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Erlangs vs Kb/s

Viewing 13 posts - 1 through 13 (of 13 total)
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  • #34233 Reply
    Eric Daly
    Guest

    General question…Is there a relationship between Erlangs and Kb/s? For example, if I knew that on a 64kb/s signalling link .22kb/s was transmitted and .20 kb/s was recieved within an hour. Is there a way of relating this to Erlangs or is there any point?

    #34234 Reply
    Looker
    Guest

    Eric, I think Erlang is a telecom traffic unit which works on circuit switching. One circuit used for 1 hour makes 1 erlang traffic. Circuit switching needs a dedicated channel (although it may use mutiplexing). Packet switching shares a circuit or channel. So here, a circuit is not dedicated to anyone. Moreover, packets can travel through alternate routes. Kb/s is a measure of data flow for packet switching. So erlang does not apply here in that sense.

    #34235 Reply
    Nil
    Guest

    You may want to relate Erlangs to Kb/s when you’re dealing with both circuit and packet data traffic. For example, if you’re dealing in GSM and GPRS systems. I’m trying to figure out what the most common method for doing this is. From what I’ve read so far, most traffic engineers seem to convert Kb/s to Erlangs. If anyone knows the this conversion I would like to find out as well.
    Nil

    #34236 Reply
    Eric
    Guest

    Nil,
    From what I’ve read,Erlang is measure of ‘occupancy’ so

    Erlang = usage / capacity

    So if you measured X kbps on a sig link, which was on a timeslot of capacity 64kbps then

    Erlang = X/64

    you may also want to additionally factor in a QoS measurement, so would never run them at above 0.8 erlang = 80% of 64 =~51k

    #34237 Reply
    Nil
    Guest

    Eric,

    Could you tell me a bit more about the QoS factor? Why would you put this factor in for QoS measurement? So that you account for QoS queries or agents to run on the system as well?

    Also, is 0.8 erlang a reasonable value fo QoS factor – I would have thought 0.9 to 0.95 erlang.

    Thanks.

    #34238 Reply
    Eric
    Guest

    Nil,

    I’m looking at it from a GSM traffic point of view.The Qos or Gos (Grade of service) will ensure that if I have peaks in traffic there will be sufficient capacity available.Most suppliers recommend that you don’t dimension above 80% of the total capacity. In reality, if you have two signalling links you might might to consider redundancy, in that you dimension them upto 40% of their capacity.
    So if one fails the other can handle the full load.
    Hope this answers your question!

    #34239 Reply
    Radhakant Das
    Guest

    Nil,
    I use to take the capacity of 64Kbps signalling link as 2Erlangs.
    1Erlang in Tx direction at 64Kbps rate & 1Erlang in Rx direction at 64Kbps.And I have never come across any sort of overloading or congestion after engireeing the systems on this concept.Can U pl. give Ur comments?

    #34240 Reply
    Nil
    Guest

    Radhakat Das,
    I think you may be allocating too many channels for your systems if you assign 2 erlangs for 64kbps data rates. My primary reasoning is that the Rx direction is not nearly as loaded as the Tx direction. And also that you are not using the 64 kbps on the Rx or Tx side continuously. The traffic loading will most likely be less than 100%. As an example, data packets will be assigned an order in a particular channel based on service session duration, queueing, average packet length, service priority, etc… so the system tries to keep the channel occupied without having services wait too long before being serviced. But there is a good chance that the sytem will not have enough requests to keep this channel busy all the time. So when allocating erlangs for data at a specific data rate the channel usage has to be taken into consideration.
    Nil

    #34241 Reply
    Radhakant Das
    Guest

    Thanx Nil, for your comments.But I asked about the maxm. or 100% capacity of a signalling link

    #34242 Reply
    nasir
    Guest

    how to relate between GoS with Erlang.

    #34243 Reply
    Ali Hammad Akbar
    Guest

    I am in NUST, Pakistan. Question: How can we possibly relate a traffic load of 2.8 Erlangs to bps or Packets/sec on ethernet [Packet Size = 1500 Bytes and MAX data rate of 10 Mbps]? I mean that Erlang is basically a PSTN traffic unit. In order to map it to data networks, we need to know certain information as Analog-to-Digital Encoding scheme, interpacket delay etc. Can somebody help? Thanks Ali

    #34244 Reply
    Luigimex
    Guest

    Hi, great forum, Erlang is oriented to Voice therefore first step is to calculate how many channels you need to support 2.88 Erlang, my calculation gives 7 circuits (2.2 Erl @0.01).

    One call using VOIP is 24 Kbps (depending in your codecs for compression), then Kbps could be:
    24 Kbps* 7 = 168 Kps. Then based on this you can convert to Ethernet packets.

    Comments or corrections are welcome

    #34245 Reply
    VVV
    Guest

    How to convert Kbytes to Erlangs

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