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To: qdog who wrote (39888)	9/6/1999 9:17:00 AM
From: Clarksterh	Read Replies (1) \| Respond to of 152472

qdog - No air interface presently used takes a fixed bandwidth and makes it carry more and more bits. There are multi-coded techniques or some of the newer air interfaces such as OFDM or BLAST that allow you to get more bits per hertz, but CDMA, TDMA or GSM by itself will not do that. Well, I agree to a certain degree, and disagree to a certain degree. Of course, cell systems are interference limited (those pesky neighbors), and thus bits/hertz limited to the extent that they can't remove their neighbors' noise. (Sectorizing helps by removing the pesky neighbors from within your own cell; CDMA does it vs TDMA by averaging the neighbors so that they behave more predictably.) OFDM may do a better job of excluding the neighbors than CDMA, but it isn't entirely clear to me. I've been looking for a while and I have yet to find a good article on interference limited OFDM performance. And in any case CDMA ain't over - when CDMA deploys MUD (MultiUser Detection) at its cell sites I would expect significantly improved performance on the reverse link - which for CDMA is the worst performing link. Both are validating some of the things that I have opined the past few weeks, which is the US carriers do not have the bandwidth in frequency to satisfy the requirements that 3G will place on it and satisfy the consumer. I've always agreed that more spectrum is better<g>. And spectrum up at 2.4 or 2.6 GHz probably doesn't behave enough differently from 1.9 GHz that it is unworkable in mobile environment. But new spectrum or asymmetric bandwidth allocation is no threat to CDMA technology although it may hurt some of the service providers. Clark PS LMDS, OTOH, is probably not a significant threat for the service providers (stationary vs mobile), but being a less interference driven system it probably doesn't need CDMA to anywhere near the same degree as mobile systems. In other words I wouldn't expect CDMA to make large inroads into the really large-pipe, fixed, business-oriented, last miles. But the mobile and semi-mobile market is plenty large enough!