Voice services over LTE networks are a major drain on smartphone batteries and reduce device battery life by 50 percent, according to a new study by Metrico Wireless Inc. .

Metrico, which was recently acquired by test specialist Spirent Communications plc , conducted tests on one U.S. operator's LTE and CDMA networks to measure the impact that voice services have on the smartphone battery on both types of network.

The company found that when voice calls were made on the CDMA network, the average current drain was 183 milliamps (mA) and the average power consumption was 680 milliwatts (mW). But when the voice call was made over the LTE network -- that is, a voice over LTE (VoLTE) call -- the average current drain was about twice as much as a CDMA voice call at 365 mA. Also, the average power consumption was roughly double the amount of a CDMA voice call at 1358 mW.

That means the 4G voice call reduced the smarthphone's battery life by 50 percent or about 252 minutes of talk time, compared to voice calls made over the CDMA network.

Metrico also tested the impact of simultaneous voice and data sessions on smartphone batteries on CDMA and LTE networks. And the multi-service results on the LTE network come out better than the voice only call results. The test found that a multi-service session running simultaneous VoLTE and data over the LTE network drained about 11 percent less current than a session in which voice ran over the CDMA network and data ran over the LTE network at the same time.

Why this matters
These test results are bad news for IP Multimedia Subsystem (IMS)-based VoLTE services, which are in the early stages of commercial rollout. But they are also discouraging for LTE network operators' efforts to convince customers to upgrade from their 3G service to new 4G services.

The test also shows just how much work is still needed to optimize VoLTE devices so that the voice services aren't such a big drain on battery life.

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— Michelle Donegan, European Editor, Light Reading Mobile