When will LTE stop sucking (your battery)?

Your LTE phone may be able to plow through file downloads and handle the most pixel-dense video streams with ease, but it’s just as adept at eating battery power as it is at eating bandwidth. Last week, I wrote about the many ways that LTE radios and networks are far power hungrier than their 3G predecessors. Now let’s look at what’s being done about it.

The good news is that handset makers and network vendors are doing plenty to boost the power efficiency of LTE devices, but the bad news is that as 4G technologies evolve, making our phone and tablet connections even faster, their radios will continue to voraciously eat up batteries. The question is can the former trend keep up with the latter.

Why your next LTE phone will be better

The first generation of LTE devices are unquestionable the most sophisticated smartphones and tablets we’ve seen to date in terms of processing power, screen-resolution and OS software. But the approach most vendors were forced to take to the radio was hardly delicate. In most cases an LTE chip was shoehorned into the device, which is hardly a formula for long battery life.

There’s a lot of work that silicon vendors are doing to squeeze better power performance out of those phones. Components that are today separated in the bowels of the phone such as the applications processor and baseband will be combined, allowing them to share power resources. The world’s largest radio chip vendor Qualcomm has released its first integrated Snapdragon processor and LTE radio modem, and according to Qualcomm product management VP Raj Talluri, we’ll see many devices supporting that next-gen chip at Mobile World Congress next week.

Texas Instruments is developing radio chips that require the device to lean less and less on a smartphone’s powerful applications processor to perform basic tasks, such as initiate NFC payments or perform quick GPS-location checks. The longer the apps processor remains dormant the less drain the phone will have on the battery.

Optimizing the network will also be a big source of power savings. As operators move their voice services onto LTE and build out both the coverage and density of their networks, they can offer LTE-only phones (Verizon is targeting its first such device for 2013). The fewer active radios there are sucking at the battery, the longer our phones will sustain charges.

As operators build denser networks, shrinking the size of LTE cells, phones won’t have to boost their transmit power as much to link to the tower. And as coverage improves, phones will stay within LTE’s warm embrace for longer intervals, eliminating the need to constantly negotiate between an operator’s multiple networks.

The tug-of-war in the handset

The big question is whether all of those tweaks and technologies will be enough. Power drain will be an ongoing problem for handset designers and their efforts are complicated by the fact that radios are becoming fundamentally less power efficient even as they become more bandwidth efficient. ABI Research analyst Jim Mielke summed up this way: “The bottom line is the higher the data rate and higher spectral efficiency, the higher the computing requirements — and thus power drain.”

That means future technologies like LTE-Advanced, which promises speeds as high 1 Gbps, will be ravenously hungry for power. Older generation technologies won’t be immune either. As T-Mobile moves to 84 Mbps HSPA+, it will add dual antennas to its devices, which suck down power just like their LTE brethren.

Mielke said some of that power drain is offset by the simple efficiency of its ultra-fast LTE modem — the faster a device can download a video or file, the sooner it can shut down the data session and de-activate the radio. Theoretically faster download speeds and the LTE radio’s inherent power inefficiency should cancel each other out, but that’s assuming that consumers use LTE phones the same way they use 3G ones. It’s no coincidence that the newest smartphones don’t just have 4G radios, but also larger higher-definition screens and multi-core processors. LTE’s speeds allow the mobile public to do so much more with their handsets, and the tendency is take advantage of that raw power to stream more video, surf more Web pages and download more files – that is until data caps kick in.

Vendors like Motorola are combating the problem by sacrificing design for fatter batteries, as it did with the new Razr Maxx. The short term solution is for device makers to devote more device cost and space to the phone’s lithium-ion footprint. But ultimately battery technology is going to have to improve if the handset industry is going to keep up with advancements in radio technology.

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