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AMR,how to calculate erlangs

Viewing 15 posts - 1 through 15 (of 25 total)
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  • #45460

    Can somebody tell me how to calculate AMR offered erlangs

    AMR utilization is not 100% since there are non-AMR handest in the market which cannot utilize potential of AMR at all in which case,the metioned subscriber is able to use only offered erlang of TCH full rate.

    Any comments


    No takers.No experts in AMR ????


    Hi Manoj,

    AFAIK, the AMR utilization is either equivalent to a full rate TCH or a half rate TCH, depending on the codec used.

    It is absolutely equivalent to FR and HR occupancy of the radio timeslots.

    Maybe your question is about AMR penetration rate in your market ? and how does it impact the traffic mix ?

    Well, you have to base your studies on QoS traffic measurements (actual erlangs, and actual split of AMR and non-AMR calls…).

    Best Regards,



    How do get this info.I am using a Nokia system and I would like to know which report exactly gives the bifurcation of AMR and Non AMR calls


    I’m using Alcatel, sorry… i know one can’t find the exact call amount in AMR, but you may be able to find certain types of HO linked to AMR usage ? Or some alternative stuff like this. And from that, you might be able to “assume” your pentration rate of AMR users.


    But is there no thumb rule to find this.I am finding out utilization of each sites and the result I get is a grossly underutilized value (Utilization=carried/offered erlangs)although the site has got a decent block in it


    are you talking about under-utilization of AMR ? i don’t really understand your issue… please share your indicators measurements, etc…


    Pix,I will put it in a simple manner

    A sector has 2 no of TRX which gives us offered erlang of 8.2.
    Supopose now we enable AMR in all timeslots so that the offred erlangs become 21.9.
    Now we may not have all customers having AMR handset.
    The sector has got a peak carried erlang of 12 and has a decent block rate too
    If you find utilization with 8.2 as offered,the utilization is >100
    and if you find it with 21.9 as offered,the utilization is very much less(even though block exists).

    Now there needs to be some factor which will give the correct value of offered erlang(which has to be something in between 8.2 and 21.9)
    depending upon the AMR handset served by this sector.

    I need that particular factor and the way to generalise it


    Pix ,any thoughts


    I dont understand how you get increased erlang when AMR is activated. AMR is a codec method therefore improves speech quality espcially in cases where frequency reuse is tight and interference may cause a problem. Activating AMR does not give you more timeslots therefore your Erlang does not increase. However AMR does give the operator the option to increase capacity at a site with tighter frequecy reuse so I guess you could increase your erlang that way. There is no way by just enabling AMR that you increase your erlang by nearly 3 x the amount.


    If you have 14 TCH TS you have 8.2Erl at 2% blocking if you enable HR or AMR-HR then you have 28 TCH TS which gives you 20.15 Erl at 2% blocking. It is interesting which value to use if you AMR penetration is not high enough. You can see the penetration from different phones used in your network, i think IMEISV from MSC/billing guys. We always use FR capacity for offered traffic and have in some places utilisation over 100%.



    Vanderley said it all 🙂

    Now, in my opinion, knowing the exact “offered capacity” of a cell is not relevant. What matters is whether or not it is congested at the peak hour.

    If it is congested, then your offered capacity is not enough.

    If it is NOT congested, then your capacity is enough.

    And that really is all that matters for a R engineer.


    Hi all,

    I just confused about Half Rate Traffic. As I know HR will double up Traffic.
    Let say , offered traffic for 2 TRX is 8.2 Erlang. If we implement the HR 100% should be 28 TCH. 28 TCH will be given 21.9 Erlang (2% GOS).
    But I have problem with my site 2 TRX (100% half rate ) which was carried 22.2 Erlang and Blocked rate was 65%.

    Can u explain !



    22.2 erlangs is higher than 21.9 erlangs, so your cell is reaching its full capacity already. But it is true that it shouldn’t reach 65% congestion… Have you tried to increase the TCH queue timer ? Have you check all TS are used in HR ? When setting up a call in this cell, it will always be in HR or will it be FR until a certain traffic load, and then HR ?



    We have recently done trials on GSM AMR-FR but the results are not very encouraging.Not only the drop call rate has gone up by around 10%, there is a slight decrease in total traffic in the cell and Erlangs minute per drop has gone down as well.
    I know that this increase in drop call rate is a known problem due to diffrence in AMR speech codec and signalling (SACCH)performance, which may suggest why we have seen drop in traffic levels.

    Can anyone share his/her experience on this?

Viewing 15 posts - 1 through 15 (of 25 total)
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