Thanks to Marcus Müller I became aware of the Packet TX and RX blocks.
I use the Packet_loopback_hier.grc example. However the example is set to 2 samples per seconds=sps. When I try to increase sps=100, the number of taps of the RRC filter becomes( 5*sps*nfilts) exceeds its limit.
../.grc_gnuradio\packet_rx.py", line 49, in __init__
self.mark_delay = mark_delay = mark_delays[sps]
IndexError: list index out of range
Is there another way to increase the speed limit?