Hi， everyone.I am now using USRP b210 and gnuradio to implement a MIMO system. In order to determine the beginning of the received signal, I use the synchronization sequence to find the frame head, and display the offset of the frame head compared with the item that the receiving antenna starts to receive on the terminal. But when I run the flow graph every time, the offset of the frame header is different. Where does the difference come from? The wireless transmission process or the gnuradio data processing process? In addition, on b210, is the transmission delay from two different transmitting antennas to two different receiving antennas the same?