- This topic has 14 replies, 1 voice, and was last updated 5 years, 7 months ago by
festus.
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bpong
Guestcan 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?Arindam
GuestHi,
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.
bpong
GuestDoes the interferer (I) mean co-channel ARFCN or adjacent channel?
Arindam
GuestWhen you’re talking about C/I, it means co-channel. For adjacent channel , the relevant parameter is C/A.
Arindam
GuestThe term “I” indeed is the co-channel interferer. When we are talking about adjacent channel interference, the relevant parameter is C/A.
bpong
GuestWhat’s the C/A value for GSM, offset at 1 channel & 2 channels away?
Arindam
GuestUsually the recommended value of C/A is 3dB. This is an Ericsson recommended value.
bpong
GuestIs it so low, 3dB? I thought it should be around 50-60dBc.
Arindam
GuestHi,
I am afraid it is not 50-60. May be ,you could give me your mail id, I can send you a document dealing with C/A and C/I.bpong
GuestI just read the GSM spec.
C/A @ 200khz = 9dbAliShah
GuestCan anyone tell me the range of C/A in GSM ???? please……… m much confused
pix
Guesth,
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
pixgm
GuestWhen 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.
gm
Guest9dB is for speech.. EGPRS can require a C/I up to 30dB ! (mcs9)
festus
GuestAm 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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