"At one of the IETF meetings last year, the 802.11b band was saturated and totally overloaded. It got so bad, many folks simply gave up and plugged their laptops back into an Ethernet cable."
"I wonder how well this would work with a high density of users:
Message 17580980
"In doing so, they say they believe they will ... dodge the growing industry fears of congestion in the unlicensed Wi-Fi radio band"
"How are they dodging congestion? Also, max speed? "
They can't dodge Shannon's laws. No way.
The channel capacity of free space (the ether) depends on max frequency, but _not_ to first order on power. (That is, if everyone just yells louder, nothing changes in the long run. Signal power is important in getting above natural and system noise, but not in getting more channel capacity.)
Just as cellphone systems can be swamped, just as Ethernet cables can be swamped, so, too, can any conference hall or baseball stadium when too many users are competing for the same channel capacity.
"Moving away from the topic of wireless broadband for consumers, what's your thought on the readiness of corporate wireless routers? Last I checked, the distance was too limited and getting through cement was an issue. Are you seeing any change? "
Beats me.
There's work on ultrawideband systems (I'm an early investor in one of them, Aetherwire), but these are not what corporations are now commercially deploying. Maybe in several years. UWB has better penetration of concrete and so on because the signal is being carried at a smear of frequencies, from a few megahertz up to tens of gigahertz. Just as it's very difficult to shield over such a range of frequencies, so, too, is signal propagation very good.
Shannon's Law still cannot be defeated, though.
Installing cables and fibers works by creating separate "spaces," or channels, each of which is limited by tradtional information theory calculations of channel capacity. Which is why the best combination of systems involves a mix of cables/fibers and then local wireless. The trendy word would be "fractal." The leaves of the tree are wireless, but communicate at low power to a local branch that then communicates along the branches and trunk to other leaves. This gets around the limitations of channel capacity.
This is also called "the last mile," for obvious reasons.
The equivalent solution in a conference hall is to have distributed transceivers with, say, a range limited to D/10, where D is the diameter of the conference hall grounds. And the laptops or PDA carried around by people must be limited in power so that they don't reach outside these "cells."
(This is what keeps the cellphone system from being swamped.)
Today's 802.11b doesn't throttle back power in this way.
--Tim May |
