Evaluation of Spatial Diversity for HAPS - LTE Downlink System

High Altitude Platform Station (HAPS) system is one of the recent wireless technologies that exploit many promising advantages from satellite system as well as from terrestrial system. Long Term Evolution (LTE) is a 4G wireless broadband technology developed by Third Generation Partnership Project (3GPP), an industry trade group. 3GPP has been centered on enhancing LTE radio standards to improve the performance of wireless communications link, receive diversity has been proposed by the 3GPP within mode 1 of transmission in the LTE standard. In this paper, we focus on the HAPS-LTE downlink system performance evaluation with optimum receive spatial diversity and has channel side information known at the receiver (CSIR) for different scenarios. Simulation results show that, HAPS channel characteristics such as elevation angle, user mobility, and channel bandwidth greatly affect the performance of the proposed system. It is also shown that, maximal-ratio combining (MRC) diversity algorithm is able to improve the system performance in bad channel conditions.