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# Erlang to minute conversion

• This topic has 23 replies, 1 voice, and was last updated 2 years, 3 months ago by Erlang(TCH) to coast conversion.
Viewing 15 posts - 1 through 15 (of 24 total)
• Author
Posts
• #49784
Latheef
Guest

If a route which have 20 circuits carried 3.3 Erlangs in one hour.
How do i convert 3.3 Erlangs to minutes.?

#49785
pix
Guest

3.3 erlangs = 3.3 hours of cumulated time of traffic onto the system

3 hours = 180 minutes
0.3 hour = 20 minutes

3.3 hours = 200 minutes

#49786
latheef
Guest

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

#49787
pix
Guest

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.

#49788
Arun
Guest

Dear Pix,

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

regds
Arun

#49789
pix
Guest

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.

#49790
Arun
Guest

Dear PIX,

Thx for clarifying the doubt.

regards
Arun

#49791
scor
Guest

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

#49792
pix
Guest

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.

#49793
scor
Guest

Mr.Pix,

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

Thanks

#49794
pix
Guest

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

#49795
Cplus
Guest

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..

#49796
Pix
Guest

Bandwidth ?

I assume you mean the number of channels compared to the number of erlangs?
6 channels can carry only 2.3 erlangs (which means that only 2.3 channels are busy during one hour, in average, but that’s enough to get 2% congestion), and so on?

Well, the reason is because the traffic has a random rate of arrivals, and you want to keep the probability of “1 call incoming while 6 are already engaged” as low as possible (below 2%).

Regards,
Pix

#49797
cplus
Guest

Dear Pix, is that last answer for my question ? Because i have doubt whether is for my question or not. Thank u very much…

#49798
pix
Guest

… yes, that was for you, Cplus.