Low-complexity message formats and procedures are disclosed, greatly simplifying the task of user devices in recognizing downlink messages in 5G/6G. A user device, not requiring high performance or low latency, may request a “custom search-space” in which downlink messages may be transmitted by the base station, thereby greatly reducing the calculation overhead of the user device. In addition, message formats are disclosed that may enable rapid identification of relevant messages, and rejection of other messages, without performing a “blind search” and other arduous procedures. In addition, messaging protocols are disclosed that may avoid unnecessary control signaling, thereby saving time and energy. Low-cost wireless devices may be enabled by such low-complexity options in future wireless networks.