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To: Steven Rachbach who wrote (6151)	5/13/1999 6:35:00 PM
From: RMiethe	Read Replies (1) \| Respond to of 10852

Gave your piece here to a satelliter. On Skybridge, at least, the "handoff" question depends on how great a frequency re-use capacity Skybridge LEOs have. "That is, the number of "cells" per footprint-- not so much the number of LEOs in the air. That question is rapidly becoming less and less germaine with frequency re-use gains over the past few years. "Teledesic, to consider it further, claims a frequency re-use capacity of some 10,000 will be available off its system, which makes the writer's comment completely moot-- if those gains are achieved. His comments had powerful validity perhaps six years ago, but the industry has certainly moved far beyond those days with the developments in beam-shaping, beam contouring, beam switching, beam hopping, optical lazer focusing, and the like. "The reason no broadband internet sat system has yet appeared is not because it has been deemed unfeasible. It is simply because the satellite providers in concert are executing a broadband plan with the ITU on a phased in basis. "It is always necessary to have facts at hand when making assertions about satellite broadband, and where it is going. Skepticism is good, but not when it is unfounded, as I believe in this case it is. I believe the problems with GEOs are perhaps somewhat more serious than they are with LEOs, while spoofing enhancements do continue, along with memory buffers for internet protocols, by way of LEO byte transmission. The systems will work very competitively with land fiber. The basic issue is the cost per byte to the satellite provider. Teledesic has made some very optimistic claims regarding their "Internet in the Sky" capabilities, and it is not appropriate to pass comment on them since the actual engineering on the system is not public. "As with all new technologies, in the beginning there may be adjustments to the systems, which Skybridge, because of its modularity will be able to effect quickly and as needed. With the writer's comments that you sent me, however, I cannot envision any satellite engineer designing the systems in question would possible agree. The point to keep in mind is frequency re-use protocols. They are, in the end, the answer to how competitive satellite systems will be with current fiber.

To: Steven Rachbach who wrote (6151)	5/13/1999 11:12:00 PM
From: Clarksterh	Respond to of 10852

Steven, Satellite Internet Access: The author of the post makes several very big errors. If I use just the GEO middle powered example for illustration some of the mistakes are: 1) The internet is bursty - the internet is often assumed to have a burstiness of 10. If you assume a peak rate of 1.5Mbps (highest speed DSL), that implies an average rate of only 150Kbps for a logged on user. 2) The biggest mistake is that in calculating the price for the surfers he assumes that it is always the same 14000 (which by #1 should really be 24000) surfers who are surfing. Of course it isn't. If you assume that the satellites are fully loaded for 16 hrs per day (businesses during the day and individuals in the evening), this translates to $300M spread out over 12 years x 365 days/yr x 16 hrs/day x 24,000 users = 1.7B user hrs which implies about 20 cents per user hour. Hardly prohibitive - at 60 hrs use per month that is much less than the current price of ADSL. (Note - take these numbers with a grain of salt. But they are probably within a factor of 3 or 4 and thus it is competitive with ground based systems.) 3) Given that the cost is at least ball park competitive with ground based systems, it is that much more competitive where no such ground based access currently exists. Clark PS Currently I have no idea what the link budget for such a satellite looks like, so I am taking his 60-90Mbps per transponder as a given. Given his other calculations and their inaccuracy this may not be the best idea.