question about cell phones

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Just curious: when a cell phone is in standby, I think it swaps
packets with the nearest cell site, just to keep in touch. How often
does that happen?

I could measure that myself, with a small antenna and a fast scope,
but I don't have any gear handy up here in the woods. My phone drains
its battery fast up here, presumably because it has to transmit harder
to stay in touch.



--  

John Larkin   Highland Technology, Inc   trk

jlarkin att highlandtechnology dott com
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Re: question about cell phones
On 23/11/2017 17:24, John Larkin wrote:
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Often enough that what you describe happens in poor signal areas and it  
screams at maximum RF output power too. If you have a battery use and  
signal level plot on your phone (Android does) it is helpful.

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Simplest solution is put it in airplane mode when out of reach of a base  
station and if you have Wifi then tell it to use that instead (or you  
can in the UK get microcells that plug into your ethernet feed).

--  
Regards,
Martin Brown

Re: question about cell phones
On Thu, 23 Nov 2017 09:24:22 -0800, John Larkin

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My Razr polls the tower once every few minutes. You could try placing
the unterminated input of a audio amp next to the phone and listen.
Sometimes I hear the exchange on my computer speakers.

Cheers

Re: question about cell phones
On Thursday, November 23, 2017 at 12:24:36 PM UTC-5, John Larkin wrote:
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The proper response would be for me to direct you to the 3GPP Standards, bu
t it's too much to digest, even for me, and I've been in this biz 30 years.
  :)

Maybe :(  I'm not sure!!

The answer is highly dependent on which technology the phone is camped on.
3G (UMTS, etc..) will be different from 4G (LTE), will be different from..  
say Sprint's TDD network at 2.5 GHz.

But in general, the guiding principle is to conserve battery life.

On LTE for example, the handset (UE) only "checks-in" (with, for example, a
 Node-B cellular base station) as often as is required to maintain network  
synchronization, in case it receives a call. (The exact timing depends on h
ow "well" you can maintain synchronization given a host of variables not di
scussed here.

The above is further muddied if multiple Node-B's (or equiv.) are present (
which is usually the case unless you are off in the boonies, and even there
...).  In this case, the UE may switch Node-B's (sometimes back-and-forth e
specially if the carrier's OSS system parameters are jacked or there's some
 localized interference impairing the channel), and thus (re-)transmit to r
eset certain attachment variables and/or maybe also to maintain network syn
c, often at a lower power level since the reason for the change in the firs
t place probably (but not necessarily always) because the new Node-B is clo
ser and/or providing better signal, etc...  The carrier's network traffic c
ontrol schemes also play a part in this.

When you first turn on an LTE phone, there is a well-specified process the  
handset performs to locate available networks, (hopefully) synchronize with
 one, and then (if authorized) attempt to access that network via one of a  
small handful of network attachment procedures.  During the attachment phas
e, each side (Node-B and UE) inform each other of their respective identiti
es, capabilities, security levels, etc..  

I know the reply does not answer your question directly.
But unless you're in a active call (data session, etc..), you're unlikely t
o find any hard, fixed periodic transmission "check-in" from a modern cellp
hone.

To your last point:
Interference in the uplink (UE to tower) will definitely drain your battery
!!
Some handsets offer "test mode" screens, which may allow you to inspect var
iables such as output power, timing advance (which can generally tell you h
ow distant the Node-B is), etc...  Google your handset brand and "test mode
".  Maybe you'll get lucky?


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Re: question about cell phones
On Thursday, 23 November 2017 19:21:16 UTC, mpm  wrote:

The key point is that all modern mobile phone systems use adaptive
transmitter power control, so they avoid using more transmit power
than necessary.  Therefore you should place the phone is the position
where it has the best signal strength and try to orient it optimally
once you have found that position.  It is sure to be somewhere  
inconveniently high up.

John


Re: question about cell phones
On Thursday, November 23, 2017 at 6:18:13 PM UTC-5, snipped-for-privacy@gmail.com wrote:
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I generally agree with John's additional information.
I would just add that it's not always about signal strength.
Signal quality is actually more important -- though the two measurements are typically positively correlated.

