Happy Christmas to you all.
Satellite Internet home page

Satellite Internet Forum.

Welcome, Guest.
Welcome to this satellite broadband discussion forum. Wherever you are and whatever your problem we are here to help each other. Connecting to the internet via satellite is not always easy but is critically important to those in remote places or with poor terrestrial infrastructure. Both service providers and customers are encouraged to contribute. Register at the bottom of the forum home page if you wish to contribute or ask question. May 2018: GDPR: Updates to Privacy and Cookies policies: As you may know, a new EU data protection law called GDPR will apply from Friday 25th May 2018. As part of satsig's commitment to protecting the privacy of site visitors and forum members, I have therefore updated the Privacy and Cookie policies. There are now links leading to these policies: Disclaimer, Terms of Use and Privacy, Forum User Agreement, Forum Rules and Cookies at the bottom of the home page and all forum pages. Read the Forum rules.
      Satellite internet forum          
Pages: 1

why gps cordinates needed to setup linkstar modem

(Read 2127 times)
Ex Member
Ex Member


Aug 2nd, 2009 at 11:32am  
Why dose the sevice provider need the gps cordinates to setup the modem? Can i move the modem to another site after being locked on? They say i cannot move more than 30 km ist it so?

Thanks
Robert
Back to top
 
 
IP Logged
 
Eric Johnston
YaBB Moderator
*****
Offline


Personal text from Profile,
Options, Top line

Posts: 2108
Reply #1 - Aug 2nd, 2009 at 12:38pm  
The LinkStar return link system uses Time Division Multiple Access (TDMA) for transmissions from remote sites to the teleport hub.

Remotes transmit occasional brief packet bursts, for example when you click the mouse.  If you send a long file you are allocated a series of time slots and then send a series of packet bursts.  The exact timing of all these bursts, as they arrive at the satellite, is critical.  Your transmitter shares the same transmit frequency as other sites, so it is important that your transmit bursts arrive at the satellite at the correct time, so they do not overlap in time with bursts from the other sites.  Each remote terminal is told by the hub when to transmit and this timing is based on the time slot position in the TDMA frame when the burst is intended to arrive at the satellite and also the path length distance from your site to the satellite. The path length distance is based on your lat/long and the current position of the satellite.

A knowledge of the site lat/long helps the initial acquisition of the site at commissioning.  Once an acquisition burst is successfully received at the hub (via a wide, empty time slot), the hub will do a very accurate ranging test. If you move a site your bursts will drift sideways (in time) and will interfere with someone else.  Tell the hub so they can do a ranging update and check your polarisation alignment.

The diagrammatic image below illustrates a highly simplified and very slow TDMA time frame:
...
Real TDMA frames are normally shorter, with many more bursts per frame from all the different sites. The guard time between bursts allows for small errors path length.

Read more: Explanation of TDMA

Best regards, Eric.
Back to top
« Last Edit: Aug 2nd, 2009 at 1:48pm by Eric Johnston »  
 
IP Logged
 
Ex Member
Ex Member


Reply #2 - Aug 2nd, 2009 at 1:01pm  
Hi Cris thanks for the explanation how will i know if the time frame is dynamic, the one sp from south africa said it is not a problem to move the modem they can just send a log file to the modem at the new site. The other sp is in namibia and uses an hub in italy i think. I need to set up a site in far north angola and want to use the namibian sp as it is cheaper but they do nt want to go into angola i think it is because of licences,can you help with sugestions.

Regards
Robert
Back to top
 
 
IP Logged
 
Pages: 1