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The Telecom Digest for October 11, 2011
Volume 30 : Issue 257 : "text" Format
====== 30 years of TELECOM Digest -- Founded August 21, 1981 ======
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Telecom and VOIP (Voice over Internet Protocol) Digest for the
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are definitely unwelcome.
We must fight spam for the same reason we fight crime: not because we
are naive enough to believe that we will ever stamp it out, but because
we do not want the kind of world that results when no one stands
against crime. - Geoffrey Welsh
See the bottom of this issue for subscription and archive details
and the name of our lawyer, and other stuff of interest.
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Date: Sun, 9 Oct 2011 21:23:56 -0700 (PDT)
From: Jimmy <JimmyGeldburg@mailinator.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Incoming Calls: Charged?
Message-ID: <b2e78548-2341-41f1-b2f6-74afbee6aaf3@h10g2000yqd.googlegroups.com>
"John Levine" <jo...@iecc.com> wrote:
> Back when mobile phones were new, US users would get all worked up
> about incoming calls, not list their numbers, and tell people never
> ever to call them unless it was really REALLY important.
Have you ever heard of someone listing their cell number in the
phone book? If it's even possible, it would be an add-on service that
costs extra.
Jimmy
Date: Sun, 9 Oct 2011 22:31:06 -0700 (PDT)
From: HAncock4 <withheld@invalid.telecom-digest.org>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Incoming Calls: Charged?
Message-ID: <75c6e623-caae-410a-b63f-f44534514e5c@z19g2000vby.googlegroups.com>
On Oct 9, 10:57 pm, tlvp <mPiOsUcB.EtLlL...@att.net> wrote:
> heh-heh ... you think that's an option, John, but really, an
> unanswered call will just transfer to your voice mail box (unless
> you've succeeded in turning off forward-to-voice-mail on no-answer),
> costing you both the minutes the incoming call is active and
> the minutes for the new outgoing (nominally from your handset)
> call to the voicemail box.
I don't believe my Verizon cell phone charges me any minutes when a
call is forwarded to voice mail.
For myself, whenever possible, I access my voice mail from a landline,
not my cell phone. I do this (a) not to use up minutes, and (b)
because it's easier to work the menu from a conventional desk phone
than my cell phone.
Date: Sun, 9 Oct 2011 23:53:19 -0400
From: "Bob Goudreau" <BobGoudreau@nc.rr.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Apple Launches iPhone 4S, iOS 5 & iCloud
Message-ID: <608BFA5B28D84819A13043322DDABA6B@meng.lab.emc.com>
Scott Dorsey wrote:
>Bob Goudreau <BobGoudreau@nc.rr.com> wrote:
>>
>>I think you've misread this feature, and thereby missed its point. The
>>screen on an iPhone is not 1080p (think of it as "640p", since the display
>>>resolution is 640 by 960). Rather, the new model's camera is able to
>>capture video at 1080p resolution. You can then play such video back on a
>>1080p device (such as an HDTV or a computer monitor) at that device's
>>highest resolution.
>>
>>We've come a long way since Super 8.
>
>Have we? A 6mm wide frame of Kodachrome 40 gives you about 800 resolvable
>lines (what video people call line pairs), or about the same resolution as
>1600p would.
Well, I was referring more to the ease of making a video. Now you can whip
your phone out of your pocket and immediately start shooting video whenever
you see a tornado bearing down on town, cop beating motorist, demonstrators
protesting against tyrant, etc. It's safe to say that not many people back
in the day had a ubiquitous video camera that could be exploited in such
spontaneous situations.
At any rate, I'm not sure all video conversion professionals would agree
with the numbers you give above.
http://www.videoconversionexperts.com/Film_to_DVD/Choose_Process.htm,
for example, seems to say that Super 8 yields more lines than SDTV but
less than HDTV.
Bob Goudreau
Cary, NC
Date: Sun, 9 Oct 2011 21:22:12 -0700 (PDT)
From: Jimmy <JimmyGeldburg@mailinator.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Incoming Calls: Charged?
