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Technology Stocks : Loral Space & Communications -- Ignore unavailable to you. Want to Upgrade?

To: JGoren who wrote (6150)	5/13/1999 5:56:00 PM
From: Steven Rachbach	Read Replies (2) \| Respond to of 10852

"Why satellite can't work" I found this post on AOL's ATHM board - any comments-- Subject: Why Satellite can't work Date: Thu, May 13, 1999 2:45 PM From: FIRENZA Message-id: <19990513174556.21441.00000335@ng-fi1.aol.com> pulled this off yahoo Missileman wrote it: by: missilemanindfw Quote & News Or Why The Chicken Can't Cross The Road Profile Research Insider Just thought I would pass on the technical reasons why satellite can not and will not compete with cable. I'll try to address wireless in a subsequent post. My analysis is broken into four catagories: low, medium, and high power geosynch and low power low earth orbit constellations. My most commonly quoted data source here is 'Communications Satellites' published by The Aerospace Corporation. Anyone can obtain a copy is they wish. Assumption: That any provider (AOL For example) has to size their comm. system to support the maximum number of simultaneous users. Of 18 million subscribers they claim to have lets say we must support 4 million at peak load, with a data rate comparable to DSL (256 Kps). Low Power Geosynch - Typical of this class is the galaxy type birds (one of which failed and caused the pager outage last year) Typically 24 transponders at 4-6 Ghz (36 Mhz bandwidth) and another 16 operating at 12-14 Ghz (27 Mhz Bandwidth with 8 capable of 54 Mhz). Assuming you have a large C-Band type dish, these transponders can handle a datarate of 60-90 MBS each...which means that each and every transponder can support approximately 350 users employing current data compression and error correction. It may actually be less than that because most satellite operators typically will reserve some portion of that bandwidth (5 %) for calibration and internal use. Assuming 100 % usage that means our typical existing satellite 14,000 users if all of its capacity is dedicated. That means that we need 'only' 285 birds at 300 million a pop to service AOL alone. Clearly this fiscally and physically impossible to do...thats 85 billion dollars with no ground support equipment or life cycle costs included and there are nowhere near that many orbital slots available. Assuming there were and a 12 year satellite life that means a minimum annual cost per user of nearly $ 18,000.00 a year. Anyone want to pay that for high speed access? Medium Power Geosynch - The advantages of greater transponder power and frequency mean smaller antennas here on earth...the driving force behind systems such as DirecTV. Your typical bird here operates at say 12 Ghz (allowing the smaller antenna on the ground) and transponder powers of 100-125 watts with a 24 Mhz channel bandwidth. I havent done the calcs, but lower bandwidth even with the higher frequency will leave us in more or less the same state as we have with the low power geosynchs. To support this service by the way (DuoTV) means that you also need a new dish - one 20% or so larger than the existing DirecTV dish, again assuming total datarates of 60-90 MBS per transponder. These higher power birds also have fewer transponders (typically 16) which in turn means more launches, satellites, and cost. I wouldn't be suprised if the actual implementation costs weren't higher than low power geosynch for that reason. High Power Geosynch - Though this catagory doesn't really exist in hardware yet (other than say TDRS-AT type designs) if you use the Ka-Ku Band (23-28 Ghz) you can push the datarate per transponder up to 650 MBS. These would be BIG birds though...probably at the margin of current lift capabilities...and pretty costly. Lets assume we can do the impossible though and make them equal in size to the existing C-Band birds...with the same number of transponders. (40) Now each transponder can support about 2500 users for a total per bird of 100,000. Now we are down to 40 birds for AOL alone...unfortunately there still arent anywhere near that number of geosynch slots available for good US coverage! Which brings us to LEO constellations...its the only way out of the geosynch straight jacket, and its why several companies to include microsoft have favored this approach for the 'internet in the sky'. The number of satellites for adequate US coverage given an orbital period of about 90 minutes would be in the hundreds (250-300 is the number you typically here for constellations of this type). The switching problems in such a system would immense...and software that can handle it has only recently been demon strated. Just think about the problem of 'handing off' an active user to some other bird in the constellation in real time as it goes over the horizon. Then lets add equipment failures, orbital uncertainty, etc etc and you begin to see the size of the problem. do-able? Yes! cost effective? The million dollar question...but my guess is probably not...whichmay be why no-one has yet orbited a bird of this type. Any way you cut it folks - you simply can not (physically) support large numbers of high bandwidth users from orbit. I quote directly - 'extensive competition from cable and low and medium power satellites have caused financiers to be hesitant about high power dbs ventures.' WITH GOOD REASON!!! missileman