Methods, systems and instructions stored on computer-readable media for generating, at a first node, a plurality of data units. The plurality of data units are spread with a common pseudo-noise (PN) code that is used by a plurality of nodes, including the first node and a second node, that are in communication with an access point. A random timing offset is determined, and a first data unit is transmitted to the access point at a first time based upon a slot start time and the random timing offset. The first data unit is transmitted while at least a portion of a second signal is transmitted from the second node such that both the first data unit and the second signal are received by the access point. The second signal is transmitted at a second time based on the slot time and a second random timing offset.