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In the last few years satellite began to be applied in Internet networking,
mainly by medium-big ISPs and we have seen it diffused between users. Sat connections
are a very different kind of networking than terrestrial ones, with different
timing such as higher RTT (round trip time), but also with different bandwidth
value, up to 2 Mbps or more.
We can imagine a path like this:
|||||| S A T E L L I T E ||||||||
/ /|\
Downl / | Uploading
load / | from
to /(4) | (3) server
client / |
/ |
SatCard(parabolic antenna) |
| |
\|/ |
USER PC ----make request-----> SAT-SERVER <---retrieving---> INTERNET
(1) (2)
So first we make the request (1) (using our Internet connection) to the
Sat-Server, after it will retrieve out info from Internet (2) and it will send
it to Satellite (3); in the end we would receive data from the it (4) to our
home using a parabolic antenna and a Sat Card.
Typically exist 2 kinds of request :
Both of them have a little request data and a much bigger answer size,
so satellite works very well with it, but with a big time of answer, this is
the biggest problem of satellite connection (consider a typical Sat distance,
like 36.000 km, so you would have a time access of [ 36000 km / 300.000
km/s = 0.120 s = ] 120 ms you have to add (2 times, cause first ISPs server
send it to, then you download it from) to classical Internet time access.
Recently ISP allows their clients to use also other kind of service, like
and many others.
There exist also services called "one-way", which consist in mail service
, download on-demand (where you make a file reservation to be scheduled at
some time) and site download: these services are offline, so you can access
to them without modem (or other kind of) connection.
We have to report another satellite technology: the 2-way sat connection.
It uses only the parabolic antenna to contact Internet in both 2 directions.
Its cost is much higher that 1-way connection. We expect something from it
for immediate future, for now it allows a bandwidth of 4 Mbit/s in download
and 256Kbit/s in upload.
It depends on many factors: ISP purpose, TCP window used, applications
used by the client and the more important of all, "Internet congestion".
You can expect a max bandwidth of 1-4 Mbps and a average of about 10-30
KBytes/s, but I repeat, it depends on many factors.
Anyway some ISPs tell you they give you a "Max" bandwidth, while the average
bandwidth could be very lower, due to intra-ISP congestion.
Some other ISPs guarantees you to have a "Minimal" bandwidth, which is more
meaningful than "MAX", cause it is available all the time.
Please see Appendix A for more about get downloading performance better.
We have to distinguish between hardware costs and account costs, the first
are known, while the second depend on which service you choose ("guaranteed"/"not
guaranteed", what bandwidth).
Hardware costs
To install our little satellite system we need:
- Sat card
- Parabolic antenna
- one or more feed (converter)
Noticed that we need a digital converter to use Internet via satellite.
Sat card costs depends on brand you choose, about 200US$-300US$.
Parabolic antenna is about 50 US$.
Converter is about 50US$.
So we have about 3-400 US$ of hardware cost (maybe you still have
to add installation cost!!).
If you want also receiver Crypt service:
- CI is about 100 US$.
- CAM is about 100 US$-250 US$.
Account costs
Here costs depend on what ISPs give you access, what's peak bandwidth,
if there is a guaranteed bandwidth (which is more important than peak one),
what kind of service they give you and so on.
Also some ISP gives you free access in change of viewing an always foreground
spot banner (you cannot iconize it!!): in this case you will pay when you'll
go to buy something showed in banner!!
Typically account costs are about 100-150 US$ at year for "not guaranteed"
services and 4-600 US$ or more for guaranteed ones (they guarantee you
a minimal bandwidth you can use also under congestion moments, obviously intra
Sat-ISP congestion!! When you go out to Internet nobody can guarantee you anything!!).
When we speak about satellites we mean: Astra (19.2 degree SE), Hotbird
(13.2 degree SE), new Europestar (45 degree SE), Eutelsat (8 degree SW), Astra
(26E), ArabSat 3A (26E).
In Europe we know about 8 ISPs giving Sat access for Internet:
-
EuropeOnLine - EON
-
Netsystem
-
Starspeeder
-
Sat Node
-
Eliosat
-
Falcon Stream
-
SkyDSL
-
OpenSky
-
DirecPC but this use a proprietary sat card (this is a first Sat ISP )
-
http://www.xanticbroadband.com/
EON gives access for about 150 US$ at year without guaranteed bandwidth.
Netsystem offers its services at "null cost", you just have to see its banner.
Starspeeder gives access ???
Eliosat costs 350 US$ at year with a 128 Kbps guaranteed (minimal
service, see web site for more);in addition it gives 2-way technology access
for either receive and transmit.
SkyDSL gives access full-time and it costs about 15 US$ at month
with 128Kbit/s bandwidth, but it allows a bigger bandwidth where you pay each
Mb downloaded (you can select from 256Kbit/s up to 4Mbit/s), for more you can
visit its web site.
IMPORTANT : before subscribing some satellite account, please verify "foot
of Satellite" and diameter of parabola.
OpenSky started before summer 2001 in its "beta test": it allows you to try
the sat service downloading at maximum 300 MB at month (free). To register
you need to go at
OpenSky registration procedure (which is in italian language!).
With every kind of DVB card you can also receive TV digital channels (free
channels only) and some cards have support for common interface to watch encrypted
channel.
Follows the schema:
Smart-Card -> CAM -> Common Interface -> Sat Card (with support C.I.)
CAM Card (there are many standards used for decryption: SECA, IRDETO, VIACCESS
and others) is the hardware allowing decryption (for TV, Radio and Data) while
the Common Interface or C.I. (ETSI EN 50221) allow connection between CAM and
Sat Card.
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