Erlang Formula

Hi,

Can you tell me the difference between LSR/QSR/TRD in traffic ?

ALOK U HAVE TO OAR DEEP IN THE INTERNET TO FIND ERLANG B AND ITS APPLICATIONS THE THEORY BEHIND ERLANG B IS A LITTLE EASIER TO COMPREHEND I THOUGHT THAN A AND C .i CANNOT RECALL THE SITE BUT M DEFINITE;Y SURE THAT N A FEW HITS OF GOOGLE U WOD FIND IT..

hi
I would like to know how the switch planning is to start ?
like start with 6BHCA in a typical GSM or CDMA n/w and you have any switch having different capacity what could be the subs can be connected ? what are the processor capacity ? how many Erlang is supported by switch etc. if a goood article is available on it pls provide.

my mail id- shailendra_sitoke@ril.com

GoS = “Grade Of Service” = Blocking Probability Percentage
You can check the internet (Google) for some material like the erlang B tables I found in Excel format recently.
Some explanation is also given at the following URL: http://www.dcss.mcmaster.ca/~qiao/publications/erlang/newerlang.html

Hope that helps.

Hi Tim,

your question was a good exercise. I created the following macro in VBA (you can just copy/paste). It has the following characteristics:
– limitation in the number of channels (creates buffer overflow if too many channels): I did not want to waste time solving this problem. You can have a look at it by yourself I guess.
– configurable number of circuits
– configurable GOS
– configurable precision desired on the capacity (that’s the variable “dblDesiredPrecision”)
– configurable range of research of the value.
– optimised calculation of the factorials (we dont calculate the same values over and over again. Once is enough… and so much faster!!)

In short, how is it calculated?
1) You know that your capacity is more than zero
2) you guess that your capacity is less than a certain value (I chose 1000000000 Erlangs)
3) you try some value in between (dichotomia) and you look at the corresponding GOS. If the GOS obtained corresponds to some over-estimated capacity, your new range of research is now more than zero, and less than this value…
4) repeat until the precision obtained is satisfying

—————–
Public Sub main()

Dim resultCapacity, dblGradeOfService, dblNumCircuits As Double

dblGradeOfService = 0.02 ‘”2%” is equivalent to “0.02”. You can modify this value if you have a different GOS
dblNumCircuits = 10 ‘In this example, we use 10 circuits (channels)

‘capacity calculation
resultCapacity = dblCapacity(dblGradeOfService, dblNumCircuits)

End Sub

Function factorial(ByVal myNumber As Double) As Double

Dim i As Integer

‘keeps in memory the values already calculated of factorials. This avoids to recalculate the factorial each time
Static varFactoBuffer As Variant
If (IsEmpty(varFactoBuffer)) Then
varFactoBuffer = Array(“1”, “1”)
End If

‘we extend the factorial buffer and add the corresponding values
For j = UBound(varFactoBuffer) To myNumber
ReDim Preserve varFactoBuffer(j)
varFactoBuffer(j) = varFactoBuffer(j – 1) * j
Next j

factorial = varFactoBuffer(myNumber)

End Function

Function GOS(ByRef capacity As Double, ByRef numCircuits As Double) As Double

Dim denominator, numerator As Double
Dim i As Long

Dim capacityElevatedToPower As Variant
capacityElevatedToPower = Array(“1”, capacity)
For i = 1 To numCircuits
ReDim Preserve capacityElevatedToPower(i + 1)
capacityElevatedToPower(i + 1) = capacityElevatedToPower(i) * capacity
Next i

‘ we calculate the denominator of the Erlang B formula
For i = 0 To numCircuits
denominator = denominator + capacityElevatedToPower(i) / (factorial(i))
Next i

‘ we calculate the numerator of the Erlang B formula
numerator = capacityElevatedToPower(numCircuits) / (factorial(numCircuits))

GOS = numerator / denominator

End Function

Public Function dblCapacity(ByVal dblGradeOfService As Double, ByVal dblNumCircuits As Double) As Double
‘ The program will look for the desired value of the capacity between those limits
Dim dblMinCapacity, dblMaxCapacity, dblEstimCapacity As Double
dblMinCapacity = 0
dblMaxCapacity = 1000000000
dblEstimCapacity = (dblMaxCapacity + dblMinCapacity) / 2

Dim dblEstimPrecision, dblDesiredPrecision As Double
‘ the precision (in Erlang) on the estimation of the capacity
dblEstimPrecision = (dblMaxCapacity – dblMinCapacity) / 2
‘ precision desired on the capacity (in Erlang) calculation
‘ I chose 1E-6 because this sets the error to less than 1 Erlang on the total capacity of a normal national network
dblDesiredPrecision = 0.000001

While dblEstimPrecision > dblDesiredPrecision

‘ we estimate the GOS that can be obtained by the current value of the estimated capacity
dblEstimGOS = GOS(dblEstimCapacity, dblNumCircuits)

‘ we improve our estimation of the capacity and we reduce the interval of research of the capacity
If (dblEstimGOS > dblGradeOfService) Then
dblMaxCapacity = dblEstimCapacity
dblEstimCapacity = (dblMinCapacity + dblEstimCapacity) / 2
Else
dblMinCapacity = dblEstimCapacity
dblEstimCapacity = (dblMaxCapacity + dblEstimCapacity) / 2
End If

‘ we readjust the estimated precision because we have improved our knowledge of the value of the capacity
dblEstimPrecision = (dblMaxCapacity – dblMinCapacity) / 2

Wend

dblCapacity = dblEstimCapacity

End Function

Hi,

Can anyone help me in calculating the Hourly channel utilization in a trunk group . If I know the value of Total Usage in CCS for the trunk group in an hour.

Eg: If in a Trunk Group there are 30 channels & the total number usage is 79 CCS in an hou. Then how can I calculate the number of channels used in this particular hour.

Best Regards,
Balaji.

Hi… What do you mean “to know the traffic in Erlangs”? Capacity needs to be _calculated_ whereas traffic is just _recorded_
At the OMC, or in any system to manage the raw counters and/or KPIs, you should be able to find some data that has been aggregated to let you know the usage of resources. Ask the people who manage this tool in your company, or some optimisers should be able to answer as well… But I think the name of the tables in this tool will be different from 1 company to another.

lots of questions – no answers…..