30 Years of the Digest ... founded August 21, 1981
The Telecom Digest for October 13, 2011
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Date: Wed, 12 Oct 2011 08:13:53 -0400 From: Monty Solomon <email@example.com> To: firstname.lastname@example.org. Subject: iPhone 4S Meta-Review: It's the Same, But Like Better Message-ID: <email@example.com> iPhone 4S Meta-Review: It's the Same, But Like Better By Casey Chan Gizmodo Oct 11, 2011 The first reviews are out for the iPhone 4S and they're a lot like we expected, which is to say, exactly what we expected: the same phone on the outside but much better on the inside. It's faster, has a much better camera and packs a golden bullet with Siri. ... http://gizmodo.com/iphone-4s-review/
Date: Wed, 12 Oct 2011 08:13:53 -0400 From: Monty Solomon <firstname.lastname@example.org> To: email@example.com. Subject: New iPhone Conceals Sheer Magic Message-ID: <firstname.lastname@example.org> New iPhone Conceals Sheer Magic By DAVID POGUE October 11, 2011 What's in a name? A lot, apparently. Apple's new iPhone is called the iPhone 4S. But what people really wanted was the iPhone 5. The rumors online had predicted the second coming - or, rather, the fifth coming. It would be wedge-shaped! It would be completely transparent! It would clean your basement, pick you up at the airport and eliminate unsightly blemishes! Instead, what showed up was a new iPhone that looks just like the last one: black or white, glass front and back, silver metal band around the sides. And on paper, at least, the new phone does only four new things. ... http://www.nytimes.com/2011/10/12/technology/personaltech/iphone-4s-conceals-sheer-magic-pogue.html ***** Moderator's Note ***** Thank you, David. Bill Horne Moderator
Date: Wed, 12 Oct 2011 23:05:44 +1100 From: David Clayton <email@example.com> To: firstname.lastname@example.org. Subject: Re: Lightsquared being called to account Message-ID: <email@example.com> On Tue, 11 Oct 2011 19:11:33 -0400, Gary wrote: > ***** Moderator's Note ***** >> >> I don't know what other military devices or aircraft use GPS, but I >> think it's reasonable to assume that their designers took account of >> the possibility of jamming. It's a military use, after all. Just like the TCP/IP protocol takes care of the possibility of misuse, DOS attacks etc., after all, that was created for the military to be able to work even in the event of a nuclear attack, wasn't it? > > I'm fairly certain that most of our military uses GPS, from grunts on > the ground to ships to probably anything in the air (other than shells, > at least for now :-). After all, GPS was developed to serve our > military's needs. > > What most people don't know (it's not a secret), is that there is a > second GPS band used only by the military. Using two bands allows the > receivers to compensate for variations in the ionosphere allowing for a > more accurate measurement of propagation delay from the the satellites. > The end result is military receivers are much more accurate than > civilian receivers (just how much is, of course, a secret). The second > channel is encrypted. > > Because of the second channel as well as minimal concerns about the cost > to build a good product, I'm quite certain that it is much harder to jam > a military GPS receiver than a $100 civilian receiver. ........... I still don't believe that it's a good idea to require the manufacture of transmitters using frequencies near the ones the GPS devices use and have them available for commercial use. I still remember how easy it was to "hack" CB radios to use channels way off the official ones, and that was back in the 1970's! The basics of any radio system - including GPS - is the requirement of a minimum S/N ratio to work reliably, having powerful transmitters in the vicinity of devices that have to receive tiny signals from a number of transmitters a long LONG way away to function (no matter how "directional" any antenna system may be) compromises that basic requirement. How long until the bad guys obtain and hack one of these things to directly jam military GPS devices? It will probably be a lot easier to obtain a commercial device than build one yourself. -- Regards, David. David Clayton Melbourne, Victoria, Australia. Knowledge is a measure of how many answers you have, intelligence is a measure of how many questions you have.
