Menneisyys wrote a very complete article about Mobile devices and power comsumption

Never before published tips and comparative benchmarks!

These tests show that…* The “hacked” Widcomm BT stack doesn’t at all consume more power than the (default) Microsoft BT stack on the x51v.
* You don’t need to disable the IrDA unit in your PDA in Settings/System/Power/Beam (or Connections/Beam) – keeping it enabled doesn’t consume almost any power in current Pocket PC’s.
* The preferred way of local, peer-to-peer networking connections, Bluetooth PAN, increases power consumption a bit, especially if you take into account its periodic power consumption peaks, which may be related to some kind of a networking housekeeping and may be, probably, decreased by tweaking the networking parameters. The additional power consumption of BT PAN is still very low compared to peer-to-peer Wi-Fi connections. The latter never make use of any kind of adaptive power saving mode in P2P connections, even if you enable power saving (a Pocket Loox 720 example screenshot here and a x51v screenshot here of doing this).
* Pocket PC PDA’s don’t reduce their transmit power even when the connected Pocket PC’s are adjacent to each other (and, therefore, they all sense the signal power more than sufficient as can be seen for example in this screenshot). An example of this can be seen in this screenshot, taken on the PL720 and (in the first half) showing a(n idle) P2P Wi-Fi connection. During it, I’ve taken the other PDA (the HTC Wizard) the PL720 was connected to via Wi-Fi p2p from the close vicinity (very good signal level) to far away, behind walls (poor signal level) to test whether there is any power transmission fine-tuning. As can be seen, there isn’t – the Wi-Fi unit in the Pocket Loox still used the same 288 mA as in the case of excellent circumstances (that is, the two Pocket PC’s being next to one another). Incidentally, the ~500 mA section in the screenshot shows the added ~200 mA battery load of playing the excellent multiplayer game Gold Rush in multiplayer mode. As can be seen, playing action games using Wi-Fi P2P will certainly kill the battery even on a device like the Pocket Loox 720, not to speak about much more power-hungry ones like the Dell Axim x51v. With the latter, some 700 mA would have been used at 520 MHz (and even more in automatic/turbo mode), which is really a lot.

The “hacked” Widcomm BT stack doesn’t at all consume more power than the (default) Microsoft BT stack on the x51v. You don’t need to – keeping it enabled doesn’t consume almost any power in current Pocket PC’s. The preferred way of local, peer-to-peer networking connections, Bluetooth PAN, increases power consumption a bit, especially if you take into account its periodic power consumption peaks, which may be related to some kind of a networking housekeeping and may be, probably, decreased by tweaking the networking parameters. The additional power consumption of BT PAN is still very low compared to peer-to-peer Wi-Fi connections. The latter never make use of any kind of adaptive power saving mode in P2P connections, even if you enable power saving (a Pocket Loox 720 example screenshot and a x51v screenshot of doing this). Pocket PC PDA’s don’t reduce their transmit power even when the connected Pocket PC’s are adjacent to each other (and, therefore, they all sense the signal power more than sufficient as can be seen for example ). An example of this can be seen , taken on the PL720 and (in the first half) showing a(n idle) P2P Wi-Fi connection. During it, I’ve taken the other PDA (the HTC Wizard) the PL720 was connected to via Wi-Fi p2p from the close vicinity (very good signal level) to far away, behind walls (poor signal level) to test whether there is any power transmission fine-tuning. As can be seen, there isn’t – the Wi-Fi unit in the Pocket Loox still used the same 288 mA as in the case of excellent circumstances (that is, the two Pocket PC’s being next to one another). Incidentally, the ~500 mA section in the screenshot shows the added ~200 mA battery load of playing the excellent multiplayer game in multiplayer mode. As can be seen, playing action games using Wi-Fi P2P will certainly kill the battery even on a device like the Pocket Loox 720, not to speak about much more power-hungry ones like the Dell Axim x51v. With the latter, some 700 mA would have been used at 520 MHz (and even more in automatic/turbo mode), which is really a lot.Hardware manufacturers/Wi-Fi driver writers, you should add dynamic adaptation into varying environmental conditions – for example, changing the transmit power and, therefore, reducing the battery load whenever possible!

Note that it’s only with manually reducable Wi-Fi power (see the Wi-Fi power slider in the Wizard – see this screenshot) that you can have any effect on the power consumption of built-in Wi-Fi units. It works, therefore, the same way as the Class I / Class II (software) switch in the only Pocket PC PDA that (officially) supports long-distance Class I Bluetooth, the old Fujitsu-Siemens Pocket Loox 600….”

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