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Topic # 65138 30-Jul-2010 00:55
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Dialling in *#*#INFO#*#* allows you to go to phone settings, and set the phone radio mode to GSM (PRL).
PRL = Preferred Roaming List.

Apparently this causes the phone to only search your carriers frequencies rather than all, improving battery life.
Just made the change with XT, not sure if it'll change anything due to XT being a WCDMA only network, but we'll see.

Info and explanation here. Many users are reporting massive improvements over default.

Not all though claim better battery - can we get some testing going on here for NZ Carriers?
This sounded pretty promising so I decided to try it out myself. Each day I get up at 6am, unplug my phone and (eventually) go to work. When I get there, I set my phone on my desk next to the window and don't really touch it until my shift is over.

I previously had mine set to "WCDMA preferred". By the time I got home from work (about 5pm) my battery would be between 85-90%.

Yesterday I decided to give "GSM Auto (PRL)" a try. When I got home, my battery level as at 62%. In case it was a fluke, today when I woke up, I restarted my phone and then did my normal thing. My phone was at 66% when I got home. Looks like it's back to "WCDMA Preferred" for me...

I'm on T-Mobile and work in SW Portland, OR in case anyone was curious.

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  Reply # 359119 30-Jul-2010 01:11
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More info on this, what its doing and why:
From this xda thread:
Had to hear it from the horses mouth, I called up HTC's tech support. I
asked what was the difference between WCDMA preferred and GSM AUTO PRL.
The gentleman I spoke to told me that they both have lots in common
and that the only difference is that WCDMA preferred will favor 3G and
GSM AUTO PRL will favor EDGE.

He continued to tell me that WCDMA preferred needs to reach a low
threshold to go straight into 3g from edge. GSM AUTO PRL has a higher
threshold, or higher standard has to be met (db of 3g signal) before it
will go into 3G.

He mentioned that gsm auto prl will save the user a bit more power
because it wont force the phone to continuasly hunt for a stronger
signal. Typically this option gives our n1's a weaker signal and slower
data speed. But he said it depends on our network in our city.

I also verified this information with t-mobiles tech support. They were
a bit vague though. But they did mention that WCDA preferred will
prefer 3g and that gsm auto prl is its complete opposite and will only
prefer 3g if the signal is strong enough.

What do you guys think? Does this make sense?!?

Originally Posted by icebike

What that does Roger, is tells your phone to connect using EDGE, and
obtain a Preferred Roaming List (PRL) from the tower, and THEN switch to
3G when a data channel is required (which in the N1, is pretty much
always because people are checking mail etc all the time).

WCDMA preferred has the phone try to find 3G directly. This takes more power until a connection is established.

You can verify this in the 4636 display, below the Run Ping Test button.
You will see the Network Type say EDGE, then, after a bit, it will
switch to HSPDA.

If your phone is near your computer speakers, you will hear edge chatter
as it obtains its Preferred Roaming List. You may periodically hear a
lot of EDGE chatter if you have nothing requiring a data channel
running, because it might drop to edge and stay there for unexplained

Depending on your towers and service availability, you may see no
difference in this at all. I live in a strong 3G area, and this does not
help me at all. In fringe 3G areas or in 3G areas where there are a lot
of 3G phones (cities, near schools, etc) this will help quite a bit.

In Edge only areas it saves a lot of battery by not searching for HSPDA when it does not exist.

Note: I also see something of a speed test hit on GSM (PRL), but this may be just the speed test app doing odd things.

Sounds like it will have no effect on XT?

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  Reply # 359123 30-Jul-2010 01:32
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Triple post due to the edit button liking to disappear.

Random thought - wouldn't wcdma only on xt give the best battery life as it can ignore all gsm frequencies? Can anyone comment on this logic?

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