Date: Wed, 12 Oct 2011 09:50:06 -0400 From: Telecom Digest Moderator <firstname.lastname@example.org> To: email@example.com. Subject: Re: Lightsquared being called to account Message-ID: <20111012135006.GA8451@telecom.csail.mit.edu> On Wed, Oct 12, 2011 at 11:05:44PM +1100, David Clayton wrote: > On Tue, 11 Oct 2011 19:11:33 -0400, Gary wrote: > > > ***** Moderator's Note ***** > >> > >> I don't know what other military devices or aircraft use GPS, but I > >> think it's reasonable to assume that their designers took account of > >> the possibility of jamming. It's a military use, after all. > > Just like the TCP/IP protocol takes care of the possibility of misuse, DOS > attacks etc., after all, that was created for the military to be able to > work even in the event of a nuclear attack, wasn't it? No, it wasn't. That bit of revisionist history has been around for years, but it's wrong. TCP/IP was designed to make a reliable network out of unreliable links, i.e., to leverage the voice-band data circuits of the 1970's. To accomplish that goal, the design team employed the concept of "store and forward", where each hop in a chain of links could retain packets and retransmit them again and again until the next hop confirmed that it had received a valid copy. That is why there is NO minimum transit time specification in the IP protocol, and that is why VoIP and other near-real-time applications have so many problems with latency: VoIP is only possible now because data links are so reliable now compared to the 1970's. Military networks are all about transit time and hardening assets wherever possible, and TCP/IP doesn't fit in that mold. The "store and forward" concept was applied to email messages, as well: every MTA (Mail Transfer Application) is capable of holding an email until the destination is available, sometimes for days. Although anti-spam measures have limited the capability, it's still available for use. If you want proof that TCP/IP wasn't intended to be a military network, ask yourself why DOS attacks, spam, etc. are possible at all. The answer is that the designers of the Arpanet were academics, NOT military men! Their world view did not include the possibility that someone would break the rules for commercial gain, let alone for sabotage, and no competent military design team would leave such things out of a plan. Bill -- Bill Horne Moderator
Date: Wed, 12 Oct 2011 08:30:04 -0400 From: "Gary" <firstname.lastname@example.org> To: email@example.com. Subject: Re: Lightsquared being called to account Message-ID: <firstname.lastname@example.org> **** Moderator's Note ***** > > Although Loran was still in use during the time I was working on these > sorts of issues at Verizon, it was, IIRC, not accurate enough for the > timing we required. I don't remember specifics, but (again, IIRC) I > think there was too much ambiguity caused by multi-path propagation > for us to adopt Loran. Ah, well: sic transit technology. Actually, with the right receiver, these issues could be mitigated. We used a specially designed Loran-C timing receiver that detected and handled multi-path signals and other noise like lightning (a "little" DSP goes a long way). We tested several sites by manually switching to Loran-C for timing and then monitoring the difference between Loran-C and GPS. Over the course of many days and weeks the difference stayed well within the specs needed to operate the base station. Loran-C was an elegant solution for our system as it provided not only redundancy in timing [but also] redundancy by using very different radio signals. I agree that technology moves on, however I think that Loran-C was shut down before its time. It offered a very valuable complement to GPS. Running at a very different frequency and being a terrestrial based service, it was subject to a very different set of issues that GPS. It was very unlikely that both services could be knocked out at the same time due to weather, jamming, or interference. My understanding is that Loran-C cost about $15 million a year to operate. Yes, our government needs to carefully manage our money, however Loran-C looked to me to be well worth the relatively small cost to the country. I'll stop crying in my beer now. -Gary ***** Moderator's Note ***** First, a clarification: the Loran-A system was retired in 1980, and that's the medium-wave version I mentioned in another note. Gary is writing about Loran-C, and long-wave version that operates at roughly 100 KHz. It's still in use in some parts of the world, but was retired in the U.S. and Canada in 2010. As to cost: I'm not so sure of the $15 Million figure. According to Wikipedia: On 26 February 2009, the U.S. Office of Management and Budget released the first blueprint for the Financial Year 2010 budget. This document identified the LORAN-C system as "outdated", and supported its termination at an estimated savings of $36 million in 2010 and $190 million over five years. Rest at http://en.wikipedia.org/wiki/LORAN Bill Horne Moderator