Shorthand variables / acronyms:
RSSI - Signal strength  
RSRP - Reference Signal Received Power (in LTE)
RSRQ - Reference Signal Received Quality  (similar to a Carrier-to-Interference Ratio measurement)

The Reference Signal is actually a set of OFDM symbols transmitted in specific resource blocks in the downlink.  It is not continuously broadcast.

You can have five bars of crap on your RSSI, and not be able to make a call.
And, in RF-quiet surroundings, have no RSSI bars and still have crystal-clear communications.  

Re: question about cell phones
On 23/11/2017 23:18, snipped-for-privacy@gmail.com wrote:
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The problem arises when the base station signal is almost at the range  
limit or beyond. The thing gets into an ET phone home loop and flattens  
the battery very rapidly. You can see it when you go into a good Faraday  
cage that blocks all RF with your phone still on or into a not spot.

There may be an option to show signal strength and battery decline in  
the power management graph - at least on Android phones. Never figured  
out how to get that sort of useful info out of an iPhone.

There are plenty of cell phone not spots in my area where deep valleys  
block mobile phone signals almost completely. Battery life suffers to no  
good purpose if you don't put it into airplane mode when there is no signal.

--  
Regards,
Martin Brown

Re: question about cell phones
On Thu, 23 Nov 2017 09:24:22 -0800, John Larkin

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Dunno.  It varies with service provider and protocol.  If your phone
has checked into the network, once every 15 or 30 minutes.  If you
don't have a decent signal, it will try to check in far more often.  I
can fire up the spectrum analyzer, somehow kill all RF to my cell
phone, and measure the transmit interval, but not tonite.  Maybe
tomorrow after I recover from turkey overdose.

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Yep.  Someone cut the fiber optic cable going to Santa Cruz a few
years ago, and most of the cellular providers decided that the
approprate response was to turn off all the cell sites.  My LG VX8300
antique phone went from full charge to zero in under 3 hours.
Normally, it can go for two to three days.

As I vaguely recall, you have an equally ancient Casio G'zOne Boulder
3G CDMA phone on Verizon, and are in the vicinity of Auburn CA.
Methinks that the foothills area is serviced by Sprint, with a mutual
roaming agreement with Verizon.  If you're having trouble checking in
via Sprint, try loading the latest PRL (preferred roaming list):
<https://www.verizonwireless.com/support/preferred-roaming-list-update-faqs/
See item #2.  Make sure you have the best possible signal while it's
updating.  If it complains or belches errors, give up and do it when
you get home.  If you upgraded to a 4G LTE phone, don't bother as the
PRL updates are automatic with LTE.





--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: question about cell phones
On 11/23/2017 7:52 PM, Jeff Liebermann wrote:
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The cell companies decided local calls were of no importance just  
because the fiber trunk to outside areas went down?

Re: question about cell phones
On Fri, 24 Nov 2017 07:27:08 -0800, Taxed and Spent

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Sorry, I wasn't very clear.  By "appropriate response", I more like
programmed response to a loss of backhaul communications, not
intentionally pully the plug.

The "Great Fiber Cut" was in April 2009:
<http://www.mercurynews.com/2009/04/09/san-jose-police-sabotage-caused-phone-outage-in-santa-clara-santa-cruz-counties/
The main fiber trunks to the area were down for about 24 hrs.  It was
a mess.

There was some question as to why AT&T and Verizon went off the air,
while Sprint and others remained intermittently functional.  Several
theories were offered, including that the carriers intentionally
turned off the cell sites.  That's unlikely because they would need
access to their fiber backbone from their NOC (network operations
centers) to control the cell sites and that wasn't possible.  So, the
cell sites weren't intentionally turned off.  There might have been
some kind of back door, but I could find no evidence of such a
feature.

A more likely possibility is that the cell sites had a "dead mans
switch" or "time out timer" which turned off the transmitters in the
event of a major fault or loss of control after a specified time.  It
was suggested that there may be an FCC requirement for such a feature,
but at the time, I found nothing in Part 22.  I tried to clarify what
happened by talking to various cellular insiders, but never received a
good explanation.

