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## Cplus - 8th January 2009  (15:21 GMT)

I would like to ask you a question.. I hope there is someone is able to help me thanks. .the question is :
Why do we use Erlang B tables and explain the reason of the 10 times more bandwidth than the average traffic..

## pix - 28th November 2007  (19:55 GMT)

scor,

of course :) if you activate HR at 60% traffic load on a cell with 30 TS, the actual number of carriers in your cell is :
(60% of 30) + (40% of 30)*2
= 20 + 10*2 = 40 carriers

you can compute your capacity based on this input.

Pix

## scor - 28th November 2007  (12:13 GMT)

Mr.Pix,

Is the same calculation holds good when we apply half rate erlang also.

Thanks

## pix - 23rd November 2007  (08:38 GMT)

scor,

sdcch traffic is about 10 times smaller than tch traffic (approx.)

unsuccessful calls (mean there was a failure during the call setup) do not use a TCH carrier. The failure occurs while they are on the sdcch channel. therefore they simply cannot be counted in the tch traffic.

if the failure occurs after the callsetup, then it is called a call drop. A call which is dropped occupies a tch carrier for a while, therefore it is counted in the tch erlang.

## scor - 23rd November 2007  (07:11 GMT)

Hello Mr.Pix,

IM into OMC Side.

What is the ratio between the TCH Erlangs & SDCCH Erlangs . Ideally the SDCCH Erlangs should be on the higher side. right

And the TCH Erlangs does capture the missed calls

Thanks

## Arun - 23rd November 2007  (05:32 GMT)

Dear PIX,

Thx for clarifying the doubt.

regards
Arun

## pix - 22nd November 2007  (21:53 GMT)

erlang is the amount of traffic really carried ! does an unsuccessful call put traffic on a carrier ?
- yes, on a SDCCH --> therefore unsuccesfull call increases the amount of SDCCH erlangs.

- no, not on TCH --> therefore the TCH erlangs are not impacted by unsuccesful calls.

## Arun - 22nd November 2007  (12:03 GMT)

Dear Pix,

Does that one hour include the unsuccessful calls also or is the erlang calculated only for successful calls.

regds
Arun

## pix - 22nd November 2007  (09:06 GMT)

the erlang is the cumulated time of traffic carried in the channels of the observed system.

1 erlang = 60 minutes
2 erlang = 120 minutes
3 erlangs = 180 minutes
4 erlangs = 240 minutes
40 erlangs = 2,400 minutes
400 erlangs= 24,000 minutes

and so on... there is no formula.

you measure 3 erlangs between 9am and 10am, it meands that there were 180 minutes of usage of your system at that hour.

## latheef - 22nd November 2007  (05:11 GMT)

thanks pix...

any specific formula to do this Erlnag to minute calculation.

If the hourly traffic has been read are you saying the traffice carrried on that particular is an accumulated figue?

Thanks

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