iOS 4.0 Amazing battery life!

[Nicksd84]

Not really, since you will be keeping two radios active, instead of just one.

I suspect this is a change in response to no more unlimited plans being available. Before, Apple could optimize for battery life by turning off the WiFi radio to save the battery, and be assured that the unlimited plan would be able to handle any data usage while the WiFi was off. That's no longer true, so for the sake of keeping people within their data plans, they keep WiFi active the whole time if there is a nearby known network.

actually it's for apps that will be using data in the background in the lockscreen. I know that's pretty much what you said, but performance is better on a good wifi connection than a good 3g connection. I don't think it's some diabolical plan in relation to capped data.

 

[Krevnik]

actually it's for apps that will be using data in the background in the lockscreen. I know that's pretty much what you said, but performance is better on a good wifi connection than a good 3g connection. I don't think it's some diabolical plan in relation to capped data.

And you are totally ignoring the real point here:

Active radios, participating in a network draw more power than a radio turned off and not participating in anything.

In 3.x and earlier, WiFi was turned off once the data connections stopped and wouldn't rejoin a network until you woke it back up. This saved the battery from having to power both 3G and WiFi at the same time while it was just idling in someone's pocket. If you had Pandora running in 3.x, and WiFi was on when you turned off the screen, WiFi would remain connected.

In 4.0, WiFi will remain connected by default, and won't shut off even if the data flow over the network has stopped. Apps in 4.0 still won't be able to open a connection without user intervention (only continue in the background where before they couldn't). So the behavior didn't need to be changed to support multitasking.

And there is nothing diabolical about trying to prevent data from going over 3G when there is WiFi available. It's a good thing as it helps prevent push e-mail from eroding into your data cap when you are at home or work, for example. The trade-off is that this extra radio means extra power usage. Enough to be noticeable, but probably not enough in most cases to cause problems. But considering those who are hooked up to work exchange servers can eat gobs of data from push e-mail (I think I get on the order of 100+ mails a day that get past my filters and make it into my inbox, and that doesn't include personal mail), it was the right change to make with AT&T no longer providing unlimited data plans for new customers.