Date: Wed, 12 Oct 2011 19:51:47 -0400 From: "Gary" <email@example.com> To: firstname.lastname@example.org. Subject: Re: Lightsquared being called to account Message-ID: <email@example.com> ***** Moderator's Note ***** > > As to cost: I'm not so sure of the $15 Million figure. > > According to Wikipedia: > > On 26 February 2009, the U.S. Office of Management and Budget > released the first blueprint for the Financial Year 2010 > budget. This document identified the LORAN-C system as > "outdated", and supported its termination at an estimated savings > of $36 million in 2010 and $190 million over five years. I didn't remember the exact figure; that's why I said "about" $15 million. In government speak, I was very close. :-) Even at $36 million a year, I think Loran-C was a bargain. I'd be amazed if GPS doesn't cost us taxpayers way more. And don't get me started comparing Loran-C to other things our government spends our money on... If it isn't clear, I don't think Loran-C was outdated. I believe it was a great complement to GPS that provided a redundant timing and location service. But the OMB didn't ask me. -Gary
Date: Wed, 12 Oct 2011 10:48:40 -0400 From: Bill Horne <bill@horneQRM.net> To: firstname.lastname@example.org. Subject: AF gen: GPS, LightSquared "Can't coexist" Message-ID: <4E95A8C8.email@example.com> My thanks to Bill Carton for sending in this material from the DODBUZZ website: The boss of Air Force Space Command, Gen. William Shelton, does not want to get any more mixed up in the political imbroglio between the FCC, Republicans, Democrats and the broadband startup LightSquared. His job, he told reporters Tuesday, is to protect the Global Positioning System, and to that end, he reaffirmed at the Air Force Association's trade show that GPS and LightSquared's proposed network "cannot coexist". Simple as that. He said as much during a question and answer session after a speech to the convention and then again to reporters in a press briefing afterwards. In fact, Shelton even picked up a pen and drew a diagram to illustrate how LightSquared's network effectively jams the signal that military GPS receivers need to get their precise timing and location data. Shelton pointed to his diagram and said that even under LightSquared's alternate proposal for its network, which would move its signal farther away from GPS, it would still squelch the ... frequencies that precise receivers use. Read more: http://www.dodbuzz.com/2011/09/20/af-gen-gps-lightsquared-cant-coexist/ And yes, it IS as simple as that. That's the difference between an Air Force Academy graduate and a venture capitalist: one of them can count, and the other thinks that the laws of physics are negotiable. Bill Horne (Remove QRM from my email address to write to me directly) "There's a party down at Cal's Vinnie Charles is out of jail again His Ex's will be there His daughter 'Nita has bought him an easy chair" - John Gorka
Date: Wed, 12 Oct 2011 12:16:29 -0400 From: "Charles Jackson" <firstname.lastname@example.org> To: email@example.com. Subject: Re: Lightsquared being called to account Message-ID: <firstname.lastname@example.org> An earlier message stated: For the benefit of those not familiar with Loran, it was a medium-wave technology which operated in the 160 meter band, just above the frequencies used by AM broadcasting in the U.S. to this day, i.e.,, 1.8 to 2 MHz. Propagation delays, atmospheric phenomena, and lightning all affected the performance of Loran, and those factors, in addition to the extraordinary power levels required for the transmitters, were some of the reasons for it being retired in favor of Inmarsat and GPS. I think the "current" version of Loran transmits at about 100 kHz. See the Wikipedia article or http://www.navcen.uscg.gov/?pageName=loranReference . Chuck ***** Moderator's Note ***** Chuck, thanks for the information. Bill Horne Moderator
Date: Wed, 12 Oct 2011 15:41:16 -0600 From: email@example.com To: firstname.lastname@example.org. Subject: Re: Lightsquared being called to account Message-ID: <email@example.com> > An earlier message stated: > > For the benefit of those not familiar with Loran, it was a > medium-wave technology which operated in the 160 meter band, just > above the frequencies used by AM broadcasting in the U.S. to this > day, i.e.,, 1.8 to 2 MHz. Propagation delays, atmospheric > phenomena, and lightning all affected the performance of Loran, > and those factors, in addition to the extraordinary power levels > required for the transmitters, were some of the reasons for it > being retired in favor of Inmarsat and GPS. > > I think the "current" version of Loran transmits at about 100 kHz. See > the > Wikipedia article or > > http://www.navcen.uscg.gov/?pageName=loranReference > . > > Chuck > > ***** Moderator's Note ***** > > Chuck, thanks for the information. > > Bill Horne > Moderator > > It was my understanding that Loran has been discontinued. Was that information wrong? Fred
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