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Summary:

Your LTE phone is just as adept at eating battery power as it is at eating bandwidth. Last week, I wrote about the many ways that LTE devices are far more power hungry than their 3G predecessors. Now let’s look at what’s being doing about it.

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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.

  1. It is time for the carriers to get serious about femtocells. The majority of smartphone usage occurs at home or work. Followed closely by retail business locations. All three are easily addressed by femtocells. No need to waste power on a stronger transmission multiplied over MIMO when your device is close to a femtocell.

    Many would argue that Wi-Fi does this as well, but they are wrong. First, Wi-Fi uses even more power than 3G and 4G data technologies. Second, femtocells provide a more seamless transition than Wi-Fi ensuring greater utilization. Finally, Wi-Fi has no hope of offering mobile voice whereas LTE is planned to have voice in the not to distant future.

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    1. WiFi uses more power? Then why is WiFi browsing in a smartphone always last longer?

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    2. Voice over LTE will most likely be based on GAN (i.e. VoLGA) which has been around for Wi-Fi for some time. So the day LTE has voice it will be trivial to add it for Wi-Fi.

      Wi-Fi is getting more seamless as well with authentication against the SIM card, called EAP-SIM and EAP-AKA.

      In general I would say the chances of battery life improvements are significantly higher for Wi-Fi than for LTE, mostly because of physics: shorter distance between sender/receiver means higher bit rate and lower power. Of course, if you had the same density of LTE femtos that would work but it’s very unlikely to happen.

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    3. Khürt Williams  Wednesday, February 22, 2012

      Matt, you are correct. Current cellular radio technology was designed to be used outdoors. Now that we are all replacing our landlines with cell phone means that the carrier need to rethink their strategy.

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  2. I guess I still can’t get excited about LTE. All of the illustrations of how it rocks for me are things like streaming video and I always think to myself “On a 2gig/month plan??”. Aside from the new, shiny, fastest crowd I’m not sure I see any real world benefits to LTE or other very fast connections given the tradeoff in battery life and the limitations of bandwidth in the current data plans.

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    1. I have to agree. My Clear Apollo 4G mobile hotspot can stream video and audio for hours on end – yet that’s only possible thanks to the unlimited data plan that comes with it. I solved my power issues by getting a small external battery.

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  3. I have a 4g phone and after the first week of enjoying how fast LTE is, I have it set to 3g-only so that I can have 24 hour battery life again.
    4G is nice for streaming video and such, but for background email and other notifications, everything arrives in the same time. I’m not going to be bothered turning it on every time I want more than a simple webpage so at the end of the day, I wish that my Galaxy Nexus had an alternative option sans LTE that was cheaper. I don’t see myself ever turning 4g back on because of the battery life.

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  4. Dunno, with LTE it’s always a problem. on my galaxy nexus i can only solve battery issue with my 2000mah Mugen Power battery

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  5. Guess we are not changing 3G to 4G just for fun. I see LTE a first good communication standard for a mobile device really.
    Parameters I count are:
    1. Operation quality when mobile device is moving 150km/h on the ground.
    2. Latency (roundtrip time spend ie. ping)
    3. Data rate

    2G is failing all of these. 3G is failing 1.) and 2.).
    LTE is good foor all of these.
    3G is especially failing 2. which really degrades the browsing speed & experience badly. Times vary 100ms –> second. 4G should have always below 100ms, typically 10-50ms roundtrip. The data rate in 3G is typically good enough already to do anything, but 3G modulation is not really optimized for high ground speeds and suffers from Doppler effect still (2G very badly)

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