On Effectively Determining the Downlink-to-Uplink Sub-frame Width Ratio for Mobile WiMAX Networks Using Spline Extrapolation

One of the most valuable design issues of the Worldwide Interoperability for Microwave Access (WiMAX) standard is its flexibility. It allows multiple downlink-to-uplink duration definitions concerning the width of the corresponding sub-frames, thus, the telecommunication companies and businesses are able to define the downlink-to-uplink width from 3:1 to 1:1 respectively to meet the traffic demands of the connected subscribers. However, the decision on defining the most appropriate ratio is not yet solved, since current efforts on developing scheduling and mapping schemes consider it as fixed. In this work, a novel adaptive mapping approach -- based on cubic spline extrapolation - is proposed in order to dynamically determine the most appropriate downlink-to-uplink width ratio in accordance to the downlink and uplink traffic demands. The method proposed is evaluated through realistic simulation scenarios, whereas its performance is compared with static approaches maintaining a fixed ratio. The results indicate that the approach suggested succeeds noticeable improvements in terms of network service capabilities and bandwidth utilization.