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C/I and C/A

Viewing 8 posts - 1 through 8 (of 8 total)
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new engineer
Guest

dear
can any body explain for detail expalnation for C/I and C/A and what is the threshold by example in order to see in TEMS it is come from adjacent frequency or co frequency

pix
Guest

hello,

i forgot about the details, but i remember the help (F1) of TEMS is very detailed about this. They give the method of calculation of C/A and C/I.

i remember that the C/I is not the real C/I though, it’s just an approximation.

C(co)/I > 9dB is needed in order to have good voice quality (above 12dB is even better)

C(adj)/I > -9dB in order to have god voice quality (> -6dB, even better)

new engineer
Guest

pix
would you please give more detail about C/A let say I have BCCH 20 and adjacent BCCH is 19 what must be the Rxlevel difference between them it is -9db in this case the sdjacent BCCH some times will be stronger as you make by equation C-A>=-9 is it write?????????

pix
Guest

BCCH(serving) = -70dBm

the maximum value of an adjacent frequency should be -61dBm (-9dB difference)

if the adj is -65dBm, then it’s totally fine.

yes, the adjacent frequency is stronger than the serving frequency. it’s a very useful characteristic for frequency planning with multilayer (umbrella / micro)

new engineer
Guest

pix
thanks alot and just one more Question about the last sentence(it’s a very useful characteristic for frequency planning with multilayer (umbrella / micro)) what do you mean by this would you please give me more information?

lotfi
Guest

hi all,
anyone has a detailed doc about C/I, C/A and interference probability ? I’m exactly searching for curves : interference probability = f(C/I) and interference probability = f(C/A)

thanks for help

learner
Guest

Why C/A is -ve value whereas C/I is positive value?

pix
Guest

C/A = rxlev(serving cell) – rxlev(adjacent channel)
with adjacent channel = a channel which is adjacent to the serving channel by -1,-2,-3, +1, +2, +3 offset. (depends o your configuration)

C/I = rxlev(serving cell) – rxlev(cochannel)
with cochannel = same frequency as serving cell.

they can all be +ve or -ve ! but it happens that in a gsm network, only the cochannel interference are very dangerous. So frequency planning needs to pay particular attention to C/I, and keep it as high as possible.

for C/A, it can be negative since it won’t affect voice quality.

Viewing 8 posts - 1 through 8 (of 8 total)
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