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Everyone is saying that Wi-Fi is more power-efficient than 3G on smartphones.

But, I don't think so, because two radios are turned on at the same time, the 3G radio is still active when enabling Wi-Fi

There is some reliable proof to support this?

Sklivvz
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Magnetic_dud
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    Please add a few links for someone making the claim :) – nico Apr 04 '13 at 16:31
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    You don't HAVE to have your 3G turned on when WiFi is on. Obviously having both on is going to drain more power than WiFi alone. – DJClayworth Apr 04 '13 at 16:58
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    @DJClayworth: certain phones (mine for sure) turn off the 3G when they get a WiFi signal – nico Apr 04 '13 at 17:29
  • Really? That must be extremely irritating if you are making a call and wander into a WiFi hotspot. – DJClayworth Apr 04 '13 at 17:49
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    @DJClayworth: well, oversimplifying a bit, 3G is just 2G + 3G data connection. For normal voice call you just use 2G GSM. – vartec Apr 04 '13 at 18:28
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    The issue isn't dominated by the connection method when the connection is idle. It is the transmission of data that matters. On WiFi most non-voice data will go WiFi: the question that matters is whether transmitting that *same* data via 3G would use more power. "Power efficiency" is ambiguous if you don't define what the power is being used to do. A better question would be "which uses more power to transmit, say, 1MB of data?" – matt_black Apr 04 '13 at 20:26
  • @matt_black: on 3G there is a huge difference between 1MB in chunks of 1KB every few seconds and 1MB in one request. – vartec Apr 04 '13 at 23:11
  • your claim is based on false assumptions. You're stating that 3G alone is using less power than 3G+WiFi at the same time, but the question is whether 3G uses less power than does WiFi alone... – jwenting Apr 05 '13 at 06:17

1 Answers1

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Yes, WiFi is significantly more efficient, as the protocol is completely different. Once association with access point is established, WiFi only uses energy for actual transmission of data. On the other hand 3G remains in high-power state even after transmission is done.

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source: "Energy Consumption in Mobile Phones: A Measurement Study and Implications for Network Applications" Niranjan Balasubramanian, Aruna Balasubramanian, Arun Venkataramani, Department of Computer Science, University of Massachusetts Amherst

It's also worth mentioning, that WiFi has legal limit of power output of 200mW (0.2W), while 3G devices legal power limit is 2W.

vartec
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  • The reason for WiFI being more efficient __in transferring data__ is __not__ that it switches to a low power mode faster than a 3G connection does after transmission. That fact only speaks to __tower search__ being very expensive. – bobobobo Apr 04 '13 at 20:24
  • I think the UMass Amherst link and graph provides the right answer. Most people notice that their battery drains faster with Wi-Fi enabled just because both radios are still on. My Verizon 4G phone drains really fast when I'm in 4G range even without WiFi enabled. With WiFi turned off and in 3G only range, I have the longest standby time. Another reason NOT to use WiFi when you are away from home or office is security. You do not want your phone wandering into any random WiFi networks that may be setup to do harm to your data. I turn off my WiFi radio when I leave the house or office for secur – mdSeuss Apr 04 '13 at 16:50
  • @bobobobo: you're going into details **why** it stays in high-power state – vartec Apr 05 '13 at 08:41