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DirecTV partnered with Microsoft to
produce a push-mode data service over DBS. The service broadcasts approximately
200 popular Web sites, which are cached in the
consumer's PC. Some content will be cached at the service provider's
site. Instead of having a point-to-point connection with the
Internet, consumers access content on the hard drive or
service-provider cache. In addition to Web sites, other data
services such as AgCast or stock quotes can be offered, either by
continuous feeds or by caching on the consumer's PC. The problem
with this model is that you cannot access a Web site that is not
part of the service, because no point-to-point return-path
connection exists.
One form of point-to-point data
service, called DirectPC, can reach the Internet. DirectPC is
jointly owned by DirecTV and Hughes Network Systems. DirectPC
reserves 12 Mbps of downstream service and uses a telephone as a
return path.
Because the footprint (the portion of
the Earth's surface covered by the signal from a communications
satellite) is so large for geosynchronous satellites, it is possible
that thousands of users will want to use the common 12 Mbps of
service concurrently. The more concurrent users there are, the less
bandwidth each user gets. To provide a balance between bit rate and
the number of concurrent users, DirectPC offers approximately 400 Kbps
of service to concurrent users.
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