I know my question is too basic. I just started reading on this I suppose.

My general understanding is that, in GSM, each pair of carrier in a cell (ARFCNs) is divided into eight time slots (FDMA + TDMA). And each of those time slots are channels. But the thing is, some of these time slots (channels) are for traffic purposes (actual voices or data) and some these are for control purposes (Signalling and what not!). I hope I am right this far.

So my question is, how many of these eight time slots per carrier is for traffic purpose (TCH) and how many are for control channels?

I found an excerpt from an old Ericsson cell planning pdf somewhere on the internet, and there it is said that, if there are two frequencies per cell, then traffic channel per cell will be = (2x8 -2) = 14. So, I can assume that, of the eight time slots per frequencies, one time slot is allocated as a control channel and the rest seven are Traffic channel. That is why, there 14 TCH (seven per each frequency) in this example. You can see the excerpt below in the image.
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But, in this webpage, visualizing the GSM timeframe, the first two time slots are allocated to control channels. the rest six time slots are traffic channels.

So I am at a loss about, how many time slots exactly per a single frequency are allocated for traffic channel and how many for control channel?

I appreciate any help. At least, If you could point me to any link or online material, that would be great.

Thanks in advance.

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