LTE's battery drain is a significant issue for early adopters, but more integrated chips and other innovations are improving the situation. However, as carriers start to roll out VoLTE, they may take another step backward, since the 4G voice technology can slash battery life in half.
This is the finding of a study by Metrico, a division of testing company Spirent Communications, which compared talk-time battery life on CDMA and LTE. Its tests involved calls in two major US markets, using a smartphone capable of running both CDMA and VoLTE (voice over LTE) – presumably the network was that of MetroPCS, one of just three cellcos in the world which currently supports commercial VoLTE. Its only VoLTE device at present is the LG Connect 4G.
“The device's estimated battery life was reduced by 50%, or about 252 minutes of talk time, when voice calls were placed over the LTE network, compared to voice calls placed over the CDMA network,” says the report.
Its author Ardeshir Ghanbarzadeh, director of services development at Metrico, said: “The significant difference in current drain between VoLTE and CDMA technologies for voice calling applications suggests further optimization of devices supporting VoLTE calls is needed in order to give end users talk-time battery life expectancy levels similar to that of 3G devices.”
Such findings will be a blow to carriers like Verizon Wireless, which wants to migrate users as quickly as possible from 3G to LTE-only networks. Since these will no longer be able to fall back to traditional circuit-switched 2G/3G voice, such carriers will be looking for vendors to address the battery drain issue in time for their winding down of 3G, or risk subscriber frustration.
According to Metrico, a radio field testing firm which Spirent acquired in September, the average power consumption for a 10-minute CDMA circuit switched call was 680mW, while the figure for a VoLTE call of the same duration was 1358mW. Spirent estimates that on a full charge, its test smartphone would offer 502.6 minutes of talk time using CDMA only, but only 251.8 minutes using VoLTE (assuming other data connections were turned off).
The study is the latest to highlight how many years of effort went into optimizing the older mobile technologies to be forgiving to batteries, an area in which IP is well behind. However, Metrico did find that LTE was slightly more efficient when the handset was used for simultaneous voice and data calls on the 4G network, compared to transmitting data on 4G while using the CDMA radio for voice.