Power consumption? WiFi vs USB

[Link]

I am too lazy to search this out.

Am I better off battery life wise using the internal wifi chip or a USB Dongle?  I have been carrying a dongle more often as I usually have better connections that are more stable than wifi.

I am sure it has been asked before and I probably forgot the answer.

 

[mcobit]

In my experience, the internal wifi is far less powerconsuming. That is without the powersavingsettings disabled.


If I use a minidongle on the usbport I get about an hour less of usage.

 

[_wb_]

It seems logical that USB dongles consume more, since there is the overhead of, well, USB. But I'm not exactly sure, maybe a recent wifi dongle is sufficiently more efficient than the internal wifi to compensate for that. Only way to find out is measure power consumption, e.g. with my System Info application.

 

[urjaman]

Yeah USB power logically has the disadvantage of the efficiency of the pandora 5V supply  - boosting from battery (2.7 - 4.2V) to 5V. If I needed to guess a certain range I'd say it is 80 - 95%  efficient, propably close to 85%.

And potentially also the WiFi dongle could be doing some power translation eg. USB signal levels are 3.3V and cheap USB things often create that 3.3V with a linear regulator from the 5V (eg. 66% "efficiency" of that power supply), and they might also need other voltages internally since 5V is a bit high for some of the modern stuff - and again if linear regulators are used, relatively much of power is lost... And if the design engineer is thinking that the host has AC power (or relative to usb consumption a huge battery like laptops)... it doesnt look good.

This all compared to the internal wifi operating straight from the battery... You need a really well done dongle to beat the internal wifi in efficiency - but I dont use wifi so I have no personal experience.

 

[Link]

Cool, thank you for the input on this.  Something to keep in mind when you don't know when you'll get to a power source again. 

 

[porg]

WiFi powersaving makes quite a difference !!!

 

I have tested the different power states.

Here are the absolute values (screen on with brightness 17, no BT, no USB, no TVOUT, sysinfo running and logging, WLAN in different modes)

 

Power mW WiFi state -- comment
- 945    WiFi off -- almost identical to WiFi on, powersaving on


- 950    WiFi on, powersaving on,  idle -- only occassional 1000-1600 spikes (beacons, handshakes & such I guess)


-1750    WiFi on, powersaving on,  active -- varies between 940-2300


-1750    WiFi on, powersaving off, idle -- almost identical to powersaving on active !


-2280    WiFi on, powersaving off, active -- quite a consumption

Sysinfo log attached:

 wifi-power-states-commented--20121230-221908.txt

Note: Forum software does not permit file extension CSV. Change TXT to CSV after download.

 

UPDATE: This was the wrong quote, a study on the internal WiFi with/out powersaving. Will quote the correct one below.

 

[porg]

Power consumption internal vs external WiFi:

2) Meanwhile my http://webserver-wired-100mbit.local/bigfile -O /dev/null gives me steady 2.4 MB/s.

d ) wget http://webserver-on-same-wireless-54mbit-network.local/bigfile -O /dev/null gives me stable ~1 MB/s.

3) Power usage of OpenPandora's internal WiFi versus USB WiFi adpapter:

• While active transmissions, the internal WiFi (966 mW) and USB WiFi (900 mW) consume about the same power.
• In idle mode the internal WiFi (30 mW) consumes considerably less, as for external WiFi, both the idle USB-host (160 mW) and the idle USB-WiFi (240 mW) consume more, giving a total of 400 mW for idle USB WiFi.
• While idle operation on the USB WiFi, occasionally there is an increase of 300 mW lasting only very shortly (data link layer, I guess).

Note: How did I get these numbers? I ran sysinfo. Assessed my Pandora's base consumption — 700 mW from using: CPU @ 800 Mhz OPP5, BT/USB/WiFi all off, screen on low brightness, power-LED with brightness 32/256, 2 SDs inside, XFCE window manager, Terminal window (for wget tests), sysinfo showing power tab) — and then created the other situations (enabling internal-WiFi/USB-host, plugging adapter in/out, running WiFi idle/active), and calculated the difference to the previous situation, and considered it as the consumption for this device or activity.