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Technology Stocks : Sirius Satellite Radio (SIRI) -- Ignore unavailable to you. Want to Upgrade?

To: pcstel who wrote (5298)	10/7/2006 1:03:44 AM
From: i-node	Respond to of 8420

So the current state of SDARS is using a Frequency Division scheme where the Space Segment uses about half of their licensed spectrum, and the terrestrial segment uses ~ the other half. It is a very ineffecient system in today's spectral effeciencies. As the terrestrial segment simply mimics the broadcasts of what is transmitted on the space segment. In reality, there is no reason that you could not build a system that would allow frequency reuse of the terrestrial spectrum in the space segment, and like wise the space segment reuse in terrestrial segment. So basically, the entire ~12 Mhz could be employed in both the terrestrial and the space segment. So in effect.. You would double the available spectrum. (In the real world, it would be slightly less than an exact double) I think there are some problems in there. I'm a non-engineer, of course -- but my recollection is that SIRI's 12.5 MHz is broken into 3 chunks of 4.2MHz each of which one is used for servicing repeaters and two are used for the two satellite active at any time (two are necessary to achieve the required time diversity). Thus, even if they could eliminate the spectrum usage for repeaters altogether, which they can't, they would still only increase their effective throughput by some 42%. Of course, the new satellite, with increased power, will likely enhance the probability of their Hierarchical Modulation implementation. It sounds doubtful they could implement anything on this level without making existing receivers useless. Maybe some engineer who understands this stuff will read your post and explain it in layman's terms, but personally, I think it sounds fairly pie-in-the-sky.