Interesting story from The Consumerist:
Recall an earlier article of mine (from July 2007):
I chose a technically incorrect term “Wi-Fi” because that is what most people were talking about back then, but the subject was more generally about “wireless broadband”.
It is not that NYC isn’t ready for the iPhone. It is that NYC was the first to bump up against the inherent physical limitation of wireless broadband. There is no number of towers that will be able to accommodate hundreds or thousands of people within a small vicinity all expecting reasonable wireless bandwidth. There is a little thing called the Heisenberg uncertainty principle that no amount of marketing or engineering will be able to get around.
Edit: Here is a copy of a comment below in response to the questions:
I’ll try to write a separate article, but this is about the physics of waves.
Unlike finance, the physics of electromagnetic waves is well understood. Computer programs can be written to model radio waves to many digits of accuracy.
The behavior of a wave depends on its frequency. At low frequencies, radio waves are kind of like molasses. They can ooze around corners and through buildings. That is why the (relatively low frequency) 7-800 MHz range is so valuable for cell applications.
In recent years, the frequencies of cell phones and even more recently, smart phones, has increased from a little over 1 GHz to over 2.5 GHz (and beyond).
(Note: Your microwave oven operates at the same frequency as most smart phones now.)
As frequencies increase, the waves start acting more like laser beams. They no longer ooze around corners. You start to get “shadows” or dead spots with no signal. It becomes more difficult for the signals to penetrate walls etc. These problems get worse the higher you go in frequency.
An extreme case is an actual laser. Here, it becomes more difficult to distinguish the wave dynamics from particle dynamics. Like in Star Wars, the laser beams can bounce around like particles.
So we have two extremes: low frequency molasses waves and high frequency laser beams. As bandwidth demands increase, we begin moving the dial away from molasses (where we have good wireless signals) to laser beams (where we have dark spots, shadows, with no signal, etc).
There are many clever modulation tricks that delay the inevitable, but the basic rule is that you cannot defeat Heisenberg. This is an imprecise (but I hope effective) analogy that relates to the fact that at lower frequency (and longer wavelength, i.e. larger “effective size” of the wave), you have more certainty as to “where the photon is” (because it is coming from a relatively smaller antenna) you have more uncertainty about where it goes, i.e. it goes everywhere like a good wireless signal should. At higher frequency (and shorter wavelength), the antenna is relatively larger (compared to the wave) so we know less precisely where the photons are, hence we have more certainty as to where they are going, i.e. in a straight line instead of around a corner, which is undesirable for a wireless signal.
This physical fact does not deter marketing people. You can easily set up a demonstration on a van driving down the highway at 65 mph with an antenna mounted on top downloading web content at 100-1000 mbps. Don’t fall for this trick! They are essentially shining a laser beam at the van and tracking it down the road. Ask them to do the same demo with 1000 vans stuck in LA traffic. Forget about it.
I’d guestimate that a practical limit for the available wireless bandwidth in the air in a vicinity of say a couple square NYC blocks would be 1000 mbps. This is the TOTAL BANDWIDTH AVAILABLE FOR EVERYONE WITHIN A FEW NYC BLOCKS. So now divide 1000 mpbs by the number of people downloading stuff wirelessly taking into consideration highrise buildings, etc. That is probably a decent estimate of what the long term limits of wireless broadband would be.
So you can see, for the early adopters, wireless bandwidth is great! “Geez! This wireless is faster than my ethernet!” But once you start adding some real traffic, say 100 or 1000s of people all downloading stuff wireless within a small vicinity and you can imagine that we will easily bump up against the basic physical limitations as communicated by my good friend James Clerk Maxwell.