Assignment modes for a shared communication medium

Methods and apparatuses are presented for conducting communications over a shared communication medium involving (a) sending a 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 request sent in a request segment, (b) obtaining an assignment associating the request with a scheduled transmission segment, the assignment taking into account location of the request within the request signal space, and (c) from the first node, sending a data transmission in the scheduled transmission segment associated with the request in accordance with the assignment.