Capacity Enhancement for Integrated HAPS-Terrestrial CDMA System

In this paper, we consider the uplink capacity of an integrated high altitude platform station (HAPS)-terrestrial code division multiple access (CDMA) system in which sharing band overlay configuration is used. To increase system capacity, an enhancement is investigated by assuming that directional antenna is used for high mobility users to access to the HAPS. This will lead to a reduction of not only the interference from HAPS to terrestrial, but also the interference from terrestrial to HAPS as the uplink power to HAPS can accordingly be increased. Numerical results are obtained analytically and it is shown that the system capacity can be enhanced significantly under the proposed scheme