Talk:Erlang (unit)

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Erlang article should only contain links to 3 meaning of Erlang, so current article should be moved. But how call it ? Erlang measure or what ? --Taw

'Erlang unit' perhaps? -- The Anome

I'm thinking Erlang formula or Erlang measurement, because that's how I've heard it referred to. --justfred

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"Alternatively, an Erlang may be regarded as a "use multiplier" per unit time, so 100% use is 1 Erlang, 200% use is 2 Erlangs, and so on. For example, if total cell phone use in a given area per hour is 180 minutes, this represents 180/60 = 3 Erlangs. In general, if the mean arrival rate of new calls is λ per unit time and the mean call holding time is h, then the traffic in Erlangs A is:

   A = λh "

if someone could change these units into LaTeX... --Ivan Ivanković 21:25, 1 May 2007 (UTC)

Can somebody add information about Erlang charts to this article?

How can it be a "dimensionless unit" when it is an Erlang? 1 or 2 or 3 is dimensionless, however 1 Erl or 2 Erl or 3Erl have a unit i.e. Erlang

It is the Erlang unit that is dimensionless - since it does not represent any underlying physical quantity, e.g. Mass, Length, Time, etc. The Erlang unit represents a unit 'server', so it is numeric. As such, it may be compared to, say, Radian or Decibel - which are dimensionless units. Ian Cairns 20:42, 1 Nov 2004 (UTC)

The Erlang unit is a ratio of arrival rate to service rate and the times in these rates cancel out. Thus it is dimensionless. vignaux 02:08, 2004 Nov 2 (UTC)

Merger proposal

Currently Erlang-B has a separate article (which nevertheless appears to cover much of the same material as is included here), and Erlang-C redirects to the main distribution page. I this we can include the Erlang-B stuff on Erlang unit, and redirect Erlang-C here as well. Any thoughts? Tim (Xevious) (talk) 13:20, 9 May 2008 (UTC)

• If at all, Erlang-B should be merged into Erlang_distribution, where Erlang-C is currently directed to. Erlang-B and Erlang-C describe propability distributions derived from the Erlang_distribution, while Erlang is a unit to measure traffic. 168.230.130.248 (talk) 12:37, 14 October 2008 (UTC)

• Merge Erlang-B into Erlang unit. Redirect Erlang-B to Erlang unit. Change the Erlang-C redirect to point to Erlang unit too.

Leave Erlang_distribution alone, as it seems to be the mathematical distribution description. That article would be more up the alley of a mathematician or statistician, whereas Erlang unit is describes the use of the Erlang distribution using functions meant for network engineers and traffic engineers. Since Erlang-B and Erlang-C are both branches of this, yet very similar, they should be explained in the Erlang unit article.

And 168.230.130.248, please note that IP addresses cannot vote in polls. There would be no way to know if somebody had posted multiple times to a discussion using different IP addresses. Please sign in. —Voidxor (talk) 07:55, 1 January 2009 (UTC)

• Do not merge. Allthough I am normally a mergist, I am sceptical to a merge in this case, since these articles do not overlap much, and since the "Erlang (unit)" title is confusing. The title would incorrectly give the impression that Erlang B and C formulas may be used to calculated the number of Erlangs. By including The Engset formula in the same article, the "Erlang" title is even more confusing. Normally articles about units like Volt, bps and Baud are kept separate from the corresponding physical magnitudes (Voltage, bit rate and Baud rate). An exception is Bit/s/Hz, which is redirected to spectral efficiency. However, in this case Erlang is not even corresponding unit for the magnitudes calculculaeted by the Erlang B and C formulas - the traffic load in Erlang is only an input parameter in the formulas. If you want to keep the merge, please change title to something more appropriate, or why not merge it into the Queuing theory or Agner Krarup Erlang article just as well?Mange01 (talk) 13:04, 19 May 2009 (UTC)

• Please consider a title change. Each time I've read this (while looking for the Erlang B or C formulae), I've been wrong-footed by the title "Erlang (unit)". Coming back some time later, the actual content (which I guess is a result of the merges) does seem to hang together, but for me at least a title such as "Erlang Traffic Theory" might better describe what it's about. Also the introduction doesn't mention Erlang's formulae, which are a significant part of the content. With or without a title change, would it make sense to add a few introductory sentences about them? (I'm new here, so just finding my way!) NeilOnWiki (talk) 22:11, 25 January 2018 (UTC)

@NeilOnWiki: I have tagged the article for lead improvement. Once the lead properly summarizes article content, it will be clearer whether a rename is in order. ~Kvng (talk) 16:26, 28 January 2018 (UTC)

@Kvng: I'd like to give this a go; but first I think it would benefit from splitting up the Traffic measurements of a telephone circuit section into 2 additional parts, eg: Erlang's analysis (or similar) and Calculating offered traffic. I'll try this (and some smaller edits). NeilOnWiki (talk) 20:00, 3 February 2018 (UTC)

That's long section. Sounds reasonable. No need to ask permission - WP:BOLD, WP:BRD ~Kvng (talk) 15:33, 4 February 2018 (UTC)

I've had a go at adding some extra headings and then expanding the lead section, basing the lead text on each section in the main body, loosely inspired by WP:CREATELEAD. In-line comments in the lead's mark-up show which section is being referred to. I haven't included much on the Calculating offered traffic section, which may fit better in the Offered load article.

It would be good to use a better example in the lead's first paragraph (eg. 2 circuits one of which is used for 60 minutes and the other for 30 minutes in one hour period, amounting to 1.5 erlangs). I held off doing that, as I don't know how well that would fit in with the cited reference, which I've no easy access to. NeilOnWiki (talk) 10:54, 18 February 2018 (UTC)

Notation

Any reason for the different notation on the Erlang B and C formulas? N vs. m, A vs. E. Ladypine (talk) 10:37, 8 November 2009 (UTC)

I've assumed not. I checked out variable names in various other articles before coming up with the following changes. My two golden rules were internal consistency and not to clash with how Kendall's notation uses the same variable name:

• N → m (Kendall uses c, but m is simple and has no obvious conflict; N=calling population in Kendall);
• A → E (A=arrival process in Kendall);
• kept both i and j in Erlang B formula even though they both run from 0 to m, because they have slightly different meanings;
• kept both P_b and P_W since they're probabilities of different events (but I've fussily given both subscripts the same case).

In practice, changes only affect variables in the Erlang C section.

Other authors might prefer c to m (eg. queue theorists rather than traffic engineers: I'm neither, so this is just speculation).

Using E is slightly awkward in an article about the erlang unit (also denoted E); but it seems fairly natural and the context makes it obvious which is meant. (I'm also not convinced we should continue including the Erlang formulae under Erlang (unit), but that's a different discussion.)

Comparisons:

• Engset formula: c=servers; N=sources
• Kendall's notation: A=arrival process; c=servers
• M/M/c queue: c=servers
• Offered load and Little's law each have their own alternatives to h for holding time. NeilOnWiki (talk) 20:31, 5 March 2018 (UTC)

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Erlang Limitations vs Extended Erlang B

I've added explanatory text for Extended Erlang B (EEB), which has left me unsure of its relationship to the Limitations of the Erlang formulae. The latter warns of the possible failure of Erlang B and C when congestion is especially high, resulting in repeated retries; but EEB allows for recalls when a caller is blocked.

Does EEB overcome the Limitations that we describe; or is there a point at which congestion becomes so high that even EEB fails? (In the former case, we may wish to move the EEB section after the Limitations one.) NeilOnWiki (talk) 17:54, 9 March 2018 (UTC)