[Discuss-gnuradio] tx_ofdm.grc start_of_burst end_of_burst

[xianda]

Hi all:
         I know a packet in the example tx_ofdm.grc include a preamble,a header,the payload and crc value.Recently I have used the UHD API to send packet.And I want to know whether the tx_ofdm.grc add start_of_burst and end_of_burst automatically.Namely,need I add start_of_burst at the beginning of every packet and add end_of_burst at the end of every packet?
        Thank you very much.
Best regards,
xd