- This topic has 7 replies, 1 voice, and was last updated 17 years, 7 months ago by
.
-
Posts
-
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 frequencyhello,
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)
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?????????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.
if the adj is -60dBm, then it’s bad.yes, the adjacent frequency is stronger than the serving frequency. it’s a very useful characteristic for frequency planning with multilayer (umbrella / micro)
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?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
Why C/A is -ve value whereas C/I is positive value?
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.
- The forum ‘Telecom Design’ is closed to new topics and replies.
