Teach me about C/I

[Biku]

I want to know what is meaning of C/I> 9 db and C/A>-9db or C/I> 12 in GSM frequency plan. Explain with me with some example that it will be better for me to understand.

[baby2]

c is carrier you active (camp on)
I is interference
A is adjacent cell (ex you use BCCH ch 35 ,adj is 34 or 36

easy if c/I 9 dB meaning your signal stronger than interference 9 dB

[firstmaxim]

Use C/I greater than 9 dB when you enable frequency hopping.

[veer sharma]

Use C/I greater than 9 dB when you enable frequency hopping.

C/I is carrier to interference ratio and its value is..
>15 Ok
<9 is bad

[zidan001]

Hi Biku,

C/I stands for carrier to interference ratio,is the quotient between the average received modulated carrier power S or C and the average received co-channel interference power (http://en.wikipedia.org/wiki/Signal-to-interference_ratio)

According to GSM specification required C/I for BTS transceiver to decode useful data from interference is more than 9 dB its associated with C/I > 9 dB if you use frequency hopping, and C/I > 12 for network without frequency hopping.

usually almost all operator now required C/I > 12 dB for their network nevertheles the hopping system used.

if the co channel carrier falls below C/I 9 dB, it can be called co-channel interference.

C/A (C over A) The carrier-to-adjacent ratio is defined as the signal-strength ratio between a serving carrier and an adjacent carrier.
its formulated: Serving signal strength (dBm) – Adjacent signal strength (dBm)
According to GSM specification 05.05, section 6.3:

Adjacent (200 kHz) interference: C/Ia1=- 9 dB
Adjacent (400 kHz) interference: C/Ia2=- 41 dB
Adjacent (600 kHz) interference: C/Ia3=- 49 dB

its mean, one adjacent channel becoming interferer if the number above surpassed.
And will be impact to FER and BER on serving carrier.
how to fix this is to retune the requency so we can get better channel allocation.

hope its clear enough.

[halbgott]

Use C/I greater than 9 dB when you enable frequency hopping.