Satellite Internet

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

segment bandwidth

(Read 2503 times)
Ex Member
Ex Member


Oct 19th, 2010 at 7:12pm  
hi mr eric ....
please Can you guide me to learn how to explore my space segment bandwith which i leased from eutelsat by using one of NMS user interface (ibuilder, isite, imonitor). thx
Back to top
 
 
IP Logged
 
Eric Johnston
Senior Member
***
Offline


Personal text from Profile,
Options, Top line

Posts: 2108
Reply #1 - Oct 19th, 2010 at 7:31pm  
You need a spectrum analyser to see and plot out your spectrum utilisation.

If the hub and remotes are in different beam coverages (cross-strapped) you will need to make spectrum plots using two earth stations, one in each coverage areas.

The iDirect NMS may be able to generate a pictorial representation of the used spectrum. I don't know how to do that.

The real spectrum plots will show interference as well as the wanted signals. The pictorial representation will help identify which carrier is which, if this is not obvious.

TDMA
This example image above shows a VSAT system with one large outlink carrier, on the right, and four return link carrier slots, three of which (1, 3 and 4) are active at this time.
The second return link slot is temporarily inactive (sites moved to other return link slots) while a steady interfering carrier is being investigated.

The large outlink carrier is continuous and appears as expected. If you turned it off, briefly, you could see if there was any steady interference underneath.
Use of the return link TDMA carriers only shows up as fragmentary multiple spikes, each spike due to a burst from some active remote site on that return link carrier frequency.  If you leave the analyser on MAX HOLD for 10 minutes all the spikes will amalgamate so that the envelope of the higher power remotes becomes clear. The spectrums of links 3 and 4 are starting to show the normal carrier shape.  The high spectral density 'horns' visible at either side of the return links 3 and 4 are due to the carrier/bit timing recovery sequences at the start of all bursts, which is are not scrambled.

Note the gaps between the carriers. Watch these gaps. If they ever fill up investigate why.   iDirect networks may use narrower gaps as a result of special modulation filtering to minimise such gaps.

In this example, the hub and remotes are in the same beam coverage, so the hub and the remotes can all see all of the carriers in the system.  The above spectrum was recorded at a small remote so the bursts from other remotes are very low level.

If the network traffic is negligible you will not see anything of the return links so be patient (wait an hour in max hold) or crank up the traffic from one remote on each frequency to fill up the time. A spike will appear only if a remote is bursting at the instant when the analyser resolution bandwidth sweeps across a the relevent carrier frequency. More modern, FFT analysers are better, if you can afford them !

I have added a diagrammatic spectrum picture at the bottom.  This might be displayable on the iDirect NMS ?

Best regards, Eric.
Back to top
« Last Edit: Oct 20th, 2010 at 11:42am by Admin1 »  
 
IP Logged
 
Ex Member
Ex Member


Reply #2 - Oct 24th, 2010 at 7:33am  
thank you sir for your replay.... I will try to Follow the instructions mentioned.
Back to top
 
 
IP Logged
 
Pages: 1