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To: E. Davies who wrote (3280)	3/31/1999 1:58:00 AM
From: Bernard Levy	Respond to of 12823

E Davies, ww, Frank and others: I see there are many interesting wireless posts this evening. Here are my 2 cents on a few topics already touched: a) LOS is required at high frequencies (24, 28 and 38 Ghz). In cities, this immediately restricts the usefulness of broadband wireless to situations where you place antennas on top of office or residential buildings, i.e. to business users (such as those targeted by WCII and TGNT) or to high-density apartment buildings. b) Around 2Ghz, LOS is preferred, but not absolute. A few months ago, Cisco acquired a small smart antenna company called Clarity Wireless, which had technology capable of ''virtually'' forming a LOS by time-space processing of multipath signals. This technology is targeted at 2 to 5 Ghz wireless applications (although Peter E. indicated that it might even be usable for near LOS situations at LMDS frequencies). c) There is lots of BW at high frequencies (TGNT has 400 MHz, NXLK has > 1GHz at LMDS frequencies, and WCII has about 700MHz in all top markets), and the FCC is due to put another 1.6Ghz of spectrum on the auction block soon. With point to multipoint antenna systems, and antenna sectorization, this allows the delivery of up to 50Mb/sec (VDSL rates) to users who need such rates. With wireless ATM software, the BW could also be managed dynamically, and if you throw in the possibility of using more advanced modulation schemes than the current QPSK (P-Com is testing higher order QAM systems), there is lots of BW high up in the spectrum. d) The deployment costs are rather high (but nowhere as high as for FTTC/HFC or FTTC/VDSL systems) at high frequencies because cells are small (about 2km in radius). e) At lower frequencies, it is possible to use big cells, but there are several problems. First, LOS or near-LOS is extremely difficult to ensure. Furthermore, with a 25 km radius cell, operators have far too many potential customers per cell. With high take rates, the rates that can be delivered to each customer are very small (ISDN type rates). This means that a small cell approach really needs to be used. Lower frequencies have also the disadvantage of requiring bigger antennas. On the other hand, the electronics is cheaper, and rain fade is not a factor. On the whole, while fixed broadband wireless will be successful for business customers or residential customers in tall building, I do not think it is a solution for average residential users in urban environments. For suburban users, trees create also a problem, but with some ingenuity, the situation is probably not hopeless (Project Angel will be an interesting test case). Broadband wireless by satellite will also become an option in a 3 or 4 years. Over time, it should become the wireless option of choice for residential users, provided the costs stay under control (how it will stack up against HFC networks and DSL, I can't say). Best regards, Bernard Levy