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VSAT Circuit Speed

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Sep 25th, 2007 at 6:30pm  
I need information on Vsat Ciruit Speed. I came across this term (Vsat Circuit Speed) and want to confirm if its the same as BANDWIDTH or something else.

your contrinution will be appreciated.
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Eric Johnston
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Reply #1 - Sep 25th, 2007 at 10:34pm  
Assuming a shared continuous outlink carrier and time division multiplexed return links....

The (down) outlink carrier information bit rate is shared by many sites.

Ask them what is their outlink carrier information bit rate and how many sites are sharing it ?  Divide and that will give you a measure of the long term downlink bandwidth available per site.

Regarding the (up) return links, find out what is return link information bit rate and how many sites are sharing.  Assume about 50% efficiency and then divide.  That will give you a measure of the uplink bandwidth available per site.

If you have 1 PC you need an average of about 2kbit/s up and 8kbit/s down for web browsing.   VoIP needs about 10kbit/s each way under ideal configuration conditions.  File sharing and video need more.

The term VSAT circuit speed is something I have never heard of.  Ask them what it meams.

Best regards, Eric.
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Reply #2 - Nov 4th, 2007 at 11:53am  
I agree
Usually we speak of spead, rate, symbol or data rate etc'.
Oren
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Reply #3 - Nov 4th, 2007 at 3:06pm  
I'm going to speculate that it was an advertisement written by a business major, rather than by someone with a technical background. If not, it doesn't speak well for the talent level at that provider. Anyway, I would say it's meant to represent throughput; that is, how fast you migh expect their connection (circuit) to perform

//greg//
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Reply #4 - Nov 5th, 2007 at 3:37pm  
Eric you said:  "If you have 1 PC you need an average of about 2kbit/s up and 8kbit/s down for web browsing."

I've seen other posts on SatSig recommending 10 - 30 Kbps per PC (no reference to amount up or down). 

Are you aware of any studies that show the average throughput (up and down) per PC in typical browsing environments (if in fact there is a "typical" profile). 

When you suggest 8 x 2 Kbps, are you referring to CIR, or the amount of dedicated bandwidth required?  For example a service shared at 10:1 would need 80 x 20 Kbps of bandwidth per PC? 

I read a study 5 or 6 years ago that indicated that the average PC used about 300 bps (CIR) on the upload if you measure the total number of bits transmitted and divide by the hours/minutes/seconds in a typical work day.  It didn't measure the download, but typically the download is anywhere from 2 - 8 times the upload. 

I believe that number is obsolete today given the preponderance of peer-to-peer applications, video traffic to and from sites like YouTube and MySpace, etc. 

I would like to find a study that measures average throughput (in bits per second) in various environments such as business office, Cyber Cafe, residential customer, etc. 

Any suggestions or information greatly appreciated.

Pat
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Reply #5 - Nov 7th, 2007 at 1:06pm  
I guess the one who knows the figures has a goldmine... And that more than everything, it comes with experience. I guess that a service provider that has enough customers for enough time, can start to figure out how much bandwidth per PC eact customer profile needs..and what will be the best ratio between the uplink and downlink for each profile..
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Eric Johnston
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Reply #6 - Nov 7th, 2007 at 7:21pm  
My 8kbit/s down and 2kbit/s up is my idea of the minimum 'allowance' for a PC used for just web browsing, based on the total capcity divided by the number of PCs.  It was derived from on a lecture, 2 years ago, by a big network operator and I worked backwards from the number of customers and network capacity. For example, 10000 customers needed a composite of 80 Mbit/s down and 20 Mbits up.
When questioned they said that traffic demand per customer was increasing rapidly.   I have seen elsewhere that 30kbit/s down and 5 kbits/s up provides a more generous service.  Even this figure may be wronf now.

All above assumes little or no peer to peer file sharing, video downloading or uploading, VoIP calls etc.  These cause a massive load.  VoIP needs at least 11 kbit/s each way with 30kbit/s each way common and 85 kbit/s each way possible, depending on how well or badly you configure the VoIP phones and networking equipment.

Satellite communications is expensive.  I assume $7000 per month per Mbit/s and this might be good for 800 kbit/s down and 200kbit/s up. 

Would this be suitable, shared 20:1 amongst 20 sites, each with 5 PCs giving 8 kbit/s down per PC and 2kbit/s up per PC?.

Or is 10:1 sharing, with 10 sites, each with 5 PC more realistic with 16kbit/s down and 4kbit/s up per PC ?

The monthly price per site in these two cases would be $350 and $700 per month respectively.

Please would anyone with actual traffic figures please say what is thier experience.

Best regards, Eric.
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