Message-ID: <a643f80b-b4c3-4211-ba49-183b2282a234@g23g2000vbz.googlegroups.com>
tlvp <mPiOsUcB.EtLlL...@att.net> wrote:
> an unanswered call will just transfer to your voice mail box (unless
> you've succeeded in turning off forward-to-voice-mail on no-answer),
> costing you both the minutes the incoming call is active and
> the minutes for the new outgoing (nominally from your handset)
> call to the voicemail box.
Are you sure about that? I didn't think minutes got used up when
someone is leaving a voice mail.
It wouldn't make sense, for several reasons. The call isn't actually
being transmitted over a cell tower. And the recipient would have no
control over the length of the call -- a malicious person could use up
someone else's minutes by leaving very long messages over and over
again.
Jimmy
***** Moderator's Note *****
The poster's From address goes to a service which offers "throwaway"
email addresses. Jimmy might not see email sent to it in the future.
Bill Horne
Moderator
Date: Mon, 10 Oct 2011 15:05:24 +0000 (UTC)
From: David Scheidt <dscheidt@panix.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Incoming Calls: Charged?
Message-ID: <j6v1jk$e9h$1@reader1.panix.com>
Jimmy <JimmyGeldburg@mailinator.com> wrote:
:tlvp <mPiOsUcB.EtLlL...@att.net> wrote:
:> an unanswered call will just transfer to your voice mail box (unless
:> you've succeeded in turning off forward-to-voice-mail on no-answer),
:> costing you both the minutes the incoming call is active and
:> the minutes for the new outgoing (nominally from your handset)
:> call to the voicemail box.
:Are you sure about that? I didn't think minutes got used up when
:someone is leaving a voice mail.
:It wouldn't make sense, for several reasons. The call isn't actually
:being transmitted over a cell tower. And the recipient would have no
Why would that matter to the cell phone company? Their purpose is to bill
customers, not to provide service. Charging for not providing a service
is right in line with their current practices. However, I'm not sure if
anyone still charges for leaving messages or not. It used to be common,
ten years and more ago, but abuse issues were a problem. AT&T no longer
charges for retreiving messages from your handset (well, they bill them
as mobile-to-mobile, which are generally free, unless you're roaming.)
Verizon seems to, at least most of the time. (There are inconsistencies
in their billing practices.) I don't know what other company's
practices are.
--
sig 96
Date: Mon, 10 Oct 2011 13:19:47 -0400
From: Matt Simpson <net-news69@jmatt.net>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Incoming Calls: Charged?
Message-ID: <net-news69-61978E.13194710102011@news.toast.net>
In article <2ll8sht9zfo1.myvr1k178lnm.dlg@40tude.net>,
tlvp <mPiOsUcB.EtLlLvEp@att.net> wrote:
> heh-heh ... you think that's an option, John, but really, an
> unanswered call will just transfer to your voice mail box (unless
> you've succeeded in turning off forward-to-voice-mail on no-answer),
> costing you both the minutes the incoming call is active and
> the minutes for the new outgoing (nominally from your handset)
> call to the voicemail box.
As others have pointed out, incoming calls to voice mail usually don't
cost minutes. I have a 100-minute monthly allowance, with no free
nights/weekends, and no free mobile to mobile, and I have never been
charged minutes when people leave voice mail. If you're being charged
for incoming voice mail messages, you're probably in a very small
minority.
I used to get charged for minutes when I called voice mail from my
mobile to retrieve messages. As others have pointed out, retrieving
messages from a landline is one way around that. Now that I have an
iPhone, I don't even have to worry about that. Retrieving voice mail
uses my unlimited data bytes, not my very limited voice minutes.
