Battery Drain Game

by Stuart Zipper

As most followers of this blog know, I’ve got a lot of hope for the eventual emergence of VoIP services over Long Term Evolution (LTE) wireless, indeed of VoIP over LTE (VoLTE) replacing VoIP over the non-wireless technologies of today, both fiber and copper. In other words, I’ve been predicting that some day your phone service, from or any other VoIP provider, will be delivered wirelessly.

But getting there isn’t going to be quite as simple as some think it will.

The latest glitch to emerge was uncovered by test and measurement vendor Spirent Communications recently-acquired subsidiary Metrico Wireless. It found that VoIP over LTE consumed twice as much battery power as voice over convention cellular technology. Simply put, half as much talk time for a portable device such as a so-called “cell phone.” It was testing LTE phones similar to the ones offered by MetroPCS Communications, currently the only cellular operator in the U.S. that offers VoLTE.

For the detail minded, test results showed a 10-minute call using CDMA technology consumed 680 milliwatts (mW) of power, and a VoLTE call ate up 1,358 mW, or roughly twice as much power. That meant that the phone being tested would yield 502.6 minutes of talk time on CDMA,but only 251.8 minutes using VoIP over an LTE network.

Based on those results I’ve been seeing a string of nay-sayers issuing dire predictions that the future of VoLTE has now become cloudy. I’m tempted to say something like “Beware, ye of little faith.”

In my opinion, what we have here is little more than a bump in the road, an engineering challenge that the industry will overcome pretty rapidly. After all, it wasn’t all that long ago that 1G wireless data (LTE, remember, is fourth generation or 4G) was just emerging from the laboratory. The latest finding may delay some aspects of VoLTE by a bit, but I’m quite confident that in the grand scheme of things, in retrospect the delay will be miniscule.

The first thing to remember is that the vast major of phones today consume both traditional voice (GSM or CDMA) plus data. And when there’s a CDMA call going on at the same time as LTE data transmission, the battery drain is even larger than if a VoLTE conversation is taking place at the same time as an LTE data transmission. That should be obvious, because combined CDMA/LTE situations there are two radios in use at the same time, instead of a single LTE radio.

The other thing to consider is that the power issue is not a consideration for desktop phones which, as I’ve predicted, will eventually start migrating to LTE. After all, LTE can dish up massive bandwidth, of more than 100 Mb/s, more than enough for dozens of simultaneous VoLTE conversations. And it does it without the cost, the enormous cost, of laying copper or fiber to each of hundreds of homes and businesses in a given area.