GSM (Global System for Mobile Communications) is a set of ETSI digital cellular standards organized as a hierarchical network architecture, in which cells are grouped under Base Station Controllers, which are grouped into Location Areas, which are managed by Mobile Switching Center regions. The system relies on distinct identifiers (IMEI, IMSI, MSISDN, MSRN, LAI) to separate equipment identity, subscriber identity, and telephone number, enabling user mobility independent of equipment mobility via the SIM. GSM combines FDMA/TDMA multiple access with GMSK modulation, and its architectural inefficiencies (guard bands, fixed time slots, complex frequency planning) motivate the shift toward CDMA-based systems, which Shannon's channel capacity theorem (C = B log(1+SNR)) favors for greater capacity via wider bandwidth and lower per-user SNR.
GSM (Global System for Mobile Communications) is a set of ETSI digital cellular standards organized as a hierarchical network architecture, in which cells are grouped under Base Station Controllers, …