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Erlang formula for Dual Rate TCH

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  • #40108 Reply
    Andy
    Guest

    I am trying to workout the tch erlang capacity for a “dual rate (HR/FR)” TRX in a cell sector. Any erlang formula that applies to such case. Thanks for your input.

    #40109 Reply
    alexander
    Guest

    Hi ! I duess you can consider such HR/FR TRX like ordinary TRX with capasity of HR TRX. Why you think about some specal erlang formula? It is ordinary TRX which can carry traffic, and amount of traffic channels it can carry is amount of Half Rate channels…

    alex

    #40110 Reply
    Andy
    Guest

    currently what I did to calculate the HR erlang B capacity is to include certain percentage of HR in the total tch channel in a given cell sector, my assumption is that not all MS support HR feature. Any further ideas is welcome.

    #40111 Reply
    alexander
    Guest

    I don’t think you can find MS which doesn’t support HR… I guess in whole GSM world you can find only few mobiles which still alive and does’t support HR. I’m sure that all mobiles which has been producing for last 10 years supports HR.

    alex
    http://www.dx200.biz

    #40112 Reply
    Guru
    Guest

    Something you might consider is using the HR to FR ratio on a per cell or per bsc basis. I am currently working on such a scenario at the cell level. What i did per ericsson recommendation is calculate the half-rate to full-rate penetration. Then add this percentage to the known value of available installed tch resources per cell. This will essentially adjust for potential HR usage. Figure your erlangs using this new value.

    It would be much easier on a system with HR deployed in all cells but i do not have such a scenario so i went to the cell level so that i have unique figures for each accordingly.

    I am not certain on the accuracy of this method because i have just started to use it. Only time will tell.

    #40113 Reply
    Oliver
    Guest

    I have seen tables for traffic HR calculation. Entries are HR penetration against FR TCH, these are based on simulation models.
    But i believe it is also necesary to consider the thresholds defined for BTS and BSC to access or not to HR resources.

    About MS supporting HR most of vendors are including now AMR capable instead of HR because it gives you better quality and improve resources utilization.

    #40114 Reply
    Guru
    Guest

    I agree that the FR->HR and HR->FR mode changes must be accounted for somehow. Perhaps you could use a measure of HR to FR usage per given time period and factor in that percentage. I use a report via BizObjects that displays the spread of HR vs FR for a given cell. I guess this detailed data could help increase the accuracy of the erlang projection.

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