Testing shows voice-over-LTE power drain is improving, but it’s still no 2G

VoIP calling over 4G networks may be the wave of the future, but as wireless and testing measurement company Spirent discovered last November, voice-over-LTE (VoLTE) technology still has a lot of kinks to work out before it can match the power efficiency of our old reliable 2G networks.

Tests of MetroPCS’s(s pcs) new VoLTE service found that 4G calls drained twice as much as regular CDMA ones. At the time, however, Spirent Global Director of Insights Amit Malhotra predicted that VoLTE’s power efficiency would improve as both VoLTE network and handset technology progressed. Fast-forward four months and Malhotra’s prognostication appears to be coming true.

Spirent recently performed a new batch of tests using Metro’s newest generation VoLTE handset, the LG Spirit 4G, and found that the current drain from a VoLTE call had dropped by 35 percent compared to LG’s first-generation VoLTE smartphone, the Connect. Improving power efficiency by 35 percent is a tremendous number when it comes to cellular battery life, which tends to measure progress in tiny increments. But there is still one big qualification to that good news: 2G is still a more power-efficient technology.

Spirent VoLTE round 2 LTE

With its latest generation handset, LG improved the overall radio performance of the phone by using an integrated CDMA-LTE radio, rather than the dual chips used in the older Connect (it also beefed up the Spirit with a much larger 2150 mAh battery). That resulted in an 18 percent current drain improvement for CDMA calls in addition to the improved performance in VoLTE. Even with its efficiency boost, VoLTE still ate up far more juice than a CDMA call on either the new Spirit or the old Connect.

Spirent VoLTE round 2 CDMA

Spirent’s tests concluded that the LG Spirit would support 875 minutes of talk time in CDMA mode, but only 575 minutes when solely making 4G calls. The Spirit’s bigger battery (with 38 percent more capacity than the Connect) gives the device a big boost in single-charge lifespan, but that 300-minute differential is still huge.

The bottom line is that while VoLTE’s battery drain is improving it still has a ways to go before it can match the power efficiency of 2G. CDMA and GSM technologies went through more than a decade of optimization to reach their current efficiency levels.  Hopefully VoLTE can close that gap in a much shorter interval. The big improvements LG and MetroPCS demonstrated in a single generation of handsets is a good sign that it can.

Correction: This post was updated at 11:30 AM, Tuesday, to correct a percentage. Spirent measured a 35 percent power drain improvement in VoLTE calls between the two generation of LG devices, not 33 percent.