How big are the interferes reaching the receiver, and at what frequencies ?

How big are the interferes reaching the receiver, and at what frequencies ? The presence of an interferer must not deteriorate the SNR by more than 3 dB. In a Bluetooth standard , sensitivity is -70 dBm. With out of band interferer, the signal allowed is x? dBm. What is the bandwidth of the input signals? What are the frequencies at the antenna and at internal nodes? Highest frequency at the receiver antenna and lower inside receiver Why do we have to change the frequency at the internal nodes?