No 3G on the iPhone, but why? A Battery Life Analysis
by Anand Lal Shimpi on July 13, 2007 3:53 AM EST- Posted in
- Smartphones
- Mobile
A CPU Bound Case: Streaming YouTube Videos
Bandwidth enables new usage models, it's what we saw on the desktop and it's what we're seeing in the mobile phone market as well. Streaming video to mobile phones is a definite bandwidth consumer, and something that's truly enabled by 3G wireless technologies - but at what cost to battery life?
On the Blackjack we used the YouTube Mobile site (m.youtube.com) with a hack to enable playback on Windows Mobile 5. We played back the same video over and over again until the battery died. Unfortunately the longest video we could find on YouTube Mobile that was stressful enough for our test measured around 5.5 minutes, meaning that by the end of the 3+ hour process we were ready to die.
Things were a bit easier on the iPhone as its YouTube implementation has a larger selection of videos, including our test video which was over 40 minutes long, thus requiring fewer clicks on our part to keep the video looping.
Our YouTube test is a little misleading when it comes to the iPhone because there's more than one variable being changed here. When switching between Wi-Fi and EDGE on the iPhone, the YouTube client automatically requests a different quality video depending on what wireless connection you're using. The stream over Wi-Fi looks absolutely beautiful, while over EDGE you get a much lower bitrate stream that's more reminiscent of what YouTube looks like on the web. The problem with this is that we're unable to measure the impact of Wi-Fi vs. EDGE alone, as the flipped results show (EDGE outlasting Wi-Fi).
Looking at the Blackjack results helps us make sense of the iPhone's behavior. Streaming video from YouTube is predominantly CPU bound, so much that the primary determinant of battery life is the CPU itself, not driving the wireless antennas. The end result is that while 3G draws more power than EDGE, the difference is around 6% because the CPU is eating the vast majority of the power budget and its role is identical regardless of whether the phone is running in 3G or EDGE mode.
If we assume that the same CPU bound limitation exists on the iPhone, the fact that while decoding lower quality video the iPhone would last longer makes sense. Lower quality video means a much lighter load on the iPhone's CPU, thus resulting in longer overall battery life. In this case, the significant reduction in quality results in an equally significant increase in battery life (37% or close to an extra 1.5 hours).
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jellinek - Friday, July 13, 2007 - link
Does the h.264 implementation on the iphone vs. the likely flash-based version on the blackjack impact this at all?Quicktime playback over the web (trailers set to loop?) might be a better way to determine EDGE/3G/WiFi battery life.
MrJim - Friday, July 13, 2007 - link
Anyone know if they will add MMS-messengering in iphone?GlassHouse69 - Friday, July 13, 2007 - link
fuck iphone.that's all I have to say.
stop reviewing it. it is lemming equipment that is overpriced and hobbled with a beautiful screen. feels like 5-6 years ago Mac intellect at use. get great graphical images, get stuck in the mud hardware, hobble it all somehow, charge 1000 dollars more than you need and bam, lemmings jump. wee!
DavenJ - Friday, July 13, 2007 - link
I guess this guy isn't going to buy an iPhone.Shark Tek - Friday, July 13, 2007 - link
Yeah I bet that he can't buy it.puffpio - Friday, July 13, 2007 - link
Is there a way to get this higher quality youtube feed for computers?? I'm tired of their pixelated crap.dacramer - Friday, July 13, 2007 - link
Who cares how LONG the battery lasts when loading web pages. The real test is how many web pages the battery can load per charge. Even if the battery lasts half as long over 3g, it surely must load more web pages. Is it more than double? 3g may not be so bad with regards to battery life with this taken into consideration.Icehawk - Friday, July 13, 2007 - link
I think the exact same thing - the more important metric is how many pages you can load not how long the battery lasts with constant clicking.Araemo - Friday, July 13, 2007 - link
"The biggest impact of all is, surprisingly enough, talk time; with 3G enabled, the Blackjack's talk time is cut in half, with absolutely no benefit realized from the higher bandwidth standard."Do you want to know why 3G is the default for talk time as well as data transfers? 3G has more bandwidth per cell tower, and talk over 3G uses the same total bandwidth as talk over GSM.. but since 3G increases the available bandwidth, you use less of the cell company's resources if you're talking using 3G instead of GSM. So battery life be damned, AT&T wants to make more money. ;)
cosmotic - Friday, July 13, 2007 - link
Your graph on the talk time page shows the iphone using wifi. Shouldn't that be edge?