Channel modeling for High-Altitude platform: A review

High-Altitude Platform (HAP) is the most promising infrastructure for wireless communication in the near future. An essential problem need solving for the design of HAP communication systems is to establish an effective channel model for predicting the characteristics of the communication link. There have been many papers on this problem and several channel models have been proposed. The main work of this paper is to summarize and analyze the channel models available. Here, the existing models are divided into three groups according to their respective specialties and each model is briefly introduced with emphases on analysis of their strengths and weaknesses. Some open issues are also pointed out.