Performance of Variable Step Closed Loop Power Control in CDMA High Altitude Platforms Communication Channel

This paper evaluates the performance of variable-step closed loop power control algorithm for CDMA communication employing High Altitude Platforms (HAPs). In HAPs, the channel is predicted to have different characteristics compared to that in terrestrial. Users that are distributed within HAPs coverage will have different channel characteristics depending on their elevation angle. In this work, HAPs channel is modeled to follow Ricean fading distribution which K-factor is obtained based on experimental measurements. The variable-step power control algorithm is then computer simulated under such a channel to evaluate its performance. The performance is presented in terms of power control mode (q), user speed, user, elevation angle and power control command error. In many cases, elevation angles have a significant impact to the power control performance, i.e. the performance of the power control is worse at lower elevation angle.