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, C and D reachable from the base station at rates of 10 Mbps, 5 Mbps, 2.5 Mbps and 1 Mbps, respectively on the downstream channel. The base station has the infinite amount of data to send to each of the nodes, and can send to any one of these four nodes during any time slot in the downstream sub-frame.