In LTE, the eNB broadcasts DCI messages on the PDCCH to all UEs. Basically these DCI messages spell out "the rules" for communicating.
There are many DCI message types. Here is a good link that denotes all the types (formats): https://www.mathworks.com/help/lte/examples/pdcch-blind-search-and-dci-decoding.html
Does wireshark have a dissector for breaking DCI messages down?
