Hi, Ray -
Well, my take on it was the old good news/bad news scenario. Though some investors will have visions of sugarplums dancing in their heads, the 2.4 GHz playground just got a lot more crowded.
While there is a business opportunity for many companies, the FCC decision will have the effect of degrading the efficacy of the spectrum for any user: IEEE 802.11a, 802.11b, Bluetooth, HomeRF, and any number of unlicensed walkie-talkie devices by any number of manufacturers.
Frank posted a question, a while back, on the likelihood of interference in the 2.4 GHz spectrum, when using an in-building enterprise LAN. In the short dialogue that ensued, I made reference to the Master's thesis of Timothy Shephard at MIT: his paper(s) can be accessed here,
for anyone who wants a head-spinning dive into the mathematical basis of the probabilities of interference:
citeseer.nj.nec.com
But his references were to interference in managed networks; the low probability of interference that he assigns is subject to revision in an unmanaged LAN/MAN environment.
A while back, I read an article, which you later referenced, Ray, which stated (I'm recalling this from memory, so I may be wrong, here) that data transmission rates in 802.11a would drop by around 30% when a collision necessitates a retransmission. I would expect approximately the same result in 802.11b, and HOME RF, unless a standard permits the transmission of damaged data. Reading the minutes of some IEEE meetings lately, the possibility of just such a mechanism has been discussed, but it brings with it its own set of problems.
My point is, in the 2.4 GHz spectrum, I would be leery of accepting promised throughput rates in areas with busy spectrum. OTOH, present users of the 'net run into delayed or lost packets frequently: this whole argument may be a distinction without a practical difference. The decision of the FCC (and they certainly appear to have researched the matter thoroughly) may turn out to be the right one.
Whether it's IEEE, ITU, Bluetooth, whatever, you run into references by engineers who are worrying about interference at 2.4 GHz. Will it turn out to be, like Y2K, a non-event?
I don't know. I'm just now doing some research on Home RF: to what extent transmission will be affected by a packet-header collision, is unclear.
In a larger sense, this turnaround by the FCC reflects the business, and investment uncertainties introduced by unmanaged spectrum allocation, in comparison to say, Europe. "Let the market decide" is a fine rallying call, but I wonder how the business community, and the investment community (never mind the end user) will feel if the FCC continues to re-draw the yardlines, and move the goalposts, in spectrum allocation.
FWIW ;-)
Regards,
Jim |
