VSAT is an acronym for Very Small Aperture Terminal and is essentially an
earth station with (relatively) small antennas. Some of the competing
architectures in the sat-com industry are SCPC/DAMA (Single Channel Per
Carrier/Demand Assigned Multiple Access), TDMA (Time Division Multiple
Access), etc. These technologies are used for voice, data, TV broadcasting,
etc. In United States, where the landlines for voice is well laid out,
VSATs & other sat-com architectures are used more for data transmission
(credit card verification at Gas Stations, verification at ATM machines,
etc). In other parts of the world, they are quite often used for voice as
well (with addition of Echo Cancellers, etc). CDMA, developed and licensed
by Qualcomm, is an acronym for Code Division Multiple Access and is used in
cellular phone network and I wasn't aware that they are used in satellite
communications.
Most sat-com earth stations are basically comprised of ODU (OutDoor Unit)
and IDU (InDoor Unit). ODU are further comprised of antenna, LNB,
transceivers (if it's bi-directional), some sort of power amplifiers (SSPA,
HPA, TWTA, etc), etc (since systems like DirecTV and DirectPC are
receive-only (one-way), they only have antenna and LNB and do not include
transceiver nor power amplifier). The frequency of the signals from and to
ODU are downconverted or upcoverted to and from IDU, which are comprised of
NMS, some sort of terminal devices, etc. The application (PSTN & PBX for
voice, LAN/WAN for voice, etc), of course, is connected to the IDU.
As far as VSATs and DAMA solutions, I believe Hugh Network Systems
(http://www.hns.com) and Scientific-Atlanta (http://www.sciatl.com) dominate
the global market as turn-key equipment providers.
I have to ask, though, why are you "planning to implement/replace" leased
lines VSATs if you don't have a clue about VSATs? In other words, do you
know if it's going to be a cost-effective replacement to your exsiting
leased lines? I think you might be in India, and perhaps leased lines are
just way too expensive there. If so, did you find out that VSAT is a less
expensive solution thru a local vendor or systems integrator? If so, they
should be able to answer your questions for you.
You should also be able to find quite a bit of info by searching at
www.google.com.
HTH,
Randall
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
[EMAIL PROTECTED]
Sent: Tuesday, December 04, 2001 08:18 PM
To: [EMAIL PROTECTED]
Subject: Re; How VSAT works ? [7:28156]
Hi guys,
I have cisco routers such as 3620 ,3640 with leased lines connectivity to
remote locations Now I am planning to implement/replace these lines to
VSATs, but I am not much familiar with the terms such as PAMA,DAMA,CDMA ,
Also how the operation of VSAT takes place ?Can anybody clear my doubts ,
Also is there any URL which will give details on these terms?
Thanks in advance .
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=28164&t=28156
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