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Re: Operations: where are you going to sit?
On Wed, 6 Dec 2000, Timothy J Salo wrote: > > > Subject: Re: Operations: where are you going to sit? > > From: Michael Shields <[email protected]> > > Date: 07 Dec 2000 00:22:47 +0000 > > [...] > > I think this is based on the same decision process that lead to the > > ban on cellphones in most commercial airplanes -- some unsustantiated > > anecdotes, no testing, and extremely risk-averse executives. > > [...] > > For what it is worth, I believe that the use of cellphones in airplanes > is prohibited by the FCC, not by the FAA. That is, the use of cellphones > in airplanes (in flight) adversely affects the cellphone system. A > cellphone at a high altitude is visible in numerous cells, with conflicts > with the assumption that a cellphone will be heard (more or less) only > in one cell. > > Now, about the use of other radio receivers and transmitters in airplanes... > > More trivia from, > > -tjs > OK folks. Lets get things straight. Cellular (IE analog and digital mobile phones) should, in normal instances, be seen by more than one cell site. In practice, each cell site has a signaling receiver which reports to the MTSO (Mobile Telephone Switching Office) the relative strength in which it is receiving a particular mobile telephone. This is what "hand-offs" are calculated from. If a phone is seen by 5 cell-sites but the site servicing that phone is saying "Help! I'm losing him!", the MTSO initates a transfer to the cell site which has reported that phone with the highest signal strength. Cellular telephony, while magic to some folks, should be simple to those of us who work in the IP routing world. It's "Hot Potato" routing. Just substitute "signal strength" seen by a cell site for "local pref" or "IGP vs EGP" on a router. It's that simple. Back in the olden days, I helped design cellular networks and I never could understand why people couldn't grasp the above concept. Now at least, I have something to compare it to. As for mobilephones at altitude, the phone itself is much more likely to have problems than the cell sites. The cell site will put a "channel" OOS (Out of Serivice) if the scanning receiver for that cell site detects a carrier on one of the "channels" that it uses and there isn't a "Valid" call on being serviced by that site. Anyone who wants further explaination of this concept, my billable rate is currently $280.00 per hour. (Just ask Alltel - They pay this.) --- John Fraizer EnterZone, Inc