WiMAX Question:

WiMax can not provide highest performance over 50 kilometers. As the distance increases, bit error rate thus reducing performance. Reducing distance to less than 1km allows a device to operate at higher bit rate. A user closer to base station gets better speed at around 30 mbps.
Also as an available bandwidth is shared between no of users, performance depends on number of active users connecting to that base station. So this needs a use of Quality of Service (QOS) mechanism to provide a minimum guaranteed throughput.