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# Erlang formula for Dual Rate TCH

Viewing 7 posts - 1 through 7 (of 7 total)
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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.

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

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.

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.

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.

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.

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