Agree that the cellphone hands off with no problem using because of a
coordination between the BST and MST via terrestial lines. I am not sure
that this is possible for LEO unless you have satellite cross links.
The power advantage may be offset by the complexity of the terminal antenna
system. In a cell phone terminal the antenna is omni, for a leo a
directional is needed. This means either a fast tracking antenna and
aquistion or two tracking antennae.
As for the cost, the advantage is eaten by the additional satellites needed
to allow continuos coverage. I think that is a wash.
Harry
> -----Original Message-----
> From: Peter Sterling [SMTP:[email protected]]
> Sent: Tuesday, October 03, 2000 12:22 PM
> To: Smith JR, Harry E
> Cc: [email protected]
> Subject: Re: Moving Targets
>
> Harry
>
> The thing that killed Teledesic was a company called Motorola and a
> grossly
> overpriced, no-bandwidth project called Iridium.
>
> Your cell phone hands-off as you move around with no problem and a LEO
> system can do the same with no technical problems.
>
> The LEO satellite is in view of any one spot for around 10 minutes so the
> hand-off issue is probably less than for a terrestrial system. The
> primary
> advantage of LEO is the lower power requirements to connect, hence smaller
> antenna possibilities. Also it costs one quarter the price per lb to put a
> satellite into LEO than GEO. Add the power advantage to the cost advantage
> and a global broadband LEO system can give 400% increase in available
> bandwidth per $ over a global GEO system, and there's no 1/4 second delay
> associated with LEO.
>
> Despite what the GEO crowd believes, because of the latency issue, power
> and
> LEO cost advantage, its probable that ten years from now LEO systems will
> make up half of the satcom market.
>
> Teledesic currently has a GEO-Type fixed LEO architecture with stupendous
> capital costs and high technical risks, which indicate that it may not be
> built in its current form.
>
> Peter Sterling
>
>
> ----- Original Message -----
> From: Smith JR, Harry E <[email protected]>
> To: Sat TCP mail list <[email protected]>
> Sent: Tuesday, October 03, 2000 7:49 AM
> Subject: Moving Targets
>
>
> >
> > I am not sure that LEO are a good answer. Have you thought about how
> many
> > satellites you will need. I would guess around 5 or 6 in the orbit
> trace.
> > The second problem will be the handover of the data between the
> satellites.
> > ( I think this was one of the things that killed Teledisc)
> >
> > This means either cross links or a single hub that all satellites can
> see
> > and the routing is on the ground. A third concern would be that
> > utilization. Most of the time they would not be over Australia.
> >
> > A better idea would be a set of towers along the route like 3rd
> generation
> > mobile system. While the standards only give 2Mbps for fixed station
> unless
> > you are talking about a bullet train, I think they could be considered
> as
> > stationary. It will take a little thought.
> >
> > Depending on the services offered, you might be able to use part of a
> GEO
> > transponder to feed the 3rd Gen Mobile from a single access point.
> >
> > Harry Smith
> > Lockheed Martin Mission and Data Services
> > 408 - 473 6491
> >
> >
> --------------------------------------------------------------------------
> --
> > -
> > Harry Smith
> > 408 473 6491
> >
> >
> >
This archive was generated by hypermail 2b29 : Tue Oct 03 2000 - 18:48:13 EDT