That Wi-Fi use leads to shorter smart phone (and allied devices) battery lives seems to be pretty common knowledge and standard advice is to turn off your Wi-Fi in order to extend it.
So, I ask: what is it about using Wi-Fi that causes this problem? I know that Wi-Fi leads to high power consumption but that misses the ‘why’, i.e. why does Wi-Fi consume so much compared to other wireless network protocols.
The Wikipedia article on Wi-Fi also doesn’t really address the ‘why’ of the question and Google searches lead to cascades of pages confirming the potency of Wi-Fi’s energy drain and/or the suggestion to turn it off as much as possible in order to extend your battery life. In other words, I still don’t have a clue.
Is there a relatively simple explanation available?
My WAG is that it the device keeps searching for a signal. I do know that my phone runs out of power much faster if I am traveling through a dead zone. My e-reader uses much more power unless I put it in airplane mode. And that is when it never leaves my bedroom where the signal is strong.
Hmmm. But, if that were the case, it seems a simple software fix would go a long way to avoiding the problem, no? For example, putting it to ‘sleep’ if there’s been no activity for some period.
This is correct - WiFi connections are maintained by a continuous handshaking process that consumes antenna power (and eats up some of the theoretical maximum transmission bandwidth) - I believe it’s because the protocol was designed to mimic a physical, plugged-in cable - so either end has to be always ready to respond to the other.
This is possible, but only by dropping the connection (and many smartphones do this - my Windows phone has an option to configure WiFi to drop X minutes after screen lock) - but then the connection has to be re-established when it is required, and that is the same as the normal connection process - takes a few seconds to establish.
If it’s connected for most of the day (i.e. you’re at home or somewhere else where you have an established WiFi connection), then it will be consuming a measurable portion of the battery life of a smartphone.
If it’s just switched on, but not connected (when you’re out and about, and all it’s doing is finding networks, but not connecting to them), it hardly makes a difference.
I mean, if you’re surfing the web over 3G and surfing the web over Wi-Fi, 3G is going to use a lot more power. W/MB is higher for 3G.
But maybe you guys are talking about inactive connections - why leaving Wi-Fi on uses so much power, compared to 3G, when both aren’t transmitting? That sounds likely.
Wi-Fi uses hardly any power on my phone. When I am not connected to a Wi-Fi network and am using my phone over 3G it burns power. The only times I have run into problems is when I haven’t realised that I am not using Wi-Fi and am using the 3G network for all my data. So I now reularly check that I have a Wi-Fi signal when one is vailable,
This is a great example of when it is important to distinguish between positioning and navigation. Many Americans use the term “GPS” to mean “the software that tells me how to get where I’m going”, which the Brits refer to as “SatNav”.
In my experience, having the GPS on – i.e., the software that listens to the satellites and calculates current location – does not use much power at all, even while watching myself move around in a mapping program. But if I use that mapping program to navigate somewhere, then it uses power a bit faster than my car charger can replenish it. (Which is why I always carry a fully-charged spare battery in my pocket, for my Samsung Note II. Nyah, nyah, you iPhone users with non-replaceable batteries!) The navigation program is constantly updating the map, and frequently looking at the traffic ahead, and occasionally recalculating new routes (in hopes of announcing “I just found a new route that will save you 5 minutes!”).
Without the navigation, I suspect that the recalculation of the location, and redraw of the map, is done much less frequently. In fact, if I were the programmer, I’d key the frequency to the map’s scale. At a half-mile per inch, there’s no need to redraw the map every five seconds, but at one block per two inches you’d better refresh it a few times per second.
I don’t mean either. I mean the GPS radio in the device - the actual radio hardware that listens to satellites. This potentially consumes a lot of power, especially if it keeps seeking satellites all the time (OK, that bit happens in software - probably OS or driver) - and ramping up the antenna gain to maintain this when you’re indoors etc.
But if you have Wi-Fi turned on and you’re not getting a signal, your Wi-Fi is using more power because the phone is constantly looking for a Wi-Fi signal, and it ramps up the power to look for weaker signals. If you keep Wi-Fi turned off unless you know there’s a network available you’ll find your power consumption while using 3G will go down.
I also have to question the premise of the OP a bit. Is there really a huge consumption difference, or is it more a matter of “If battery life is a serious concern, turn off crap you don’t need to help extend it, with WiFi being the most obvious example.”
That is true, but I just rebooted my phone because it lost 4G. Looking for 4G and not finding it consumed a lot more power than looking for wifi and not finding it ever did.
In both cases not being connected consumes more power than being connected, but 4G was worse.
