Receiving Data packet of Unknown Frequency using SDR

[rohithanayady]

I have one doubt about SDR. I am working on data packet transmission and reception using SDR. If we transmit a data packet at a frequency, and setting the receiver SDR LO frequency to that freq(freq with which the data packet transmitted)
we can receive the data packet.
My question/doubt is that, if the receiver  don't know the transmitting frequency of a data packet , How will we receive the data packet ? I think it is important for some wireless protocol like sigfox, where there is no channel grid or we don't know the transmitting freq of the data packet

Please give an answer to this doubt or give any reference to solve this issue

[Green_Farm]

Hello.

I would like to turn your attention that the receiver system must be tuned to a certain frequency at which it wants to receive a data packets from the transmitter. Otherwise, it couldn't receive any data packet.