Research Of The Stratospheric Communication System

In recent years, Stratospheric Platform is considered as a promising platform for providing wireless services. Stratospheric communication is using high-altitude platform (High Altitude Platform Stations) placed in the stratosphere to communicate with the ground. It generally locates on the region between 17 and 22 km above the earth surface, and use of airships and unmanned aircraft as a platform carrier. Stratospheric communications has many advantages, for example, the free-space loss is small, can achieve line of sight transmission, multi-path fading impact on small. HAPS have the potential to deliver a wide spectrum of applications to both mobile and fixed users over a broad coverage area using multiple-beam antenna.With the development of mobile communication systems, user needs high-speed data transmission services. OFDM system is a kind of orthogonal multi-carrier transmission; can easy to achieve high-speed broadband transmission. So this paper presents a HAPS platform for communication system uses OFDM as the key technology of the physical layer.The main contents of this paper are to study the wireless communication systems based on HAPS. In this paper, the communication system model based on HAPS, including system components, the channel model and the simulation model, is researched. The performance and the feasibility of the stratospheric communication system using OFDM are analyzed by simulation.Then the OFDM synchronization algorithm is researched to improve the shortcomings of HAPS platform based on OFDM that is sensitive to the timing and frequency offset. The performance of several timing estimation and frequency offset estimation algorithm are analyzed and OFDM synchronization strategy is proposed based on HAPS platform. Synchronization strategy includes the design of a specific HAPS-OFDM frame format, frame arrival detection strategy, improve the timing synchronization algorithm, frequency offset estimation. At last, the link-level simulation using this synchronization strategy is done and the results show that the system performance has greatly improved.