Methods and apparatuses are presented for conducting communications over a shared communication medium, involving (a) sending an initial request from a first node, the shared communication medium organized to include (i) a request signal space including a plurality of request segments each having a different location within the request signal space and (ii) a scheduled transmission signal space including a plurality of scheduled transmission segments each having a different location within the scheduled transmission signal space, the initial request sent in an initial request segment, (b) obtaining a request assignment associating the initial request with at least one follow-up request segment, (c) from the first node, sending a follow-up request in the at least one follow-up request segment, (d) obtaining a scheduled transmission assignment specifying a scheduled transmission segment, and (e) from the first node, sending a data transmission in the scheduled transmission segment.