Re: 2.0 and Radio Impacts/battery efficiency

Roberto is right!

the problem with multiple TCP connections is that the server can send 
packets on several connections.

Low power to full power will always be the case no matter who send data 
on (or closes) the connection, server or client.
On top of this, when the server send data on (or closes) the connection 
the system needs to page the device,
send out a signal on the common control channel in order to make the 
device re-establish its radio channel, these are in many systems quite 
loaded.
When the TCP close is initiated from the device the device does not need 
to be paged.

/Sal

-- 
Salvatore Loreto, PhD
www.sloreto.com



On 4/13/12 9:27 AM, Roberto Peon wrote:
> The most obvious reason would be that the server sends a packet which 
> requires the radio to awaken (e.g. because the tcp stack emits a 
> packet back).
> -=R
>
> On Thu, Apr 12, 2012 at 8:23 AM, Zhong Yu <zhong.j.yu@gmail.com 
> <mailto:zhong.j.yu@gmail.com>> wrote:
>
>     I don't get it. Cerntainly a new connection requires an extra round
>     trip which drains extra power, but only for the duration of the round
>     trip. Why is it "extremely expensive"?
>
>     The article says
>
>        "Every time you create a new network connection, the radio
>     transitions to the full power state."
>
>     which I don't think implies that,
>
>        "If you reuse a network connection, the radio does NOT necessarily
>     transition to the full power state."
>
>     To compress all network activities(including FIN-FIN) into a shorter
>     time span, the article event suggests that
>
>        "so it's also good practice to close your connections when they
>     aren't in use"
>
>
>     On Thu, Apr 12, 2012 at 3:52 AM, Salvatore Loreto
>     <salvatore.loreto@ericsson.com
>     <mailto:salvatore.loreto@ericsson.com>> wrote:
>     > Hi there,
>     >
>     > here a good read about "Optimizing Downloads for Efficient
>     Network Access"
>     >
>     http://developer.android.com/training/efficient-downloads/efficient-network-access.html
>     >
>     > the major points are
>     >
>     > 1) reducing the number of connections is a MUST as each new network
>     > connection is extremely expensive
>     > from a Radio/Battery prospective
>     >
>     > It is also worth to add that the server-initiated closing of  idle
>     > connection is also something to avoid.
>     > So if the client keeps the connection open longer, then the
>     specification
>     > has to mandate servers to keep
>     > the connection open for very long.
>     >
>     >
>     > 2) the ping frequency is also very important:
>     > "An app that pings the server every 20 seconds, just to
>     acknowledge that the
>     > app is running and visible to the user, will keep the radio
>     powered on
>     > indefinitely"
>     >
>     >
>     > 3) also Prefetching data need some consideration from the radio
>     prospective
>     > as Prefetching data (on a wireless connection)
>     >  may cost money but for sure has a cost from a battery prospective
>     >
>     >
>     > cheers
>     > Sal
>     >
>     > --
>     > Salvatore Loreto, PhD
>     > www.sloreto.com <http://www.sloreto.com>
>
>