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GSM backhauling on HX plaform

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May 29th, 2012 at 10:39am  
We are doing GSM backhauling on HX in order to save opex on the Satellite transponder rather than using SCPC.
My questions are :

How I can calculate the satellite bandwidth required if I know the Earlang Traffic for BTS?

Is HX supporting EDGE?

What maximum Sat Bandwith in can go for each remote?
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« Last Edit: May 29th, 2012 at 3:29pm by Admin1 »  
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Reply #1 - May 29th, 2012 at 4:16pm  
GSM backhaul is one of the intended applications of the HX system.  The manual says: "The HX system can be configured as an IP pipe and used as a global system for mobile communication (GSM) backhaul to replace T1/E1 and other ground-based base transceiver station-to-base station controller (BTS-to- BSC) network elements."  To get this implemented, you need to talk to an HX hub operator and see if they are willing to configure a link for your specific purpose.

What satellite bit rate you need in an "IP pipe" will depend on what compression (e.g. Memotec Abis) if any, that your employ at each end.  I suggest you read this: http://www.comtechefdata.com/files/articles_papers/Optimizing%20Cellular%20Solut...

Erlangs (Ref: http://en.wikipedia.org/wiki/Erlang_(unit) ) are used to determine the number of circuits required to carry so much traffic with a particular probability of failure to set up a call.  Note that efficiency is very low (and costs high) for small quantities of traffic. If you can merge a large quantity of traffic then the efficiency of your usage of the big trunk goes up:
e.g. for 0.01 probability of failure
2.5 erlangs needs 7 circuits. Efficiency = 36%
25 erlangs needs 36 circuits. Efficiency = 69%
250 erlangs needs 272 circuits. Efficiency = 92%

So, if you can somehow share your traffic amongst all other traffic on an HX system so you useage corresponds to your instantaneous demand that would be far better, cost wise, than a dedicated "IP pipe", which to me sounds like the equivalent of SCPC. The question is can such sharing be done in a QOS manner that enables your service to operate without interrupted calls, delayed speech etc.  Ask about feasibility. If the "IP pipe" is the equivalent of an encapsulated GRE tunnel then its capacity will vary with your demand. i.e. not like SCPC and so more efficient, but may be more susceptible to congestion.
Best regards, Eric.
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« Last Edit: May 30th, 2012 at 10:39am by Admin1 »  
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