Dear all could you please help me with my understanding or advise an appropriate place to post?:

  • GSM channels are separated between each other by 200 kHz (channel frequency being in the middle).

  • If channel frequency is 914.8 MHz its bandwidth is 914.7 - 914.9 MHz interval.

  • So once mobile is switched on it scans all channels (914.8 915 915.2 915.4 etc., etc.) bandwidths (each width of 200 kHz) to find the strongest signal strength in terms of dBms.

  • Once it finds the strongest channel / bandwidth what is mobile doing?

Is it searching for so called frequency correction burst which is in fact a pure sine wave in this 200 kHz bandwidth.

As per GSM spec frequency correction burst is ~ 67 kHz above the carrier frequency so it means that if mobile finds frequency correction burst (sine wave) on some particular frequency within this bandwidth it simply subtracts 67 kHz and becomes synchronized with carrier frequency?

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    \$\begingroup\$ The standard doesn't specify how the phone initializes and synchronizes; how to do that is up to the phone; and while I'm sure the frequency differences in original GSM were chose such that it makes sense because the difference is some multiple of another used frequency, modern baseband chipsets will just do a broadband observation, estimate frequency and timing – for something that does 4G / 5G, doing GSM "on the side" is really kind of not a big deal. \$\endgroup\$ yesterday

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