Incidentally, in Oct 2017, we had a local brush fire that cut a major
AT&T backbone.
<http://www.santacruztechbeat.com/2017/10/18/santa-cruz-fights-fire-fiber/
From the lessons learned after 2009, the outages were minimal.

--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: question about cell phones
On Friday, November 24, 2017 at 10:27:14 AM UTC-5, Taxed and Spent wrote:

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It doesn't work that way.
The cell towers are just nodes in the wireless network.
They have a fiber backhaul to the switch.
Without the switch, they really can't do much.

So, you can envision many situations where a perfectly good cell site is idle due to lack of backhaul.   For example, Puerto Rico, post-hurricane.  Even those that survived were offline - mostly due to cut fiber.


Re: question about cell phones



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I'd guess the sites were isolated from Mother, and incompetent
to do anything by their lonesome.  

This is an issue with POTS. Many many areas are served by remote
mux's aka SLC/DCL's alongside the road. The bigger ones may be
a replacement for a town's existing local switch; cheaper to
support, handles everything needed.

But when they lose connectivity to the host switch....

For that reason, WECO/Lucent sold ORM's; Optically connected
Remote Modules, ISTM. These were far more than a Remote, less
than a full 5ESS.  When isolated, they could complete local
calls inc. 911. (And I assume, would divert 911 to local  
destinations as required.)


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A host is a host from coast to snipped-for-privacy@nrk.com
& no one will talk to a host that's close..........................
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Re: question about cell phones
wrote:

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If I'm driving down a highway, the phone would have to be handed off
to another tower every few minutes.  

I'll try to measure it.


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"The Rock." Indestructable. In town, I recharge it less than once a
week. In the mountains, maybe every 2 days.


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That's interesting; I'll try that at home.

I suppose one day I'll have to get a smart phone, but I've broken the
screen of everything but The Rock.

I suppose that people who hold a phone in front of their face 100% of
the time don't break screens. I stuff a phone into my pocket with a
lot of other junk and pull it out a few times a week.


--  

John Larkin   Highland Technology, Inc   trk

jlarkin att highlandtechnology dott com
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Re: question about cell phones
Den fredag den 24. november 2017 kl. 17.17.01 UTC+1 skrev John Larkin:
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I keep my phone in one pocket and all the other junk like keys in another  


Re: question about cell phones
On Fri, 24 Nov 2017 08:30:21 -0800 (PST), Lasse Langwadt Christensen

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Give up a pocket? Then where would I keep my wallet, keys, my backup
keys [1], five pens, magnifier, swiss army knife, kleenex, flashlight,
loose change, and my notebook?

[1] the Audi will lock you out, even with the keys in the ignition.


--  

John Larkin   Highland Technology, Inc   trk

jlarkin att highlandtechnology dott com
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Re: question about cell phones

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with a smartphone you can drop the flashlight, magnifier and notebook

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you can probably get that disabled by anyone with a programming interface

Re: question about cell phones



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My old basic Nokia handset has a flashlight - never bothered using it.  


Re: question about cell phones
On Sat, 25 Nov 2017 11:10:24 -0800 (PST), Lasse Langwadt Christensen


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And what's with the pen?
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Using the smart phone.  ;-)

My truck has buttons on the door to unlock it.  I don't think it'll
lock with keys in the ignition, either.


Re: question about cell phones
On Friday, November 24, 2017 at 11:17:01 AM UTC-5, John Larkin wrote:
...>  
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If it's still offered in your area / provider...
Check out the Kyoceramobile Brigadier.

https://www.kyoceramobile.com/brigadier/

Not the best audio, memory, or feature sets, but built like a brick sh!t house. :)

I was very, very tempted to get one of these, but couldn't get past the relatively low on-board memory (compared to other offerings at the time).


Re: question about cell phones
wrote:

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That looks good, in case the Rock ever dies. I don't need memory; I
just use my phone as a phone.


--  

John Larkin   Highland Technology, Inc   trk

jlarkin att highlandtechnology dott com
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