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FCC Says No to Mobile Phones on Airplane
GayBliss writes "CNN is reporting that the FCC has decided to keep a rule in place that would ban mobile phone usage on airplanes. The FAA has a similar ban, but for different reasons. 'In an order released Tuesday, the agency noted that "insufficient technical information" was available on whether airborne cell phone calls would jam networks below. [...]Unlike the Federal Aviation Administration, which bans the use of cell phones and other portable electronic devices for fear they will interfere with navigational and communications systems, the FCC's concern is interference with other cell phone signals on the ground.'"
Aircraft communications and navigation typically take place at VHF frequencies, between 108-132MHz. Voice communication is almost always AM in this frequency range.
Cell phones ~824-894MHz (traditional cellular) ~1900MHz (PCS - Sprint, Verizon, et al) - In the United States, anyway.
Regardless, the issue isn't interference with Avionics and communication, but the implications it would have on the cell network with one handset being able to reach (interfere with) hundreds of towers at one time.
"[H]earing only one side of a conversation makes it more noticeable and intrusive." (Sorry, no full article without paying, unless you're at an .edu with access, but the abstract pretty much sums it up.)
I agree with the researchers' conclusions. A full conversation usually stays in the background for me. Hearing one side is very jarring and I can't ignore it. I wish cellphones would be banned on airplanes, period, even when on the ground; the key difference between an airplane and a train/a building/the street is that in an airplane you can't get away.
Perhaps "rediculous", but, yes, that is the valid concern.
One of the ways that cellular providers reuse the spectrum is by dividing the landscape into . . . "cells". There are arrays of antennas in these cells that communicate with the instruments in the area. Additional spectral efficiency is gained by subdividing the cells and only using the antenna array pointing in your direction to communicate with your phone. The landscape is modeled as a 2-d environment for these purposes. The cell networks take all this landscape into account when they deploy their systems. If you want to use an additional component of altitude to the mix, you'd need different antenna arrays and you'd need to re-layout the whole mess. For these reasons, the FCC does not allow cell phone use in planes, helicopters, balloons, etc. As you say, it's a straight shot from an airplane to cell towers below -- including towers that you couldn't "see" (radio-wise) if you were on the ground directly below.
I am not a crackpot.
Alternative Theory
The official crash report does not mention cell phone activity as a primary cause of the crash, and instead attributes it to pilot error.[9] However, a separate investigation into the cause of the crash showed that the autopilot system malfunctioned at the same time that a passenger's cell phone on board the plane received an SMS message and another received a call. After this information was made public, a number of countries that had previously been reluctant to do so outlawed cell phones on flights (including Switzerland).[10][11][12] Some passengers on any given flight are likely to forget to turn off their mobile devices[13], therefore it is unlikely this explanation is a likely cause.
("Crossair Flight 498." Wikipedia, The Free Encyclopedia. 8 Mar 2007, 18:16 UTC. Wikimedia Foundation, Inc. 4 Apr 2007 <http://en.wikipedia.org/w/index.php?title=Crossai r_Flight_498&oldid=113623260>.)
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Well, a little understanding of how the cell phone networks work would help here... The number of channels (frequencies, if you will) available to a single cell site is limited. Let's say that Verizon is assigned (by the FCC) sufficient bandwidth to have 100 simultaneous calls in the city of Phoenix. Now, they could (like the Television stations) place a gigantic antenna on the top of the biggest mountain in the city, thus covering an area of, say, 100 miles radius. They would only be able to have 100 customers talking at a time; not a very good situation. So, Verizon gets smart. They put 1000 antennas around the city, on very short towers so each one covers, say, 1 mile. Now each of these antennnas can support 100 customers talking at a time, and Verizon can now have 100,000 customers talking simultaneously. With some overlap on the towers, Verizon can tell that you're driving towards the edge of the coverage of one tower, and seamlessly tell your phone to change channels and start talking to a new tower. Ever had your call dropped while driving along? Probably because the tower you were coming into range of was full, or there was a software glitch in the handoff to the new tower. Now, let's assume you are flying over Phoenix, talking to the wifey about what the rugrats did today. The channel that you're using cannot be reused by any of the 1000 cell towers in the city, because all of the cell towers have a clear line-of-sight to your airplane. You have just taken up cell phone bandwidth equivalent to 1000 customers. That's why the FCC is concerned. /frank
And the worms ate into his brain.