Subject: Moving Targets

From: "Smith JR, Harry E" <[email-masked]>
Date: Tue, 03 Oct 2000 07:49:38 -0700

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

---

From: "Peter Sterling" <[email-masked]>
Date: Tue, 3 Oct 2000 12:22:23 -0700

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

---

From: "Sing Lin" <[email-masked]>
Date: Thu, 12 Oct 2000 09:27:53 -0400

Shaun:

With proper engineering, one may use the terrestrial 3G IMT-2000 wireless
systems in the densely populated area to serve the moving train and use the
HAPS in the rural, low population density areas to serve the moving train.

In densely populated areas, there are enough subscribers to justify
deployment of terrestrial 3G IMT-2000 systems, whereas in the rural, low
population density areas, it is more economical to deploy HAPS. Since
terrestrial 3G IMT-2000 systems will not be deployed in rural areas, there
is less possibility of radio interference problems for HAPS to operate in
the 2 GHz IMT-2000 frequency bands in the rural areas.

Sing Lin
***********

Abheek:

In addition to the 70 GHz band allocation for HAPS, the proponent of HAPS
also proposed HAPS for the 2GHz band allocated for the 3G IMT-2000 wireless
systems. Substantial work have been done on the frequency coordination
criteria and coordination distance to make sure that HAPS and terrestrial
and satellite based 3G IMT-2000 wireless systems will not interfer with each
other. Therefore, under suitable conditions, HAPS may operate in the 2 GHz
IMT-2000 bands.

Sing Lin
***************

Shaun:

USA, Japan and Europe have been doing substantial R&D on High Altitude
Platform Station (HAPS) in recent few years. The technical contributions
from these R&D sources to ITU-R WP8F/TG8/1 in the last two years have
resulted in a Preliminary Draft New Recommendation (PDNR) and a Draft
Handbook on HAPS in ITU-R WP8F working on the Third Generation (3G) wireless
technologies and beyond. Therefore, HAPS is a serious project and technology
to consider. Each platform is at about 21 Km above the ground and can cover
a very large area.

Sing Lin