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# Minutes conversion ( GSM)

Viewing 11 posts - 1 through 11 (of 11 total)
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Gloria
Guest

Dear all,

I’am in Telecommunications business and currently I’m facing a problem of converting the Erlang traffic value in minutes. Could any one of help assist me in sorting out this problem?
Exemple:156Erlang is used by a BTS at pick hour, can you tell me the conversion in terms of minutes?

Thank you for any help on this matter.

dmck
Guest

1 Erlang/hour is the equivalent of 1 call holding for 1 hour. Peak traffic of 156 Erlangs (really = erlang /hours) is the eqivalent of 156 calls each of 1 hour. So the conversion to call-minutes is 156 x 60 = 9360 call-minutes, x60 again = 561,600 call-seconds. Divide by 100 = 5616 “centi-call-seconds” an American traffic figure.

Gloria
Guest

Dear DMCK, thank you for your help.
I wouldn’t want to disturb too much, but I have two more questions: You have 36 Erlang Traffic and you are using half rate coding, how can you determine the number of simultaneous calls in a GSM network?

How can you determine the capacity of a BTS or(RBS)?

Last question: How do you fix the number of E1 necessary to connect your GSM network to the PSTN?

Thank you very much in advance?

Gloria

dmck
Guest

I assume 36E is peak traffic. To handle 36 E requires 48 channels, therefore 48 similtaneous calls are possible. (assuming a 1% failure rate or GOS=.01)

capacity of BTS/RBS, sorry I have no knowledge of mobile network confiurations.

E1’s required. Determine the number of channels required (eg as above) and divide by the number of channels the E1 is capable of carrying.eg in a carrier grade voice network an E1 is capable of carrying 30 channels, with 32 Kb voice compression it carries 60 channels, with 16kb voice it carries 120 channels. I do not know the point at which compression is occuring for the mobile-PSTN point -of-interconnect so I cant be specific. My guess is that for a PSTN connection you will have 30 channels, therefor for the above 36E=48 channels = 2 x E1

farah
Guest

hi dmck
how did u calculate 36e=48channels

dmck
Guest

at the top of this page is a ‘button’ labelled FREE CALCULATORS, click on it then click on the link for Erlang B calculator.
Enter 36 in the peak traffic cell (left hand side), set the middle cell (Grade of Service) = 0.01 and click on the calculate button. THe right hand cell gives the answer 48, for the number of channels/trunks/lines needed.

farah
Guest

thx dmck
pls tell me how do u cal.GOService,
say for a callattempts of 1780 wht would be the G.o.s

dmck
Guest

Grade Of Service is a target value selected by the network engineer as a Service Level to give to the customers (callers). It defines the average percentage of calls that may fail because there are insufficient lines to carry the traffic load. It may be expressed as a percentage (1%) or a probability (0.01)

It is measured (to ensure the real failure rate is near the target failure) by calculating how many calls are offered to the trunk route (Offered Traffic, OT) and how many are acually carried (Carrier Traffic CT). THe difference (OT-CT) are assumed to have failed because there were no lines/trunks/channels available.

THe percentage or GOS is then a simple arithmetic, GOS=(OT-CT)/OT

farah
Guest

thx dmck,
actaully i am new into telecom,hence alot of questions.tell wht r u into ..

dmck
Guest

I’ve been in voice telecommuncations for 30+ years. I specialise in implementing and managing large private corporate networks.