On Thu, Mar 18, 2004 at 04:25:49PM -0500, blitz wrote: > Quite realistic? > Its heading for a dead end. Sorry to say. > As in many things, its success will be its downfall. One can now scan the > ISM spectrum and see a perceivable rise in the noise floor. Links that once > worked will fall victim to ever increasing noise floors, and become less > and less reliable. Expansion of bands will be a must, but all the good > stuff will be polluted, leaving less and less frequencies to be developed > at higher and higher frequencies, all with less range.
It's not quite as bad as that. I do think that things are going to get worse before they get better, but slowly technology is coming to market that will help to fit more users into the bands. For example, transmit power control, such as 802.11 products by Atheros provide, helps reduce the interference range. There is also the Javelin chip by Motia (www.motia.com), which adaptively mixes four antennas' inputs to essentially select a low-interference, high-gain "spatial channel" for receiving. The receive parameters can be "reversed" to transmit back to a station on the same spatial channel it was received on. This will improve performance and coexistence of 802.11 stations. BTW, I think that great strides can be made in the "bits versus air-time" efficiency of existing 802.11 radios. Sometimes, backwards-compatible software changes are all that is necessary. Just for example, there are a lot of systems out there that use a very naive link adaptation algorithm, with bad effects on both their performance and their "co-existability." Just for example, it actually makes things worse if two 802.11b stations that are receiving interference either from each other or else from a microwave oven or a FHSS station, to both change their data rate from 11 to 5.5 to 2 to 1Mbps! Nevertheless, that is what many stations will do. I think that there might be places where the FCC can intervene to improve matters. I don't yet see how the market rewards LinkSys, D-Link, and other makers of *home APs* (I think the enterprise is different) for adding transmit power control to their products, and I don't think that they see it, either. Maybe the FCC should intervene? I do see how Javelin-like technology can improve their wireless products' marketability---superior link adaptation, too. The FCC could actually hinder improvements by mandating any particular technology for adaptive antennas or link adaptation. I think that the FCC should compel radio makers to provide more open access to documentation about the software interfaces to their chips, since that will speed up wireless innovation. Dave -- David Young OJC Technologies [EMAIL PROTECTED] Urbana, IL * (217) 278-3933 -- general wireless list, a bawug thing <http://www.bawug.org/> [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless
