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# HR calculation ALU

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• #60940 Reply Jane
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hi
how can i calculate the exact number for THR_FR_LOAD_U_SV1&3 and THR_FR_LOAD_L_SV1&3 if i want to make HR tuning is there any formula

#60941 Reply Rex
Guest

Hi Jane,
THR_FR_LOAD_U_SV1=(Number of HR TCH/Total nb of Tch)*100. Default value according to ALU is 70.

THR_FR_LOAD_L_SV1= 20 (for 2 TRX), 30 (for 3 TRX)and 40 (for 4 TRX or more than 4 TRX )

THR_FR_LOAD_U(L)_SV1(3) are for AMR_HR.
Regards,
Rex

#60942 Reply Jane
Guest

Hi Rex
Thank you , but this one is not related to traffic
let say if i have 3 TRX and already taking 25 20 Erl what would be the setting

#60943 Reply Rex
Guest

Hi Jane,
3 TRX, 1 BCCH and if you declared 2 SDCCH then remains 21 TCH.
25 Erl with 2% blocking needed about 34 TCHs. So, you need more 2 TRXs. If you declare 2 TRX in HalfRate and assume first TRX has 1 SDCCH and second 1 SDCCH then second and third TRX together have 8+7=15 TCHs which would be in Half Rate. 6 TCH in BCCH TRX that’s all together 6+15*2=36 TCHs, enough to avoid congestion.
Now, (15 TCH in Hal Rate/(15+6))*100=71.42%. So, THR_FR_LOAD_U_SV1=71 (aprox 70) and THR_FR_LOAD_L_SV1=30 (because you have 3 TRXs)
I hoppe it helps,
Rex.

#60944 Reply Rex
Guest

I forgot to add more,
if loading reaches 30 % that’s 0.7*21=14.7 TCH (take as 15 TCH) then HR is activated and deactivated (work on Full Rate) till unloading reaches 30% that’s 0.3*21=6.3 (7 TCHs).

#60945 Reply Rex
Guest

Sorry, instead of “if loading reaches 30 %” should be “if loading reaches 70 %”.

#60946 Reply Pix
Guest

Rex, Jane,

Rex, your post seems to reach valid conclusions but the process is a little unclear.

The variable is AV_LOAD, which is the current load of the cell.
AV LOAD = number of busy TCH in the cell / number of available TCH in the cell.
For example : 3 TRX, 21 timeslots “TCH”
Assume : 11 HR Calls + 5 FR Calls
It means that there are 6 timeslots currently defined as HR (= carrying 2 TCH), while the other 15 timeslots are “Full” (= 1 TCH)

AV_LOAD = (11 + 5) busy TCH / (6*2 + 15) available TCH = 16 / 27 = 59%

The 2 parameters to control HR “non-AMR” are
THR_FR_LOAD_U_SV1
THR_FR_LOAD_L_SV1

If AV LOAD > THR_FR_LOAD_U_SV1
Then *New* calls are setup in HR

If AV LOAD < THR_FR_LOAD_L_SV1 Then *New* calls are setup in FR. It is important to understand that even though the load is decreasing below THR_FR_LOAD_U_SV1 (the upper threshold) ... the new calls are still setup in HR. They are setup in HR as long as the load is floating above the THR_FR_LOAD_L_SV1. Draw the graph to really understand this. Basically, my advice is to tune the THR_FR_LOAD_L_SV1= 30% THR_FR_LOAD_U_SV1 = 70% and if you see there is still congestion, then try this : THR_FR_LOAD_L_SV1= 20% THR_FR_LOAD_U_SV1 = 60% It is a game of trials, to find the best balance between FR (good quality) and HR (good capacity). For AMR, the algorithm is exactly the same, except that 1/ the thresholds end with "SV3" 2/ the impactis that (a) the new calls are setup in HR AND (b) the current ongoing calls are changed from FR to HR ! That's also very important to understand that. Regards, Pix

#60947 Reply jane
Guest

Thanks alot pix and rex may i know why the gap between upper and lower is around 40%

#60948 Reply Pix
Guest

Jane,

it can be whatever you want.

pix

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