 This topic has 9 replies, 1 voice, and was last updated 19 years, 1 month ago by Rommel.

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asim tahirGuest
i want to know the number of trunks with the following data.
NO. OF SUBSCRIBERS 3008
ERLANG/SUBSCRIBER .125
ERLANG/TRUNK .8Muhammad Salman KhanGuestI think this formula is the best one i saw ever. As far as the calculation point of view is concerned , this must be improved to the user level extent so that user of every level can understand the “in depth” of this formula.
I am an Electrical Engineer and i have studied Telecommunication in terms of engineering point of view. But i didnt have any intro of this formula. but when i came to know about this formula, i understand it at once.
But sir i strongly recvommend if you please tell methe book which should tell me the know how of this formula. i want to know the calculation involved in it.
asim tahirGuesti am still looking for the better reply of my question.Further i also want to know foe releasing subscribers in an exchange what one should take into account to avoid congestion.
Eduardo OlguinGuestI’am looking for the formula that calculate the values in Erlangs
or code of this formula for make a application in delphiasim tahirGuestwiyh a grade of service .001 how many calls one route can serve with sixty trunks.
ellind zubiriGuesthwo many trunks are needed for the following:How many agents?
8,000 minutes per busiest month?
3.0 minutes average length of callRavindra Mohan MathurGuestAsim,
I think data provided by you is not sifficient for the calculation of trunks. You should provide information like percentage of internal call and calls going or coming into the system i.e. the Call distribution ratio.If we assume that 70% calls are the external call i.e. incoming call from external world and going out of the system then we can say 329 trunks are needed.
No. of subscriber=3008
Erlang/sub=0.125
Erlang/trunk=0.8Total traffic=3000×0.125=376 Erlang
Assuming 70% Traffic is incoming/outgoing for the system and 30% calls considered as internal calls then required trunks are given as:
(376×0.70)/0.8=329
I think these figures are right. I want opinion of others also.
Ravindra
ravindra_1970@hotmail.comRommelGuestHmmm…
Ravindra –Since Erlang is the amount of traffic carried on a traffic sensitive facility for 1 hr, why are you assuming that 30% are interal?
Asim –
Since you know the amount of traffic you want to present to each trunk, why do you need a formula to compute it for you. Voice traffic engineering is based on 3 facts…blocking, load, and # of servers (DS0)s and assumptions about the traffic model generally random arrival patterns, infinite amount of sources and blocked calls lost.
You do not have all three so we cannot compute this for you…but you do have the amount of traffic and the amount of traffic you want in each circuit.3008×0.125 = 376 Erlangs
376/.8 = 470 circuitsUsing the Erlang B formula we find that the blocking is incredibly low…You will have too many idle circuits and are in a sense wasting money.
The proper way to design it is by finding the amount of traffic and determining what your company wants as their Grade of Service(GOS)If we assume a P001 blocking rate, random arrival and 376 Erlangs of traffic you need approximately 425 DS0s.
60 DS0s @ P001 yields 40.794 Erlangs of traffic
Ellind
I cannot answer yours because there is not enough information. How many days are in your month? 20? 28? 30? 31? Is the traffic evenly dispursed throughout the week or is it only dispursed through the business week? What percentage of the calls in one day are during the busy hour? most assume 17 – 20%. What is your grade of service? This will get us the lines and can be based on an erlang B formula…if want to take retrial rates into account you would need to provide the retrial rate and use an Extended Erlang B formula. To determine the amount of agents you will need to give us the amount of delay that a user can sustain, in order to find out the number of agents.Regards,
Rommel
Yaron BGuestwhen calculating ports\minutes
is erlang results are two ports per call or one port per callRommelGuestAn Erlang is the amount of traffic it takes to keep a traffic sensitive facility busy for one hour.
If I have 1 Erlang of traffic with a smooth arrival pattern, I would only use 1 trunk. The 1 Erlang of traffic can be 1 call for 1 hour or 20 calls at 3 minutes each one after the other.I would suggest reading the following:
http://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/voipsol/ta_isd.htm#42424 
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