Hi Nasir,
BB2F card in nokia BTS solutions has main function of handling baseband signal processing in BTS(hence BB in the name which stands for base band). One card controls 2 TRX’s.
Each BB2F card has two identical circuits inside with DSP and other processors to handle functionality of each TRX such as controlling TRX oscillators according to defined frequencies and hopping parametes and other RF parameters, processing baseband signal and align it to and from E1 or T1 interface and baseband error correction.