 This topic has 14 replies, 1 voice, and was last updated 5 years, 7 months ago by festus.

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bpongGuest
can anyone confirm if C/I= 12dB for GSM?
can I interpret that if I got a wanted signal at 90dBm, the interference cannot be higher than 102dBm?ArindamGuestHi,
In GSM the acceptable value of C/I is 12dB or higher. Allthough some vendors say that with hopping even 9dB or higher can be acceptable.This means if your serving frequency (C) should be at least 12dB higher than the interferer(I).
So if you have a serving ARFCN at 90, then the interferer should be at 102 or lower.
bpongGuestDoes the interferer (I) mean cochannel ARFCN or adjacent channel?
ArindamGuestWhen you’re talking about C/I, it means cochannel. For adjacent channel , the relevant parameter is C/A.
ArindamGuestThe term “I” indeed is the cochannel interferer. When we are talking about adjacent channel interference, the relevant parameter is C/A.
bpongGuestWhat’s the C/A value for GSM, offset at 1 channel & 2 channels away?
ArindamGuestUsually the recommended value of C/A is 3dB. This is an Ericsson recommended value.
bpongGuestIs it so low, 3dB? I thought it should be around 5060dBc.
ArindamGuestHi,
I am afraid it is not 5060. May be ,you could give me your mail id, I can send you a document dealing with C/A and C/I.bpongGuestI just read the GSM spec.
C/A @ 200khz = 9dbAliShahGuestCan anyone tell me the range of C/A in GSM ???? please……… m much confused
pixGuesth,
C/A is just the C/I with I = the adjacent freq.
an ok value is C/A > 9dB, for speech purposes.
You can find all the thresholds you need in 45.003 i believe.
regards
pixgmGuestWhen predicting C/Ic=9dB for the purpose of frequency planning, one must keep in mind that a prediction is a prediction. In reality, the measured value can be higher or smaller with a probability of 50%. Theoretical mathematical calculation can show more details. Therefore it is better to predict a value higher than 9dB, at least 12dB or 18dB or more.
gmGuest9dB is for speech.. EGPRS can require a C/I up to 30dB ! (mcs9)
festusGuestAm finding it difficualtto calculate the percentage of C/I while prepering report for ssv. could someone help me with the fomular?

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