Feeds

Boffin hacks Wi-Fi to double mobile gadget battery life

Saving your beacon

Internet Security Threat Report 2014

Want to significantly boost your smartphone's battery life? US Duke University researcher Justin Manweiler reckons he's worked out how.

Manweiler's work centres on Wi-Fi, specifically when the phone - or tablet or laptop, for that matter - is operating within range of more than one wireless access point.

If access points are able to co-operatively manage their shared radio environment, client gadgets can keep their Wi-Fi adaptors in sleep mode for longer, extending battery life.

Currently, clients periodically wake up their radios to check in with their associated access point and see if data is available to be transfered. Existing Wi-Fi energy saving technology, called Wi-Fi Power Save Mode (PSM), ensures data is buffered in the access point to ensure the client radio doesn't need to be woken up for dribs and drabs.

Instead, data packets are bundled and sent as bursts big enough to maximise radio sleep time without introducing so much latency that the user perceives that the data isn't being streamed - video playback that isn't smooth, for example.

Now throw multiple access points into the mix and the upshot is that a given client's radio needs to stay awake for greater periods - up to five times longer, Manweiler found - than it would when in range of a single access point, thanks to contention between access points.

As so many of we city dwellers and workers know, these days there are lots of access points around us, and the longer the device's radio is on, the more power it's burning.

Manweiler's solution, dubbed SleepWell, has a compatible access point dynamically reschedule those bursts of traffic to its clients so they don't occur when other access points are sending data to their clients. Clients sleep when other clients are active, and can be sure they can download data without interruption when it's their turn.

"By carefully modifying the timestamps - as a part of the Wi-Fi clock synchronisation process - the SleepWell AP regulates the client’s sleep and wake-up schedules," writes Manweiler in his paper Avoiding the Rush Hours: Wi-Fi Energy Management via Traffic Isolation.

"Results show a median gain of up to 2x when Wi-Fi links are strong," he says. "When links are weak and the network density is high, the gains can be even more."

SleepWell was implemented by tweaking the open source ath9k driver for Atheros 802.11n PCIe interfaces.

Since bursts take place periodically, SleepWell can work out the best time to send its data even if some or all of the surrounding APs are not SleepWell-enabled themselves.

Manweiler said that SleepWell only needs to be implemented at the access point, so there's no need to change the radio code running on the client - it's compatible with all existing client devices.

Testing SleepWell with a variety of laptops and smartphones, Manweiler said he recorded "energy reductions vary between 38 per cent to 51 per cent, across a variety of real online applications, including YouTube, Pandora, Last.fm and... FTP".

The gotcha is VoIP and other "interactive, highly latency sensitive traffic", which requires lower levels of latency than even PSM can ordinarily introduce without being noticed.

You can read Manweiler's paper on the Duke University website (PDF). ®

Providing a secure and efficient Helpdesk

More from The Register

next story
Will.i.am gets CUFFED as he announces his new wristjob, the PULS
It's got four KILOWATTS of something, apparently
Don't wait for that big iPad, order a NEXUS 9 instead, industry little bird says
Google said to debut next big slab, Android L ahead of Apple event
Netscape Navigator - the browser that started it all - turns 20
It was 20 years ago today, Marc Andreeesen taught the band to play
A drone of one's own: Reg buyers' guide for UAV fanciers
Hardware: Check. Software: Huh? Licence: Licence...?
Jaguar Sportbrake: The chicken tikka masala of van-sized posh cars
Indian-owned Jag's latest offering curries favour with us
iPhone 6 shunned by fanbois in Apple's GREAT FAIL of CHINA
Just 100 Beijing fanbois queue to pick up new mobe
The Apple launch AS IT HAPPENED: Totally SERIOUS coverage, not for haters
Fandroids, Windows Phone fringe-oids – you wouldn't understand
Here's your chance to buy an ancient, working APPLE ONE
Warning: Likely to cost a lot even for a Mac
Is living with Dolby Atmos worth the faff?
Subtle, naturalistic ambiance – perfect for Transformers 4
prev story

Whitepapers

Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Win a year’s supply of chocolate
There is no techie angle to this competition so we're not going to pretend there is, but everyone loves chocolate so who cares.
Why cloud backup?
Combining the latest advancements in disk-based backup with secure, integrated, cloud technologies offer organizations fast and assured recovery of their critical enterprise data.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.