/Spirent were due to the fact that CDMA/LTE systems rely upon SVLTE for VoLTE calls, which keeps both the CDMA radio and the LTE radio in full operation during a voice call. "The consequence of this is clearly visible in the Metrico data, which also shows the obvious fact that VoLTE+LTE consume less power than CDMA+LTE," he wrote.

Neither LTE networks with a 3GPP-based legacy nor CDMA plus LTE solutions based on fall-back schemes, such as the one used in Apple's (NASDAQ:AAPL) iPhone 5, suffer from the power-consumption issues identified by the Metrico/Spirent study, said Ekelund.

The chipmaker also contends that power-management issues are evident in first-generation VoLTE implementations because the first-generation LTE chipsets were developed "with a focus on time to market and on plain data services rather than more complex ones."

Improvements in software architecture, radio hardware and transmission protocols promise to enable reductions in VoLTE power consumption going forward. "Together with protocols for call establishment, codec negotiation, etc., the VoLTE standard comes with some new radio protocol enhancements aimed to reduce both spectrum usage and battery power. Few if any of them are activated in networks today," said ST-Ericsson, citing in particular semi-persistent scheduling (SPS), TTI bundling and discontinuous reception (DRX).

The white paper concluded with the observation that because over-the-top (OTT) applications such as Skype are restricted to running in the handset's application processor, they will not benefit from advanced protocols developed for VoLTE.

ST-Ericsson is a joint venture of Ericsson (NASDAQ:ERIC) and STMicroelectronics. Late last month, Ericsson said it would take a $1.2 billion charge in the fourth quarter related to the money-losing chipset joint venture. The write-down came less than two weeks after STMicroelectronics said it expects to sell off its stake in ST-Ericsson during the third quarter of 2013.

For more:
- see this ST-Ericsson white paper (PDF)

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