Hi there, I am using GNU Radio 3.8 on Ubuntu 20.04, and I have encountered a situation that I am struggling to understand. I have a flowgraph that includes two hier blocks representing the TX and RX parts of a modem. The TX block receives PDUs with the packets to be transmitted and generates a stream of complex samples. The RX block, on the other hand, expects complex samples as input and outputs the demodulated and decoded packets in PDU form. It is important to note that neither of these hierarchical blocks uses any OOT blocks; everything is implemented using native GNU Radio core blocks. The problem arises when the TX block is fed with a single packet. In this situation, it seems like there are not enough samples generated to "push" the samples all the way to the end of the flowgraph. This happens when no hardware device is used, i.e., only in software simulation. After analyzing the chain, it seems that the issue is not in the TX block itself but in the RX block. Even when feeding the RX block with a recording of complex samples from a single packet, no output is generated. However, if I append more samples (even just noise) to the end of the recording, the message appears to be correctly received. My question is: Am I interpreting something wrong regarding the sample flow in GNU Radio? Is it necessary to have some kind of constant "push" to make the samples move downstream? I thought the sample flow would automatically propagate through the graph. Any ideas, references, or suggestions to better understand this behavior would be greatly appreciated. Thanks in advance. Guillermo.