Date: Mon, 10 Oct 2011 14:57:01 -0400
From: Monty Solomon <monty@roscom.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Steve Jobs: How to live before you die
Message-ID: <p0624089ecab8ec638862@[10.0.1.9]>
Steve Jobs: How to live before you die
Steve Jobs' 2005 Stanford Commencement Address
http://www.ted.com/talks/steve_jobs_how_to_live_before_you_die.html
Steve Jobs: Stanford commencement address, June 2005
In 2005, a year after he was first diagnosed with cancer, Apple CEO
Steve Jobs made a candid speech to graduating students at Stanford
University. Here we reproduce that text, and our columnist John
Naughton provides his own annotations.
http://www.guardian.co.uk/technology/2011/oct/09/steve-jobs-stanford-commencement-address
Date: Mon, 10 Oct 2011 20:02:00 +0000 (UTC)
From: tls@panix.com (Thor Lancelot Simon)
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Lightsquared being called to account
Message-ID: <j6vivn$oua$1@reader1.panix.com>
In article <CAFY5RQ+enZmZaSrKW=rb5-_gfsGT9CxY6N59dJFk8VJ2C=-kDg@mail.gmail.com>,
Bill Horne <bill@horneQRM.net> wrote:
>
>AFAICT, LightSquared is hoping to create a house of cards that will stand
>just long enough to get past the current election cycle, and then commence
>ruining the most accurate source of location and time information available
>to consumers. I hope they fail.
I disagree. The frequencies in question have been allocated to LightSquared for
a long time. Why should they suffer because consumer GPS manufacturers
decided to save a few bucks on proper signal filtering?
--
Thor Lancelot Simon tls@panix.com
"All of my opinions are consistent, but I cannot present them all
at once." -Jean-Jacques Rousseau, On The Social Contract
Date: Mon, 10 Oct 2011 19:29:12 -0400
From: Bill Horne <bilL@horneQRM.net>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Lightsquared being called to account
Message-ID: <20111010232912.GA22875@telecom.csail.mit.edu>
On Mon, Oct 10, 2011 at 08:02:00PM +0000, Thor Lancelot Simon wrote:
> In article <CAFY5RQ+enZmZaSrKW=rb5-_gfsGT9CxY6N59dJFk8VJ2C=-kDg@mail.gmail.com>,
> Bill Horne <bill@horneQRM.net> wrote:
> >
> >AFAICT, LightSquared is hoping to create a house of cards that will stand
> >just long enough to get past the current election cycle, and then commence
> >ruining the most accurate source of location and time information available
> >to consumers. I hope they fail.
>
> I disagree. The frequencies in question have been allocated to LightSquared for
> a long time. Why should they suffer because consumer GPS manufacturers
> decided to save a few bucks on proper signal filtering?
As I understand it, Lightsquared was originally assigned those
frequencies for use in a different, satellite-based service, and has
now lobbied the FCC to change the assignments for use with a
terrestrial application.
"Proper signal filtering" depends on having proper signals to filter,
and the square-law rule comes into play: a transmitter one mile away
has FOUR times more signal strength than one two miles away, all other
things being equal. That means that GPS satellites, in orbit hundreds
of miles above the earth and running on solar cells with severe power
demands and low transmitted output, can't compete with a terrestrial
service, no matter how "proper" the signal filtering of GPS receivers
is.
In any case, even if the original assignments to Lightsquared had been
for the service and power level that the firm is now attempting to
have approved, I would argue that the GPS band deserves better
protection than some idiot at the FCC was willing to provide for:
consumer-grade receivers, in moving vehicles, trying to receive
simultaneous radio signals from a constellation of GPS satellites
need all the help they can get.
This whole thing stinks of inside influence, double-dealing, and
political sleight-of-hand. I smell a rat, and I think that this is a
back-room deal in the making.
YMMV.
--
Bill Horne
(Remove QRM from my email address to write to me directly)
"Soldiers fight, and soldiers die
Soldiers live to wonder why
Semper fi, fee foe fum
Look out peacetime, here we come"
- John Gorka
Date: Tue, 11 Oct 2011 00:12:02 +0000 (UTC)
From: David Scheidt <dscheidt@panix.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Lightsquared being called to account
Message-ID: <j701ki$ep0$2@reader1.panix.com>
Bill Horne <bilL@horneqrm.net> wrote:
:On Mon, Oct 10, 2011 at 08:02:00PM +0000, Thor Lancelot Simon wrote:
:> In article <CAFY5RQ+enZmZaSrKW=rb5-_gfsGT9CxY6N59dJFk8VJ2C=-kDg@mail.gmail.com>,
:> Bill Horne <bill@horneQRM.net> wrote:
:> >
:> >AFAICT, LightSquared is hoping to create a house of cards that will stand
:> >just long enough to get past the current election cycle, and then commence
:> >ruining the most accurate source of location and time information available
:> >to consumers. I hope they fail.
