03.643GPPGeneral Packet Radio Service (GPRS)Overall description of the GPRS radio interfaceStage 2TS
The GSM Physical RF layer is defined in GSM 05.xx series recommendations, which specify among other things:
– The carrier frequencies characteristics and GSM radio channel structures (GSM 05.02 );
– The modulation of the transmitted wave forms and the raw data rates of GSM channels (GSM 05.04 ); and
– The transmitter and receiver characteristics and performance requirements (GSM 05.05 ).
In the case of EGPRS, the modulation format is inherently signalled by the rotation factor of the training sequences as specified in GSM 05.04  and GSM 05.02  , enabling blind detection in the receiver.