On Tue Sep 1 09:09:06 2009, Fabio Forno wrote:
On Mon, Aug 31, 2009 at 10:33 PM, Vincent
BARAT<[email protected]> wrote:
> Additional information regarding battery consuption (in favor of
XMPP):
> according to our tests (using an ammeter), keeping a TCP/IP
socket open DOES
> NOT CONSUME MORE POWER than having none open at all, as long as
there is no
> activity on the socket.
With which phones did you test it and which type of network? I'm
asking because we don't don't have the same experience, in
particular
with 3G phones. Our tests show that TCP with a keepalive is much
better than UDP sockets, but there is still a noticeable reduction
of
battery life (for example with no traffic we are still waiting for
symbian phone able to stay connected for more than 36h over edge,
utms
is worse; in comparison when idle battery lasts a week).
I'd note that "with keepalive" makes all the difference.
A TCP session with no data traffic on it has no packets sent or
received, so should be the same as having the packet data session
live, but no connections over it, at least in principle.
If there are data packets going over, then that means actual
transmissions, which will inevitably cost much more.
We believe
this depends on many factors, density of cells, firmware version of
phone and cells too, since we noticed a considerable improvement in
the last 2years (for example a nokia n95 went from just 12h of
battery
life to more than a day with a simple firmware upgrade).
There's also the structure and behaviour of the mobile operator's IP
network. Orange in the UK dramatically improved over the past few
years, for instance. I've no idea what they did, but they changed
from dropping dormant TCP sessions within a minute or two to keeping
non-silent TCP sessions live for several minutes while the handset
was outside coverage.
So I'm quite willing to believe that on some networks, it's possible
to use no keepalives at all, and get really very good battery life
out of the handset.
(I used to be on Orange - still am, actually - but I'm moving to 3,
so no doubt I'll discover their networks foibles soon enough...)
Dave.
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