1. For the zero feedback delay, in the first TTI there is no feedback, as no ACKs are available. For the rest of the TTIs, the feedback is equal to the current channel state information already stored at the UE object (see function receive_UE_feedback(obj) stored at +network_elements/eNodeB_sector.m.)
2. There was a bug in the LTE_sim_main.m file. The error occurred in your case because the link quality model was not called before calling the function set_SINRs_according_to_schedule(). Replace the lines 414 to 470 with the code available in this link:
In the launcher file it is important to also specify the trace version which directly relates to the precoding mode:
a) trace version ‘v1’ – non runtime precoding
b) trace version ‘v2’- runtime precoding
since the two modes are treated differently, and also note that only some transmission modes are supported by trace version ‘v2’.
Thanks for the bug report and let us know if you further encounter any problems.