Consider the following idealized WiMAX scenario. The downstream sub-frame (see Figure 6.17) is slotted in time, with N downstream slots per sub-frame, with all time slots of equal length in time. There are four nodes, A, B, e. and D, reachable from the base station at rates of 10 Mbps, 5 Mbps, 2.5 Mbps, and I Mbps, respectively, on the downstream channel. The base station has an infinite amount of data to send to each of the nodes, and can send to anyone of these four nodes during any time slot in the downstream sub-frame.