:>
:> I disagree. The frequencies in question have been allocated to LightSquared for
:> a long time. Why should they suffer because consumer GPS manufacturers
:> decided to save a few bucks on proper signal filtering?
:As I understand it, Lightsquared was originally assigned those
:frequencies for use in a different, satellite-based service, and has
:now lobbied the FCC to change the assignments for use with a
:terrestrial application.
:"Proper signal filtering" depends on having proper signals to filter,
:and the square-law rule comes into play: a transmitter one mile away
:has FOUR times more signal strength than one two miles away, all other
:things being equal. That means that GPS satellites, in orbit hundreds
:of miles above the earth and running on solar cells with severe power
:demands and low transmitted output, can't compete with a terrestrial
:service, no matter how "proper" the signal filtering of GPS receivers
:is.
:In any case, even if the original assignments to Lightsquared had been
:for the service and power level that the firm is now attempting to
:have approved, I would argue that the GPS band deserves better
:protection than some idiot at the FCC was willing to provide for:
:consumer-grade receivers, in moving vehicles, trying to receive
:simultaneous radio signals from a constellation of GPS satellites
:need all the help they can get.
:This whole thing stinks of inside influence, double-dealing, and
:political sleight-of-hand. I smell a rat, and I think that this is a
:back-room deal in the making.
Yeah, on the part of makers of consumer grade junk who have, for
a decade, been making stuff that would not operate properly when an
event they knew was coming (lightsquared turning on terrestrial
service, which was approved in 2000 or 2001) came. Now, of course,
they're whinning "We made and sold junk we knew was junk, because we
knew we could count on our friends at the FCC and in congress to bail
us out and protect the entrenched rent seeking of the existing
wireless industry." Except, of course, they're not honest enough to
say that, and instead spread fear among people who don't have a strong
enough techincal background to know they're full of it, and are
protecting economic interests at the expense of the public's.
--
sig 108
Date: Mon, 10 Oct 2011 18:16:42 -0700
From: Thad Floryan <thad@thadlabs.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Lightsquared being called to account
Message-ID: <4E9398FA.60702@thadlabs.com>
On 10/10/2011 4:29 PM, Bill Horne wrote:
> On Mon, Oct 10, 2011 at 08:02:00PM +0000, Thor Lancelot Simon wrote:
>> In article <CAFY5RQ+enZmZaSrKW=rb5-_gfsGT9CxY6N59dJFk8VJ2C=-kDg@mail.gmail.com>,
>> Bill Horne <bill@horneQRM.net> wrote:
>>> AFAICT, LightSquared is hoping to create a house of cards that will stand
>>> just long enough to get past the current election cycle, and then commence
>>> ruining the most accurate source of location and time information available
>>> to consumers. I hope they fail.
>> I disagree. The frequencies in question have been allocated to LightSquared for
>> a long time. Why should they suffer because consumer GPS manufacturers
>> decided to save a few bucks on proper signal filtering?
>
> As I understand it, Lightsquared was originally assigned those
> frequencies for use in a different, satellite-based service, and has
> now lobbied the FCC to change the assignments for use with a
> terrestrial application.
>
> "Proper signal filtering" depends on having proper signals to filter,
> and the square-law rule comes into play: a transmitter one mile away
> has FOUR times more signal strength than one two miles away, all other
> things being equal. That means that GPS satellites, in orbit hundreds
> of miles above the earth and running on solar cells with severe power
> demands and low transmitted output, can't compete with a terrestrial
> service, no matter how "proper" the signal filtering of GPS receivers
> is.
>
> In any case, even if the original assignments to Lightsquared had been
> for the service and power level that the firm is now attempting to
> have approved, I would argue that the GPS band deserves better
> protection than some idiot at the FCC was willing to provide for:
> consumer-grade receivers, in moving vehicles, trying to receive
> simultaneous radio signals from a constellation of GPS satellites
> need all the help they can get.
