Performance Research Of Haps-Cdma Mobile Cellular Network

High altitude platform station (HAPS) is a new way of communication, which operates in stratosphere whose altitude is about20km. Compared to traditional satellite communication and terrestrial cellular mobile communication, the HAPS has several significant advantages, such as lower cost of deployment, larger system capacity, larger area of coverage, faster speed of distribution network, and more suitable for areas with less population density and contingencies such as emergency communications. In recent years, it has been the concern of many countries and research institutions. This paper focuses on the performances and features of the HAPS-CDMA mobile cellular network, and makes some preparatory work for the development of this system.For any communication system research, channel modeling is a very important part. HAPS communition channel has the dual characteristics of the terrestrial mobile communication channel and satellite communication channel. The best way to study the performance of the channel is measurement and analysis in the actual communication environment. But it is almost impossible to achieve by real-time testing and data collection in the stratosphere environment. In this paper, considering the characteristics of the HAPS communication system, the large-scale fading, small scale fading are analysed, and the HAPS system’s channel modeling methods are summarized. In generally, the signal energy of light of sight and once reflected multipath are larger than other multipath signals’. In this paper, using the method of the ellisposidal model of the satellite communication system to analyze the probability of the light of sight and once reflected multipath signals. The work of the HAPS system channel provides a basis for the following study. In this paper, the capacity of the HAPS-CDMA system is analysed. The results show that the inter-cell interference factor is smaller than the terrestrial CDMA communication system’s, and the capacity is larger than the terrstiral one’s. However, HAPS may suffer from stratospheric winds. Platform can maintain the platform in the quasi-static states, which will lead to instability of the system, such as large-scale user switching, dropped calls, resulting in lower system capacity. This paper define the quasi-stationary state three types:the platform swing, platform displacement (horizontal and vertical), and platform rotation, and assess the impact on system performance from several aspects. Finally, the algorithm of combined receiving signal with the adjacent HAPS base station, and the networking solutions of using existing ground base stations are proposed.The honeycomb network structure is widely used in the terrestial mobile communication system, and a number of base stations is distribution located in the center of the cells, covering the cell by the omni-directional or directional antenna. Frequency multiplexing is realized by natural path loss decreases, and the ratio of the frequency utilization is increased. Different from the terrestrial mobile communication system, the HAPS communication system cover different areas through the multiple beams producted by the multi-beam antennas which are installed on the platform below of the platform, and each beam coverage area is defined as a cell. Because of this, the beam energy distribution in the ground is uneven according to the ITU proposed coverage programs. First, the paper accesses the ITU programs from the cell radius, buttery loss and system capacity. The analysis results show that the farther from the platform, the greater the overlap region between the beam, the more serious inter-cell interference and the system capacity is also smaller. This QoS unfairness affects the HAPS-CDMA system commercialized. In the present conditions, the simplest solution is using existing ground mobile communication base stations to provide supplement service for the system capacity "hot spots", where the user density is high. The results show that the effect is very objective.In summary, this paper analyses the characteristics of the HAPS-CDMA mobile cellular network, combined with satellite communication and terrestrial mobile communication system, and provides helpful suggestions.