The BSC is the functional entity within the GSM architecture that is
responsible for RR (Radio Resource) allocation to a MS (Mobile
Station), frequency administration and handover between BTS (Base
Transceiver Station) controlled by the BSC. The BSC function may be
physically located with the BTS. If this is the case there is no
requirement for the Abis interface, and a preparatory interface to map
signalling and traffic destined for the MS may be employed.

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