>
> This whole thing stinks of inside influence, double-dealing, and
> political sleight-of-hand. I smell a rat, and I think that this is a
> back-room deal in the making.
And you would be 100% correct as we can read here:
http://nlpc.org/stories/2011/09/16/lightsquared-scandal-explodes
" Allegations that we first made in February about White House
" political favors for a company called LightSquared are starting
" to get the attention they deserve.
"
" LightSquared is owned by the Harbinger Capital hedge fund, headed
" by billionaire investor Phil Falcone. He visited the White House
" and made large donations to the Democratic Senatorial Campaign
" Committee. Soon after, the Federal Communications
" Commission (FCC) granted LightSquared a highly unusual waiver
" that allows the company to build out a national 4G wireless
" network on the cheap.
"
" The deal has been criticized not only for its 'pay to play'
" appearance but also because the LightSquared network would
" interfere with the part of the wireless spectrum that is used by
" Global Positioning Systems (GPS).
"
" On its iwatch news website, the Center for Public Integrity
" published a blockbuster special report on Wednesday confirming
" that LightSquared "pressed its case... at times citing its
" fundraising for Democratic causes and President Obama..." The
" report by Fred Schulte and John Aloysius Farrell is based on 300
" emails obtained by the authors under the Freedom of Information
" Act. The emails contradict repeated denials by LightSquared and
" the White House that the campaign contributions were related to
" the FCC action.
"
" Meanwhile, the White House is facing accusations that it tried to
" pressure an Air Force general to change his testimony on the GPS
" interference issue. According to the Washington Post:
"
" GOP staffers of the House strategic forces subcommittee accused
" the White House of trying to influence the testimony of an Air
" Force general who was speaking about the project's potential to
" interfere with the Global Positioning System, the satellite
" network relied on by the military and private industry. The
" staffers said Gen. William Shelton revealed in an earlier closed
" meeting that the White House pressured him to include language in
" his testimony Thursday supporting LightSquared's venture.
"
" The accusation that Shelton was pressured came at the same time
" the White House was attempting to explain its role in the
" awarding of $500-million loan guarantee to now-bankrupt Solyndra,
" in which billionaire Obama bundler George Kaiser was a major
" investor.
"
" Media coverage and commentary has been extensive, typified by
" this observation by Chris Stirewalt writing on FoxNews.com:
"
" First there was Fast and Furious, then there was Solyndra and
" now there is LightSquared -- three high-level scandals that
" involve allegations of cover-ups inside the Obama administration.
"
" For a president who is already dragging an unpopular agenda
" and low marks on his handling of the economy along the campaign
" trail, this scandal troika is seriously bad news.
"
" On February 2, NLPC first made the allegation that Falcone's
" campaign contributions helped grease the skids for the FCC action
" in a letter to House Committee on Oversight and Government
" Reform.
Additional info:
Obama Invested in Company That Got Sweet Deal From FCC
http://nlpc.org/stories/2011/03/25/obama-invested-company-got-sweet-deal-fcc
Will FCC's Political Favor for LightSquared Result in GPS Interference
http://nlpc.org/stories/2011/03/01/will-fccs-political-favor-harbinger-hedge-fund-result-gps-interference
Letter alleging Falcone's campaign contributions
http://nlpc.org/stories/2011/02/02/did-harbinger-hedge-fund-buy-influence-white-house-probe-asked-fcc-spectrum-givea
http://www.iwatchnews.org/2011/09/14/6458/emails-show-wireless-firms-communications-white-house-campaign-donations-were-made
http://www.washingtonpost.com/business/economy/gop-lawmakers-scrutinizelightsquared/2011/09/15/gIQAFK1iVK_story.html
http://www.washingtonpost.com/blogs/post-tech/post/lightsquared-interferes-with-gpsreport/2011/06/30/AGXhyAsH_blog.html
http://www.foxnews.com/politics/2011/09/16/scandals-undercut-obama-re-election-message/#ixzz1Y7xpiCxm
***** Moderator's Note *****
BTW, there's more than one telecom angle to this debacle: Verizon, (and
I assume other LECs) makes extensive use of GPS to provide Stratum II+
timing information for synchronization of DS3 and other DS-* rate signals
between offices. If the synchronization goes away, so does the digital
data.
