Posted on 07/03/2010 1:34:14 PM PDT by Swordmaker
I'm speaking from an end user, not a designer perspective. Yes, I was using caving as the extreme indicator. Office buildings and the average user location have nowhere near the resistance to transmission signals as a cave. In larger buildings, like malls and high rises, blocking and interference with transmission signals is a known issue. On 9/11, one of the reasons so many firefighters were killed was because radio transmissions inside the WTC were not received due to building interference. A mayday was called, but many firefighters did not receive the transmission. Of course, the massive overload in all transmission channels from cell phones, television remote units, fire, ems, police and state and federal agencies also contributed. Most modern fire codes now include provisions requiring buildings exceeding a specific size to install internal building repeaters that mimic the tower repeaters located around the municipality for emergency services.
In cave rescue, transmission issues underground have been known for a long time. I am not aware of any receiving device that will work wirelessly in a cave. The issue starts as soon as you are deep enough in the cave that you lose line of sight with the exterior, although transmission may extend a little deeper in solid rock caves where transmissions will extend a little deeper as transmissions bounce, but are usually not good for more than twenty feet inside a cave. Our solution was to use an old army line wire radio with about a mile of wire and the handsets that would clamp onto the wire at any location to make a connection. The wire was on a spool, and the insulation was self healing so you didn't damage it when you attached the hand set.
If you know of a method of actually transmitting through rock, freep mail me. We can be millionaires.
As to our original discussion, I understand that we're talking about a guppy and a whale when talking about the differences between covering an antenna with your hand and transmitting inside a cave, but your response was extremely interesting, and ran me off on this tangent.
??? Look how finicky digital broadcast TV is. Obstruction -- no signal. Movement -- no signal. Antenna tuned to wrong band -- no signal (actually, inability to lock on or stay locked on in each of those cases). Lots of people who got a passable analog signal in marginal reception areas get no lock on ever with digital.
i need a couple of minutes.
1. In the struggle for battery life, they cut down the phone’s transmitter power by going digital.
2. In the struggle for channel capacity, they went digital.
Consequences:
1. Fadeouts and dropped calls became, if anything, more common.
2. Background noise at the talking end and fadeouts in the channel rendered the received speech unintelligible.
Of course, the marketing departments performed heroic feats in their panegyrics to the “New! Digital!! ModernUpToTheMinuteTechnology!!!” system.
I was worried they’d mess it up, but so far they’ve been as good as the originals.
what you said is indicate of a high’beam pulse.
this is what we call electommagnetici interference
I can say, there is NO WAY I’m returning my iPhone 4! I love it.
My brother is a regional store representative for AT&T and even he was on a waiting list. He got his phone by accident when he visited one of his stores and they just happened to have one in stock.
His first phone call was to me, and I couldn’t hear him talking. I called him back and it worked the second time. =)
By the way Radio Shack..a new iPhone dealer, is offering a 100 to 200 buck trade-in for 3g and 3gs that are in good shape. I'm trading mine in and grandfathering my unlimited data plan (30 bucks a mo) into a new contract for the total of 100 bucks ((16G).
By the way new data contracts are no longer unlimited with big overage charges if you exceed the limit.
I may have failed to make clear that I was referring to the switch from analog to digital, years ago. Nothing specific to an iPhone.
I think I’ll amplify on my previous mini-rant. Before I do, I should reiterate that I’m discussing the transition from analog to digital cellphones that took place beginning almost twenty years ago. Systems have evolved substantially since then, in order to handle the newer digital services to handheld devices like the iPhone; however, the same basic engineering principles continue to apply, although improved design methodologies (and maybe even a dose of humility on the part of system designers!) may have improved things for the customer.
Now, onward.
Two decades ago or so, the system engineers preparing to switch the various cellular services from analog to digital had at their disposal all manner of mathematical models and computer simulations of system performance.
These models included extensive simulations of propagation effects, including antenna performance of a nominal handheld phone, and also such issues as multipath, co-channel and adjacent channel interference, and many other factors.
The models had many virtual knobs which the engineers could tweak. A couple of the most important ones were bandwidth/data rate and transmit power (both in the phone and in the cell site).
The evaluations of the performance of the models also had numerous dimensions.
For the future customer, the most important of these were the frequency of dropped calls and the intelligibility of speech as received over the simulated system in a “standard” phone.
[[By the way, the telephone industry has well-defined procedures for the rating of speech intelligibilty using carefully prepared experiments with panels of human listeners. Methods have been in place for generations.]]
For the service provider, the most important criteria were how many simultaneous connections could be supported at a time at a cell site given the FCC assigned channels; how wide an area could a cell site be made to cover (where phone traffic was sparse); and how much standby or talk time could a “standard” phone be expected to achieve.
Managment wanted the engineers to maximize capacity in a given bandwidth to minimize the capital cost of a talk channel at a cell site, and to maximize the site’s potential for expansion of the number of channels. A contradictory desire was to maximize battery life of a typical handheld phone (by minimizing the power of its transmitter). So the engineers set to work studying tradeoffs and running many variations through their models (by twiddling all those chromium knobs in the software). At the same time, they had a minimum standard for the frequency of dropped calls and for acceptable voice quality. To improve either of these meant a tradeoff against the phone’s battery life and the number of calls a cell site could handle.
IMHO, they set the quality standards too low; probably because their models contained optimistic assumptions, but possibly also under pressure from managment to maximize channel capacity.
End of rant.
“Webb and a colleague decided to run their own tests, which he admits were brief and subjective. “This was a non-scientific test, but it was done by two engineers who deal with RF devices for a living,” he says.”
LOL ... A brief, subjective, non-scientific test
Nothing to see here folks, move along
BTW -
This article has a statement from the same guy calling the iphone antenna design “…that’s one’s of the dumbest things I’ve ever seen,”
http://www.pcmag.com/article2/0,2817,2365650,00.asp
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