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. If you are showing as 'Guest', please register at the bottom of this 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

TDM

(Read 1923 times)
nkast
Ex Member


Jan 20th, 2010 at 10:52am  
Hi,

I understand outbound fromt the HUB is TDM traffica and inbound is TDMA.

Why we cant apply TDM to the outbound traffic?

Regards
Back to top
 
 
IP Logged
 
Eric Johnston
Senior Member
***
Offline


Personal text from Profile,
Options, Top line

Posts: 2108
Reply #1 - Jan 20th, 2010 at 11:07am  
The question does not make sense to me.

The high speed outbound continuous carrier from the hub, is received at all remote sites.  Within the data stream are various packets, joined end to end without any interruption of the timed data stream, intended for particular remote sites. The remote sites recognise and extract such packets to forward to their attached customer PC.  Such an outbound carrier is called TDM (time division multiplex) since the data stream comprises packets that have come from various internet servers and are being multiplexed together in time sequence before transmission of the composite data stream from the hub.  

The return link carrier slot from the remotes to the hub is an intermittent operation.  The remote sites transmit occasional bursts, all on the same frequency, but only one site at a time to avoid interference.  This is called TDMA, time division multiple access.  A site typically transmits as burst when a mouse is clicked or series of bursts when a long file is being sent.

Is there an alternative to TDMA for the inbound ?.
Yes.  You can use SCPC type modems.  Each remote site has a permanent continuous carrier to the hub.  This is ideal for voice, GSM backhaul, large business, ISP or internet/phone booth cafe.   Traffic is not subject to congestion by other people or FAP and you have steady dedicated bit rates 24/7.   Use iDirect 5000 series modems or Comtech CDM570.

Best regards, Eric.
Back to top
 
 
IP Logged
 
dot
Ex Member


Reply #2 - Jan 20th, 2010 at 3:09pm  
In actual fact if you added an iSCPC link (iDirect's SCPC product) you would effectively have TDM out and a TDM return. This can run alongside other star topology remotes that use the TDMA method for their return channels and it will all be managed by the same NMS. iDirect has announced that they will release SCPC return channels in an on-demand or as-required fashion in the near future as well. Bear in mind that the iDirect platform is IP-based and all the interfaces are Ethernet.
Back to top
 
 
IP Logged
 
Pages: 1