GPS-driven clocks have, of course, "holdover" capability to compensate
for brief outages, but they are NOT, in and of themselves, Stratum II
timing sources, so any prolonged outage will cause them to lose
synchronization and cause failures in digital data and digitized voice
transmission.
If Lightsquared's use of "satellite" spectrum for terrestrial
transmitters causes the GPS network receivers to become unreliable,
then Verizon (and, possibly, other LECs) will have to replace the
GPS-based timing sources with Stratum I atomic clocks, resulting in
millions of dollars spent for engineering effort, hardware expense,
transition planning, training, and implementation.
Bill Horne
Moderator
Date: Tue, 11 Oct 2011 04:07:22 +0000 (UTC)
From: tls@panix.com (Thor Lancelot Simon)
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Lightsquared being called to account
Message-ID: <j70fdq$raa$1@reader1.panix.com>
In article <20111010232912.GA22875@telecom.csail.mit.edu>,
Bill Horne <bilL@horneQRM.net> wrote:
>
>"Proper signal filtering" depends on having proper signals to filter,
>and the square-law rule comes into play: a transmitter one mile away
>has FOUR times more signal strength than one two miles away, all other
>things being equal. That means that GPS satellites, in orbit hundreds
>of miles above the earth and running on solar cells with severe power
>demands and low transmitted output, can't compete with a terrestrial
>service, no matter how "proper" the signal filtering of GPS receivers
>is.
You know that Lightsquared is not actually using the GPS frequencies,
or even their duly allocated frequency band closest to them, right?
(Lightsquared voluntarily agreed to not use this band in their
initial deployment, IIUC).
What the consumer GPS manufacturers are whining about are harmonics
they certainly could have arranged to filter -- but chose not to,
because it saved some bucks, likely both on the analog and DSP
ends of the implementation.
--
Thor Lancelot Simon tls@panix.com
"All of my opinions are consistent, but I cannot present them all
at once." -Jean-Jacques Rousseau, On The Social Contract
Date: Tue, 11 Oct 2011 02:08:53 -0400
From: Bill Horne <bill@horneQRM.net>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Lightsquared being called to account
Message-ID: <20111011060853.GA16205@telecom.csail.mit.edu>
On Tue, Oct 11, 2011 at 04:07:22AM +0000, Thor Lancelot Simon wrote:
> In article <20111010232912.GA22875@telecom.csail.mit.edu>,
> Bill Horne <bilL@horneQRM.net> wrote:
> >
> >"Proper signal filtering" depends on having proper signals to filter,
> >and the square-law rule comes into play: a transmitter one mile away
> >has FOUR times more signal strength than one two miles away, all other
> >things being equal. That means that GPS satellites, in orbit hundreds
> >of miles above the earth and running on solar cells with severe power
> >demands and low transmitted output, can't compete with a terrestrial
> >service, no matter how "proper" the signal filtering of GPS receivers
> >is.
>
> You know that Lightsquared is not actually using the GPS frequencies,
> or even their duly allocated frequency band closest to them, right?
> (Lightsquared voluntarily agreed to not use this band in their
> initial deployment, IIUC).
>
> What the consumer GPS manufacturers are whining about are harmonics
> they certainly could have arranged to filter -- but chose not to,
> because it saved some bucks, likely both on the analog and DSP
> ends of the implementation.
OK, please bear with me: I'm going to have to delve into my radio
background, both as a ham operator and a commercial radio technician,
to explain the issues here.
This isn't a problem with harmonics: harmonic radiation from
transmitters can't be filtered by a receiver, since it occurs at
multiples of the assigned transmitter frequency and represents a
separate, distinct radio frequency signal. Harmonics are either
filtered out at the transmitter (by using a low-pass filter) or the
problem is obviated by careful choice of oscillator frequency,
transmitter design, mixing frequency selection, and other factors
which have nothing to do with the receivers that the transmitter's
harmonic radiation might cause interference to.
