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Voice calls over 4G LTE networks are battery killers

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Every mobile carrier wants to replace their old voice services with new VoIP-based systems utilizing their 4G networks, but it looks like they’ve got some big kinks to iron out in the technology first. Wireless testing and measurement vendor Spirent Communications has identified a big problem with voice over LTE (VoLTE): it consumes twice as much power as a traditional 2G call, which could have big implications for mobile phone battery life.

Metrico Wireless, a radio field testing company Spirent acquired in September, conducted voice trials on a commercial VoLTE-enabled network in two U.S. cities, comparing the power consumption of VoIP calls made over LTE against the power used by the same carrier’s CDMA systems. Spirent-Metrico didn’t name the carrier, but it’s not hard to guess.

MetroPCS(s pcs) is the only U.S. operator with a live VoLTE service and a commercially available handset. The 1540 milliamp hour (mAh)-battery on Metro’s sole VoLTE handset, the LG Connect 4G, also lines up with the battery capacity of the device Spirent tested.

The results of those tests should give carriers and consumers pause. The average power consumption for a 10-minute CDMA circuit-switched call was 680 milliwatts (mW) while the average consumption for a VoLTE call of the same duration was 1358 mW. That’s double the power drain. Spirent estimated that on a full charge, its test smartphone could support 502.6 minutes of talk time using CDMA only, but the same charge would only deliver 251.8 minutes of talk time using VoIP on the 4G network. And that’s with all other data communications turned off.

What it comes down to is that our old GSM and CDMA circuit-switched voice technologies — despite their limitations — have been optimized over the last two decadesto be energy efficient, Spirent Global Director of Insights Amit Malhotra told GigaOM in an email interview. It’s hard to replicate that kind of efficiency overnight in a generic data modem.

“The disadvantage in battery life of VoLTE compared to circuit-switched voice is driven by a few different factors,” Malhotra said. “One is the more strenuous exercise of the device, including conversion of voice to packet data, transmission and receipt over the data network, and reconversion back to voice. Another is the use of less power-efficient components such as data modems versus voice transceivers.”

If this proves to be typical for VoLTE handsets, it will be a big problem. The battery life of the first generation of LTE smartphones was atrocious, and handset vendors have tried to address the problem by slapping fat 3000+ mAh power cells onto their phones. Some carriers are already reluctant to embrace VoLTE since they can still squeeze plenty of life out of their 2G and 3G voice services. If VoLTE proves to be a battery killer, they will be even less inclined to move mobile voice into the IP age.

There is some good news in Spirent’s findings though. It found LTE performed better than CDMA when the phone is used to make simultaneous voice and data calls. When the phone was in 4G-only mode — i.e., using only the LTE network for both VoIP and data — it performed slightly more efficiently than when the 2G radio was used for voice while the 4G radio transmitted data, Spirent discovered. That makes sense since powering two radios simultaneously could take an enormous toll on battery life.

That would seem to indicate that if you tend to talk and consume data at the same time, then VoLTE is a more efficient technology. That’s true, but only to the tiniest degree. The study found that both in both scenarios the hyperactivity of the device drained tremendous amount of energy. Battery life estimates dropped below 120 minutes in both cases. No matter which radios you use, talking and surfing consumes a tremendous amount of power.

Malhotra, however, said LTE power efficiency is bound to improve as both data modem technology and network coverage gets better. Today’s LTE networks have limited footprints, forcing phones to continuously check for signals. Eventually the data modems in our handsets will be optimized for VoIP calling.

“These issues will be mitigated over time, especially as components continue to become more power efficient, and devices do not need to switch between different modes of voice call processing,” Malhotra said.

16 Responses to “Voice calls over 4G LTE networks are battery killers”

  1. Margie Dempsey

    this is all well and good but the average, say, hair stylist in New York whose searching the internet for styles to try doesn’t care if her 4GLTE is eating up her battery, only that it’s fast. If they all die early, you’re back to a level playing field. Nothing AT&t or anyone else can do about it.

    • Kevin Fitchard

      Margie, huh? You don’t think a hair stylist cares if her phone dies after a half-day of use? I think everyone cares about battery life. Phones are only useful if they’re on

  2. Ryan Chung

    Dose it means , both VoLTE and CS fallback are needed by a platform ? When system detected no data transforing is on going , voice call fallback to 3/2G …when data tragic is needed , system keep it , and make the voice call via VoLTE

  3. Zato Gibson

    In order to make the test a fair efficiency comparison between the 2G and LTE voice over IP, the audio bandwidth should be equalized. VOIP audio bandwidth is often advertised as “CD” quality. A 10 min. call with the audio bandwidth extended down to 100hz or lower will use a lot more power.

  4. This data seems to be little bit inaccurate. I have practically used both CDMA and VoLTE phones. My observation was that fully charged CDMA phone was drained in 10 hours of active call and VoLTE phone drained with 8.5 hours of continuous call.

  5. This is SOOO wrong. VOLTE properly implemented should consume 50% less battery than 2G voice. This is a crappy head-over-heels 1st generation Samsung implementation running the entire protocol stack and voice processing in the application processor…

  6. Dan Warren

    I’d be interested to see the differences in power drain fro data usage? Is all of this difference genuinely just down to the vocie call or is there some that can be attributed to support of additional RF Filters and PA’s just because you have an LTE handset?

  7. Lenin VJ Nair

    LTE in actuality does not take up too much battery. It is how the operators are giving the service that is at fault. LTE is in fact saving battery power. but verizon and others are not deploying it properly

    VJ Blue Bugle.

  8. Doug Varney

    Hmmm … Spirent’s Amit Malhotra might want to brush up on his technology when he explains the increased battery drain from VoLTE over CDMA Circuit Switched Voice: “One is the more strenuous exercise of the device, including conversion of voice to packet data, transmission and receipt over the data network, and reconversion back to voice. Another is the use of less power-efficient components such as data modems versus voice transceivers.”

    CDMA 1x is packet data at its core – thus there is the need for all those steps he listed when using CDMA “Circuit Switched voice technology”. Of course, CDMA 1x has had years and years of optimization unlike VoLTE, so the end results of the Spirent testing are not surprising, just the explanation on why.