The issue in the Lightsquared case is a combination of something
called intermodulation and another problem known as overloading. I
don't claim to be an RF engineer, but I hope I can explain the basic
issue well enough to make my concerns more clear.
I'll quote from a document shown at
http://www.gpsworld.com/gnss-system/signal-processing/lightsquared-jamming-report-11030
... in which the United States GPS Industry Council quotes a report
issued by Garmin Corp. which states -
This application proposes to fundamentally change the usage of
the L band 1 spectrum (1525 - 1559 MHz) from MSS (very low power,
space to earth signals) to fixed, high power, terrestrial
broadband service. The L band 1 is adjacent to the GPS band (1559
- 1610 MHz) where the GPS and other satellite based
radionavigation systems operate.
Here's the basic problem with overloading: a receiver has to have
enough "dynamic range" to filter out strong signals adjacent to the
desired signal they are made to use, but must also be sensitive enough
to properly receive the desired signal under adverse conditions - and
it's hard to get more adverse than receiving a satellite signal in a
moving vehicle. The energy being sent from Lightsquared's transmitters
will overload GPS receivers in the immediate vicinity, since it's
nearly impossible to design a receiver which is both sensitive (on the
GPS band) and which has enough dynamic range to reject signals on
adjacents frequencies which are, by reason of the fact that they are
coming from transmittes hundreds of miles closer to the receiver than
the GPS satellites, nearly impossible to suppress.
There is also a problem called "intermodulation": radio frequency
signals can combine to provide new signals that are equal to either
the sum of, or the difference between, the two original signals. That
means that Lightsquared's transmitters, sending signals in the 1525 to
1559 MHz range, can combine with signals from nearby taxicab, police,
fire, amateur, fixed, and Citizens Band transmitters to produce new
signals which are in the GPS band, and will thus cause interference
to GPS receivers as if a low-power transmitter had been deliberately
tuned to the GPS band in order to jam GPS reception. It is impossible
to filter this interference out at the receiver, because it would
occur IN the GPS band.
It does us no good to say these frequencies were "duly allocated" to
Lightsquared: it's just too big a problem to be solved by refering to
a rulebook. Let's leave aside the fact that FCC rules might have
allowed terrestrial use of satellite frequencies in special
circumstances: there is no satellite in orbit, and Lightsquared
doesn't want to pay for one. The company is trying to drive a bus
through a regulatory wormhole which is intended to allow companies
that have paid for satellites to augment their coverage in certain
limited circumstances, and too many businesses and people can get hurt
to allow it to continue.
Bill
--
Bill Horne
(Remove QRM from my email address to write me directly)
"Memories, they can't be bought
They can't be won at carnivals for free
It took me years to get those souvenirs
And I don't know how they slipped away from me"
- John Prine
Date: Mon, 10 Oct 2011 20:21:32 -0400
From: Monty Solomon <monty@roscom.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Free Texts Pose Threat to Carriers
Message-ID: <p062408a2cab91412d553@[10.0.1.9]>
Free Texts Pose Threat to Carriers
By JENNA WORTHAM
October 9, 2011
At a time when e-mail and many other forms of electronic
communication are essentially free, wireless carriers are still
charging as much as 20 cents to send a text message to a phone, and
another 20 cents to receive it.
Paying so much to transmit a handful of words is starting to look as
antiquated as buying stamps.
There are now a growing number of ways to bypass text-message charges
using an Internet connection - much as Skype allows people to make
calls without relying on a traditional telephone line. If these
services catch on in a big way, analysts say, they could take a big
bite out of the profits that text messages generate for wireless
carriers.
On Wednesday, Apple plans to introduce a new service called iMessage,
which could quickly become the biggest fish in this pond. The service
lets iPhone owners send messages with text, photos and video to other
iPhone owners over a Wi-Fi or cellular data connection. The service,
part of an update to Apple's iOS mobile operating system, will
automatically handle messages sent between iPhone, iPad and iPod
Touch users who have upgraded to the latest software.
...
http://www.nytimes.com/2011/10/10/technology/paying-to-text-is-becoming-passe-companies-fret.html
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